Merge pull request 'release/0.5.0' (#15) from release/0.5.0 into main

Reviewed-on: #15

Cargo.lock

@@ -247,6 +247,26 @@ dependencies = [
  "static_assertions",
 ]
 
+[[package]]
+name = "const-random"
+version = "0.1.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "87e00182fe74b066627d63b85fd550ac2998d4b0bd86bfed477a0ae4c7c71359"
+dependencies = [
+ "const-random-macro",
+]
+
+[[package]]
+name = "const-random-macro"
+version = "0.1.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f9d839f2a20b0aee515dc581a6172f2321f96cab76c1a38a4c584a194955390e"
+dependencies = [
+ "getrandom 0.2.17",
+ "once_cell",
+ "tiny-keccak",
+]
+
 [[package]]
 name = "convert_case"
 version = "0.10.0"
@@ -292,6 +312,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "crunchy"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "460fbee9c2c2f33933d720630a6a0bac33ba7053db5344fac858d4b8952d77d5"
+
 [[package]]
 name = "crypto-common"
 version = "0.1.7"
@@ -414,6 +440,15 @@ dependencies = [
  "windows-sys",
 ]
 
+[[package]]
+name = "dlv-list"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "442039f5147480ba31067cb00ada1adae6892028e40e45fc5de7b7df6dcc1b5f"
+dependencies = [
+ "const-random",
+]
+
 [[package]]
 name = "document-features"
 version = "0.2.12"
@@ -429,6 +464,15 @@ version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
 
+[[package]]
+name = "encoding_rs"
+version = "0.8.35"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "75030f3c4f45dafd7586dd6780965a8c7e8e285a5ecb86713e63a79c5b2766f3"
+dependencies = [
+ "cfg-if",
+]
+
 [[package]]
 name = "env_filter"
 version = "1.0.0"
@@ -580,6 +624,12 @@ dependencies = [
  "wasip3",
 ]
 
+[[package]]
+name = "hashbrown"
+version = "0.14.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e5274423e17b7c9fc20b6e7e208532f9b19825d82dfd615708b70edd83df41f1"
+
 [[package]]
 name = "hashbrown"
 version = "0.15.5"
@@ -679,6 +729,17 @@ version = "1.0.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "92ecc6618181def0457392ccd0ee51198e065e016d1d527a7ac1b6dc7c1f09d2"
 
+[[package]]
+name = "java-properties"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37bf6f484471c451f2b51eabd9e66b3fa7274550c5ec4b6c3d6070840945117f"
+dependencies = [
+ "encoding_rs",
+ "lazy_static",
+ "regex",
+]
+
 [[package]]
 name = "jiff"
 version = "0.2.23"
@@ -853,15 +914,18 @@ dependencies = [
 
 [[package]]
 name = "mould"
-version = "0.4.3"
+version = "0.5.0"
 dependencies = [
  "anyhow",
  "clap",
  "crossterm",
  "dirs",
  "env_logger",
+ "java-properties",
  "log",
+ "quick-xml",
  "ratatui",
+ "rust-ini",
  "serde",
  "serde_json",
  "serde_yaml",
@@ -956,6 +1020,16 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "ordered-multimap"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49203cdcae0030493bad186b28da2fa25645fa276a51b6fec8010d281e02ef79"
+dependencies = [
+ "dlv-list",
+ "hashbrown 0.14.5",
+]
+
 [[package]]
 name = "parking_lot"
 version = "0.12.5"
@@ -1114,6 +1188,16 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "quick-xml"
+version = "0.39.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "958f21e8e7ceb5a1aa7fa87fab28e7c75976e0bfe7e23ff069e0a260f894067d"
+dependencies = [
+ "memchr",
+ "serde",
+]
+
 [[package]]
 name = "quote"
 version = "1.0.45"
@@ -1284,6 +1368,16 @@ version = "0.8.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dc897dd8d9e8bd1ed8cdad82b5966c3e0ecae09fb1907d58efaa013543185d0a"
 
+[[package]]
+name = "rust-ini"
+version = "0.21.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "796e8d2b6696392a43bea58116b667fb4c29727dc5abd27d6acf338bb4f688c7"
+dependencies = [
+ "cfg-if",
+ "ordered-multimap",
+]
+
 [[package]]
 name = "rustc_version"
 version = "0.4.1"
@@ -1366,6 +1460,7 @@ version = "1.0.149"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "83fc039473c5595ace860d8c4fafa220ff474b3fc6bfdb4293327f1a37e94d86"
 dependencies = [
+ "indexmap",
  "itoa",
  "memchr",
  "serde",
@@ -1642,10 +1737,19 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7694e1cfe791f8d31026952abf09c69ca6f6fa4e1a1229e18988f06a04a12dca"
 
 [[package]]
-name = "toml"
-version = "1.0.6+spec-1.1.0"
+name = "tiny-keccak"
+version = "2.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "399b1124a3c9e16766831c6bba21e50192572cdd98706ea114f9502509686ffc"
+checksum = "2c9d3793400a45f954c52e73d068316d76b6f4e36977e3fcebb13a2721e80237"
+dependencies = [
+ "crunchy",
+]
+
+[[package]]
+name = "toml"
+version = "1.0.7+spec-1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dd28d57d8a6f6e458bc0b8784f8fdcc4b99a437936056fa122cb234f18656a96"
 dependencies = [
  "indexmap",
  "serde_core",
@@ -1658,27 +1762,27 @@ dependencies = [
 
 [[package]]
 name = "toml_datetime"
-version = "1.0.0+spec-1.1.0"
+version = "1.0.1+spec-1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "32c2555c699578a4f59f0cc68e5116c8d7cabbd45e1409b989d4be085b53f13e"
+checksum = "9b320e741db58cac564e26c607d3cc1fdc4a88fd36c879568c07856ed83ff3e9"
 dependencies = [
  "serde_core",
 ]
 
 [[package]]
 name = "toml_parser"
-version = "1.0.9+spec-1.1.0"
+version = "1.0.10+spec-1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "702d4415e08923e7e1ef96cd5727c0dfed80b4d2fa25db9647fe5eb6f7c5a4c4"
+checksum = "7df25b4befd31c4816df190124375d5a20c6b6921e2cad937316de3fccd63420"
 dependencies = [
  "winnow",
 ]
 
 [[package]]
 name = "toml_writer"
-version = "1.0.6+spec-1.1.0"
+version = "1.0.7+spec-1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ab16f14aed21ee8bfd8ec22513f7287cd4a91aa92e44edfe2c17ddd004e92607"
+checksum = "f17aaa1c6e3dc22b1da4b6bba97d066e354c7945cac2f7852d4e4e7ca7a6b56d"
 
 [[package]]
 name = "tui-input"
@@ -1990,9 +2094,9 @@ dependencies = [
 
 [[package]]
 name = "winnow"
-version = "0.7.15"
+version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "df79d97927682d2fd8adb29682d1140b343be4ac0f08fd68b7765d9c059d3945"
+checksum = "a90e88e4667264a994d34e6d1ab2d26d398dcdca8b7f52bec8668957517fc7d8"
 
 [[package]]
 name = "wit-bindgen"

Cargo.toml

@@ -1,3 +1,9 @@
+[package]
+authors = ["Nils Pukropp <nils@narl.io>"]
+edition = "2024"
+name = "mould"
+version = "0.5.0"
+
 [[bin]]
 name = "mould"
 path = "src/main.rs"
@@ -7,27 +13,18 @@ anyhow = "1.0.102"
 crossterm = "0.29.0"
 dirs = "6.0.0"
 env_logger = "0.11.9"
+java-properties = "2.0.0"
 log = "0.4.29"
 ratatui = "0.30.0"
-serde_json = "1.0.149"
+rust-ini = "0.21.3"
+serde = { version = "1.0.228", features = ["derive"] }
+serde_json = { version = "1.0.149", features = ["preserve_order"] }
 serde_yaml = "0.9.34"
 thiserror = "2.0.18"
-toml = "1.0.6"
+toml = { version = "1.0.7", features = ["preserve_order"] }
 tui-input = "0.15.0"
-
-[dependencies.clap]
-features = ["derive"]
-version = "4.6.0"
-
-[dependencies.serde]
-features = ["derive"]
-version = "1.0.228"
+clap = { version = "4.6.0", features = ["derive"] }
+quick-xml = { version = "0.39.2", features = ["serde", "serialize"] }
 
 [dev-dependencies]
 tempfile = "3.27.0"
-
-[package]
-authors = ["Nils Pukropp <nils@narl.io>"]
-edition = "2024"
-name = "mould"
-version = "0.4.3"

README.md

@@ -1,12 +1,13 @@
 # mould
 
-mould is a modern Terminal User Interface (TUI) tool designed for interactively generating and editing configuration files from templates. Whether you are setting up a `.env` file from an example, creating a `docker-compose.override.yml`, or editing nested `JSON`, `YAML`, or `TOML` configurations, mould provides a fast, Vim-inspired workflow to get your environment ready.
+mould is a modern Terminal User Interface (TUI) tool designed for interactively generating and editing configuration files from templates. Whether you are setting up a `.env` file from an example, creating a `docker-compose.override.yml`, or editing nested `JSON`, `YAML`, `TOML`, `XML`, `INI`, or `Properties` configurations, mould provides a fast, Vim-inspired workflow to get your environment ready.
 
 ## Features
 
-- **Universal Format Support**: Handle `.env`, `JSON`, `YAML`, and `TOML` seamlessly.
-- **Tree View Navigation**: Edit nested data structures (JSON, YAML, TOML) in a beautiful, depth-colored tree view.
-- **Smart Template Comparison**: Automatically discovers `.env.example` vs `.env` relationships and highlights missing or modified keys.
+- **Universal Format Support**: Handle `.env`, `JSON`, `YAML`, `TOML`, `XML`, `INI`, and `Properties` seamlessly.
+- **Tree View Navigation**: Edit nested data structures in a beautiful, depth-colored tree view.
+- **Smart Template Discovery**: Rule-based resolver automatically discovers relationships (e.g., `.env.example` vs `.env`, `config.template.properties` vs `config.properties`) and highlights differences.
+- **Strict Type Preservation**: Intelligently preserves data types (integers, booleans, strings) during edit-save cycles, ensuring your configuration stays valid.
 - **Add Missing Keys**: Instantly pull missing keys and their default values from your template into your active configuration with a single keystroke.
 - **Neovim Integration**: Comes with a built-in Neovim plugin for seamless in-editor configuration management.
 - **Docker Compose Integration**: Automatically generate `docker-compose.override.yml` from `docker-compose.yml`.

src/app.rs

@@ -1,5 +1,6 @@
-use crate::format::ConfigItem;
+use crate::format::{ConfigItem, PathSegment};
 use tui_input::Input;
+use crate::undo::UndoTree;
 
 /// Represents the current operating mode of the application.
 pub enum Mode {
@@ -7,6 +8,8 @@ pub enum Mode {
     Normal,
     /// Active text entry mode for modifying values.
     Insert,
+    /// Active text entry mode for modifying keys.
+    InsertKey,
     /// Active search mode for filtering keys.
     Search,
 }
@@ -33,14 +36,15 @@ pub struct App {
     pub input: Input,
     /// The current search query for filtering keys.
     pub search_query: String,
-    /// Stack of previous variable states for undo functionality.
-    pub undo_stack: Vec<Vec<ConfigItem>>,
+    /// Undo history structured as a tree
+    pub undo_tree: UndoTree,
 }
 
 impl App {
     /// Initializes a new application instance with the provided variables.
     pub fn new(vars: Vec<ConfigItem>) -> Self {
-        let initial_input = vars.get(0).and_then(|v| v.value.clone()).unwrap_or_default();
+        let initial_input = vars.first().and_then(|v| v.value.clone()).unwrap_or_default();
+        let undo_tree = UndoTree::new(vars.clone(), 0);
         Self {
             vars,
             selected: 0,
@@ -49,7 +53,7 @@ impl App {
             status_message: None,
             input: Input::new(initial_input),
             search_query: String::new(),
-            undo_stack: Vec::new(),
+            undo_tree,
         }
     }
 
@@ -143,26 +147,108 @@ impl App {
     /// Updates the input buffer to reflect the value of the currently selected variable.
     pub fn sync_input_with_selected(&mut self) {
         if let Some(var) = self.vars.get(self.selected) {
-            let val = var.value.clone().unwrap_or_default();
+            let val = match self.mode {
+                Mode::InsertKey => var.key.clone(),
+                _ => var.value.clone().unwrap_or_default(),
+            };
             self.input = Input::new(val);
         }
     }
 
-    /// Commits the current text in the input buffer back to the selected variable's value.
-    pub fn commit_input(&mut self) {
-        if let Some(var) = self.vars.get_mut(self.selected) {
-            if !var.is_group {
-                var.value = Some(self.input.value().to_string());
-                var.status = crate::format::ItemStatus::Modified;
+    /// Commits the current text in the input buffer back to the selected variable's value or key.
+    /// Returns true if commit was successful, false if there was an error (e.g. collision).
+    pub fn commit_input(&mut self) -> bool {
+        match self.mode {
+            Mode::Insert => {
+                if let Some(var) = self.vars.get_mut(self.selected)
+                    && !var.is_group {
+                        var.value = Some(self.input.value().to_string());
+                        var.status = crate::format::ItemStatus::Modified;
+                    }
+                true
             }
+            Mode::InsertKey => {
+                let new_key = self.input.value().trim().to_string();
+                if new_key.is_empty() {
+                    self.status_message = Some("Key cannot be empty".to_string());
+                    return false;
+                }
+                
+                let selected_var = self.vars[self.selected].clone();
+                if selected_var.key == new_key {
+                    return true;
+                }
+                
+                // Collision check: siblings share the same parent path
+                let parent_path = if selected_var.path.len() > 1 {
+                    &selected_var.path[..selected_var.path.len() - 1]
+                } else {
+                    &[]
+                };
+                
+                let exists = self.vars.iter().enumerate().any(|(i, v)| {
+                    i != self.selected 
+                    && v.path.len() == selected_var.path.len() 
+                    && v.path.starts_with(parent_path)
+                    && v.key == new_key
+                });
+                
+                if exists {
+                    self.status_message = Some(format!("Key already exists: {}", new_key));
+                    return false;
+                }
+                
+                // Update selected item's key and path
+                let old_path = selected_var.path.clone();
+                let mut new_path = parent_path.to_vec();
+                new_path.push(PathSegment::Key(new_key.clone()));
+                
+                {
+                    let var = self.vars.get_mut(self.selected).unwrap();
+                    var.key = new_key;
+                    var.path = new_path.clone();
+                    var.status = crate::format::ItemStatus::Modified;
+                }
+                
+                // Update paths of all children if it's a group
+                if selected_var.is_group {
+                    for var in self.vars.iter_mut() {
+                        if var.path.starts_with(&old_path) && var.path.len() > old_path.len() {
+                            let mut p = new_path.clone();
+                            p.extend(var.path[old_path.len()..].iter().cloned());
+                            var.path = p;
+                            var.status = crate::format::ItemStatus::Modified;
+                        }
+                    }
+                }
+                true
+            }
+            _ => true,
+        }
+    }
+
+    /// Transitions the application into Insert Mode for keys.
+    pub fn enter_insert_key(&mut self) {
+        if !self.vars.is_empty() {
+            if let Some(var) = self.vars.get(self.selected)
+                && matches!(var.path.last(), Some(PathSegment::Index(_))) {
+                    self.status_message = Some("Cannot rename array indices".to_string());
+                    return;
+                }
+            self.mode = Mode::InsertKey;
+            self.sync_input_with_selected();
         }
     }
 
     /// Transitions the application into Insert Mode with a specific variant.
     pub fn enter_insert(&mut self, variant: InsertVariant) {
         if let Some(var) = self.vars.get(self.selected) {
-            if !var.is_group {
-                self.save_undo_state();
+            if var.is_group {
+                self.enter_insert_key();
+            } else {
+                if !matches!(variant, InsertVariant::Substitute) {
+                    self.sync_input_with_selected();
+                }
                 self.mode = Mode::Insert;
                 match variant {
                     InsertVariant::Start => {
@@ -183,8 +269,17 @@ impl App {
 
     /// Commits the current input and transitions the application into Normal Mode.
     pub fn enter_normal(&mut self) {
-        self.commit_input();
+        if self.commit_input() {
+            self.save_undo_state();
+            self.mode = Mode::Normal;
+        }
+    }
+
+    /// Cancels the current input and transitions the application into Normal Mode.
+    pub fn cancel_insert(&mut self) {
         self.mode = Mode::Normal;
+        self.sync_input_with_selected();
+        self.status_message = None;
     }
 
     /// Deletes the currently selected item. If it's a group, deletes all children.
@@ -193,25 +288,20 @@ impl App {
             return;
         }
 
-        self.save_undo_state();
         let selected_path = self.vars[self.selected].path.clone();
         let is_group = self.vars[self.selected].is_group;
 
-        // Identify if the item being removed is an array item
-        let array_info = parse_index(&selected_path);
-
         // 1. Identify all items to remove
         let mut to_remove = Vec::new();
         to_remove.push(self.selected);
 
         if is_group {
-            let prefix_dot = format!("{}.", selected_path);
-            let prefix_bracket = format!("{}[", selected_path);
             for (i, var) in self.vars.iter().enumerate() {
                 if i == self.selected {
                     continue;
                 }
-                if var.path.starts_with(&prefix_dot) || var.path.starts_with(&prefix_bracket) {
+                // An item is a child if its path starts with the selected path
+                if var.path.starts_with(&selected_path) {
                     to_remove.push(i);
                 }
             }
@@ -224,21 +314,22 @@ impl App {
         }
 
         // 3. Re-index subsequent array items if applicable
-        if let Some((base, removed_idx)) = array_info {
-            let base = base.to_string();
+        if let Some(PathSegment::Index(removed_idx)) = selected_path.last() {
+            let base_path = &selected_path[..selected_path.len() - 1];
+            
             for var in self.vars.iter_mut() {
-                if var.path.starts_with(&base) {
-                    // We need to find the index segment that matches this array
-                    if let Some((b, i, suffix)) = find_array_segment(&var.path, &base) {
-                        if b == base && i > removed_idx {
+                if var.path.starts_with(base_path) && var.path.len() >= selected_path.len() {
+                    // Check if the element at the level of the removed index is an index
+                    if let PathSegment::Index(i) = var.path[selected_path.len() - 1]
+                        && i > *removed_idx {
                             let new_idx = i - 1;
-                            var.path = format!("{}[{}]{}", base, new_idx, suffix);
-                            // Also update key if it matches the old index exactly
-                            if var.key == format!("[{}]", i) {
+                            var.path[selected_path.len() - 1] = PathSegment::Index(new_idx);
+                            
+                            // If this was an array element itself (not a child property), update its key
+                            if var.path.len() == selected_path.len() {
                                 var.key = format!("[{}]", new_idx);
                             }
                         }
-                    }
                 }
             }
         }
@@ -248,77 +339,209 @@ impl App {
             self.selected = self.vars.len() - 1;
         }
         self.sync_input_with_selected();
+        self.save_undo_state();
     }
 
-    /// Adds a new item to an array if the selected item is part of one.
-    pub fn add_array_item(&mut self, after: bool) {
+    /// Adds a new item relative to the selected item.
+    pub fn add_item(&mut self, after: bool, is_group: bool, as_child: bool) {
         if self.vars.is_empty() {
+            let new_key = if is_group { "NEW_GROUP".to_string() } else { "NEW_VAR".to_string() };
+            self.vars.push(ConfigItem {
+                key: new_key.clone(),
+                path: vec![PathSegment::Key(new_key)],
+                value: if is_group { None } else { Some("".to_string()) },
+                template_value: None,
+                default_value: None,
+                depth: 0,
+                is_group,
+                status: crate::format::ItemStatus::Modified,
+                value_type: if is_group { crate::format::ValueType::Null } else { crate::format::ValueType::String },
+            });
+            self.selected = 0;
+            self.sync_input_with_selected();
+            self.save_undo_state();
+            if is_group {
+                self.enter_insert_key();
+            } else {
+                self.enter_insert(InsertVariant::Start);
+            }
             return;
         }
 
-        self.save_undo_state();
-        let (base, idx, depth) = {
-            let selected_item = &self.vars[self.selected];
-            if selected_item.is_group {
-                return;
-            }
-            let path = &selected_item.path;
-            if let Some((base, idx)) = parse_index(path) {
-                (base.to_string(), idx, selected_item.depth)
-            } else {
-                return;
-            }
-        };
+        let selected_item = self.vars[self.selected].clone();
+        
+        // 1. Determine new item properties (path, key, depth, position)
+        let mut new_path;
+        let new_depth;
+        let insert_pos;
+        let mut is_array_item = false;
 
-        let new_idx = if after { idx + 1 } else { idx };
-        let insert_pos = if after {
-            self.selected + 1
-        } else {
-            self.selected
-        };
-
-        // 1. Shift all items in this array that have index >= new_idx
-        for var in self.vars.iter_mut() {
-            if var.path.starts_with(&base) {
-                if let Some((b, i)) = parse_index(&var.path) {
-                    if b == base && i >= new_idx {
-                        var.path = format!("{}[{}]", base, i + 1);
-                        // Also update key if it was just the index
-                        if var.key == format!("[{}]", i) {
-                            var.key = format!("[{}]", i + 1);
+        if !as_child && let Some(PathSegment::Index(idx)) = selected_item.path.last() {
+            // ARRAY ITEM LOGIC (Adding sibling to an existing index)
+            is_array_item = true;
+            let base_path = selected_item.path[..selected_item.path.len() - 1].to_vec();
+            let new_idx = if after { idx + 1 } else { *idx };
+            insert_pos = if after { self.selected + 1 } else { self.selected };
+            
+            // Shift subsequent indices
+            for var in self.vars.iter_mut() {
+                if var.path.starts_with(&base_path) && var.path.len() > base_path.len()
+                    && let PathSegment::Index(i) = var.path[base_path.len()]
+                        && i >= new_idx {
+                            var.path[base_path.len()] = PathSegment::Index(i + 1);
+                            if var.path.len() == base_path.len() + 1 {
+                                var.key = format!("[{}]", i + 1);
+                            }
                         }
-                    }
+            }
+            
+            new_path = base_path;
+            new_path.push(PathSegment::Index(new_idx));
+            new_depth = selected_item.depth;
+        } else if as_child && selected_item.is_group {
+            // ADD AS CHILD OF GROUP
+            insert_pos = self.selected + 1;
+            new_path = selected_item.path.clone();
+            new_depth = selected_item.depth + 1;
+            
+            // Check if this group already contains array items
+            if self.is_array_group(&selected_item.path) {
+                is_array_item = true;
+                let new_idx = 0; // Prepend to array
+                new_path.push(PathSegment::Index(new_idx));
+                
+                // Shift existing children
+                for var in self.vars.iter_mut() {
+                    if var.path.starts_with(&selected_item.path) && var.path.len() > selected_item.path.len()
+                        && let PathSegment::Index(i) = var.path[selected_item.path.len()] {
+                            var.path[selected_item.path.len()] = PathSegment::Index(i + 1);
+                            if var.path.len() == selected_item.path.len() + 1 {
+                                var.key = format!("[{}]", i + 1);
+                            }
+                        }
+                }
+            }
+        } else {
+            // ADD AS SIBLING
+            let parent_path = if selected_item.path.len() > 1 {
+                selected_item.path[..selected_item.path.len() - 1].to_vec()
+            } else {
+                Vec::new()
+            };
+            
+            insert_pos = if after {
+                let mut p = self.selected + 1;
+                while p < self.vars.len() && self.vars[p].path.starts_with(&selected_item.path) {
+                    p += 1;
+                }
+                p
+            } else {
+                self.selected
+            };
+            
+            new_path = parent_path;
+            new_depth = selected_item.depth;
+            
+            // If the parent is an array group, this is also an array item
+            if !new_path.is_empty() && self.is_array_group(&new_path) {
+                is_array_item = true;
+                if let Some(PathSegment::Index(idx)) = selected_item.path.last() {
+                    let new_idx = if after { idx + 1 } else { *idx };
+                    new_path.push(PathSegment::Index(new_idx));
+                } else {
+                    new_path.push(PathSegment::Index(0));
                 }
             }
         }
 
-        // 2. Insert new item
+        // 2. Generate a unique key for non-array items
+        let final_key = if is_array_item {
+            if let Some(PathSegment::Index(idx)) = new_path.last() {
+                format!("[{}]", idx)
+            } else {
+                "NEW_VAR".to_string()
+            }
+        } else {
+            let mut count = 1;
+            let mut candidate = if is_group { "NEW_GROUP".to_string() } else { "NEW_VAR".to_string() };
+            let parent_path_slice = new_path.as_slice();
+            
+            while self.vars.iter().any(|v| {
+                v.path.starts_with(parent_path_slice) 
+                && v.path.len() == parent_path_slice.len() + 1 
+                && v.key == candidate
+            }) {
+                candidate = if is_group { format!("NEW_GROUP_{}", count) } else { format!("NEW_VAR_{}", count) };
+                count += 1;
+            }
+            new_path.push(PathSegment::Key(candidate.clone()));
+            candidate
+        };
+
+        // 3. Insert new item
         let new_item = ConfigItem {
-            key: format!("[{}]", new_idx),
-            path: format!("{}[{}]", base, new_idx),
-            value: Some("".to_string()),
+            key: final_key,
+            path: new_path,
+            value: if is_group { None } else { Some("".to_string()) },
             template_value: None,
             default_value: None,
-            depth,
-            is_group: false,
+            depth: new_depth,
+            is_group,
             status: crate::format::ItemStatus::Modified,
-            value_type: crate::format::ValueType::String,
+            value_type: if is_group { crate::format::ValueType::Null } else { crate::format::ValueType::String },
         };
+
         self.vars.insert(insert_pos, new_item);
         self.selected = insert_pos;
-        self.sync_input_with_selected();
-        self.enter_insert(InsertVariant::Start);
+        self.save_undo_state();
+        
+        if is_array_item {
+            self.sync_input_with_selected();
+            self.enter_insert(InsertVariant::Start);
+        } else {
+            self.enter_insert_key();
+        }
         self.status_message = None;
     }
 
+    /// Toggles the group status of the currently selected item.
+    pub fn toggle_group_selected(&mut self) {
+        if let Some(var) = self.vars.get_mut(self.selected) {
+            // Cannot toggle array items (always vars)
+            if matches!(var.path.last(), Some(PathSegment::Index(_))) {
+                self.status_message = Some("Cannot toggle array items".to_string());
+                return;
+            }
+
+            var.is_group = !var.is_group;
+            if var.is_group {
+                var.value = None;
+                var.value_type = crate::format::ValueType::Null;
+            } else {
+                var.value = Some("".to_string());
+                var.value_type = crate::format::ValueType::String;
+            }
+            var.status = crate::format::ItemStatus::Modified;
+            self.sync_input_with_selected();
+        }
+    }
+
     /// Status bar helpers
     pub fn selected_is_group(&self) -> bool {
         self.vars.get(self.selected).map(|v| v.is_group).unwrap_or(false)
     }
 
+    pub fn is_array_group(&self, group_path: &[PathSegment]) -> bool {
+        self.vars.iter().any(|v| 
+            v.path.starts_with(group_path) 
+            && v.path.len() == group_path.len() + 1 
+            && matches!(v.path.last(), Some(PathSegment::Index(_)))
+        )
+    }
+
     pub fn selected_is_array(&self) -> bool {
         self.vars.get(self.selected)
-            .map(|v| !v.is_group && v.path.contains('['))
+            .map(|v| !v.is_group && matches!(v.path.last(), Some(PathSegment::Index(_))))
             .unwrap_or(false)
     }
 
@@ -328,18 +551,16 @@ impl App {
             .unwrap_or(false)
     }
 
-    /// Saves the current state of variables to the undo stack.
+    /// Saves the current state of variables to the undo tree.
     pub fn save_undo_state(&mut self) {
-        self.undo_stack.push(self.vars.clone());
-        if self.undo_stack.len() > 50 {
-            self.undo_stack.remove(0);
-        }
+        self.undo_tree.push(self.vars.clone(), self.selected);
     }
 
-    /// Reverts to the last saved state of variables.
+    /// Reverts to the previous state in the undo tree.
     pub fn undo(&mut self) {
-        if let Some(previous_vars) = self.undo_stack.pop() {
-            self.vars = previous_vars;
+        if let Some(action) = self.undo_tree.undo() {
+            self.vars = action.state.clone();
+            self.selected = action.selected;
             if self.selected >= self.vars.len() && !self.vars.is_empty() {
                 self.selected = self.vars.len() - 1;
             }
@@ -349,33 +570,19 @@ impl App {
             self.status_message = Some("Nothing to undo".to_string());
         }
     }
-}
 
-fn parse_index(path: &str) -> Option<(&str, usize)> {
-    if let Some(end) = path.rfind(']') {
-        let segment = &path[..=end];
-        if let Some(start) = segment.rfind('[') {
-            if let Ok(idx) = segment[start + 1..end].parse::<usize>() {
-                // Return the base and index
-                return Some((&path[..start], idx));
+    /// Advances to the next state in the undo tree.
+    pub fn redo(&mut self) {
+        if let Some(action) = self.undo_tree.redo() {
+            self.vars = action.state.clone();
+            self.selected = action.selected;
+            if self.selected >= self.vars.len() && !self.vars.is_empty() {
+                self.selected = self.vars.len() - 1;
             }
+            self.sync_input_with_selected();
+            self.status_message = Some("Redo applied".to_string());
+        } else {
+            self.status_message = Some("Nothing to redo".to_string());
         }
     }
-    None
-}
-
-/// Helper to find an array segment in a path given a base prefix.
-fn find_array_segment<'a>(path: &'a str, base: &str) -> Option<(&'a str, usize, &'a str)> {
-    if !path.starts_with(base) {
-        return None;
-    }
-    let remaining = &path[base.len()..];
-    if remaining.starts_with('[') {
-        if let Some(end) = remaining.find(']') {
-            if let Ok(idx) = remaining[1..end].parse::<usize>() {
-                return Some((&path[..base.len()], idx, &remaining[end + 1..]));
-            }
-        }
-    }
-    None
 }

src/config.rs

@@ -120,16 +120,21 @@ pub struct KeybindsConfig {
     pub prepend_item: String,
     pub delete_item: String,
     pub undo: String,
-}
+    pub redo: String,
+    pub rename: String,
+    pub append_group: String,
+    pub prepend_group: String,
+    pub toggle_group: String,
+    }
 
-impl Default for KeybindsConfig {
+    impl Default for KeybindsConfig {
     fn default() -> Self {
         Self {
             down: "j".to_string(),
             up: "k".to_string(),
             edit: "i".to_string(),
-            edit_append: "A".to_string(),
-            edit_substitute: "S".to_string(),
+            edit_append: "a".to_string(),
+            edit_substitute: "s".to_string(),
             save: ":w".to_string(),
             quit: ":q".to_string(),
             normal_mode: "Esc".to_string(),
@@ -142,9 +147,14 @@ impl Default for KeybindsConfig {
             prepend_item: "O".to_string(),
             delete_item: "dd".to_string(),
             undo: "u".to_string(),
+            redo: "U".to_string(),
+            rename: "r".to_string(),
+            append_group: "alt+o".to_string(),
+            prepend_group: "alt+O".to_string(),
+            toggle_group: "t".to_string(),
         }
     }
-}
+    }
 
 /// Root configuration structure for mould.
 #[derive(Debug, Deserialize, Serialize, Default, Clone)]
@@ -162,13 +172,11 @@ pub fn load_config() -> Config {
         config_dir.push("mould");
         config_dir.push("config.toml");
 
-        if config_dir.exists() {
-            if let Ok(content) = fs::read_to_string(config_dir) {
-                if let Ok(config) = toml::from_str(&content) {
+        if config_dir.exists()
+            && let Ok(content) = fs::read_to_string(config_dir)
+                && let Ok(config) = toml::from_str(&content) {
                     return config;
                 }
-            }
-        }
     }
     Config::default()
 }

src/error.rs

@@ -1,14 +1,10 @@
-use std::io;
 use thiserror::Error;
 
 /// Custom error types for the mould application.
 #[derive(Error, Debug)]
 pub enum MouldError {
     #[error("IO error: {0}")]
-    Io(#[from] io::Error),
-
-    #[error("Format error: {0}")]
-    Format(String),
+    Io(#[from] std::io::Error),
 
     #[error("File not found: {0}")]
     FileNotFound(String),

src/format/env.rs

@@ -1,12 +1,12 @@
-use super::{ConfigItem, FormatHandler, ItemStatus, ValueType};
+use super::{ConfigItem, FormatHandler, ItemStatus, ValueType, PathSegment};
 use std::fs;
-use std::io::{self, Write};
+use std::io::Write;
 use std::path::Path;
 
 pub struct EnvHandler;
 
 impl FormatHandler for EnvHandler {
-    fn parse(&self, path: &Path) -> io::Result<Vec<ConfigItem>> {
+    fn parse(&self, path: &Path) -> anyhow::Result<Vec<ConfigItem>> {
         let content = fs::read_to_string(path)?;
         let mut vars = Vec::new();
 
@@ -18,9 +18,10 @@ impl FormatHandler for EnvHandler {
 
             if let Some((key, val)) = line.split_once('=') {
                 let parsed_val = val.trim().trim_matches('"').trim_matches('\'').to_string();
+                let key_str = key.trim().to_string();
                 vars.push(ConfigItem {
-                    key: key.trim().to_string(),
-                    path: key.trim().to_string(),
+                    key: key_str.clone(),
+                    path: vec![PathSegment::Key(key_str)],
                     value: Some(parsed_val.clone()),
                     template_value: Some(parsed_val.clone()),
                     default_value: Some(parsed_val),
@@ -35,54 +36,7 @@ impl FormatHandler for EnvHandler {
         Ok(vars)
     }
 
-    fn merge(&self, path: &Path, vars: &mut Vec<ConfigItem>) -> io::Result<()> {
-        if !path.exists() {
-            return Ok(());
-        }
-
-        let content = fs::read_to_string(path)?;
-        for line in content.lines() {
-            let line = line.trim();
-            if line.is_empty() || line.starts_with('#') {
-                continue;
-            }
-
-            if let Some((key, val)) = line.split_once('=') {
-                let key = key.trim();
-                let parsed_val = val.trim().trim_matches('"').trim_matches('\'').to_string();
-
-                if let Some(var) = vars.iter_mut().find(|v| v.key == key) {
-                    if var.value.as_deref() != Some(&parsed_val) {
-                        var.value = Some(parsed_val);
-                        var.status = ItemStatus::Modified;
-                    }
-                } else {
-                    vars.push(ConfigItem {
-                        key: key.to_string(),
-                        path: key.to_string(),
-                        value: Some(parsed_val),
-                        template_value: None,
-                        default_value: None,
-                        depth: 0,
-                        is_group: false,
-                        status: ItemStatus::MissingFromTemplate,
-                        value_type: ValueType::String,
-                    });
-                }
-            }
-        }
-        
-        // Mark missing from active
-        for var in vars.iter_mut() {
-            if var.status == ItemStatus::Present && var.value.is_none() {
-                var.status = ItemStatus::MissingFromActive;
-            }
-        }
-
-        Ok(())
-    }
-
-    fn write(&self, path: &Path, vars: &[ConfigItem]) -> io::Result<()> {
+    fn write(&self, path: &Path, vars: &[ConfigItem]) -> anyhow::Result<()> {
         let mut file = fs::File::create(path)?;
         for var in vars {
             if !var.is_group {
@@ -126,27 +80,36 @@ mod tests {
 
     #[test]
     fn test_merge_env() {
-        let mut example_file = NamedTempFile::new().unwrap();
-        writeln!(example_file, "KEY1=default1\nKEY2=default2").unwrap();
         let handler = EnvHandler;
-        let mut vars = handler.parse(example_file.path()).unwrap();
 
         let mut env_file = NamedTempFile::new().unwrap();
         writeln!(env_file, "KEY1=custom1\nKEY3=custom3").unwrap();
+        let mut vars = handler.parse(env_file.path()).unwrap(); // Active vars
 
-        handler.merge(env_file.path(), &mut vars).unwrap();
+        let mut example_file = NamedTempFile::new().unwrap();
+        writeln!(example_file, "KEY1=default1\nKEY2=default2").unwrap();
 
+        handler.merge(example_file.path(), &mut vars).unwrap(); // Merge template into active
+
+        // Should preserve order of active, then append template
         assert_eq!(vars.len(), 3);
+        
+        // Active key that exists in template
         assert_eq!(vars[0].key, "KEY1");
-        assert_eq!(vars[0].value.as_deref(), Some("custom1"));
+        assert_eq!(vars[0].value.as_deref(), Some("custom1")); // Keeps active value
+        assert_eq!(vars[0].template_value.as_deref(), Some("default1")); // Gets template default
         assert_eq!(vars[0].status, ItemStatus::Modified);
 
-        assert_eq!(vars[1].key, "KEY2");
-        assert_eq!(vars[1].value.as_deref(), Some("default2"));
+        // Active key that DOES NOT exist in template
+        assert_eq!(vars[1].key, "KEY3");
+        assert_eq!(vars[1].value.as_deref(), Some("custom3"));
+        assert_eq!(vars[1].status, ItemStatus::Present);
         
-        assert_eq!(vars[2].key, "KEY3");
-        assert_eq!(vars[2].value.as_deref(), Some("custom3"));
-        assert_eq!(vars[2].status, ItemStatus::MissingFromTemplate);
+        // Template key that DOES NOT exist in active
+        assert_eq!(vars[2].key, "KEY2");
+        assert_eq!(vars[2].value.as_deref(), None); // Missing from active
+        assert_eq!(vars[2].template_value.as_deref(), Some("default2"));
+        assert_eq!(vars[2].status, ItemStatus::MissingFromActive);
     }
 
     #[test]
@@ -154,7 +117,7 @@ mod tests {
         let file = NamedTempFile::new().unwrap();
         let vars = vec![ConfigItem {
             key: "KEY1".to_string(),
-            path: "KEY1".to_string(),
+            path: vec![PathSegment::Key("KEY1".to_string())],
             value: Some("value1".to_string()),
             template_value: None,
             default_value: None,

src/format/hierarchical.rs

@@ -1,7 +1,6 @@
-use super::{ConfigItem, FormatHandler, FormatType, ItemStatus, ValueType};
+use super::{ConfigItem, FormatHandler, FormatType, ItemStatus, ValueType, PathSegment};
 use serde_json::{Map, Value};
 use std::fs;
-use std::io;
 use std::path::Path;
 
 pub struct HierarchicalHandler {
@@ -13,63 +12,234 @@ impl HierarchicalHandler {
         Self { format_type }
     }
 
-    fn read_value(&self, path: &Path) -> io::Result<Value> {
+    fn read_value(&self, path: &Path) -> anyhow::Result<Value> {
         let content = fs::read_to_string(path)?;
         let value = match self.format_type {
-            FormatType::Json => serde_json::from_str(&content)
-                .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?,
-            FormatType::Yaml => serde_yaml::from_str(&content)
-                .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?,
-            FormatType::Toml => toml::from_str(&content)
-                .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?,
+            FormatType::Json => serde_json::from_str(&content)?,
+            FormatType::Yaml => serde_yaml::from_str(&content)?,
+            FormatType::Toml => toml::from_str(&content)?,
+            FormatType::Xml => xml_to_json(&content)?,
             _ => unreachable!(),
         };
         Ok(value)
     }
 
-    fn write_value(&self, path: &Path, value: &Value) -> io::Result<()> {
+    fn write_value(&self, path: &Path, value: &Value) -> anyhow::Result<()> {
         let content = match self.format_type {
-            FormatType::Json => serde_json::to_string_pretty(value)
-                .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?,
-            FormatType::Yaml => serde_yaml::to_string(value)
-                .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?,
+            FormatType::Json => serde_json::to_string_pretty(value)?,
+            FormatType::Yaml => serde_yaml::to_string(value)?,
             FormatType::Toml => {
                 // toml requires the root to be a table
                 if value.is_object() {
-                    let toml_value: toml::Value = serde_json::from_value(value.clone())
-                        .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
-                    toml::to_string_pretty(&toml_value)
-                        .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?
+                    let toml_value: toml::Value = serde_json::from_value(value.clone())?;
+                    toml::to_string_pretty(&toml_value)?
                 } else {
-                    return Err(io::Error::new(
-                        io::ErrorKind::InvalidData,
-                        "Root of TOML must be an object",
-                    ));
+                    anyhow::bail!("Root of TOML must be an object");
                 }
             }
+            FormatType::Xml => json_to_xml(value),
             _ => unreachable!(),
         };
-        fs::write(path, content)
+        fs::write(path, content)?;
+        Ok(())
     }
 }
 
-fn flatten(value: &Value, prefix: &str, depth: usize, key_name: &str, vars: &mut Vec<ConfigItem>) {
-    let path = if prefix.is_empty() {
-        key_name.to_string()
-    } else if key_name.is_empty() {
-        prefix.to_string()
-    } else if key_name.starts_with('[') {
-        format!("{}{}", prefix, key_name)
+fn xml_to_json(content: &str) -> anyhow::Result<Value> {
+    use quick_xml::reader::Reader;
+    use quick_xml::events::Event;
+
+    let mut reader = Reader::from_str(content);
+    reader.config_mut().trim_text(true);
+    let mut buf = Vec::new();
+    
+    fn parse_recursive(reader: &mut Reader<&[u8]>) -> anyhow::Result<Value> {
+        let mut map = Map::new();
+        let mut text = String::new();
+        let mut buf = Vec::new();
+
+        loop {
+            match reader.read_event_into(&mut buf) {
+                Ok(Event::Start(e)) => {
+                    let name = String::from_utf8_lossy(e.name().as_ref()).to_string();
+                    let val = parse_recursive(reader)?;
+                    
+                    if let Some(existing) = map.get_mut(&name) {
+                        if let Some(arr) = existing.as_array_mut() {
+                            arr.push(val);
+                        } else {
+                            let old = existing.take();
+                            *existing = Value::Array(vec![old, val]);
+                        }
+                    } else {
+                        map.insert(name, val);
+                    }
+                }
+                Ok(Event::End(_)) => break,
+                Ok(Event::Text(e)) => {
+                    text.push_str(&String::from_utf8_lossy(e.as_ref()));
+                }
+                Ok(Event::Eof) => break,
+                _ => {}
+            }
+            buf.clear();
+        }
+
+        if map.is_empty() {
+            if text.is_empty() {
+                Ok(Value::Null)
+            } else {
+                Ok(Value::String(text))
+            }
+        } else {
+            if !text.is_empty() {
+                map.insert("$text".to_string(), Value::String(text));
+            }
+            Ok(Value::Object(map))
+        }
+    }
+
+    // Move to the first start tag
+    loop {
+        match reader.read_event_into(&mut buf) {
+            Ok(Event::Start(e)) => {
+                let name = String::from_utf8_lossy(e.name().as_ref()).to_string();
+                let val = parse_recursive(&mut reader)?;
+                let mut root = Map::new();
+                root.insert(name, val);
+                return Ok(Value::Object(root));
+            }
+            Ok(Event::Eof) => break,
+            _ => {}
+        }
+        buf.clear();
+    }
+
+    Ok(Value::Object(Map::new()))
+}
+
+fn json_to_xml(value: &Value) -> String {
+    use quick_xml::Writer;
+    use quick_xml::events::{Event, BytesStart, BytesEnd, BytesText};
+
+    let mut writer = Writer::new_with_indent(Vec::new(), b' ', 4);
+    
+    fn write_recursive(writer: &mut Writer<Vec<u8>>, value: &Value, key_name: Option<&str>) {
+        if let Some(k) = key_name
+            && k == "$text" {
+                if let Some(s) = value.as_str() {
+                    writer.write_event(Event::Text(BytesText::new(s))).unwrap();
+                }
+                return;
+            }
+        
+        match value {
+            Value::Object(map) => {
+                if let Some(k) = key_name {
+                    writer.write_event(Event::Start(BytesStart::new(k))).unwrap();
+                }
+                for (k, v) in map {
+                    if let Some(arr) = v.as_array() {
+                        for item in arr {
+                            write_recursive(writer, item, Some(k));
+                        }
+                    } else {
+                        write_recursive(writer, v, Some(k));
+                    }
+                }
+                if let Some(k) = key_name {
+                    writer.write_event(Event::End(BytesEnd::new(k))).unwrap();
+                }
+            }
+            Value::Array(arr) => {
+                for v in arr {
+                    write_recursive(writer, v, key_name);
+                }
+            }
+            Value::String(s) => {
+                if let Some(k) = key_name {
+                    writer.write_event(Event::Start(BytesStart::new(k))).unwrap();
+                }
+                writer.write_event(Event::Text(BytesText::new(s))).unwrap();
+                if let Some(k) = key_name {
+                    writer.write_event(Event::End(BytesEnd::new(k))).unwrap();
+                }
+            }
+            Value::Number(n) => {
+                if let Some(k) = key_name {
+                    writer.write_event(Event::Start(BytesStart::new(k))).unwrap();
+                }
+                writer.write_event(Event::Text(BytesText::new(&n.to_string()))).unwrap();
+                if let Some(k) = key_name {
+                    writer.write_event(Event::End(BytesEnd::new(k))).unwrap();
+                }
+            }
+            Value::Bool(b) => {
+                if let Some(k) = key_name {
+                    writer.write_event(Event::Start(BytesStart::new(k))).unwrap();
+                }
+                writer.write_event(Event::Text(BytesText::new(&b.to_string()))).unwrap();
+                if let Some(k) = key_name {
+                    writer.write_event(Event::End(BytesEnd::new(k))).unwrap();
+                }
+            }
+            Value::Null => {
+                if let Some(k) = key_name {
+                    writer.write_event(Event::Empty(BytesStart::new(k))).unwrap();
+                }
+            }
+        }
+    }
+
+    if value.is_object() {
+        for (k, v) in value.as_object().unwrap() {
+            if let Some(arr) = v.as_array() {
+                for item in arr {
+                    write_recursive(&mut writer, item, Some(k));
+                }
+            } else {
+                write_recursive(&mut writer, v, Some(k));
+            }
+        }
     } else {
-        format!("{}.{}", prefix, key_name)
+        write_recursive(&mut writer, value, None);
+    }
+    
+    // Quick-XML adds a trailing newline occasionally, or we might need one
+    let mut out = String::from_utf8(writer.into_inner()).unwrap();
+    if !out.ends_with('\n') {
+        out.push('\n');
+    }
+    out
+}
+
+fn flatten(value: &Value, current_path: Vec<PathSegment>, key_name: Option<String>, depth: usize, vars: &mut Vec<ConfigItem>) {
+    let mut next_path = current_path.clone();
+    
+    if let Some(ref k) = key_name {
+        if !current_path.is_empty() {
+            // It's a key in an object, so append to path
+            next_path.push(PathSegment::Key(k.clone()));
+        } else {
+            // First element, maybe root
+            if !k.is_empty() {
+                next_path.push(PathSegment::Key(k.clone()));
+            }
+        }
+    }
+
+    let display_key = match next_path.last() {
+        Some(PathSegment::Key(k)) => k.clone(),
+        Some(PathSegment::Index(i)) => format!("[{}]", i),
+        None => "".to_string(),
     };
 
     match value {
         Value::Object(map) => {
-            if !path.is_empty() {
+            if !next_path.is_empty() {
                 vars.push(ConfigItem {
-                    key: key_name.to_string(),
-                    path: path.clone(),
+                    key: display_key,
+                    path: next_path.clone(),
                     value: None,
                     template_value: None,
                     default_value: None,
@@ -79,16 +249,16 @@ fn flatten(value: &Value, prefix: &str, depth: usize, key_name: &str, vars: &mut
                     value_type: ValueType::Null,
                 });
             }
-            let next_depth = if path.is_empty() { depth } else { depth + 1 };
+            let next_depth = if next_path.is_empty() { depth } else { depth + 1 };
             for (k, v) in map {
-                flatten(v, &path, next_depth, k, vars);
+                flatten(v, next_path.clone(), Some(k.clone()), next_depth, vars);
             }
         }
         Value::Array(arr) => {
-            if !path.is_empty() {
+            if !next_path.is_empty() {
                 vars.push(ConfigItem {
-                    key: key_name.to_string(),
-                    path: path.clone(),
+                    key: display_key,
+                    path: next_path.clone(),
                     value: None,
                     template_value: None,
                     default_value: None,
@@ -98,16 +268,17 @@ fn flatten(value: &Value, prefix: &str, depth: usize, key_name: &str, vars: &mut
                     value_type: ValueType::Null,
                 });
             }
-            let next_depth = if path.is_empty() { depth } else { depth + 1 };
+            let next_depth = if next_path.is_empty() { depth } else { depth + 1 };
             for (i, v) in arr.iter().enumerate() {
-                let array_key = format!("[{}]", i);
-                flatten(v, &path, next_depth, &array_key, vars);
+                let mut arr_path = next_path.clone();
+                arr_path.push(PathSegment::Index(i));
+                flatten(v, arr_path, None, next_depth, vars);
             }
         }
         Value::String(s) => {
             vars.push(ConfigItem {
-                key: key_name.to_string(),
-                path: path.clone(),
+                key: display_key,
+                path: next_path.clone(),
                 value: Some(s.clone()),
                 template_value: Some(s.clone()),
                 default_value: Some(s.clone()),
@@ -120,8 +291,8 @@ fn flatten(value: &Value, prefix: &str, depth: usize, key_name: &str, vars: &mut
         Value::Number(n) => {
             let s = n.to_string();
             vars.push(ConfigItem {
-                key: key_name.to_string(),
-                path: path.clone(),
+                key: display_key,
+                path: next_path.clone(),
                 value: Some(s.clone()),
                 template_value: Some(s.clone()),
                 default_value: Some(s.clone()),
@@ -134,8 +305,8 @@ fn flatten(value: &Value, prefix: &str, depth: usize, key_name: &str, vars: &mut
         Value::Bool(b) => {
             let s = b.to_string();
             vars.push(ConfigItem {
-                key: key_name.to_string(),
-                path: path.clone(),
+                key: display_key,
+                path: next_path.clone(),
                 value: Some(s.clone()),
                 template_value: Some(s.clone()),
                 default_value: Some(s.clone()),
@@ -147,8 +318,8 @@ fn flatten(value: &Value, prefix: &str, depth: usize, key_name: &str, vars: &mut
         }
         Value::Null => {
             vars.push(ConfigItem {
-                key: key_name.to_string(),
-                path: path.clone(),
+                key: display_key,
+                path: next_path.clone(),
                 value: Some("".to_string()),
                 template_value: Some("".to_string()),
                 default_value: Some("".to_string()),
@@ -162,51 +333,14 @@ fn flatten(value: &Value, prefix: &str, depth: usize, key_name: &str, vars: &mut
 }
 
 impl FormatHandler for HierarchicalHandler {
-    fn parse(&self, path: &Path) -> io::Result<Vec<ConfigItem>> {
+    fn parse(&self, path: &Path) -> anyhow::Result<Vec<ConfigItem>> {
         let value = self.read_value(path)?;
         let mut vars = Vec::new();
-        flatten(&value, "", 0, "", &mut vars);
+        flatten(&value, Vec::new(), Some("".to_string()), 0, &mut vars);
         Ok(vars)
     }
 
-    fn merge(&self, path: &Path, vars: &mut Vec<ConfigItem>) -> io::Result<()> {
-        if !path.exists() {
-            return Ok(());
-        }
-        let existing_value = self.read_value(path)?;
-        let mut existing_vars = Vec::new();
-        flatten(&existing_value, "", 0, "", &mut existing_vars);
-
-        for var in vars.iter_mut() {
-            if let Some(existing) = existing_vars.iter().find(|v| v.path == var.path) {
-                if var.value != existing.value {
-                    var.value = existing.value.clone();
-                    var.status = ItemStatus::Modified;
-                }
-            } else {
-                var.status = ItemStatus::MissingFromActive;
-            }
-        }
-        
-        // Find keys in active that are not in template
-        let mut to_add = Vec::new();
-        for existing in existing_vars {
-            if !vars.iter().any(|v| v.path == existing.path) {
-                let mut new_item = existing.clone();
-                new_item.status = ItemStatus::MissingFromTemplate;
-                new_item.template_value = None;
-                new_item.default_value = None;
-                to_add.push(new_item);
-            }
-        }
-        
-        // Basic insertion logic for extra keys (could be improved to insert at correct depth/position)
-        vars.extend(to_add);
-
-        Ok(())
-    }
-
-    fn write(&self, path: &Path, vars: &[ConfigItem]) -> io::Result<()> {
+    fn write(&self, path: &Path, vars: &[ConfigItem]) -> anyhow::Result<()> {
         let mut root = Value::Object(Map::new());
         for var in vars {
             if !var.is_group {
@@ -220,50 +354,52 @@ impl FormatHandler for HierarchicalHandler {
     }
 }
 
-fn insert_into_value(root: &mut Value, path: &str, new_val_str: &str, value_type: ValueType) {
-    let mut parts = path.split('.');
-    let last_part = match parts.next_back() {
-        Some(p) => p,
-        None => return,
-    };
+fn insert_into_value(root: &mut Value, path: &[PathSegment], new_val_str: &str, value_type: ValueType) {
+    if path.is_empty() {
+        return;
+    }
 
     let mut current = root;
-    for part in parts {
-        let (key, idx) = parse_array_key(part);
-        if !current.is_object() {
-            *current = Value::Object(Map::new());
-        }
-        let map = current.as_object_mut().unwrap();
+    
+    // Traverse all but the last segment
+    for i in 0..path.len() - 1 {
+        let segment = &path[i];
+        let next_segment = &path[i + 1];
 
-        let next_node = map.entry(key.to_string()).or_insert_with(|| {
-            if idx.is_some() {
-                Value::Array(Vec::new())
-            } else {
-                Value::Object(Map::new())
+        match segment {
+            PathSegment::Key(key) => {
+                if !current.is_object() {
+                    *current = Value::Object(Map::new());
+                }
+                let map = current.as_object_mut().unwrap();
+                
+                let next_node = map.entry(key.clone()).or_insert_with(|| {
+                    match next_segment {
+                        PathSegment::Index(_) => Value::Array(Vec::new()),
+                        PathSegment::Key(_) => Value::Object(Map::new()),
+                    }
+                });
+                current = next_node;
             }
-        });
-
-        if let Some(i) = idx {
-            if !next_node.is_array() {
-                *next_node = Value::Array(Vec::new());
+            PathSegment::Index(idx) => {
+                if !current.is_array() {
+                    *current = Value::Array(Vec::new());
+                }
+                let arr = current.as_array_mut().unwrap();
+                while arr.len() <= *idx {
+                    match next_segment {
+                        PathSegment::Index(_) => arr.push(Value::Array(Vec::new())),
+                        PathSegment::Key(_) => arr.push(Value::Object(Map::new())),
+                    }
+                }
+                current = &mut arr[*idx];
             }
-            let arr = next_node.as_array_mut().unwrap();
-            while arr.len() <= i {
-                arr.push(Value::Object(Map::new()));
-            }
-            current = &mut arr[i];
-        } else {
-            current = next_node;
         }
     }
 
-    let (final_key, final_idx) = parse_array_key(last_part);
-    if !current.is_object() {
-        *current = Value::Object(Map::new());
-    }
-    let map = current.as_object_mut().unwrap();
-
-    // Use the preserved ValueType instead of aggressive inference
+    // Handle the final segment
+    let final_segment = &path[path.len() - 1];
+    
     let final_val = match value_type {
         ValueType::Number => {
             if let Ok(n) = new_val_str.parse::<i64>() {
@@ -289,31 +425,24 @@ fn insert_into_value(root: &mut Value, path: &str, new_val_str: &str, value_type
         _ => Value::String(new_val_str.to_string()),
     };
 
-    if let Some(i) = final_idx {
-        let next_node = map
-            .entry(final_key.to_string())
-            .or_insert_with(|| Value::Array(Vec::new()));
-        if !next_node.is_array() {
-            *next_node = Value::Array(Vec::new());
+    match final_segment {
+        PathSegment::Key(key) => {
+            if !current.is_object() {
+                *current = Value::Object(Map::new());
+            }
+            let map = current.as_object_mut().unwrap();
+            map.insert(key.clone(), final_val);
         }
-        let arr = next_node.as_array_mut().unwrap();
-        while arr.len() <= i {
-            arr.push(Value::Null);
+        PathSegment::Index(idx) => {
+            if !current.is_array() {
+                *current = Value::Array(Vec::new());
+            }
+            let arr = current.as_array_mut().unwrap();
+            while arr.len() <= *idx {
+                arr.push(Value::Null);
+            }
+            arr[*idx] = final_val;
         }
-        arr[i] = final_val;
-    } else {
-        map.insert(final_key.to_string(), final_val);
-    }
-}
-
-fn parse_array_key(part: &str) -> (&str, Option<usize>) {
-    if part.ends_with(']') && part.contains('[') {
-        let start_idx = part.find('[').unwrap();
-        let key = &part[..start_idx];
-        let idx = part[start_idx + 1..part.len() - 1].parse::<usize>().ok();
-        (key, idx)
-    } else {
-        (part, None)
     }
 }
 
@@ -322,7 +451,7 @@ mod tests {
     use super::*;
 
     #[test]
-    fn test_flatten_unflatten() {
+    fn test_json_flatten_unflatten() {
         let mut vars = Vec::new();
         let json = serde_json::json!({
             "services": {
@@ -335,7 +464,7 @@ mod tests {
             }
         });
 
-        flatten(&json, "", 0, "", &mut vars);
+        flatten(&json, Vec::new(), Some("".to_string()), 0, &mut vars);
         assert_eq!(vars.len(), 6);
 
         let mut root = Value::Object(Map::new());
@@ -345,9 +474,145 @@ mod tests {
             }
         }
 
-        // When unflattening, it parses bool back
         let unflattened_json = serde_json::to_string(&root).unwrap();
         assert!(unflattened_json.contains("\"8080:80\""));
         assert!(unflattened_json.contains("true"));
     }
+
+    #[test]
+    fn test_type_preservation() {
+        let mut vars = Vec::new();
+        let json = serde_json::json!({
+            "port_num": 8080,
+            "port_str": "8080",
+            "is_enabled": true,
+            "is_enabled_str": "true",
+            "float_num": 42.42,
+            "float_str": "42.42"
+        });
+
+        flatten(&json, Vec::new(), Some("".to_string()), 0, &mut vars);
+        
+        let mut root = Value::Object(Map::new());
+        for var in vars {
+            if !var.is_group {
+                insert_into_value(&mut root, &var.path, var.value.as_deref().unwrap_or(""), var.value_type);
+            }
+        }
+
+        let unflattened = root.as_object().unwrap();
+        
+        assert!(unflattened["port_num"].is_number(), "port_num should be a number");
+        assert_eq!(unflattened["port_num"].as_i64(), Some(8080));
+        
+        assert!(unflattened["port_str"].is_string(), "port_str should be a string");
+        assert_eq!(unflattened["port_str"].as_str(), Some("8080"));
+        
+        assert!(unflattened["is_enabled"].is_boolean(), "is_enabled should be a boolean");
+        assert_eq!(unflattened["is_enabled"].as_bool(), Some(true));
+        
+        assert!(unflattened["is_enabled_str"].is_string(), "is_enabled_str should be a string");
+        assert_eq!(unflattened["is_enabled_str"].as_str(), Some("true"));
+        
+        assert!(unflattened["float_num"].is_number(), "float_num should be a number");
+        assert_eq!(unflattened["float_num"].as_f64(), Some(42.42));
+        
+        assert!(unflattened["float_str"].is_string(), "float_str should be a string");
+        assert_eq!(unflattened["float_str"].as_str(), Some("42.42"));
+    }
+
+    #[test]
+    fn test_yaml_flatten_unflatten() {
+        let yaml_str = "
+server:
+  port: 8080
+  port_str: \"8080\"
+  enabled: true
+";
+        let yaml_val: Value = serde_yaml::from_str(yaml_str).unwrap();
+        let mut vars = Vec::new();
+        flatten(&yaml_val, Vec::new(), Some("".to_string()), 0, &mut vars);
+        
+        let mut root = Value::Object(Map::new());
+        for var in vars {
+            if !var.is_group {
+                insert_into_value(&mut root, &var.path, var.value.as_deref().unwrap_or(""), var.value_type);
+            }
+        }
+        
+        let unflattened_yaml = serde_yaml::to_string(&root).unwrap();
+        assert!(unflattened_yaml.contains("port: 8080"));
+        assert!(unflattened_yaml.contains("port_str: '8080'") || unflattened_yaml.contains("port_str: \"8080\""));
+        assert!(unflattened_yaml.contains("enabled: true"));
+    }
+
+    #[test]
+    fn test_toml_flatten_unflatten() {
+        let toml_str = "
+[server]
+port = 8080
+port_str = \"8080\"
+enabled = true
+";
+        let toml_val: toml::Value = toml::from_str(toml_str).unwrap();
+        let json_val: Value = serde_json::to_value(toml_val).unwrap();
+
+        let mut vars = Vec::new();
+        flatten(&json_val, Vec::new(), Some("".to_string()), 0, &mut vars);
+        
+        let mut root = Value::Object(Map::new());
+        for var in vars {
+            if !var.is_group {
+                insert_into_value(&mut root, &var.path, var.value.as_deref().unwrap_or(""), var.value_type);
+            }
+        }
+        
+        let toml_root: toml::Value = serde_json::from_value(root).unwrap();
+        let unflattened_toml = toml::to_string(&toml_root).unwrap();
+        
+        assert!(unflattened_toml.contains("port = 8080"));
+        assert!(unflattened_toml.contains("port_str = \"8080\""));
+        assert!(unflattened_toml.contains("enabled = true"));
+    }
+
+    #[test]
+    fn test_group_rename_write() {
+        let mut vars = Vec::new();
+        let json = serde_json::json!({
+            "old_group": {
+                "key": "val"
+            }
+        });
+
+        flatten(&json, Vec::new(), Some("".to_string()), 0, &mut vars);
+        assert_eq!(vars.len(), 2);
+        assert_eq!(vars[0].key, "old_group");
+        assert_eq!(vars[0].is_group, true);
+        assert_eq!(vars[1].key, "key");
+        assert_eq!(vars[1].path_string(), "old_group.key");
+
+        // Manually simulate a rename of "old_group" to "new_group"
+        let old_path = vars[0].path.clone();
+        let new_key = "new_group".to_string();
+        let mut new_path = vec![PathSegment::Key(new_key.clone())];
+        
+        vars[0].key = new_key;
+        vars[0].path = new_path.clone();
+        
+        // Update child path
+        vars[1].path = vec![PathSegment::Key("new_group".to_string()), PathSegment::Key("key".to_string())];
+        
+        let handler = HierarchicalHandler::new(FormatType::Json);
+        let mut root = Value::Object(Map::new());
+        for var in &vars {
+            if !var.is_group {
+                insert_into_value(&mut root, &var.path, var.value.as_deref().unwrap_or(""), var.value_type);
+            }
+        }
+        
+        let out = serde_json::to_string(&root).unwrap();
+        assert!(out.contains("\"new_group\""));
+        assert!(out.contains("\"key\":\"val\""));
+        assert!(!out.contains("\"old_group\""));
+    }
 }

src/format/ini.rs

@@ -0,0 +1,125 @@
+use super::{ConfigItem, FormatHandler, ItemStatus, ValueType, PathSegment};
+use ini::Ini;
+use std::path::Path;
+
+pub struct IniHandler;
+
+impl FormatHandler for IniHandler {
+    fn parse(&self, path: &Path) -> anyhow::Result<Vec<ConfigItem>> {
+        let conf = Ini::load_from_file(path)?;
+        let mut vars = Vec::new();
+
+        for (section, prop) in &conf {
+            let section_name = section.unwrap_or_default();
+            
+            if !section_name.is_empty() {
+                vars.push(ConfigItem {
+                    key: section_name.to_string(),
+                    path: vec![PathSegment::Key(section_name.to_string())],
+                    value: None,
+                    template_value: None,
+                    default_value: None,
+                    depth: 0,
+                    is_group: true,
+                    status: ItemStatus::Present,
+                    value_type: ValueType::Null,
+                });
+            }
+
+            for (key, value) in prop {
+                let path = if section_name.is_empty() {
+                    vec![PathSegment::Key(key.to_string())]
+                } else {
+                    vec![PathSegment::Key(section_name.to_string()), PathSegment::Key(key.to_string())]
+                };
+
+                vars.push(ConfigItem {
+                    key: key.to_string(),
+                    path,
+                    value: Some(value.to_string()),
+                    template_value: Some(value.to_string()),
+                    default_value: Some(value.to_string()),
+                    depth: if section_name.is_empty() { 0 } else { 1 },
+                    is_group: false,
+                    status: ItemStatus::Present,
+                    value_type: ValueType::String,
+                });
+            }
+        }
+
+        Ok(vars)
+    }
+
+    fn write(&self, path: &Path, vars: &[ConfigItem]) -> anyhow::Result<()> {
+        let mut conf = Ini::new();
+        for var in vars {
+            if !var.is_group {
+                let val = var.value.as_deref()
+                    .or(var.template_value.as_deref())
+                    .unwrap_or("");
+                
+                if var.path.len() == 2 {
+                    if let (PathSegment::Key(section), PathSegment::Key(key)) = (&var.path[0], &var.path[1]) {
+                        conf.with_section(Some(section)).set(key, val);
+                    }
+                } else if var.path.len() == 1
+                    && let PathSegment::Key(key) = &var.path[0] {
+                        conf.with_section(None::<String>).set(key, val);
+                    }
+            }
+        }
+        conf.write_to_file(path)?;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tempfile::NamedTempFile;
+    use std::io::Write;
+
+    #[test]
+    fn test_section_rename_write() {
+        let handler = IniHandler;
+        let mut vars = vec![
+            ConfigItem {
+                key: "server".to_string(),
+                path: vec![PathSegment::Key("server".to_string())],
+                value: None,
+                template_value: None,
+                default_value: None,
+                depth: 0,
+                is_group: true,
+                status: ItemStatus::Present,
+                value_type: ValueType::Null,
+            },
+            ConfigItem {
+                key: "port".to_string(),
+                path: vec![PathSegment::Key("server".to_string()), PathSegment::Key("port".to_string())],
+                value: Some("8080".to_string()),
+                template_value: Some("8080".to_string()),
+                default_value: Some("8080".to_string()),
+                depth: 1,
+                is_group: false,
+                status: ItemStatus::Present,
+                value_type: ValueType::String,
+            }
+        ];
+
+        // Rename "server" to "srv"
+        vars[0].key = "srv".to_string();
+        vars[0].path = vec![PathSegment::Key("srv".to_string())];
+        
+        // Update child path
+        vars[1].path = vec![PathSegment::Key("srv".to_string()), PathSegment::Key("port".to_string())];
+        
+        let file = NamedTempFile::new().unwrap();
+        handler.write(file.path(), &vars).unwrap();
+        
+        let content = std::fs::read_to_string(file.path()).unwrap();
+        assert!(content.contains("[srv]"));
+        assert!(content.contains("port=8080"));
+        assert!(!content.contains("[server]"));
+    }
+}

src/format/mod.rs

@@ -1,14 +1,14 @@
-use std::io;
 use std::path::Path;
 
 pub mod env;
 pub mod hierarchical;
+pub mod ini;
+pub mod properties;
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum ItemStatus {
     Present,
     MissingFromActive,
-    MissingFromTemplate,
     Modified,
 }
 
@@ -20,10 +20,25 @@ pub enum ValueType {
     Null,
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum PathSegment {
+    Key(String),
+    Index(usize),
+}
+
+impl std::fmt::Display for PathSegment {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            PathSegment::Key(k) => write!(f, "{}", k),
+            PathSegment::Index(i) => write!(f, "[{}]", i),
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct ConfigItem {
     pub key: String,
-    pub path: String,
+    pub path: Vec<PathSegment>,
     pub value: Option<String>,
     pub template_value: Option<String>,
     pub default_value: Option<String>,
@@ -33,18 +48,74 @@ pub struct ConfigItem {
     pub value_type: ValueType,
 }
 
+impl ConfigItem {
+    pub fn path_string(&self) -> String {
+        let mut s = String::new();
+        for (i, segment) in self.path.iter().enumerate() {
+            match segment {
+                PathSegment::Key(k) => {
+                    if i > 0 {
+                        s.push('.');
+                    }
+                    s.push_str(k);
+                }
+                PathSegment::Index(idx) => {
+                    s.push_str(&format!("[{}]", idx));
+                }
+            }
+        }
+        s
+    }
+}
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum FormatType {
     Env,
     Json,
     Yaml,
     Toml,
+    Xml,
+    Ini,
+    Properties,
 }
 
 pub trait FormatHandler {
-    fn parse(&self, path: &Path) -> io::Result<Vec<ConfigItem>>;
-    fn merge(&self, path: &Path, vars: &mut Vec<ConfigItem>) -> io::Result<()>;
-    fn write(&self, path: &Path, vars: &[ConfigItem]) -> io::Result<()>;
+    fn parse(&self, path: &Path) -> anyhow::Result<Vec<ConfigItem>>;
+    fn merge(&self, path: &Path, vars: &mut Vec<ConfigItem>) -> anyhow::Result<()> {
+        if !path.exists() {
+            return Ok(());
+        }
+
+        let template_vars = self.parse(path).unwrap_or_default();
+
+        for var in vars.iter_mut() {
+            if let Some(template_var) = template_vars.iter().find(|v| v.path == var.path) {
+                var.template_value = template_var.value.clone();
+                var.default_value = template_var.value.clone();
+                
+                if var.value != template_var.value {
+                    var.status = ItemStatus::Modified;
+                } else {
+                    var.status = ItemStatus::Present;
+                }
+            } else {
+                // Exists in active, but not in template
+                var.status = ItemStatus::Present;
+            }
+        }
+        
+        // Add items from template that are missing in active
+        for template_var in template_vars {
+            if !vars.iter().any(|v| v.path == template_var.path) {
+                let mut new_item = template_var.clone();
+                new_item.status = ItemStatus::MissingFromActive;
+                new_item.value = None;
+                vars.push(new_item);
+            }
+        }
+
+        Ok(())
+    }
+    fn write(&self, path: &Path, vars: &[ConfigItem]) -> anyhow::Result<()>;
 }
 
 pub fn detect_format(path: &Path, override_format: Option<String>) -> FormatType {
@@ -54,19 +125,22 @@ pub fn detect_format(path: &Path, override_format: Option<String>) -> FormatType
             "json" => return FormatType::Json,
             "yaml" | "yml" => return FormatType::Yaml,
             "toml" => return FormatType::Toml,
+            "xml" => return FormatType::Xml,
+            "ini" => return FormatType::Ini,
+            "properties" => return FormatType::Properties,
             _ => {}
         }
     }
 
-    let file_name = path.file_name().unwrap_or_default().to_string_lossy();
-    if file_name.ends_with(".json") {
-        FormatType::Json
-    } else if file_name.ends_with(".yaml") || file_name.ends_with(".yml") {
-        FormatType::Yaml
-    } else if file_name.ends_with(".toml") {
-        FormatType::Toml
-    } else {
-        FormatType::Env
+    let ext = path.extension().and_then(|s| s.to_str()).unwrap_or_default();
+    match ext {
+        "json" => FormatType::Json,
+        "yaml" | "yml" => FormatType::Yaml,
+        "toml" => FormatType::Toml,
+        "xml" => FormatType::Xml,
+        "ini" => FormatType::Ini,
+        "properties" => FormatType::Properties,
+        _ => FormatType::Env,
     }
 }
 
@@ -76,5 +150,8 @@ pub fn get_handler(format: FormatType) -> Box<dyn FormatHandler> {
         FormatType::Json => Box::new(hierarchical::HierarchicalHandler::new(FormatType::Json)),
         FormatType::Yaml => Box::new(hierarchical::HierarchicalHandler::new(FormatType::Yaml)),
         FormatType::Toml => Box::new(hierarchical::HierarchicalHandler::new(FormatType::Toml)),
+        FormatType::Xml => Box::new(hierarchical::HierarchicalHandler::new(FormatType::Xml)),
+        FormatType::Ini => Box::new(ini::IniHandler),
+        FormatType::Properties => Box::new(properties::PropertiesHandler),
     }
 }

src/format/properties.rs

@@ -0,0 +1,133 @@
+use super::{ConfigItem, FormatHandler, ItemStatus, ValueType, PathSegment};
+use java_properties::{LineContent, PropertiesIter, PropertiesWriter};
+use std::fs::File;
+use std::io::{BufReader, BufWriter};
+use std::path::Path;
+
+pub struct PropertiesHandler;
+
+impl FormatHandler for PropertiesHandler {
+    fn parse(&self, path: &Path) -> anyhow::Result<Vec<ConfigItem>> {
+        let file = File::open(path)?;
+        let reader = BufReader::new(file);
+        let iter = PropertiesIter::new(reader);
+
+        let mut vars = Vec::new();
+        let mut groups = std::collections::HashSet::new();
+
+        for line_result in iter {
+            let line = line_result?;
+            
+            if let LineContent::KVPair(path, value) = line.consume_content() {
+                // Add groups based on dot notation
+                let parts: Vec<&str> = path.split('.').collect();
+                let mut current_path = Vec::new();
+                
+                for (i, part) in parts.iter().enumerate().take(parts.len().saturating_sub(1)) {
+                    current_path.push(PathSegment::Key(part.to_string()));
+                    
+                    if groups.insert(current_path.clone()) {
+                        vars.push(ConfigItem {
+                            key: part.to_string(),
+                            path: current_path.clone(),
+                            value: None,
+                            template_value: None,
+                            default_value: None,
+                            depth: i,
+                            is_group: true,
+                            status: ItemStatus::Present,
+                            value_type: ValueType::Null,
+                        });
+                    }
+                }
+
+                let mut final_path = current_path.clone();
+                let last_key = parts.last().unwrap_or(&"").to_string();
+                final_path.push(PathSegment::Key(last_key.clone()));
+
+                vars.push(ConfigItem {
+                    key: last_key,
+                    path: final_path,
+                    value: Some(value.clone()),
+                    template_value: Some(value.clone()),
+                    default_value: Some(value.clone()),
+                    depth: parts.len().saturating_sub(1),
+                    is_group: false,
+                    status: ItemStatus::Present,
+                    value_type: ValueType::String,
+                });
+            }
+        }
+
+        // We don't sort here to preserve the original file order!
+        Ok(vars)
+    }
+
+    fn write(&self, path: &Path, vars: &[ConfigItem]) -> anyhow::Result<()> {
+        let file = File::create(path)?;
+        let writer = BufWriter::new(file);
+        let mut prop_writer = PropertiesWriter::new(writer);
+        
+        for var in vars {
+            if !var.is_group {
+                let val = var.value.as_deref()
+                    .or(var.template_value.as_deref())
+                    .unwrap_or("");
+                prop_writer.write(&var.path_string(), val)?;
+            }
+        }
+
+        prop_writer.finish()?;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tempfile::NamedTempFile;
+    use std::io::Write;
+
+    #[test]
+    fn test_group_rename_write() {
+        let handler = PropertiesHandler;
+        let mut vars = vec![
+            ConfigItem {
+                key: "server".to_string(),
+                path: vec![PathSegment::Key("server".to_string())],
+                value: None,
+                template_value: None,
+                default_value: None,
+                depth: 0,
+                is_group: true,
+                status: ItemStatus::Present,
+                value_type: ValueType::Null,
+            },
+            ConfigItem {
+                key: "port".to_string(),
+                path: vec![PathSegment::Key("server".to_string()), PathSegment::Key("port".to_string())],
+                value: Some("8080".to_string()),
+                template_value: Some("8080".to_string()),
+                default_value: Some("8080".to_string()),
+                depth: 1,
+                is_group: false,
+                status: ItemStatus::Present,
+                value_type: ValueType::String,
+            }
+        ];
+
+        // Rename "server" to "srv"
+        vars[0].key = "srv".to_string();
+        vars[0].path = vec![PathSegment::Key("srv".to_string())];
+        
+        // Update child path
+        vars[1].path = vec![PathSegment::Key("srv".to_string()), PathSegment::Key("port".to_string())];
+        
+        let file = NamedTempFile::new().unwrap();
+        handler.write(file.path(), &vars).unwrap();
+        
+        let content = std::fs::read_to_string(file.path()).unwrap();
+        assert!(content.contains("srv.port=8080"));
+        assert!(!content.contains("server.port=8080"));
+    }
+}

src/main.rs

@@ -6,6 +6,7 @@ mod format;
 mod runner;
 mod ui;
 mod resolver;
+mod undo;
 
 use app::App;
 use config::load_config;
@@ -96,10 +97,7 @@ fn main() -> anyhow::Result<()> {
         }
     } else if vars.is_empty() {
         // Fallback if no template and active is empty
-         vars = handler.parse(&input_path).map_err(|e| {
-            error!("Failed to parse input file: {}", e);
-            MouldError::Format(format!("Failed to parse {}: {}", input_path.display(), e))
-        })?;
+         vars = handler.parse(&input_path)?;
     }
 
     if vars.is_empty() {

src/resolver.rs

@@ -24,6 +24,12 @@ pub const RULES: &[Rule] = &[
     Rule { template_suffix: ".template.yaml", active_suffix: ".yaml", is_exact_match: false },
     Rule { template_suffix: ".example.toml", active_suffix: ".toml", is_exact_match: false },
     Rule { template_suffix: ".template.toml", active_suffix: ".toml", is_exact_match: false },
+    Rule { template_suffix: ".example.xml", active_suffix: ".xml", is_exact_match: false },
+    Rule { template_suffix: ".template.xml", active_suffix: ".xml", is_exact_match: false },
+    Rule { template_suffix: ".example.ini", active_suffix: ".ini", is_exact_match: false },
+    Rule { template_suffix: ".template.ini", active_suffix: ".ini", is_exact_match: false },
+    Rule { template_suffix: ".example.properties", active_suffix: ".properties", is_exact_match: false },
+    Rule { template_suffix: ".template.properties", active_suffix: ".properties", is_exact_match: false },
 ];
 
 pub const DEFAULT_CANDIDATES: &[&str] = &[
@@ -44,12 +50,10 @@ pub fn determine_output_path(input: &Path) -> PathBuf {
             if file_name == rule.template_suffix {
                 return input.with_file_name(rule.active_suffix);
             }
-        } else {
-            if file_name == rule.template_suffix {
-                return input.with_file_name(rule.active_suffix);
-            } else if let Some(base) = file_name.strip_suffix(rule.template_suffix) {
-                return input.with_file_name(format!("{}{}", base, rule.active_suffix));
-            }
+        } else if file_name == rule.template_suffix {
+            return input.with_file_name(rule.active_suffix);
+        } else if let Some(base) = file_name.strip_suffix(rule.template_suffix) {
+            return input.with_file_name(format!("{}{}", base, rule.active_suffix));
         }
     }
 

src/runner.rs

@@ -67,6 +67,7 @@ where
         match self.app.mode {
             Mode::Normal => self.handle_normal_mode(key),
             Mode::Insert => self.handle_insert_mode(key),
+            Mode::InsertKey => self.handle_insert_key_mode(key),
             Mode::Search => self.handle_search_mode(key),
         }
     }
@@ -109,8 +110,22 @@ where
 
     /// Handles primary navigation (j/k) and transitions to insert or command modes.
     fn handle_navigation_mode(&mut self, key: KeyEvent) -> io::Result<()> {
-        if let KeyCode::Char(c) = key.code {
-            self.key_sequence.push(c);
+        let key_str = if let KeyCode::Char(c) = key.code {
+            let mut s = String::new();
+            if key.modifiers.contains(event::KeyModifiers::ALT) {
+                s.push_str("alt+");
+            }
+            s.push(c);
+            s
+        } else {
+            String::new()
+        };
+
+        if !key_str.is_empty() {
+            self.key_sequence.push_str(&key_str);
+
+            let mut exact_match = None;
+            let mut prefix_match = false;
 
             // Collect all configured keybinds
             let binds = [
@@ -119,6 +134,7 @@ where
                 (&self.config.keybinds.edit, "edit"),
                 (&self.config.keybinds.edit_append, "edit_append"),
                 (&self.config.keybinds.edit_substitute, "edit_substitute"),
+                (&"S".to_string(), "edit_substitute"),
                 (&self.config.keybinds.search, "search"),
                 (&self.config.keybinds.next_match, "next_match"),
                 (&self.config.keybinds.previous_match, "previous_match"),
@@ -128,14 +144,16 @@ where
                 (&self.config.keybinds.prepend_item, "prepend_item"),
                 (&self.config.keybinds.delete_item, "delete_item"),
                 (&self.config.keybinds.undo, "undo"),
+                (&self.config.keybinds.redo, "redo"),
+                (&self.config.keybinds.rename, "rename"),
+                (&self.config.keybinds.append_group, "append_group"),
+                (&self.config.keybinds.prepend_group, "prepend_group"),
+                (&self.config.keybinds.toggle_group, "toggle_group"),
                 (&"a".to_string(), "add_missing"),
                 (&":".to_string(), "command"),
                 (&"q".to_string(), "quit"),
             ];
 
-            let mut exact_match = None;
-            let mut prefix_match = false;
-
             for (bind, action) in binds.iter() {
                 if bind == &&self.key_sequence {
                     exact_match = Some(*action);
@@ -145,6 +163,21 @@ where
                 }
             }
 
+            if exact_match.is_none() && !prefix_match {
+                // Not a match and not a prefix, restart with current key
+                self.key_sequence.clear();
+                self.key_sequence.push_str(&key_str);
+                
+                for (bind, action) in binds.iter() {
+                    if bind == &&self.key_sequence {
+                        exact_match = Some(*action);
+                        break;
+                    } else if bind.starts_with(&self.key_sequence) {
+                        prefix_match = true;
+                    }
+                }
+            }
+
             if let Some(action) = exact_match {
                 self.key_sequence.clear();
                 match action {
@@ -162,12 +195,19 @@ where
                     "previous_match" => self.app.jump_previous_match(),
                     "jump_top" => self.app.jump_top(),
                     "jump_bottom" => self.app.jump_bottom(),
-                    "append_item" => self.app.add_array_item(true),
-                    "prepend_item" => self.app.add_array_item(false),
+                    "append_item" => self.app.add_item(true, false, false),
+                    "prepend_item" => self.app.add_item(false, false, false),
                     "delete_item" => self.app.delete_selected(),
                     "undo" => self.app.undo(),
-                    "add_missing" => {
+                    "redo" => self.app.redo(),
+                    "rename" => self.app.enter_insert_key(),
+                    "append_group" => self.app.add_item(true, true, true),
+                    "prepend_group" => self.app.add_item(false, true, true),
+                    "toggle_group" => {
+                        self.app.toggle_group_selected();
                         self.app.save_undo_state();
+                    }
+                    "add_missing" => {
                         self.add_missing_item();
                     }
                     "command" => {
@@ -178,9 +218,7 @@ where
                     _ => {}
                 }
             } else if !prefix_match {
-                // Not an exact match and not a prefix for any bind, clear and restart seq
                 self.key_sequence.clear();
-                self.key_sequence.push(c);
             }
         } else {
             // Non-character keys reset the sequence buffer
@@ -198,21 +236,40 @@ where
 
     /// Adds a missing item from the template to the active configuration.
     fn add_missing_item(&mut self) {
-        if let Some(var) = self.app.vars.get_mut(self.app.selected) {
-            if var.status == crate::format::ItemStatus::MissingFromActive {
+        if let Some(var) = self.app.vars.get_mut(self.app.selected)
+            && var.status == crate::format::ItemStatus::MissingFromActive {
                 var.status = crate::format::ItemStatus::Present;
                 if !var.is_group {
                     var.value = var.template_value.clone();
                 }
                 self.app.sync_input_with_selected();
+                self.app.save_undo_state();
             }
-        }
     }
 
     /// Delegates key events to the `tui_input` handler during active editing.
     fn handle_insert_mode(&mut self, key: KeyEvent) -> io::Result<()> {
         match key.code {
-            KeyCode::Esc | KeyCode::Enter => {
+            KeyCode::Esc => {
+                self.app.cancel_insert();
+            }
+            KeyCode::Enter => {
+                self.app.enter_normal();
+            }
+            _ => {
+                self.app.input.handle_event(&Event::Key(key));
+            }
+        }
+        Ok(())
+    }
+
+    /// Handles keys in InsertKey mode.
+    fn handle_insert_key_mode(&mut self, key: KeyEvent) -> io::Result<()> {
+        match key.code {
+            KeyCode::Esc => {
+                self.app.cancel_insert();
+            }
+            KeyCode::Enter => {
                 self.app.enter_normal();
             }
             _ => {

src/ui.rs

@@ -103,24 +103,30 @@ pub fn draw(f: &mut Frame, app: &mut App, config: &Config) {
                 Span::styled(&var.key, key_style),
             ];
 
-            // Add status indicator if not present (only for leaf variables)
-            if !var.is_group {
-                match var.status {
-                    crate::format::ItemStatus::MissingFromActive => {
-                        let missing_style = if is_selected {
-                            Style::default().fg(theme.fg_highlight()).add_modifier(Modifier::BOLD)
-                        } else {
-                            Style::default().fg(theme.fg_warning()).add_modifier(Modifier::BOLD)
-                        };
-                        key_spans.push(Span::styled(" (missing)", missing_style));
-                    }
-                    crate::format::ItemStatus::Modified => {
-                        if !is_selected {
-                            key_spans.push(Span::styled(" (*)", Style::default().fg(theme.fg_modified())));
-                        }
-                    }
-                    _ => {}
+            // Add status indicator if not present
+            match var.status {
+                crate::format::ItemStatus::MissingFromActive if !var.is_group => {
+                    let missing_style = if is_selected {
+                        Style::default().fg(theme.fg_highlight()).add_modifier(Modifier::BOLD)
+                    } else {
+                        Style::default().fg(theme.fg_warning()).add_modifier(Modifier::BOLD)
+                    };
+                    key_spans.push(Span::styled(" (missing)", missing_style));
                 }
+                crate::format::ItemStatus::MissingFromActive if var.is_group => {
+                    let missing_style = if is_selected {
+                        Style::default().fg(theme.fg_highlight()).add_modifier(Modifier::BOLD)
+                    } else {
+                        Style::default().fg(theme.fg_warning()).add_modifier(Modifier::BOLD)
+                    };
+                    key_spans.push(Span::styled(" (missing group)", missing_style));
+                }
+                crate::format::ItemStatus::Modified => {
+                    if !is_selected {
+                        key_spans.push(Span::styled(" (*)", Style::default().fg(theme.fg_modified())));
+                    }
+                }
+                _ => {}
             }
 
             let item_style = if is_selected {
@@ -150,8 +156,8 @@ pub fn draw(f: &mut Frame, app: &mut App, config: &Config) {
                     Span::styled(val, value_style),
                 ];
 
-                if let Some(t_val) = &var.template_value {
-                    if Some(t_val) != var.value.as_ref() {
+                if let Some(t_val) = &var.template_value
+                    && Some(t_val) != var.value.as_ref() {
                         let t_style = if is_selected {
                             Style::default().fg(theme.bg_normal()).add_modifier(Modifier::DIM)
                         } else {
@@ -159,7 +165,6 @@ pub fn draw(f: &mut Frame, app: &mut App, config: &Config) {
                         };
                         val_spans.push(Span::styled(format!(" [Def: {}]", t_val), t_style));
                     }
-                }
 
                 ListItem::new(vec![Line::from(key_spans), Line::from(val_spans)]).style(item_style)
             }
@@ -189,10 +194,12 @@ pub fn draw(f: &mut Frame, app: &mut App, config: &Config) {
     let mut extra_info = String::new();
 
     if let Some(var) = current_var {
-        if var.is_group {
-            input_title = format!(" Group: {} ", var.path);
+        if matches!(app.mode, Mode::InsertKey) {
+            input_title = format!(" Rename Key: {} ", var.path_string());
+        } else if var.is_group {
+            input_title = format!(" Group: {} ", var.path_string());
         } else {
-            input_title = format!(" Editing: {} ", var.path);
+            input_title = format!(" Editing: {} ", var.path_string());
             if let Some(t_val) = &var.template_value {
                 extra_info = format!("  [Template: {}]", t_val);
             }
@@ -200,7 +207,7 @@ pub fn draw(f: &mut Frame, app: &mut App, config: &Config) {
     }
 
     let input_border_color = match app.mode {
-        Mode::Insert => theme.border_active(),
+        Mode::Insert | Mode::InsertKey => theme.border_active(),
         Mode::Normal | Mode::Search => theme.border_normal(),
     };
 
@@ -209,7 +216,9 @@ pub fn draw(f: &mut Frame, app: &mut App, config: &Config) {
 
     // Show template value in normal mode if it differs
     let display_text = if let Some(var) = current_var {
-        if var.is_group {
+        if matches!(app.mode, Mode::InsertKey) {
+            input_text.to_string()
+        } else if var.is_group {
             "<group>".to_string()
         } else if matches!(app.mode, Mode::Normal) {
             format!("{}{}", input_text, extra_info)
@@ -237,7 +246,7 @@ pub fn draw(f: &mut Frame, app: &mut App, config: &Config) {
     f.render_widget(input, chunks[2]);
 
     // Position the terminal cursor correctly when in Insert mode.
-    if let Mode::Insert = app.mode {
+    if matches!(app.mode, Mode::Insert) || matches!(app.mode, Mode::InsertKey) {
         f.set_cursor_position(ratatui::layout::Position::new(
             chunks[2].x + 1 + cursor_pos as u16,
             chunks[2].y + 1,
@@ -260,6 +269,13 @@ pub fn draw(f: &mut Frame, app: &mut App, config: &Config) {
                 .fg(theme.bg_normal())
                 .add_modifier(Modifier::BOLD),
         ),
+        Mode::InsertKey => (
+            " RENAME ",
+            Style::default()
+                .bg(theme.bg_active())
+                .fg(theme.bg_normal())
+                .add_modifier(Modifier::BOLD),
+        ),
         Mode::Search => (
             " SEARCH ",
             Style::default()
@@ -283,11 +299,16 @@ pub fn draw(f: &mut Frame, app: &mut App, config: &Config) {
                 if !app.selected_is_group() {
                     parts.push(format!("{}/{}/{} edit", kb.edit, kb.edit_append, kb.edit_substitute));
                 }
+                parts.push(format!("{} rename", kb.rename));
+                parts.push(format!("{} toggle", kb.toggle_group));
                 if app.selected_is_missing() {
                     parts.push(format!("{} add", "a")); // 'a' is currently hardcoded in runner
                 }
                 if app.selected_is_array() {
                     parts.push(format!("{}/{} array", kb.append_item, kb.prepend_item));
+                } else {
+                    parts.push(format!("{}/{} add", kb.append_item, kb.prepend_item));
+                    parts.push(format!("{}/{} group", kb.append_group, kb.prepend_group));
                 }
                 parts.push(format!("{} del", kb.delete_item));
                 parts.push(format!("{} undo", kb.undo));
@@ -295,7 +316,8 @@ pub fn draw(f: &mut Frame, app: &mut App, config: &Config) {
                 parts.push(format!("{} quit", kb.quit));
                 parts.join(" · ")
             }
-            Mode::Insert => "Esc normal · Enter commit".to_string(),
+            Mode::Insert => "Esc cancel · Enter commit".to_string(),
+            Mode::InsertKey => "Esc cancel · Enter rename".to_string(),
             Mode::Search => "Esc normal · type to filter".to_string(),
         }
     };

src/undo.rs

@@ -0,0 +1,187 @@
+use crate::format::ConfigItem;
+use std::collections::HashMap;
+
+pub struct EditAction {
+    pub state: Vec<ConfigItem>,
+    pub selected: usize,
+}
+
+pub struct UndoNode {
+    pub action: EditAction,
+    pub parent: Option<usize>,
+    pub children: Vec<usize>,
+}
+
+pub struct UndoTree {
+    nodes: HashMap<usize, UndoNode>,
+    current_node: usize,
+    next_id: usize,
+    // Track the latest child added to a node to know which branch to follow on redo
+    latest_branch: HashMap<usize, usize>,
+}
+
+impl UndoTree {
+    pub fn new(initial_state: Vec<ConfigItem>, initial_selected: usize) -> Self {
+        let root_id = 0;
+        let root_node = UndoNode {
+            action: EditAction {
+                state: initial_state,
+                selected: initial_selected,
+            },
+            parent: None,
+            children: Vec::new(),
+        };
+
+        let mut nodes = HashMap::new();
+        nodes.insert(root_id, root_node);
+
+        Self {
+            nodes,
+            current_node: root_id,
+            next_id: 1,
+            latest_branch: HashMap::new(),
+        }
+    }
+
+    pub fn push(&mut self, state: Vec<ConfigItem>, selected: usize) {
+        let new_id = self.next_id;
+        self.next_id += 1;
+
+        let new_node = UndoNode {
+            action: EditAction { state, selected },
+            parent: Some(self.current_node),
+            children: Vec::new(),
+        };
+
+        // Add to nodes
+        self.nodes.insert(new_id, new_node);
+
+        // Update parent's children
+        if let Some(parent_node) = self.nodes.get_mut(&self.current_node) {
+            parent_node.children.push(new_id);
+        }
+
+        // Record this as the latest branch for the parent
+        self.latest_branch.insert(self.current_node, new_id);
+
+        // Move current pointer
+        self.current_node = new_id;
+    }
+
+    pub fn undo(&mut self) -> Option<&EditAction> {
+        if let Some(current) = self.nodes.get(&self.current_node)
+            && let Some(parent_id) = current.parent {
+                self.current_node = parent_id;
+                return self.nodes.get(&parent_id).map(|n| &n.action);
+            }
+        None
+    }
+
+    pub fn redo(&mut self) -> Option<&EditAction> {
+        if let Some(next_id) = self.latest_branch.get(&self.current_node).copied() {
+            self.current_node = next_id;
+            return self.nodes.get(&next_id).map(|n| &n.action);
+        } else {
+            // Fallback: if there is no recorded latest branch but there are children
+            let current_id = self.current_node;
+            if let Some(current) = self.nodes.get(&current_id)
+                && let Some(&first_child_id) = current.children.last() {
+                    self.current_node = first_child_id;
+                    self.latest_branch.insert(current_id, first_child_id);
+                    return self.nodes.get(&first_child_id).map(|n| &n.action);
+                }
+        }
+        None
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::format::{ItemStatus, ValueType};
+
+    fn dummy_item(key: &str) -> ConfigItem {
+        ConfigItem {
+            key: key.to_string(),
+            path: vec![],
+            value: Some(key.to_string()),
+            template_value: None,
+            default_value: None,
+            depth: 0,
+            is_group: false,
+            status: ItemStatus::Present,
+            value_type: ValueType::String,
+        }
+    }
+
+    #[test]
+    fn test_undo_redo_tree() {
+        let state1 = vec![dummy_item("A")];
+        let mut tree = UndoTree::new(state1.clone(), 0);
+
+        // Push state 2
+        let state2 = vec![dummy_item("B")];
+        tree.push(state2.clone(), 1);
+
+        // Push state 3
+        let state3 = vec![dummy_item("C")];
+        tree.push(state3.clone(), 2);
+
+        // Undo -> State 2
+        let action = tree.undo().unwrap();
+        assert_eq!(action.state[0].key, "B");
+        assert_eq!(action.selected, 1);
+
+        // Undo -> State 1
+        let action = tree.undo().unwrap();
+        assert_eq!(action.state[0].key, "A");
+        assert_eq!(action.selected, 0);
+
+        // Undo again -> None (already at root)
+        assert!(tree.undo().is_none());
+
+        // Redo -> State 2
+        let action = tree.redo().unwrap();
+        assert_eq!(action.state[0].key, "B");
+        assert_eq!(action.selected, 1);
+
+        // Redo -> State 3
+        let action = tree.redo().unwrap();
+        assert_eq!(action.state[0].key, "C");
+        assert_eq!(action.selected, 2);
+
+        // Branching: Undo twice to State 1
+        tree.undo();
+        tree.undo();
+        
+        // Push State 4 (from State 1)
+        let state4 = vec![dummy_item("D")];
+        tree.push(state4.clone(), 3);
+
+        // Undo -> State 1
+        let action = tree.undo().unwrap();
+        assert_eq!(action.state[0].key, "A");
+
+        // Redo -> State 4 (follows latest branch D, not old branch B)
+        let action = tree.redo().unwrap();
+        assert_eq!(action.state[0].key, "D");
+    }
+
+    #[test]
+    fn test_redo_fallback_fix() {
+        let state1 = vec![dummy_item("A")];
+        let mut tree = UndoTree::new(state1.clone(), 0);
+
+        let state2 = vec![dummy_item("B")];
+        tree.push(state2.clone(), 1);
+
+        tree.undo();
+        // Redo should move to state 2
+        let action = tree.redo().unwrap();
+        assert_eq!(action.state[0].key, "B");
+
+        // Calling redo again should NOT change the current node or returned action
+        // (since it's already at the latest child)
+        assert!(tree.redo().is_none());
+    }
+}