implemented undotree with redo

src/undo.rs

@@ -0,0 +1,159 @@
+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
+            if let Some(current) = self.nodes.get(&self.current_node)
+                && let Some(&first_child_id) = current.children.last() {
+                    self.current_node = first_child_id;
+                    self.latest_branch.insert(self.current_node, 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);
+
+        // Branching: Push State 4 (from State 2)
+        let state4 = vec![dummy_item("D")];
+        tree.push(state4.clone(), 3);
+
+        // Undo -> State 2
+        let action = tree.undo().unwrap();
+        assert_eq!(action.state[0].key, "B");
+
+        // Redo -> State 4 (follows latest branch D, not old branch C)
+        let action = tree.redo().unwrap();
+        assert_eq!(action.state[0].key, "D");
+    }
+}