//! User configuration: theming and keybindings.
//!
//! Everything the TUI reacts to is declared here. Actions are resolved through
//! one table built from the user's config, so a rebound key takes effect
//! everywhere — including the on-screen hints and the help overlay.

use ratatui::style::Color;
use serde::{Deserialize, Serialize};
use std::fs;

/// Configuration for the application's appearance.
#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(default)]
pub struct ThemeConfig {
    /// If true, skip rendering the background block to let the terminal's transparency show.
    pub transparent: bool,
    /// Default background.
    pub bg_normal: String,
    /// Background for selected items and standard UI elements.
    pub bg_highlight: String,
    /// Active element background (e.g., insert mode).
    pub bg_active: String,
    /// Active element background (e.g., search mode).
    pub bg_search: String,
    /// Standard text.
    pub fg_normal: String,
    /// Secondary/inactive text.
    pub fg_dimmed: String,
    /// Text on selected items.
    pub fg_highlight: String,
    /// Red/Alert color for missing items.
    pub fg_warning: String,
    /// Accent color for items edited this session.
    pub fg_modified: String,
    /// High-contrast accent for titles and active UI elements.
    pub fg_accent: String,
    /// Borders.
    pub border_normal: String,
    /// Active borders (e.g., input mode).
    pub border_active: String,
    /// Color for tree indentation depth 1.
    pub tree_depth_1: String,
    /// Color for tree indentation depth 2.
    pub tree_depth_2: String,
    /// Color for tree indentation depth 3.
    pub tree_depth_3: String,
    /// Color for tree indentation depth 4.
    pub tree_depth_4: String,
}

impl ThemeConfig {
    /// Internal helper to parse a hex color string ("#RRGGBB") into a TUI Color.
    fn parse_hex(hex: &str) -> Color {
        let hex = hex.trim_start_matches('#');
        if hex.len() == 6 {
            let r = u8::from_str_radix(&hex[0..2], 16).unwrap_or(0);
            let g = u8::from_str_radix(&hex[2..4], 16).unwrap_or(0);
            let b = u8::from_str_radix(&hex[4..6], 16).unwrap_or(0);
            Color::Rgb(r, g, b)
        } else {
            Color::Reset
        }
    }

    pub fn bg_normal(&self) -> Color { Self::parse_hex(&self.bg_normal) }
    pub fn bg_highlight(&self) -> Color { Self::parse_hex(&self.bg_highlight) }
    pub fn bg_active(&self) -> Color { Self::parse_hex(&self.bg_active) }
    pub fn bg_search(&self) -> Color { Self::parse_hex(&self.bg_search) }
    pub fn fg_normal(&self) -> Color { Self::parse_hex(&self.fg_normal) }
    pub fn fg_dimmed(&self) -> Color { Self::parse_hex(&self.fg_dimmed) }
    pub fn fg_highlight(&self) -> Color { Self::parse_hex(&self.fg_highlight) }
    pub fn fg_warning(&self) -> Color { Self::parse_hex(&self.fg_warning) }
    pub fn fg_modified(&self) -> Color { Self::parse_hex(&self.fg_modified) }
    pub fn fg_accent(&self) -> Color { Self::parse_hex(&self.fg_accent) }
    pub fn border_normal(&self) -> Color { Self::parse_hex(&self.border_normal) }
    pub fn border_active(&self) -> Color { Self::parse_hex(&self.border_active) }
    pub fn tree_depth_1(&self) -> Color { Self::parse_hex(&self.tree_depth_1) }
    pub fn tree_depth_2(&self) -> Color { Self::parse_hex(&self.tree_depth_2) }
    pub fn tree_depth_3(&self) -> Color { Self::parse_hex(&self.tree_depth_3) }
    pub fn tree_depth_4(&self) -> Color { Self::parse_hex(&self.tree_depth_4) }
}

impl Default for ThemeConfig {
    /// Default theme: Semantic Catppuccin Mocha.
    fn default() -> Self {
        Self {
            transparent: false,
            bg_normal: "#1e1e2e".to_string(), // base
            bg_highlight: "#89b4fa".to_string(), // blue
            bg_active: "#a6e3a1".to_string(), // green
            bg_search: "#cba6f7".to_string(), // mauve
            fg_normal: "#cdd6f4".to_string(), // text
            fg_dimmed: "#6c7086".to_string(), // overlay0
            fg_highlight: "#1e1e2e".to_string(), // base (dark for contrast against highlights)
            fg_warning: "#f38ba8".to_string(), // red
            fg_modified: "#fab387".to_string(), // peach
            fg_accent: "#b4befe".to_string(), // lavender
            border_normal: "#45475a".to_string(), // surface1
            border_active: "#a6e3a1".to_string(), // green
            tree_depth_1: "#b4befe".to_string(), // lavender
            tree_depth_2: "#cba6f7".to_string(), // mauve
            tree_depth_3: "#89b4fa".to_string(), // blue
            tree_depth_4: "#fab387".to_string(), // peach
        }
    }
}

/// Every action the user can trigger from Normal mode.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum Action {
    Down,
    Up,
    JumpTop,
    JumpBottom,
    Search,
    NextMatch,
    PreviousMatch,
    Edit,
    EditAppend,
    EditSubstitute,
    Rename,
    AppendItem,
    PrependItem,
    AppendGroup,
    PrependGroup,
    ToggleGroup,
    DeleteItem,
    AddMissing,
    AcceptAll,
    ToggleFold,
    FoldAll,
    UnfoldAll,
    Undo,
    Redo,
    UndoBranchPrev,
    UndoBranchNext,
    Help,
    Command,
    Quit,
}

impl Action {
    /// Short human-readable label, used by the status bar and help overlay.
    pub fn label(self) -> &'static str {
        match self {
            Action::Down => "move down",
            Action::Up => "move up",
            Action::JumpTop => "jump to top",
            Action::JumpBottom => "jump to bottom",
            Action::Search => "search keys and values",
            Action::NextMatch => "next match",
            Action::PreviousMatch => "previous match",
            Action::Edit => "edit value (cursor at start)",
            Action::EditAppend => "edit value (cursor at end)",
            Action::EditSubstitute => "replace value",
            Action::Rename => "rename key",
            Action::AppendItem => "add item below",
            Action::PrependItem => "add item above",
            Action::AppendGroup => "add child group below",
            Action::PrependGroup => "add child group above",
            Action::ToggleGroup => "toggle group / value",
            Action::DeleteItem => "delete item",
            Action::AddMissing => "take template default",
            Action::AcceptAll => "take all missing defaults",
            Action::ToggleFold => "fold / unfold group",
            Action::FoldAll => "fold everything",
            Action::UnfoldAll => "unfold everything",
            Action::Undo => "undo",
            Action::Redo => "redo",
            Action::UndoBranchPrev => "previous undo branch",
            Action::UndoBranchNext => "next undo branch",
            Action::Help => "show this help",
            Action::Command => "command prompt",
            Action::Quit => "quit",
        }
    }

    /// Help-overlay grouping.
    pub fn section(self) -> &'static str {
        match self {
            Action::Down
            | Action::Up
            | Action::JumpTop
            | Action::JumpBottom
            | Action::Search
            | Action::NextMatch
            | Action::PreviousMatch
            | Action::ToggleFold
            | Action::FoldAll
            | Action::UnfoldAll => "Navigate",
            Action::Edit | Action::EditAppend | Action::EditSubstitute | Action::Rename => "Edit",
            Action::AppendItem
            | Action::PrependItem
            | Action::AppendGroup
            | Action::PrependGroup
            | Action::ToggleGroup
            | Action::DeleteItem => "Structure",
            Action::AddMissing | Action::AcceptAll => "Template",
            Action::Undo | Action::Redo | Action::UndoBranchPrev | Action::UndoBranchNext => {
                "History"
            }
            Action::Help | Action::Command | Action::Quit => "Session",
        }
    }
}

/// Custom keybindings for navigation and application control.
///
/// A binding may list several alternatives separated by commas (`"<Tab>,za"`).
/// Non-character keys are written in angle brackets: `<Space>`, `<Tab>`.
#[derive(Debug, Deserialize, Serialize, Clone)]
#[serde(default)]
pub struct KeybindsConfig {
    pub down: String,
    pub up: String,
    pub edit: String,
    pub edit_append: String,
    pub edit_substitute: String,
    /// Command string that saves, entered at the `:` prompt.
    pub save: String,
    /// Command string that quits, entered at the `:` prompt.
    pub quit: String,
    /// Normal-mode key that quits directly.
    pub quit_key: String,
    /// Normal-mode key that opens the `:` prompt.
    pub command: String,
    pub search: String,
    pub next_match: String,
    pub previous_match: String,
    pub jump_top: String,
    pub jump_bottom: String,
    pub append_item: String,
    pub prepend_item: String,
    pub delete_item: String,
    pub undo: String,
    pub redo: String,
    pub undo_branch_prev: String,
    pub undo_branch_next: String,
    pub rename: String,
    pub append_group: String,
    pub prepend_group: String,
    pub toggle_group: String,
    pub add_missing: String,
    pub accept_all: String,
    pub toggle_fold: String,
    pub fold_all: String,
    pub unfold_all: String,
    pub help: String,
}

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,S".to_string(),
            save: ":w".to_string(),
            quit: ":q".to_string(),
            quit_key: "q".to_string(),
            command: ":".to_string(),
            search: "/".to_string(),
            next_match: "n".to_string(),
            previous_match: "N".to_string(),
            jump_top: "gg".to_string(),
            jump_bottom: "G".to_string(),
            append_item: "o".to_string(),
            prepend_item: "O".to_string(),
            delete_item: "dd".to_string(),
            undo: "u".to_string(),
            redo: "U".to_string(),
            undo_branch_prev: "g-".to_string(),
            undo_branch_next: "g+".to_string(),
            rename: "r".to_string(),
            append_group: "alt+o".to_string(),
            prepend_group: "alt+O".to_string(),
            toggle_group: "t".to_string(),
            add_missing: "<Space>".to_string(),
            accept_all: "A".to_string(),
            toggle_fold: "<Tab>,za".to_string(),
            fold_all: "zM".to_string(),
            unfold_all: "zR".to_string(),
            help: "?".to_string(),
        }
    }
}

impl KeybindsConfig {
    /// The full Normal-mode action table, in help-overlay order.
    ///
    /// Returned as `(binding spec, action)`; a spec may hold comma-separated
    /// alternatives, which [`Self::resolved`] expands.
    pub fn table(&self) -> Vec<(&str, Action)> {
        vec![
            (&self.down, Action::Down),
            (&self.up, Action::Up),
            (&self.jump_top, Action::JumpTop),
            (&self.jump_bottom, Action::JumpBottom),
            (&self.search, Action::Search),
            (&self.next_match, Action::NextMatch),
            (&self.previous_match, Action::PreviousMatch),
            (&self.toggle_fold, Action::ToggleFold),
            (&self.fold_all, Action::FoldAll),
            (&self.unfold_all, Action::UnfoldAll),
            (&self.edit, Action::Edit),
            (&self.edit_append, Action::EditAppend),
            (&self.edit_substitute, Action::EditSubstitute),
            (&self.rename, Action::Rename),
            (&self.append_item, Action::AppendItem),
            (&self.prepend_item, Action::PrependItem),
            (&self.append_group, Action::AppendGroup),
            (&self.prepend_group, Action::PrependGroup),
            (&self.toggle_group, Action::ToggleGroup),
            (&self.delete_item, Action::DeleteItem),
            (&self.add_missing, Action::AddMissing),
            (&self.accept_all, Action::AcceptAll),
            (&self.undo, Action::Undo),
            (&self.redo, Action::Redo),
            (&self.undo_branch_prev, Action::UndoBranchPrev),
            (&self.undo_branch_next, Action::UndoBranchNext),
            (&self.help, Action::Help),
            (&self.command, Action::Command),
            (&self.quit_key, Action::Quit),
        ]
    }

    /// Every individual key sequence with the action it triggers.
    pub fn resolved(&self) -> Vec<(String, Action)> {
        let mut out = Vec::new();
        for (spec, action) in self.table() {
            for key in spec.split(',').map(str::trim).filter(|k| !k.is_empty()) {
                out.push((key.to_string(), action));
            }
        }
        out
    }

    /// The first key sequence bound to an action, for display in hints.
    pub fn key_for(&self, action: Action) -> String {
        self.table()
            .iter()
            .find(|(_, a)| *a == action)
            .and_then(|(spec, _)| spec.split(',').next())
            .unwrap_or("")
            .trim()
            .to_string()
    }

    /// Reports any key sequence bound to more than one action.
    ///
    /// Without this an accidental collision silently shadows an action, which is
    /// exactly how `add_missing` ended up unreachable behind `edit_append`.
    pub fn conflicts(&self) -> Vec<String> {
        let resolved = self.resolved();
        let mut conflicts = Vec::new();
        for (i, (key, action)) in resolved.iter().enumerate() {
            if let Some((_, other)) = resolved[..i].iter().find(|(k, _)| k == key) {
                conflicts.push(format!(
                    "'{}' is bound to both {} and {}",
                    key,
                    other.label(),
                    action.label()
                ));
            }
        }
        conflicts
    }
}

/// Root configuration structure for mould.
#[derive(Debug, Deserialize, Serialize, Default, Clone)]
pub struct Config {
    #[serde(default)]
    pub theme: ThemeConfig,
    #[serde(default)]
    pub keybinds: KeybindsConfig,
}

/// Loads the configuration from the user's config directory (`~/.config/mould/config.toml`).
///
/// Returns the config alongside an optional problem description. A broken config
/// still falls back to defaults, but the caller surfaces the reason instead of
/// leaving the user wondering why their settings did nothing.
pub fn load_config() -> (Config, Option<String>) {
    let Some(mut path) = dirs::config_dir() else {
        return (Config::default(), None);
    };
    path.push("mould");
    path.push("config.toml");

    if !path.exists() {
        return (Config::default(), None);
    }

    let config = match fs::read_to_string(&path) {
        Ok(content) => match toml::from_str::<Config>(&content) {
            Ok(config) => config,
            Err(e) => return (Config::default(), Some(e.message().to_string())),
        },
        Err(e) => return (Config::default(), Some(e.to_string())),
    };

    let conflicts = config.keybinds.conflicts();
    let warning = conflicts.first().cloned();
    (config, warning)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn defaults_have_no_conflicting_binds() {
        assert!(KeybindsConfig::default().conflicts().is_empty());
    }

    #[test]
    fn conflicts_are_reported() {
        let kb = KeybindsConfig {
            add_missing: "a".to_string(),
            ..Default::default()
        };
        let conflicts = kb.conflicts();
        assert_eq!(conflicts.len(), 1);
        assert!(conflicts[0].contains("'a'"));
    }

    /// The shipped example must stay loadable, or it teaches people a broken config.
    #[test]
    fn example_config_parses_and_matches_defaults() {
        let path = concat!(env!("CARGO_MANIFEST_DIR"), "/config.example.toml");
        let content = std::fs::read_to_string(path).unwrap();
        let config: Config = toml::from_str(&content).unwrap();

        assert!(config.keybinds.conflicts().is_empty());
        let defaults = KeybindsConfig::default();
        for ((spec, action), (default_spec, _)) in
            config.keybinds.table().iter().zip(defaults.table())
        {
            assert_eq!(
                *spec, default_spec,
                "example config drifted from the default for {:?}",
                action
            );
        }
        assert_eq!(config.theme.bg_normal, ThemeConfig::default().bg_normal);
    }

    #[test]
    fn alternatives_expand() {
        let kb = KeybindsConfig::default();
        let resolved = kb.resolved();
        assert!(resolved.iter().any(|(k, a)| k == "<Tab>" && *a == Action::ToggleFold));
        assert!(resolved.iter().any(|(k, a)| k == "za" && *a == Action::ToggleFold));
        // Hints show the first alternative.
        assert_eq!(kb.key_for(Action::ToggleFold), "<Tab>");
    }
}