use std::collections::HashMap;
use std::fmt;
use std::sync::Arc;

use crossterm::event::{KeyCode, KeyModifiers};

use crate::ui::app::AppMode;
use crate::ui::effect::Effect;

use super::cmd::{self, CmdContext, CmdRegistry};
// `cmd` module imported for `default_registry()` in default_keymaps()

/// A key pattern that can be matched against a KeyEvent.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum KeyPattern {
    /// Single key with modifiers
    Key(KeyCode, KeyModifiers),
    /// Matches any Char key (for text-entry modes).
    AnyChar,
    /// Matches any key at all (lowest priority fallback).
    Any,
}

/// Identifies which mode a binding applies to.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum ModeKey {
    Normal,
    Help,
    FormulaPanel,
    CategoryPanel,
    ViewPanel,
    TileSelect,
    Editing,
    FormulaEdit,
    CategoryAdd,
    ItemAdd,
    ExportPrompt,
    CommandMode,
    SearchMode,
    ImportWizard,
}

impl ModeKey {
    pub fn from_app_mode(mode: &AppMode, search_mode: bool) -> Option<Self> {
        match mode {
            AppMode::Normal if search_mode => Some(ModeKey::SearchMode),
            AppMode::Normal => Some(ModeKey::Normal),
            AppMode::Help => Some(ModeKey::Help),
            AppMode::FormulaPanel => Some(ModeKey::FormulaPanel),
            AppMode::CategoryPanel => Some(ModeKey::CategoryPanel),
            AppMode::ViewPanel => Some(ModeKey::ViewPanel),
            AppMode::TileSelect => Some(ModeKey::TileSelect),
            AppMode::Editing { .. } => Some(ModeKey::Editing),
            AppMode::FormulaEdit { .. } => Some(ModeKey::FormulaEdit),
            AppMode::CategoryAdd { .. } => Some(ModeKey::CategoryAdd),
            AppMode::ItemAdd { .. } => Some(ModeKey::ItemAdd),
            AppMode::ExportPrompt { .. } => Some(ModeKey::ExportPrompt),
            AppMode::CommandMode { .. } => Some(ModeKey::CommandMode),
            AppMode::ImportWizard => Some(ModeKey::ImportWizard),
            _ => None,
        }
    }
}

/// What a key binding resolves to.
#[derive(Debug, Clone)]
pub enum Binding {
    /// A command name + arguments, looked up in the registry at dispatch time.
    Cmd {
        name: &'static str,
        args: Vec<String>,
    },
    /// A prefix sub-keymap (Emacs-style).
    Prefix(Arc<Keymap>),
}

/// A keymap maps key patterns to bindings (command names or prefix sub-keymaps).
pub struct Keymap {
    bindings: HashMap<KeyPattern, Binding>,
}

impl fmt::Debug for Keymap {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Keymap")
            .field("binding_count", &self.bindings.len())
            .finish()
    }
}

impl Keymap {
    pub fn new() -> Self {
        Self {
            bindings: HashMap::new(),
        }
    }

    /// Bind a key to a command name (no args).
    pub fn bind(&mut self, key: KeyCode, mods: KeyModifiers, name: &'static str) {
        self.bindings.insert(
            KeyPattern::Key(key, mods),
            Binding::Cmd {
                name,
                args: vec![],
            },
        );
    }

    /// Bind a key to a command name with arguments.
    pub fn bind_args(
        &mut self,
        key: KeyCode,
        mods: KeyModifiers,
        name: &'static str,
        args: Vec<String>,
    ) {
        self.bindings
            .insert(KeyPattern::Key(key, mods), Binding::Cmd { name, args });
    }

    /// Bind a prefix key that activates a sub-keymap.
    pub fn bind_prefix(&mut self, key: KeyCode, mods: KeyModifiers, sub: Arc<Keymap>) {
        self.bindings
            .insert(KeyPattern::Key(key, mods), Binding::Prefix(sub));
    }

    /// Bind a catch-all for any Char key.
    pub fn bind_any_char(&mut self, name: &'static str, args: Vec<String>) {
        self.bindings
            .insert(KeyPattern::AnyChar, Binding::Cmd { name, args });
    }

    /// Bind a catch-all for any key at all.
    pub fn bind_any(&mut self, name: &'static str) {
        self.bindings.insert(
            KeyPattern::Any,
            Binding::Cmd {
                name,
                args: vec![],
            },
        );
    }

    /// Look up the binding for a key.
    pub fn lookup(&self, key: KeyCode, mods: KeyModifiers) -> Option<&Binding> {
        self.bindings
            .get(&KeyPattern::Key(key, mods))
            .or_else(|| {
                if matches!(key, KeyCode::Char(_)) {
                    self.bindings.get(&KeyPattern::AnyChar)
                } else {
                    None
                }
            })
            .or_else(|| self.bindings.get(&KeyPattern::Any))
    }

    /// Dispatch a key: look up binding, resolve through registry, return effects.
    pub fn dispatch(
        &self,
        registry: &CmdRegistry,
        ctx: &CmdContext,
        key: KeyCode,
        mods: KeyModifiers,
    ) -> Option<Vec<Box<dyn Effect>>> {
        let binding = self.lookup(key, mods)?;
        match binding {
            Binding::Cmd { name, args } => {
                let cmd = registry.interactive(name, args, ctx).ok()?;
                Some(cmd.execute(ctx))
            }
            Binding::Prefix(sub) => Some(vec![Box::new(SetTransientKeymap(sub.clone()))]),
        }
    }
}

/// Effect that sets the transient keymap on the App.
#[derive(Debug)]
pub struct SetTransientKeymap(pub Arc<Keymap>);

impl Effect for SetTransientKeymap {
    fn apply(&self, app: &mut crate::ui::app::App) {
        app.transient_keymap = Some(self.0.clone());
    }
}

/// Maps modes to their root keymaps + owns the command registry.
pub struct KeymapSet {
    mode_maps: HashMap<ModeKey, Arc<Keymap>>,
    registry: CmdRegistry,
}

impl KeymapSet {
    pub fn new(registry: CmdRegistry) -> Self {
        Self {
            mode_maps: HashMap::new(),
            registry,
        }
    }

    pub fn insert(&mut self, mode: ModeKey, keymap: Arc<Keymap>) {
        self.mode_maps.insert(mode, keymap);
    }

    pub fn registry(&self) -> &CmdRegistry {
        &self.registry
    }

    /// Dispatch a key event: returns effects if a binding matched.
    pub fn dispatch(
        &self,
        ctx: &CmdContext,
        key: KeyCode,
        mods: KeyModifiers,
    ) -> Option<Vec<Box<dyn Effect>>> {
        let mode_key = ModeKey::from_app_mode(ctx.mode, ctx.search_mode)?;
        let keymap = self.mode_maps.get(&mode_key)?;
        keymap.dispatch(&self.registry, ctx, key, mods)
    }

    /// Dispatch against a specific keymap (for transient/prefix keymaps).
    pub fn dispatch_transient(
        &self,
        keymap: &Keymap,
        ctx: &CmdContext,
        key: KeyCode,
        mods: KeyModifiers,
    ) -> Option<Vec<Box<dyn Effect>>> {
        keymap.dispatch(&self.registry, ctx, key, mods)
    }

    /// Build the default keymap set with all bindings.
    pub fn default_keymaps() -> Self {
        let registry = cmd::default_registry();
        let mut set = Self::new(registry);
        let none = KeyModifiers::NONE;
        let ctrl = KeyModifiers::CONTROL;
        let shift = KeyModifiers::SHIFT;

        // ── Normal mode ──────────────────────────────────────────────────
        let mut normal = Keymap::new();

        // Navigation
        for (key, dr, dc) in [
            (KeyCode::Up, -1, 0),
            (KeyCode::Down, 1, 0),
            (KeyCode::Left, 0, -1),
            (KeyCode::Right, 0, 1),
        ] {
            normal.bind_args(key, none, "move-selection", vec![dr.to_string(), dc.to_string()]);
        }
        for (ch, dr, dc) in [('k', -1, 0), ('j', 1, 0), ('h', 0, -1), ('l', 0, 1)] {
            normal.bind_args(
                KeyCode::Char(ch),
                none,
                "move-selection",
                vec![dr.to_string(), dc.to_string()],
            );
        }

        // Jump to boundaries
        normal.bind(KeyCode::Char('G'), shift, "jump-last-row");
        normal.bind(KeyCode::Char('0'), none, "jump-first-col");
        normal.bind(KeyCode::Char('$'), shift, "jump-last-col");

        // Scroll
        normal.bind_args(KeyCode::Char('d'), ctrl, "scroll-rows", vec!["5".into()]);
        normal.bind_args(KeyCode::Char('u'), ctrl, "scroll-rows", vec!["-5".into()]);

        // Cell operations
        normal.bind(KeyCode::Char('x'), none, "clear-cell");
        normal.bind(KeyCode::Char('p'), none, "paste");

        // View
        normal.bind(KeyCode::Char('t'), none, "transpose");

        // Mode changes
        normal.bind(KeyCode::Char('q'), ctrl, "force-quit");
        normal.bind_args(
            KeyCode::Char(':'),
            shift,
            "enter-mode",
            vec!["command".into()],
        );
        normal.bind(KeyCode::Char('/'), none, "search");
        normal.bind(KeyCode::Char('s'), ctrl, "save");
        normal.bind(KeyCode::F(1), none, "enter-mode");
        normal.bind_args(KeyCode::F(1), none, "enter-mode", vec!["help".into()]);
        normal.bind_args(KeyCode::Char('?'), shift, "enter-mode", vec!["help".into()]);

        // Panel toggles
        normal.bind_args(
            KeyCode::Char('F'),
            shift,
            "toggle-panel-and-focus",
            vec!["formula".into()],
        );
        normal.bind_args(
            KeyCode::Char('C'),
            shift,
            "toggle-panel-and-focus",
            vec!["category".into()],
        );
        normal.bind_args(
            KeyCode::Char('V'),
            shift,
            "toggle-panel-and-focus",
            vec!["view".into()],
        );
        normal.bind_args(
            KeyCode::Char('f'),
            ctrl,
            "toggle-panel-visibility",
            vec!["formula".into()],
        );
        normal.bind_args(
            KeyCode::Char('c'),
            ctrl,
            "toggle-panel-visibility",
            vec!["category".into()],
        );
        normal.bind_args(
            KeyCode::Char('v'),
            ctrl,
            "toggle-panel-visibility",
            vec!["view".into()],
        );
        normal.bind(KeyCode::Tab, none, "cycle-panel-focus");

        // Editing entry
        normal.bind(KeyCode::Char('i'), none, "enter-edit-mode");
        normal.bind(KeyCode::Char('a'), none, "enter-edit-mode");
        normal.bind(KeyCode::Enter, none, "enter-advance");
        normal.bind(KeyCode::Char('e'), ctrl, "enter-export-prompt");

        // Search / category add
        normal.bind_args(KeyCode::Char('n'), none, "search-navigate", vec!["forward".into()]);
        normal.bind(KeyCode::Char('N'), shift, "search-or-category-add");

        // Page navigation
        normal.bind(KeyCode::Char(']'), none, "page-next");
        normal.bind(KeyCode::Char('['), none, "page-prev");

        // Group / hide
        normal.bind(KeyCode::Char('z'), none, "toggle-group-under-cursor");
        normal.bind(KeyCode::Char('H'), shift, "hide-selected-row-item");

        // Tile select
        normal.bind(KeyCode::Char('T'), shift, "enter-tile-select");
        normal.bind(KeyCode::Left, ctrl, "enter-tile-select");
        normal.bind(KeyCode::Right, ctrl, "enter-tile-select");
        normal.bind(KeyCode::Up, ctrl, "enter-tile-select");
        normal.bind(KeyCode::Down, ctrl, "enter-tile-select");

        // Prefix keys
        let mut g_map = Keymap::new();
        g_map.bind(KeyCode::Char('g'), none, "jump-first-row");
        g_map.bind(KeyCode::Char('z'), none, "toggle-col-group-under-cursor");
        normal.bind_prefix(KeyCode::Char('g'), none, Arc::new(g_map));

        let mut y_map = Keymap::new();
        y_map.bind(KeyCode::Char('y'), none, "yank");
        normal.bind_prefix(KeyCode::Char('y'), none, Arc::new(y_map));

        let mut z_map = Keymap::new();
        z_map.bind(KeyCode::Char('Z'), shift, "save-and-quit");
        normal.bind_prefix(KeyCode::Char('Z'), shift, Arc::new(z_map));

        set.insert(ModeKey::Normal, Arc::new(normal));

        // ── Help mode ────────────────────────────────────────────────────
        let mut help = Keymap::new();
        help.bind_args(KeyCode::Esc, none, "enter-mode", vec!["normal".into()]);
        help.bind_args(KeyCode::Char('q'), none, "enter-mode", vec!["normal".into()]);
        set.insert(ModeKey::Help, Arc::new(help));

        // ── Formula panel ────────────────────────────────────────────────
        let mut fp = Keymap::new();
        fp.bind_args(KeyCode::Esc, none, "enter-mode", vec!["normal".into()]);
        fp.bind_args(KeyCode::Tab, none, "enter-mode", vec!["normal".into()]);
        for key in [KeyCode::Up, KeyCode::Char('k')] {
            fp.bind_args(key, none, "move-panel-cursor", vec!["formula".into(), "-1".into()]);
        }
        for key in [KeyCode::Down, KeyCode::Char('j')] {
            fp.bind_args(key, none, "move-panel-cursor", vec!["formula".into(), "1".into()]);
        }
        fp.bind(KeyCode::Char('a'), none, "enter-formula-edit");
        fp.bind(KeyCode::Char('n'), none, "enter-formula-edit");
        fp.bind(KeyCode::Char('o'), none, "enter-formula-edit");
        fp.bind(KeyCode::Char('d'), none, "delete-formula-at-cursor");
        fp.bind(KeyCode::Delete, none, "delete-formula-at-cursor");
        set.insert(ModeKey::FormulaPanel, Arc::new(fp));

        // ── Category panel ───────────────────────────────────────────────
        let mut cp = Keymap::new();
        cp.bind_args(KeyCode::Esc, none, "enter-mode", vec!["normal".into()]);
        cp.bind_args(KeyCode::Tab, none, "enter-mode", vec!["normal".into()]);
        for key in [KeyCode::Up, KeyCode::Char('k')] {
            cp.bind_args(key, none, "move-panel-cursor", vec!["category".into(), "-1".into()]);
        }
        for key in [KeyCode::Down, KeyCode::Char('j')] {
            cp.bind_args(key, none, "move-panel-cursor", vec!["category".into(), "1".into()]);
        }
        cp.bind(KeyCode::Enter, none, "cycle-axis-at-cursor");
        cp.bind(KeyCode::Char(' '), none, "cycle-axis-at-cursor");
        cp.bind_args(
            KeyCode::Char('n'),
            none,
            "enter-mode",
            vec!["category-add".into()],
        );
        cp.bind(KeyCode::Char('a'), none, "open-item-add-at-cursor");
        cp.bind(KeyCode::Char('o'), none, "open-item-add-at-cursor");
        set.insert(ModeKey::CategoryPanel, Arc::new(cp));

        // ── View panel ───────────────────────────────────────────────────
        let mut vp = Keymap::new();
        vp.bind_args(KeyCode::Esc, none, "enter-mode", vec!["normal".into()]);
        vp.bind_args(KeyCode::Tab, none, "enter-mode", vec!["normal".into()]);
        for key in [KeyCode::Up, KeyCode::Char('k')] {
            vp.bind_args(key, none, "move-panel-cursor", vec!["view".into(), "-1".into()]);
        }
        for key in [KeyCode::Down, KeyCode::Char('j')] {
            vp.bind_args(key, none, "move-panel-cursor", vec!["view".into(), "1".into()]);
        }
        vp.bind(KeyCode::Enter, none, "switch-view-at-cursor");
        vp.bind(KeyCode::Char('n'), none, "create-and-switch-view");
        vp.bind(KeyCode::Char('o'), none, "create-and-switch-view");
        vp.bind(KeyCode::Char('d'), none, "delete-view-at-cursor");
        vp.bind(KeyCode::Delete, none, "delete-view-at-cursor");
        set.insert(ModeKey::ViewPanel, Arc::new(vp));

        // ── Tile select ──────────────────────────────────────────────────
        let mut ts = Keymap::new();
        ts.bind_args(KeyCode::Esc, none, "enter-mode", vec!["normal".into()]);
        ts.bind_args(KeyCode::Tab, none, "enter-mode", vec!["normal".into()]);
        ts.bind_args(KeyCode::Left, none, "move-tile-cursor", vec!["-1".into()]);
        ts.bind_args(KeyCode::Char('h'), none, "move-tile-cursor", vec!["-1".into()]);
        ts.bind_args(KeyCode::Right, none, "move-tile-cursor", vec!["1".into()]);
        ts.bind_args(KeyCode::Char('l'), none, "move-tile-cursor", vec!["1".into()]);
        ts.bind(KeyCode::Enter, none, "cycle-axis-for-tile");
        ts.bind(KeyCode::Char(' '), none, "cycle-axis-for-tile");
        ts.bind_args(KeyCode::Char('r'), none, "set-axis-for-tile", vec!["row".into()]);
        ts.bind_args(KeyCode::Char('c'), none, "set-axis-for-tile", vec!["column".into()]);
        ts.bind_args(KeyCode::Char('p'), none, "set-axis-for-tile", vec!["page".into()]);
        ts.bind_args(KeyCode::Char('n'), none, "set-axis-for-tile", vec!["none".into()]);
        set.insert(ModeKey::TileSelect, Arc::new(ts));

        // ── Editing mode ─────────────────────────────────────────────────
        let mut ed = Keymap::new();
        ed.bind_args(KeyCode::Esc, none, "enter-mode", vec!["normal".into()]);
        ed.bind(KeyCode::Enter, none, "commit-cell-edit");
        ed.bind_args(KeyCode::Backspace, none, "pop-char", vec!["edit".into()]);
        ed.bind_any_char("append-char", vec!["edit".into()]);
        set.insert(ModeKey::Editing, Arc::new(ed));

        // ── Formula edit ─────────────────────────────────────────────────
        let mut fe = Keymap::new();
        fe.bind_args(KeyCode::Esc, none, "enter-mode", vec!["formula-panel".into()]);
        fe.bind(KeyCode::Enter, none, "commit-formula");
        fe.bind_args(KeyCode::Backspace, none, "pop-char", vec!["formula".into()]);
        fe.bind_any_char("append-char", vec!["formula".into()]);
        set.insert(ModeKey::FormulaEdit, Arc::new(fe));

        // ── Category add ─────────────────────────────────────────────────
        let mut ca = Keymap::new();
        ca.bind_args(KeyCode::Esc, none, "enter-mode", vec!["category-panel".into()]);
        ca.bind(KeyCode::Enter, none, "commit-category-add");
        ca.bind(KeyCode::Tab, none, "commit-category-add");
        ca.bind_args(KeyCode::Backspace, none, "pop-char", vec!["category".into()]);
        ca.bind_any_char("append-char", vec!["category".into()]);
        set.insert(ModeKey::CategoryAdd, Arc::new(ca));

        // ── Item add ─────────────────────────────────────────────────────
        let mut ia = Keymap::new();
        ia.bind_args(KeyCode::Esc, none, "enter-mode", vec!["category-panel".into()]);
        ia.bind(KeyCode::Enter, none, "commit-item-add");
        ia.bind(KeyCode::Tab, none, "commit-item-add");
        ia.bind_args(KeyCode::Backspace, none, "pop-char", vec!["item".into()]);
        ia.bind_any_char("append-char", vec!["item".into()]);
        set.insert(ModeKey::ItemAdd, Arc::new(ia));

        // ── Export prompt ────────────────────────────────────────────────
        let mut ep = Keymap::new();
        ep.bind_args(KeyCode::Esc, none, "enter-mode", vec!["normal".into()]);
        ep.bind(KeyCode::Enter, none, "commit-export");
        ep.bind_args(KeyCode::Backspace, none, "pop-char", vec!["export".into()]);
        ep.bind_any_char("append-char", vec!["export".into()]);
        set.insert(ModeKey::ExportPrompt, Arc::new(ep));

        // ── Command mode ─────────────────────────────────────────────────
        let mut cm = Keymap::new();
        cm.bind_args(KeyCode::Esc, none, "enter-mode", vec!["normal".into()]);
        cm.bind(KeyCode::Enter, none, "execute-command");
        cm.bind(KeyCode::Backspace, none, "command-mode-backspace");
        cm.bind_any_char("append-char", vec!["command".into()]);
        set.insert(ModeKey::CommandMode, Arc::new(cm));

        // ── Search mode ──────────────────────────────────────────────────
        let mut sm = Keymap::new();
        sm.bind(KeyCode::Esc, none, "exit-search-mode");
        sm.bind(KeyCode::Enter, none, "exit-search-mode");
        sm.bind(KeyCode::Backspace, none, "search-pop-char");
        sm.bind_any_char("search-append-char", vec![]);
        set.insert(ModeKey::SearchMode, Arc::new(sm));

        // ── Import wizard ────────────────────────────────────────────────
        let mut wiz = Keymap::new();
        wiz.bind_any("handle-wizard-key");
        set.insert(ModeKey::ImportWizard, Arc::new(wiz));

        set
    }
}