// src/input/engine.rs
use crate::config::binds::config::Config;
use crate::config::binds::key_sequences::KeySequenceTracker;
use crate::input::action::{AppAction, BufferAction, CoreAction};
use crate::movement::MovementAction;
use crate::modes::handlers::mode_manager::AppMode;
use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
use crate::input::leader::{leader_has_any_start, leader_is_prefix, leader_match_action};
use tracing::info;

#[derive(Debug, Clone, Copy)]
pub struct InputContext {
  pub app_mode: AppMode,
  pub overlay_active: bool,
  pub allow_navigation_capture: bool,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum InputOutcome {
  Action(AppAction),
  Pending,      // sequence in progress
  PassThrough,  // let page/canvas handle it
}

pub struct InputEngine {
  seq: KeySequenceTracker,
  leader_seq: KeySequenceTracker,
}

impl InputEngine {
    pub fn new(normal_timeout_ms: u64, leader_timeout_ms: u64) -> Self {
        Self {
            seq: KeySequenceTracker::new(normal_timeout_ms),
            leader_seq: KeySequenceTracker::new(leader_timeout_ms),
        }
    }

    pub fn reset_sequence(&mut self) {
        info!("InputEngine.reset_sequence() leader_seq_before={:?}", self.leader_seq.current_sequence);
        self.seq.reset();
        self.leader_seq.reset();
    }

    pub fn has_active_sequence(&self) -> bool {
        !self.seq.current_sequence.is_empty()
            || !self.leader_seq.current_sequence.is_empty()
    }

    pub fn process_key(
        &mut self,
        key_event: KeyEvent,
        ctx: &InputContext,
        config: &Config,
    ) -> InputOutcome {
        // Command mode keys are special (exit/execute/backspace) and typed chars
        if ctx.app_mode == AppMode::Command {
            if config.is_exit_command_mode(key_event.code, key_event.modifiers) {
                self.seq.reset();
                return InputOutcome::Action(AppAction::ExitCommandMode);
            }
            if config.is_command_execute(key_event.code, key_event.modifiers) {
                self.seq.reset();
                return InputOutcome::Action(AppAction::CommandExecute);
            }
            if config.is_command_backspace(key_event.code, key_event.modifiers) {
                self.seq.reset();
                return InputOutcome::Action(AppAction::CommandBackspace);
            }
            // Let command-line collect characters and other keys pass through
            self.seq.reset();
            return InputOutcome::PassThrough;
        }

        // If overlays are active, do not intercept (palette, navigation, etc.)
        if ctx.overlay_active {
            self.seq.reset();
            // Also reset leader sequence to avoid leaving a stale "space" active
            info!("Overlay active → reset leader_seq (was {:?})", self.leader_seq.current_sequence);
            self.leader_seq.reset();
            return InputOutcome::PassThrough;
        }

        // Space-led multi-key sequences (leader = space)
        let space = KeyCode::Char(' ');
        let leader_active = !self.leader_seq.current_sequence.is_empty()
            && self.leader_seq.current_sequence[0] == space;

        // Keep collecting leader sequence even if allow_navigation_capture is false.
        if leader_active {
            self.leader_seq.add_key(key_event.code);
            let sequence = self.leader_seq.get_sequence();
            info!(
                "Leader active updated: {:?} (added {:?})",
                sequence, key_event.code
            );

            if let Some(action_str) = leader_match_action(config, &sequence) {
                info!("Leader matched '{}' with sequence {:?}", action_str, sequence);
                if let Some(app_action) = map_action_string(action_str, ctx) {
                    self.leader_seq.reset();
                    return InputOutcome::Action(app_action);
                }
                self.leader_seq.reset();
                return InputOutcome::PassThrough;
            }

            if leader_is_prefix(config, &sequence) {
                info!("Leader prefix continuing...");
                return InputOutcome::Pending;
            }

            info!("Leader sequence reset (no match/prefix).");
            self.leader_seq.reset();
            // fall through to regular handling of this key
        } else if ctx.allow_navigation_capture
            && key_event.code == space
            && leader_has_any_start(config)
        {
            // Start a leader sequence only if capturing is allowed
            self.leader_seq.reset();
            self.leader_seq.add_key(space);
            info!("Leader started: {:?}", self.leader_seq.get_sequence());
            return InputOutcome::Pending;
        }

        // Single-key mapping: try general binds first (arrows, open_search, enter_command_mode)
        if let Some(action_str) =
            config.get_general_action(key_event.code, key_event.modifiers)
        {
            if let Some(app_action) = map_action_string(action_str, ctx) {
                return InputOutcome::Action(app_action);
            }
            // Unknown to app layer (likely canvas movement etc.) → pass
            return InputOutcome::PassThrough;
        }

        // Then app-level common/read-only/edit/highlight for UI toggles or core actions
        if let Some(action_str) = config.get_app_action(key_event.code, key_event.modifiers) {
            if let Some(app_action) = map_action_string(action_str, ctx) {
                return InputOutcome::Action(app_action);
            }
        }

        InputOutcome::PassThrough
    }
}

fn str_to_movement(s: &str) -> Option<MovementAction> {
  match s {
    "up" => Some(MovementAction::Up),
    "down" => Some(MovementAction::Down),
    "left" => Some(MovementAction::Left),
    "right" => Some(MovementAction::Right),
    "next" => Some(MovementAction::Next),
    "previous" => Some(MovementAction::Previous),
    "select" => Some(MovementAction::Select),
    "esc" => Some(MovementAction::Esc),
    _ => None,
  }
}

fn map_action_string(action: &str, ctx: &InputContext) -> Option<AppAction> {
  match action {
    // Global/UI
    "toggle_sidebar" => Some(AppAction::ToggleSidebar),
    "toggle_buffer_list" => Some(AppAction::ToggleBufferList),
    "open_search" => Some(AppAction::OpenSearch),
    "find_file_palette_toggle" => Some(AppAction::FindFilePaletteToggle),

    // Buffers
    "next_buffer" => Some(AppAction::Buffer(BufferAction::Next)),
    "previous_buffer" => Some(AppAction::Buffer(BufferAction::Previous)),
    "close_buffer" => Some(AppAction::Buffer(BufferAction::Close)),

    // Command mode
    "enter_command_mode" => Some(AppAction::EnterCommandMode),
    "exit_command_mode" => Some(AppAction::ExitCommandMode),
    "command_execute" => Some(AppAction::CommandExecute),
    "command_backspace" => Some(AppAction::CommandBackspace),

    // Navigation across UI (only if allowed)
    s if str_to_movement(s).is_some() && ctx.allow_navigation_capture => {
      Some(AppAction::Navigate(str_to_movement(s).unwrap()))
    }

    // Core actions
    "save" => Some(AppAction::Core(CoreAction::Save)),
    "force_quit" => Some(AppAction::Core(CoreAction::ForceQuit)),
    "save_and_quit" => Some(AppAction::Core(CoreAction::SaveAndQuit)),
    "revert" => Some(AppAction::Core(CoreAction::Revert)),

    // Unknown to app layer: ignore (canvas-specific actions, etc.)
    _ => None,
  }
}