use std::collections::{HashMap, HashSet};

use bevy_ecs::{
    event::EventWriter,
    resource::Resource,
    system::{NonSendMut, Res, ResMut},
};
use glam::Vec2;
use sdl2::{event::Event, keyboard::Keycode, EventPump};

use crate::systems::components::DeltaTime;
use crate::{
    events::{GameCommand, GameEvent},
    map::direction::Direction,
};

#[derive(Resource, Default, Debug, Copy, Clone)]
pub enum CursorPosition {
    #[default]
    None,
    Some {
        position: Vec2,
        remaining_time: f32,
    },
}

#[derive(Resource, Debug, Clone)]
pub struct Bindings {
    key_bindings: HashMap<Keycode, GameCommand>,
    movement_keys: HashSet<Keycode>,
    pressed_movement_keys: Vec<Keycode>,
}

impl Default for Bindings {
    fn default() -> Self {
        let mut key_bindings = HashMap::new();

        // Player movement
        key_bindings.insert(Keycode::Up, GameCommand::MovePlayer(Direction::Up));
        key_bindings.insert(Keycode::W, GameCommand::MovePlayer(Direction::Up));
        key_bindings.insert(Keycode::Down, GameCommand::MovePlayer(Direction::Down));
        key_bindings.insert(Keycode::S, GameCommand::MovePlayer(Direction::Down));
        key_bindings.insert(Keycode::Left, GameCommand::MovePlayer(Direction::Left));
        key_bindings.insert(Keycode::A, GameCommand::MovePlayer(Direction::Left));
        key_bindings.insert(Keycode::Right, GameCommand::MovePlayer(Direction::Right));
        key_bindings.insert(Keycode::D, GameCommand::MovePlayer(Direction::Right));

        // Game actions
        key_bindings.insert(Keycode::P, GameCommand::TogglePause);
        key_bindings.insert(Keycode::Space, GameCommand::ToggleDebug);
        key_bindings.insert(Keycode::M, GameCommand::MuteAudio);
        key_bindings.insert(Keycode::R, GameCommand::ResetLevel);
        key_bindings.insert(Keycode::Escape, GameCommand::Exit);
        key_bindings.insert(Keycode::Q, GameCommand::Exit);

        let movement_keys = HashSet::from([
            Keycode::W,
            Keycode::A,
            Keycode::S,
            Keycode::D,
            Keycode::Up,
            Keycode::Down,
            Keycode::Left,
            Keycode::Right,
        ]);

        Self {
            key_bindings,
            movement_keys,
            pressed_movement_keys: Vec::new(),
        }
    }
}

/// A simplified input event used for deterministic testing and logic reuse
/// without depending on SDL's event pump.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SimpleKeyEvent {
    KeyDown(Keycode),
    KeyUp(Keycode),
}

/// Processes a frame's worth of simplified key events and returns the resulting
/// `GameEvent`s that would be emitted by the input system for that frame.
///
/// This mirrors the behavior of `input_system` for keyboard-related logic:
/// - KeyDown emits the bound command immediately (movement or otherwise)
/// - Tracks pressed movement keys in order to continue movement on subsequent frames
/// - KeyUp removes movement keys; if another movement key remains, it resumes
pub fn process_simple_key_events(bindings: &mut Bindings, frame_events: &[SimpleKeyEvent]) -> Vec<GameEvent> {
    let mut emitted_events = Vec::new();
    let mut movement_key_pressed = false;

    for event in frame_events {
        match *event {
            SimpleKeyEvent::KeyDown(key) => {
                if let Some(command) = bindings.key_bindings.get(&key).copied() {
                    emitted_events.push(GameEvent::Command(command));
                }

                if bindings.movement_keys.contains(&key) {
                    movement_key_pressed = true;
                    if !bindings.pressed_movement_keys.contains(&key) {
                        bindings.pressed_movement_keys.push(key);
                    }
                }
            }
            SimpleKeyEvent::KeyUp(key) => {
                if bindings.movement_keys.contains(&key) {
                    bindings.pressed_movement_keys.retain(|&k| k != key);
                }
            }
        }
    }

    if !movement_key_pressed {
        if let Some(&last_movement_key) = bindings.pressed_movement_keys.last() {
            if let Some(command) = bindings.key_bindings.get(&last_movement_key).copied() {
                emitted_events.push(GameEvent::Command(command));
            }
        }
    }

    emitted_events
}

pub fn input_system(
    delta_time: Res<DeltaTime>,
    mut bindings: ResMut<Bindings>,
    mut writer: EventWriter<GameEvent>,
    mut pump: NonSendMut<&'static mut EventPump>,
    mut cursor: ResMut<CursorPosition>,
) {
    let mut cursor_seen = false;
    // Collect all events for this frame.
    let frame_events: Vec<Event> = pump.poll_iter().collect();

    // Handle non-keyboard events inline and build a simplified keyboard event stream.
    let mut simple_key_events = Vec::new();
    for event in &frame_events {
        match *event {
            Event::Quit { .. } => {
                writer.write(GameEvent::Command(GameCommand::Exit));
            }
            Event::MouseMotion { x, y, .. } => {
                *cursor = CursorPosition::Some {
                    position: Vec2::new(x as f32, y as f32),
                    remaining_time: 0.20,
                };
                cursor_seen = true;
            }
            Event::KeyDown {
                keycode: Some(key),
                repeat: false,
                ..
            } => {
                simple_key_events.push(SimpleKeyEvent::KeyDown(key));
            }
            Event::KeyUp {
                keycode: Some(key),
                repeat: false,
                ..
            } => {
                simple_key_events.push(SimpleKeyEvent::KeyUp(key));
            }
            _ => {}
        }
    }

    // Delegate keyboard handling to shared logic used by tests and production.
    let emitted = process_simple_key_events(&mut bindings, &simple_key_events);
    for event in emitted {
        writer.write(event);
    }

    if let (false, CursorPosition::Some { remaining_time, .. }) = (cursor_seen, &mut *cursor) {
        *remaining_time -= delta_time.0;
        if *remaining_time <= 0.0 {
            *cursor = CursorPosition::None;
        }
    }
}