use crate::{
    game::{Board, BoardIndex, Piece, SelectedTile},
    prelude::*,
};

const SCALE: f32 = 4.0;
const TILE_SIZE: f32 = 16.0;

pub struct Display2dPlugin;

impl Plugin for Display2dPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(
            Startup,
            (initialize_camera, load_spritesheet).run_if(in_state(GameState::Loading)),
        )
        .add_systems(
            Update,
            (
                initialize_board.run_if(resource_added::<SpriteSheet>()),
                draw_board
                    .run_if(resource_exists::<SpriteSheet>())
                    .run_if(resource_changed::<Board>()) // TODO: run_if(in_state(Display2d))
                    .run_if(any_with_component::<BoardIndex>()),
                cursor_position.run_if(in_state(GameState::Display2d)),
                selected.run_if(resource_changed::<SelectedTile>()),
            ),
        )
        .add_systems(OnEnter(GameState::Display2d), (activate, draw_board));
    }
}

/// Sprite sheet Resource for later reference
#[derive(Debug, Resource)]
struct SpriteSheet {
    handle: Handle<TextureAtlas>,
}

/// Marker component for the 2d board entity
#[derive(Debug, Component)]
struct Board2d;

/// Marker for 2d piece entities
#[derive(Debug, Component)]
struct Piece2d;

/// STARTUP: Initialize 2d gameplay Camera
fn initialize_camera(mut commands: Commands) {
    commands.spawn(Camera2dBundle {
        camera: Camera {
            is_active: false,
            ..default()
        },
        ..default()
    });
}

/// STARTUP: Load sprite sheet and insert texture atlas
fn load_spritesheet(
    mut texture_atlases: ResMut<Assets<TextureAtlas>>,
    server: Res<AssetServer>,
    mut commands: Commands,
) {
    let atlas = TextureAtlas::from_grid(
        server.load("sprites.png"),
        Vec2::new(TILE_SIZE, TILE_SIZE),
        5,
        1,
        None,
        None,
    );
    commands.insert_resource(SpriteSheet {
        handle: texture_atlases.add(atlas),
    });
}

/// STARTUP: Initialize the board for representation
fn initialize_board(sprite_sheet: Option<Res<SpriteSheet>>, mut commands: Commands) {
    if let Some(sprite_sheet) = sprite_sheet {
        commands
            .spawn((
                SpatialBundle {
                    transform: Transform::from_xyz(
                        -SCALE * TILE_SIZE * 7.0 / 2.0, // TODO: WHY???
                        -SCALE * TILE_SIZE * 3.0 / 2.0, // Why 7 and 3??
                        0.0,
                    ),
                    ..default()
                },
                Board2d,
            ))
            .with_children(|parent| {
                for i in 0..32 {
                    let x = i % 8;
                    let y = i / 8;
                    let s = (x % 2) ^ (y % 2);

                    let transform = Transform::from_scale(Vec3::splat(SCALE)).with_translation(
                        Vec3::new(SCALE * 16.0 * x as f32, SCALE * 16.0 * y as f32, 0.0),
                    );

                    let sprite = TextureAtlasSprite::new(s);

                    let texture_atlas = sprite_sheet.handle.clone();

                    let index = BoardIndex { x, y };

                    // Rectangle
                    parent.spawn((
                        SpriteSheetBundle {
                            texture_atlas,
                            sprite,
                            transform,
                            ..default()
                        },
                        index,
                    ));
                }
            });
    }
}

fn draw_board(
    board: Option<Res<Board>>,
    mut commands: Commands,
    tiles: Query<(&Transform, &BoardIndex)>,
    pieces: Query<Entity, With<Piece2d>>,
    root: Query<Entity, With<Board2d>>,
    sprite_sheet: Option<Res<SpriteSheet>>,
) {
    if let (Some(board), Some(sprite_sheet)) = (board, sprite_sheet) {
        commands.entity(root.single()).with_children(|parent| {
            info!("Board and sprite sheet ready, drawing board");
            board
                .pieces()
                .iter()
                .filter_map(|(board_index, piece)| {
                    tiles.iter().find_map(|(transform, this_index)| {
                        (*this_index == *board_index).then(|| (piece, transform))
                    })
                })
                .for_each(|(piece, transform)| {
                    let texture_atlas = sprite_sheet.handle.clone();
                    let s = match piece {
                        Piece::Queen => 2,
                        Piece::Drone => 3,
                        Piece::Pawn => 4,
                    };
                    let sprite = TextureAtlasSprite::new(s);
                    // TODO: transform is slightly different, set sprite
                    parent.spawn((
                        piece.clone(),
                        SpriteSheetBundle {
                            texture_atlas,
                            sprite,
                            transform: Transform {
                                ..transform.clone()
                            },
                            ..default()
                        },
                        Piece2d,
                    ));
                });
        });
    }
}

fn activate(
    mut cameras: Query<&mut Camera, With<Camera2d>>,
    mut boards: Query<&mut Visibility, With<Board2d>>,
) {
    cameras.iter_mut().for_each(|mut camera| {
        camera.is_active = true;
    });
    boards.iter_mut().for_each(|mut visibility| {
        *visibility = Visibility::Visible;
    });
}

fn cursor_position(
    mut events: EventReader<CursorMoved>,
    sprite_q: Query<(
        &TextureAtlasSprite,
        &Handle<TextureAtlas>,
        &GlobalTransform,
        &BoardIndex,
    )>,
    camera_q: Query<(&Camera, &GlobalTransform), With<Camera2d>>,
    atlases: Res<Assets<TextureAtlas>>,
    mut selected: ResMut<SelectedTile>,
) {
    events.iter().for_each(|CursorMoved { position, .. }| {
        if let Some(position) = camera_q
            .iter()
            .find_map(|(camera, transform)| camera.viewport_to_world_2d(transform, *position))
        {
            let idx = sprite_q.iter().find_map(
                |(TextureAtlasSprite { index, anchor, .. }, handle, transform, board_index)| {
                    // Implementation credit goes to the sprite bevy_mod_picking backend
                    // TODO: Upstream changes
                    let pos = transform.translation();

                    let size = {
                        let sprite_size = atlases
                            .get(handle)
                            .map(|atlas| atlas.textures.get(*index).expect("Get this rect"))
                            .expect("get this rect")
                            .size();
                        let (transform_scale, _, _) = transform.to_scale_rotation_translation();
                        sprite_size * transform_scale.truncate()
                    };

                    let center = pos.truncate() - (anchor.as_vec() * size);
                    let rect = Rect::from_center_half_size(center, size / 2.0);

                    rect.contains(position).then_some(board_index)
                },
            );
            if selected.idx != idx.cloned() {
                selected.idx = idx.cloned();
            }
        }
    });
}

fn selected(selected: Res<SelectedTile>, board: Res<Board>) {
    selected.idx.iter().for_each(|idx| {
        info!("Selected Tile: {:?} contains {:?}", idx, board.at(idx));
    });
}