use bevy::math::Vec3;
use bevy::prelude::*;
use gems::constants;
use rand::{
    distributions::{Distribution, Standard},
    Rng,
};

#[derive(Debug, PartialEq, Clone, Copy)]
enum Occupant {
    None,
    Green,
    Yellow,
    Red,
    Diamond,
    Explosion,
}

impl Default for Occupant {
    fn default() -> Occupant {
        Occupant::None
    }
}

impl Occupant {
    pub fn to_index(&self) -> u32 {
        match self {
            Occupant::Green => 0,
            Occupant::Yellow => 1,
            Occupant::Red => 2,
            Occupant::Diamond => 3,
            Occupant::Explosion => 4,
            Occupant::None => 13,
        }
    }
}

impl Distribution<Occupant> for Standard {
    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Occupant {
        match rng.gen_range(0..=3) {
            0 => Occupant::Green,
            1 => Occupant::Yellow,
            2 => Occupant::Diamond,
            3 => Occupant::Red,
            _ => Occupant::None,
        }
    }
}

#[derive(Debug, Clone, Default, Copy)]
struct Cell {
    x: usize,
    y: usize,
    occupant: Occupant,
    selected: bool,
    hovered: bool,
}

impl Cell {
    pub fn new(x: usize, y: usize) -> Cell {
        Cell {
            x,
            y,
            occupant: Occupant::None,
            selected: false,
            hovered: false,
        }
    }
}

fn cell_insert_system(mut cell_query: Query<(&mut Cell, &mut TextureAtlasSprite)>) {
    for (mut cell, mut sprite) in cell_query.iter_mut() {
        if cell.occupant == Occupant::None && cell.y == constants::ROWS - 1 {
            cell.occupant = rand::random();
            sprite.index = cell.occupant.to_index();
        }
    }
}

fn explosion_animation_system(
    time: Res<Time>,
    commands: &mut Commands,
    mut cell_query: Query<(
        Entity,
        &mut Cell,
        &mut TextureAtlasSprite,
        Option<&mut Timer>,
    )>,
) {
    for (entity, mut cell, mut sprite, timer) in cell_query.iter_mut() {
        if cell.occupant == Occupant::Explosion {
            if let Some(mut timer) = timer {
                timer.tick(time.delta_seconds());
                if timer.finished() {
                    if sprite.index < 7 && sprite.index >= 4 {
                        sprite.index += 1;
                    } else {
                        cell.occupant = Occupant::None;
                        sprite.index = cell.occupant.to_index();
                        commands.remove_one::<Timer>(entity);
                    }
                }
            } else {
                commands.insert(entity, (Timer::from_seconds(0.1, true),));
            }
        }
    }
}

fn cell_check_system(mut cell_query: Query<(&mut Cell, &mut TextureAtlasSprite)>) {
    let mut cells = [[Cell::default(); constants::COLUMNS]; constants::ROWS];
    for (cell, _) in cell_query.iter_mut() {
        cells[cell.x][cell.y] = *cell;
    }

    let mut last = Occupant::None;
    let mut connected = Vec::new();

    for (i, _) in cells.iter().enumerate() {
        let mut c = Vec::new();
        for j in 0..constants::ROWS {
            if cells[i][j].occupant == last && last != Occupant::None {
                c.push((i, j));
                c.push((i, j - 1));
            } else {
                connected.push(c.clone());
                c.clear();
            }
            last = cells[i][j].occupant;
        }
        connected.push(c);
        last = Occupant::None;
    }

    for c in connected.iter() {
        if c.len() > 4 {
            for (i, j) in c.iter() {
                for (mut cell, mut sprite) in cell_query.iter_mut() {
                    if &cell.x == i && &cell.y == j && cell.occupant != Occupant::Explosion {
                        cell.occupant = Occupant::Explosion;
                        sprite.index = cell.occupant.to_index();
                    }
                }
            }
        }
    }

    connected.clear();

    for (i, row) in cells.iter().enumerate() {
        let mut c = Vec::new();
        for (j, _) in row.iter().enumerate() {
            if cells[j][i].occupant == last && last != Occupant::None {
                c.push((j, i));
                c.push((j - 1, i));
            } else {
                connected.push(c.clone());
                c.clear();
            }
            last = cells[j][i].occupant;
        }
        connected.push(c);
        last = Occupant::None;
    }

    for c in connected.iter() {
        if c.len() > 4 {
            for (i, j) in c.iter() {
                for (mut cell, mut sprite) in cell_query.iter_mut() {
                    if &cell.x == i && &cell.y == j && cell.occupant != Occupant::Explosion {
                        cell.occupant = Occupant::Explosion;
                        sprite.index = cell.occupant.to_index();
                    }
                }
            }
        }
    }
}

fn cell_falling_system(mut cell_query: Query<(&mut Cell, &mut TextureAtlasSprite)>) {
    let mut have_gems = Vec::new();
    for (cell, _sprite) in cell_query.iter_mut() {
        if cell.occupant != Occupant::None {
            have_gems.push(*cell);
        }
    }

    let mut moved_gems = Vec::new();
    for (mut cell, mut sprite) in cell_query.iter_mut() {
        if cell.occupant == Occupant::None {
            if let Some(c) = have_gems
                .iter()
                .find(|&c| (c.x, c.y) == (cell.x, cell.y + 1))
            {
                cell.occupant = c.occupant;
                sprite.index = cell.occupant.to_index();
                moved_gems.push(c);
            }
        }
    }

    for (mut cell, mut sprite) in cell_query.iter_mut() {
        if moved_gems.iter().any(|c| (c.x, c.y) == (cell.x, cell.y)) {
            cell.occupant = Occupant::None;
            sprite.index = cell.occupant.to_index();
        }
    }
}

pub fn setup(
    commands: &mut Commands,
    asset_server: Res<AssetServer>,
    mut materials: ResMut<Assets<ColorMaterial>>,
    mut texture_atlases: ResMut<Assets<TextureAtlas>>,
) {
    let background = asset_server.load("background.png");
    let tileset = asset_server.load("tileset.png");

    let atlas = TextureAtlas::from_grid(tileset, Vec2::new(16.0, 16.0), 4, 4);
    let atlas_handle = texture_atlases.add(atlas);

    commands
        .spawn(Camera2dBundle::default())
        .spawn(SpriteBundle {
            material: materials.add(background.into()),
            transform: Transform {
                translation: Vec3 {
                    x: 50.0,
                    y: 0.0,
                    z: 0.0,
                },
                scale: Vec3::splat(3.5),
                ..Default::default()
            },
            ..Default::default()
        })
        .spawn(SpriteSheetBundle {
            sprite: TextureAtlasSprite::new(8),
            texture_atlas: atlas_handle.clone(),
            transform: Transform {
                translation: Vec3 {
                    x: 225.0,
                    y: -200.0,
                    z: 0.0,
                },
                scale: Vec3::splat(3.5),
                ..Default::default()
            },
            ..Default::default()
        })
        .spawn(SpriteSheetBundle {
            sprite: TextureAtlasSprite::new(12),
            texture_atlas: atlas_handle.clone(),
            transform: Transform {
                translation: Vec3 {
                    x: 225.0,
                    y: -200.0 + (-16.0) * 3.5,
                    z: 0.0,
                },
                scale: Vec3::splat(3.5),
                ..Default::default()
            },
            ..Default::default()
        });

    for i in 0..constants::COLUMNS {
        for j in 0..constants::ROWS {
            commands
                .spawn(SpriteSheetBundle {
                    texture_atlas: atlas_handle.clone(),
                    sprite: TextureAtlasSprite::new(11),
                    transform: Transform {
                        translation: Vec3 {
                            x: ((i as f32) * 16.0 * 3.5) - 320.0,
                            y: ((j as f32) * 16.0 * 3.5) - 160.0,
                            z: 0.0,
                        },
                        scale: Vec3::splat(3.5),
                        ..Default::default()
                    },
                    ..Default::default()
                })
                .with(Cell::new(i, j));
        }
    }
}

fn cosmonaut_animation_system(
    commands: &mut Commands,
    time: Res<Time>,
    mut cell_query: Query<(Entity, &mut Timer, &mut TextureAtlasSprite), Without<Cell>>,
) {
    for (entity, mut timer, mut sprite) in cell_query.iter_mut() {
        timer.tick(time.delta_seconds());
        if timer.finished() {
            let index = match sprite.index {
                9 => 10,
                10 => 13,
                13 => 14,
                11 => 12,
                _ => 11,
            };
            sprite.index = index;
            if index == 12 {
                commands.remove_one::<Timer>(entity);
                commands.remove_one::<TextureAtlasSprite>(entity);
            }
        }
    }
}

fn cosmonaut_detect_system(
    commands: &mut Commands,
    windows: Res<Windows>,
    mut cell_query: Query<(&Transform, &TextureAtlasSprite)>,
) {
    if let Some(mut cursor_position) = windows
        .get_primary()
        .and_then(|window| window.cursor_position())
    {
        cursor_position.x -= 400.0 - 16.0 * 3.5 * 0.5;
        cursor_position.y -= 300.0 - 16.0 * 3.5 * 0.5;
        for (transform, sprite) in cell_query.iter_mut() {
            if transform.translation.x < cursor_position.x
                && transform.translation.x + 16.0 * 3.5 > cursor_position.x
                && transform.translation.y < cursor_position.y
                && transform.translation.y + 16.0 * 3.5 > cursor_position.y
                && sprite.index == 8
            {
                commands
                    .spawn(SpriteSheetBundle {
                        sprite: TextureAtlasSprite::new(9),
                        transform: *transform,
                        ..Default::default()
                    })
                    .with(Timer::from_seconds(0.1, true));
            }
        }
    }
}

fn mouse_system(
    windows: Res<Windows>,
    mut cell_query: Query<(&mut Cell, &mut Transform, &mut TextureAtlasSprite)>,
    mouse_button_input: Res<Input<MouseButton>>,
) {
    if let Some(mut cursor_position) = windows
        .get_primary()
        .and_then(|window| window.cursor_position())
    {
        cursor_position.x -= 400.0 - 16.0 * 3.5 * 0.5;
        cursor_position.y -= 300.0 - 16.0 * 3.5 * 0.5;

        for (cell, _, mut sprite) in cell_query.iter_mut() {
            if cell.selected {
                sprite.color.set_a(0.2);
            } else if cell.hovered {
                sprite.color.set_a(0.5);
            } else {
                sprite.color.set_a(1.0);
            }
        }

        for (mut cell, transform, mut sprite) in cell_query.iter_mut() {
            if transform.translation.x < cursor_position.x
                && transform.translation.x + 16.0 * 3.5 > cursor_position.x
                && transform.translation.y < cursor_position.y
                && transform.translation.y + 16.0 * 3.5 > cursor_position.y
            {
                cell.hovered = true;
                sprite.color.set_a(0.5);
                if mouse_button_input.just_pressed(MouseButton::Left) {
                    cell.selected = true;
                }
            } else {
                cell.hovered = false;
            }
        }

        if mouse_button_input.just_released(MouseButton::Left) {
            let mut cells: Vec<Cell> = Vec::new();
            for (cell, _, _) in cell_query.iter_mut() {
                cells.push(*cell);
            }
            if let Some(mut selected) = cells.clone().iter_mut().find(|c| c.selected) {
                if let Some(mut hovered) = cells.iter_mut().find(|c| c.hovered) {
                    if (selected.x == hovered.x + 1 && selected.y == hovered.y)
                        || (selected.x == hovered.x - 1 && selected.y == hovered.y)
                        || (selected.y == hovered.y + 1 && selected.x == hovered.x)
                        || (selected.y == hovered.y - 1 && selected.x == hovered.x)
                    {
                        let tmp = selected.occupant;
                        selected.occupant = hovered.occupant;
                        hovered.occupant = tmp;
                        for (mut cell, _, mut sprite) in cell_query.iter_mut() {
                            if cell.x == selected.x && cell.y == selected.y {
                                cell.occupant = selected.occupant;
                                sprite.index = cell.occupant.to_index();
                            } else if cell.x == hovered.x && cell.y == hovered.y {
                                cell.occupant = hovered.occupant;
                                sprite.index = cell.occupant.to_index();
                            }
                        }
                    }
                }
            }
            for (mut cell, _, _) in cell_query.iter_mut() {
                cell.selected = false;
            }
        }
    }
}

pub struct GemsPlugin;
impl Plugin for GemsPlugin {
    fn build(&self, app: &mut AppBuilder) {
        app.add_startup_system(setup.system());
        app.add_system(cell_insert_system.system());
        app.add_system(cell_falling_system.system());
        app.add_system(cell_check_system.system());
        app.add_system(explosion_animation_system.system());
        app.add_system(mouse_system.system());
        app.add_system(cosmonaut_detect_system.system());
        app.add_system(cosmonaut_animation_system.system());
    }
}

pub fn main() {
    App::build()
        .add_resource(WindowDescriptor {
            title: "gems".to_string(),
            width: 800.0,
            height: 600.0,
            resizable: false,
            ..Default::default()
        })
        .add_plugins(DefaultPlugins)
        .add_plugin(GemsPlugin)
        .run();
}