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,
}

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

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 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() > 3 {
            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;
                        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() > 3 {
            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;
                        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));
        }
    }
}

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());
    }
}

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();
}