use ggez::event::{self, EventHandler};
use ggez::graphics::{
    self, spritebatch::SpriteBatch, Color, DrawMode, DrawParam, FilterMode, Image, Mesh, Rect,
    StrokeOptions, WrapMode,
};
use ggez::input::mouse;
use ggez::mint::{Point2, Vector2};
use ggez::{Context, ContextBuilder, GameResult};
use rand::{
    distributions::{Distribution, Standard},
    Rng,
};

pub const TILE_SCALE: f32 = 3.0;
pub const TILE_HEIGHT: f32 = 16.0;
pub const TILE_WIDTH: f32 = 16.0;
pub const BORDER_SIZE: f32 = 3.0;
pub const SHIFT_X: f32 = 50.0;
pub const SHIFT_Y: f32 = 50.0;
pub const COLUMNS: usize = 8;
pub const ROWS: usize = 8;

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

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(Clone, Copy)]
struct Cell {
    occupant: Occupant,
    position: Point2<f32>,
    hover: bool,
    clicked: bool,
}

impl Cell {
    pub fn new(position: Point2<f32>) -> Cell {
        Cell {
            occupant: rand::random(),
            position,
            hover: false,
            clicked: false,
        }
    }

    pub fn contains(&self, position: Point2<f32>) -> bool {
        if position.x > self.position.x
            && position.y > self.position.y
            && position.x < self.position.x + TILE_WIDTH * TILE_SCALE
            && position.y < self.position.y + TILE_WIDTH * TILE_SCALE
        {
            return true;
        }

        false
    }

    pub fn clicked_on(&mut self) {
        self.clicked = true;
    }

    pub fn clicked_off(&mut self) {
        self.clicked = false;
    }

    pub fn hover_on(&mut self) {
        self.hover = true;
    }

    pub fn hover_off(&mut self) {
        self.hover = false;
    }

    pub fn draw(&self, context: &mut Context, spritebatch: &mut SpriteBatch) -> GameResult {
        let source = match self.occupant {
            Occupant::None => None,
            Occupant::Explosion => None,
            Occupant::Green => Some(Rect::new(0.0, 0.0, 0.25, 1.0)),
            Occupant::Yellow => Some(Rect::new(0.25, 0.0, 0.25, 1.0)),
            Occupant::Diamond => Some(Rect::new(0.50, 0.0, 0.25, 1.0)),
            Occupant::Red => Some(Rect::new(0.75, 0.0, 0.25, 1.0)),
        };

        if let Some(source) = source {
            spritebatch.add(
                DrawParam::default()
                    .src(source)
                    .dest(self.position)
                    .scale(Vector2 {
                        x: TILE_SCALE,
                        y: TILE_SCALE,
                    }),
            );
        }

        if self.hover {
            let mesh = Mesh::new_rectangle(
                context,
                DrawMode::Stroke(StrokeOptions::default()),
                Rect::new(
                    self.position.x,
                    self.position.y,
                    TILE_WIDTH * TILE_SCALE,
                    TILE_HEIGHT * TILE_SCALE,
                ),
                Color::from_rgb(255, 100, 100),
            )?;
            graphics::draw(context, &mesh, DrawParam::default())?;
        }
        if self.clicked {
            let mesh = Mesh::new_rectangle(
                context,
                DrawMode::Stroke(StrokeOptions::default()),
                Rect::new(
                    self.position.x,
                    self.position.y,
                    TILE_WIDTH * TILE_SCALE,
                    TILE_HEIGHT * TILE_SCALE,
                ),
                Color::from_rgb(100, 255, 100),
            )?;
            graphics::draw(context, &mesh, DrawParam::default())?;
        }
        Ok(())
    }
}

struct Game {
    selected: Option<(usize, usize)>,
    spritebatch: SpriteBatch,
    grid: Vec<Vec<Cell>>,
    background: Image,
}

impl Game {
    fn new(context: &mut Context) -> GameResult<Game> {
        let mut background = Image::new(context, "/background.png")?;
        background.set_filter(FilterMode::Nearest);

        let mut image = Image::new(context, "/gem.png")?;
        image.set_filter(FilterMode::Nearest);
        image.set_wrap(WrapMode::Mirror, WrapMode::Mirror);

        let mut grid = Vec::new();
        let mut y = 0.0;

        for _ in 0..COLUMNS {
            let mut column = Vec::new();
            for j in 0..ROWS {
                column.push(Cell::new(Point2 {
                    x: (j as f32) * (TILE_WIDTH * TILE_SCALE + BORDER_SIZE) + SHIFT_X,
                    y: y + SHIFT_Y,
                }));
            }
            y += TILE_HEIGHT * TILE_SCALE + BORDER_SIZE;
            grid.push(column);
        }

        Ok(Game {
            grid,
            selected: None,
            spritebatch: SpriteBatch::new(image),
            background,
        })
    }
}

impl EventHandler for Game {
    fn update(&mut self, context: &mut Context) -> GameResult {
        for row in self.grid.iter_mut() {
            for cell in row.iter_mut() {
                cell.hover_off();
            }
        }

        let position = mouse::position(context);

        for row in self.grid.iter_mut() {
            for cell in row.iter_mut() {
                if cell.contains(position) {
                    cell.hover_on();
                }
            }
        }

        let mut last = Occupant::None;
        let mut connected = Vec::new();
        for i in 0..COLUMNS {
            let mut c = Vec::new();
            for j in 0..ROWS {
                if self.grid[i][j].occupant == last {
                    c.push((i, j));
                    c.push((i, j - 1));
                } else {
                    connected.push(c.clone());
                    c.clear();
                }
                last = self.grid[i][j].occupant;
            }
            connected.push(c);
            last = Occupant::None;
        }

        for c in connected.iter() {
            if c.len() > 3 {
                for (i, j) in c.iter() {
                    self.grid[*i][*j].occupant = Occupant::Explosion;
                }
            }
        }

        connected.clear();
        for i in 0..COLUMNS {
            let mut c = Vec::new();
            for j in 0..ROWS {
                if self.grid[j][i].occupant == last {
                    c.push((j, i));
                    c.push((j - 1, i));
                } else {
                    connected.push(c.clone());
                    c.clear();
                }
                last = self.grid[j][i].occupant;
            }
            connected.push(c);
            last = Occupant::None;
        }

        for c in connected.iter() {
            if c.len() > 3 {
                for (j, i) in c.iter() {
                    self.grid[*j][*i].occupant = Occupant::Explosion;
                }
            }
        }

        Ok(())
    }

    fn mouse_button_down_event(
        &mut self,
        _context: &mut Context,
        button: mouse::MouseButton,
        x: f32,
        y: f32,
    ) {
        if button == mouse::MouseButton::Left {
            let position = Point2 { x, y };
            for (i, row) in self.grid.iter_mut().enumerate() {
                for (j, cell) in row.iter_mut().enumerate() {
                    if cell.contains(position) {
                        self.selected = Some((i, j));
                        cell.clicked_on();
                    }
                }
            }
        }
    }

    fn mouse_button_up_event(
        &mut self,
        _context: &mut Context,
        button: mouse::MouseButton,
        x: f32,
        y: f32,
    ) {
        if button == mouse::MouseButton::Left {
            for row in self.grid.iter_mut() {
                for cell in row.iter_mut() {
                    cell.clicked_off();
                }
            }

            if let Some(selected) = self.selected {
                let position = Point2 { x, y };
                let mut swap = None;
                for (i, row) in self.grid.iter_mut().enumerate() {
                    for (j, cell) in row.iter_mut().enumerate() {
                        if cell.contains(position)
                            && (((i + 1 == selected.0) && (j == selected.1))
                                || ((i.overflowing_sub(1).0 == selected.0) && (j == selected.1))
                                || ((i == selected.0) && (j + 1 == selected.1))
                                || ((i == selected.0) && (j.overflowing_sub(1)).0 == selected.1))
                        {
                            swap = Some((i, j));
                        }
                    }
                }
                if let Some((i, j)) = swap {
                    let clone = self.grid[i][j].occupant;
                    self.grid[i][j].occupant = self.grid[selected.0][selected.1].occupant;
                    self.grid[selected.0][selected.1].occupant = clone;
                    self.selected = None;
                }
            }
        }
    }

    fn draw(&mut self, context: &mut Context) -> GameResult {
        graphics::clear(context, [0.0, 0.0, 0.0, 1.0].into());
        graphics::draw(context, &self.background, DrawParam::default())?;

        for row in self.grid.iter() {
            for cell in row.iter() {
                cell.draw(context, &mut self.spritebatch)?;
            }
        }

        graphics::draw(context, &self.spritebatch, DrawParam::default())?;

        self.spritebatch.clear();

        graphics::present(context)?;
        Ok(())
    }
}

pub fn main() -> GameResult {
    let (ref mut context, ref mut event_loop) = ContextBuilder::new("gems", "jw&tb")
        .add_resource_path("./resources")
        .build()?;
    let game = &mut Game::new(context)?;
    event::run(context, event_loop, game)
}