// Rust sokoban
// main.rs

use glam::Vec2;
use ggez::{conf, event, Context, GameResult,
    graphics::{self, DrawParam, Image}};
use specs::{
    join::Join, Builder, Component, ReadStorage, RunNow, System, VecStorage, World, WorldExt,
};

use std::path;

const TILE_WIDTH: f32 = 32.0;

// Components
#[derive(Debug, Component, Clone, Copy)]
#[storage(VecStorage)]
pub struct Position {
    x: u8,
    y: u8,
    z: u8,
}

#[derive(Component)]
#[storage(VecStorage)]
pub struct Renderable {
    path: String,
}

#[derive(Component)]
#[storage(VecStorage)]
pub struct Wall {}

#[derive(Component)]
#[storage(VecStorage)]
pub struct Player {}

#[derive(Component)]
#[storage(VecStorage)]
pub struct Box {}

#[derive(Component)]
#[storage(VecStorage)]
pub struct BoxSpot {}

// Systems
pub struct RenderingSystem<'a> {
    context: &'a mut Context,
}

// System implementation
impl<'a> System<'a> for RenderingSystem<'a> {
    // Data
    type SystemData = (ReadStorage<'a, Position>, ReadStorage<'a, Renderable>);

    fn run(&mut self, data: Self::SystemData) {
        let (positions, renderables) = data;

        // Clearing the screen (this gives us the backround colour)
        graphics::clear(self.context, graphics::Color::new(0.95, 0.95, 0.95, 1.0));

        // Get all the renderables with their positions and sort by the position z
        // This will allow us to have entities layered visually.
        let mut rendering_data = (&positions, &renderables).join().collect::<Vec<_>>();
        rendering_data.sort_by_key(|&k| k.0.z);

        // Iterate through all pairs of positions & renderables, load the image
        // and draw it at the specified position.
        for (position, renderable) in rendering_data.iter() {
            // Load the image
            let image = Image::new(self.context, renderable.path.clone()).expect("expected image");
            let x = position.x as f32 * TILE_WIDTH;
            let y = position.y as f32 * TILE_WIDTH;

            // draw
            let draw_params = DrawParam::new().dest(Vec2::new(x, y));
            graphics::draw(self.context, &image, draw_params).expect("expected render");
        }

        // Finally, present the context, this will actually display everything
        // on the screen.
        graphics::present(self.context).expect("expected to present");
    }
}

// This struct will hold all our game state
// For now there is nothing to be held, but we'll add
// things shortly.
struct Game {
    world: World,
}

// This is the main event loop. ggez tells us to implement
// two things:
// - updating
// - rendering
impl event::EventHandler<ggez::GameError> for Game {
    fn update(&mut self, _context: &mut Context) -> GameResult {
        Ok(())
    }

    fn draw(&mut self, context: &mut Context) -> GameResult {
        // Render game entities
        {
            let mut rs = RenderingSystem { context };
            rs.run_now(&self.world);
        }

        Ok(())
    }
}

// Register components with the world
pub fn register_components(world: &mut World) {
    world.register::<Position>();
    world.register::<Renderable>();
    world.register::<Player>();
    world.register::<Wall>();
    world.register::<Box>();
    world.register::<BoxSpot>();
}

// Create a wall entity
pub fn create_wall(world: &mut World, position: Position) {
    world
        .create_entity()
        .with(Position { z: 10, ..position })
        .with(Renderable {
            path: "/images/wall.png".to_string(),
        })
        .with(Wall {})
        .build();
}

pub fn create_floor(world: &mut World, position: Position) {
    world
        .create_entity()
        .with(Position { z: 5, ..position })
        .with(Renderable {
            path: "/images/floor.png".to_string(),
        })
        .build();
}

pub fn create_box(world: &mut World, position: Position) {
    world
        .create_entity()
        .with(Position { z: 10, ..position })
        .with(Renderable {
            path: "/images/box.png".to_string(),
        })
        .with(Box {})
        .build();
}

pub fn create_box_spot(world: &mut World, position: Position) {
    world
        .create_entity()
        .with(Position { z: 9, ..position })
        .with(Renderable {
            path: "/images/box_spot.png".to_string(),
        })
        .with(BoxSpot {})
        .build();
}

pub fn create_player(world: &mut World, position: Position) {
    world
        .create_entity()
        .with(Position { z: 10, ..position })
        .with(Renderable {
            path: "/images/player.png".to_string(),
        })
        .with(Player {})
        .build();
}

// Initialize the level
pub fn initialize_level(world: &mut World) {
    const MAP: &str = "
    N N W W W W W W
    W W W . . . . W
    W . . . B . . W
    W . . . . . . W 
    W . P . . . . W
    W . . . . . . W
    W . . S . . . W
    W . . . . . . W
    W W W W W W W W
    ";

    load_map(world, MAP.to_string());
}

pub fn load_map(world: &mut World, map_string: String) {
    // read all lines
    let rows: Vec<&str> = map_string.trim().split('\n').map(|x| x.trim()).collect();

    for (y, row) in rows.iter().enumerate() {
        let columns: Vec<&str> = row.split(' ').collect();

        for (x, column) in columns.iter().enumerate() {
            // Create the position at which to create something on the map
            let position = Position {
                x: x as u8,
                y: y as u8,
                z: 0, // we will get the z from the factory functions
            };

            // Figure out what object we should create
            match *column {
                "." => create_floor(world, position),
                "W" => {
                    create_floor(world, position);
                    create_wall(world, position);
                }
                "P" => {
                    create_floor(world, position);
                    create_player(world, position);
                }
                "B" => {
                    create_floor(world, position);
                    create_box(world, position);
                }
                "S" => {
                    create_floor(world, position);
                    create_box_spot(world, position);
                }
                "N" => (),
                c => panic!("unrecognized map item {}", c),
            }
        }
    }
}
pub fn main() -> GameResult {
    let mut world = World::new();
    register_components(&mut world);
    initialize_level(&mut world);

    // Create a game context and event loop
    let context_builder = ggez::ContextBuilder::new("rust_sokoban", "sokoban")
        .window_setup(conf::WindowSetup::default().title("Rust Sokoban!"))
        .window_mode(conf::WindowMode::default().dimensions(800.0, 600.0))
        .add_resource_path(path::PathBuf::from("./resources"));

    let (context, event_loop) = context_builder.build()?;

    // Create the game state
    let game = Game { world };
    // Run the main event loop
    event::run(context, event_loop, game)
}
