extern crate rltk;
use rltk::{Console, GameState, Rltk, RGB, VirtualKeyCode};
extern crate specs;
use specs::prelude::*;
#[macro_use]
extern crate specs_derive;

#[derive(Component)]
struct Position {
    x: i32,
    y: i32,
}

#[derive(Component)]
struct Renderable {
    glyph: u8,
    fg: RGB,
    bg: RGB,
}

#[derive(Component)]
struct LeftMover {}
 
#[derive(Component, Debug)]
struct Player {}

struct State {
    ecs: World,
    systems: Dispatcher<'static, 'static>
}

fn try_move_player(delta_x: i32, delta_y: i32, ecs: &mut World) {
    let mut positions = ecs.write_storage::<Position>();
    let mut players = ecs.write_storage::<Player>();

    for (_player, pos) in (&mut players, &mut positions).join() {
        pos.x += delta_x;
        pos.y += delta_y;

        if pos.x < 0 { pos.x = 0; }
        if pos.x > 79 { pos.y = 79; }
        if pos.y < 0 { pos.y = 0; }
        if pos.y > 49 { pos.y = 49; }
    }
}

fn player_input(gs: &mut State, ctx: &mut Rltk) {
    // Player movement
    match ctx.key {
        None => {} // Nothing happened
        Some(key) => match key {
            VirtualKeyCode::Left => try_move_player(-1, 0, &mut gs.ecs),
            VirtualKeyCode::Right => try_move_player(1, 0, &mut gs.ecs),
            VirtualKeyCode::Up => try_move_player(0, -1, &mut gs.ecs),
            VirtualKeyCode::Down => try_move_player(0, 1, &mut gs.ecs),
            _ => {}
        },
    }
}

impl GameState for State {
    fn tick(&mut self, ctx : &mut Rltk) {
        ctx.cls();

        player_input(self, ctx);
        self.systems.dispatch(&self.ecs);

        let positions = self.ecs.read_storage::<Position>();
        let renderables = self.ecs.read_storage::<Renderable>();

        for (pos, render) in (&positions, &renderables).join() {
            ctx.set(pos.x, pos.y, render.fg, render.bg, render.glyph);
        }
    }
}

struct LeftWalker {}

impl<'a> System<'a> for LeftWalker {
    type SystemData = (ReadStorage<'a, LeftMover>, 
                        WriteStorage<'a, Position>);

    fn run(&mut self, (lefty, mut pos) : Self::SystemData) {
        for (_lefty,pos) in (&lefty, &mut pos).join() {
            pos.x -= 1;
            if pos.x < 0 { pos.x = 79; }
        }
    }
}

fn main() {
    let context = Rltk::init_simple8x8(80, 50, "Hello Rust World", "../resources");
    let mut gs = State {
        ecs: World::new(),
        systems : DispatcherBuilder::new()
            .with(LeftWalker{}, "left_walker", &[])
            .build()
    };
    gs.ecs.register::<Position>();
    gs.ecs.register::<Renderable>();
    gs.ecs.register::<LeftMover>();
    gs.ecs.register::<Player>();

    gs.ecs
        .create_entity()
        .with(Position { x: 40, y: 25 })
        .with(Renderable {
            glyph: rltk::to_cp437('@'),
            fg: RGB::named(rltk::YELLOW),
            bg: RGB::named(rltk::BLACK),
        })
        .with(Player{})
        .build();

    for i in 0..10 {
        gs.ecs
        .create_entity()
        .with(Position { x: i * 7, y: 20 })
        .with(Renderable {
            glyph: rltk::to_cp437('☺'),
            fg: RGB::named(rltk::RED),
            bg: RGB::named(rltk::BLACK),
        })
        .with(LeftMover{})
        .build();
    }

    rltk::main_loop(context, gs);
}