use crate::View;
use crate::{inspector::HideFromInspector, prelude::*};
use bevy::tasks::{block_on, futures_lite::future, AsyncComputeTaskPool, Task};
use bevy_ecs_tilemap::prelude::*;
use rand::prelude::*;
use rand_pcg::Pcg64;
use rand_seeder::Seeder;
use std::sync::mpsc::{channel, Receiver};
use std::sync::Mutex;

#[derive(Component, Debug)]
pub struct Tilemap;

#[derive(Component, Debug)]
pub struct TileChan(Mutex<Receiver<TileBundle>>);

#[derive(Component, Debug)]
pub struct TileInit(Task<()>);

pub fn init(mut commands: Commands, assets: Res<AssetServer>) {
    // TODO: I'm pretty determined to not have this sieze up the game despite the large number of entities being added. Should work with a "loading" screen and doing this in the background?

    let mut rng: Pcg64 = Seeder::from("default_seed").make_rng();
    let size = TilemapSize::new(1024, 1024);
    let tile_size = TilemapTileSize::new(16., 16.);
    let grid_size = TilemapGridSize::new(16., 16.);
    let map_type = TilemapType::Square;
    let texture = TilemapTexture::Single(assets.load("img/Tileset Grass.png"));
    let storage = TileStorage::empty(size);

    let tilemap = commands
        .spawn((
            Tilemap,
            Name::new("Tilemap"),
            TilemapBundle {
                grid_size,
                map_type,
                size,
                storage,
                texture,
                tile_size,
                transform: get_tilemap_center_transform(&size, &grid_size, &map_type, f32::MIN),
                ..Default::default()
            },
        ))
        .id();

    let pool = AsyncComputeTaskPool::get();
    let (tx, rx) = channel::<TileBundle>();
    let task = pool.spawn(async move {
        for x in 0..size.x {
            for y in 0..size.y {
                let position = TilePos::new(x, y);
                let texture_index = TileTextureIndex(if rng.gen_range(0..1000) > 925 {
                    rng.gen_range(0..(16 * 8))
                } else {
                    0
                });
                tx.send(TileBundle {
                    position,
                    tilemap_id: TilemapId(tilemap),
                    texture_index,
                    ..Default::default()
                })
                .unwrap();
            }
        }
        return ();
    });

    commands
        .entity(tilemap)
        .insert((TileInit(task), TileChan(Mutex::new(rx))));
}

const MAX_TILES_TO_LOAD_IN_ONE_UPDATE: usize = 5_000;
pub fn tile_loaders(
    mut commands: Commands,
    mut query: Query<(Entity, &mut TileStorage), With<Tilemap>>,
    mut chan: Query<&TileChan, With<Tilemap>>,
    mut tasks: Query<&mut TileInit>,
    mut app_state: ResMut<NextState<View>>,
) {
    // TODO: to avoid locking up the universe we only want to handle a certain number per iteration (Update)
    let mut tiles_done = true;
    let (tilemap, mut storage) = query.single_mut();

    if let Ok(chan) = chan.get_single_mut() {
        let chan = chan.0.lock().unwrap();
        tiles_done = false;
        let mut counter = 0;
        loop {
            match chan.recv() {
                Ok(ev) => {
                    let ref_position = &ev.position;
                    let tile = commands.spawn((HideFromInspector, ev)).id();
                    storage.set(ref_position, tile);
                    counter += 1;
                    if counter >= MAX_TILES_TO_LOAD_IN_ONE_UPDATE {
                        info!("Finished {}!", counter);
                        break;
                    }
                }
                Err(_) => {
                    commands.entity(tilemap).remove::<TileChan>();
                    if counter > 0 {
                        info!("Finished {counter}! Probably finishing mapgen soon...");
                    }
                    // the channel is likely closed, so let's note that and be done
                    tiles_done = true;
                    break;
                }
            }
        }
    }

    for mut task in &mut tasks {
        let poll = future::poll_once(&mut task.0);
        if block_on(poll).is_some() {
            // task is done, remove it so we don't poll it again
            commands.entity(tilemap).remove::<TileInit>();
        }
    }
    if tasks.iter().peekable().peek().is_none() && tiles_done {
        app_state.set(View::InGame);
    }
}

pub fn exit(mut commands: Commands, q: Query<Entity, With<Tilemap>>) {
    for id in q.iter() {
        commands.entity(id).despawn_recursive();
    }
}