use bevy_ecs_tilemap::{
    helpers::geometry::get_tilemap_center_transform,
    map::{TilemapId, TilemapSize, TilemapTexture, TilemapTileSize},
    tiles::{TileBundle, TilePos, TileStorage, TileTextureIndex},
    TilemapBundle,
};
use std::{collections::HashMap, io::ErrorKind};
use thiserror::Error;

use bevy::{
    asset::{io::Reader, AsyncReadExt},
    reflect::TypePath,
};
use bevy::{
    asset::{AssetLoader, AssetPath, LoadContext},
    prelude::*,
};
use bevy_ecs_tilemap::map::TilemapType;

#[derive(Default)]
pub struct LdtkPlugin;

impl Plugin for LdtkPlugin {
    fn build(&self, app: &mut App) {
        app.init_asset::<LdtkMap>()
            .register_asset_loader(LdtkLoader)
            .add_systems(Update, process_loaded_tile_maps);
    }
}

#[derive(TypePath, Asset)]
pub struct LdtkMap {
    pub project: ldtk_rust::Project,
    pub tilesets: HashMap<i64, Handle<Image>>,
}

#[derive(Default, Component)]
pub struct LdtkMapConfig {
    pub selected_level: usize,
}

#[derive(Default, Bundle)]
pub struct LdtkMapBundle {
    pub ldtk_map: Handle<LdtkMap>,
    pub ldtk_map_config: LdtkMapConfig,
    pub transform: Transform,
    pub global_transform: GlobalTransform,
}

pub struct LdtkLoader;

#[derive(Debug, Error)]
pub enum LdtkAssetLoaderError {
    /// An [IO](std::io) Error
    #[error("Could not load LDTk file: {0}")]
    Io(#[from] std::io::Error),
}

impl AssetLoader for LdtkLoader {
    type Asset = LdtkMap;
    type Settings = ();
    type Error = LdtkAssetLoaderError;

    async fn load<'a>(
        &'a self,
        reader: &'a mut Reader<'_>,
        _settings: &'a Self::Settings,
        load_context: &'a mut LoadContext<'_>,
    ) -> Result<Self::Asset, Self::Error> {
        let mut bytes = Vec::new();
        reader.read_to_end(&mut bytes).await?;

        let project: ldtk_rust::Project = serde_json::from_slice(&bytes).map_err(|e| {
            std::io::Error::new(
                ErrorKind::Other,
                format!("Could not read contents of Ldtk map: {e}"),
            )
        })?;
        let dependencies: Vec<(i64, AssetPath)> = project
            .defs
            .tilesets
            .iter()
            .filter_map(|tileset| {
                tileset.rel_path.as_ref().map(|rel_path| {
                    (
                        tileset.uid,
                        load_context.path().parent().unwrap().join(rel_path).into(),
                    )
                })
            })
            .collect();

        let ldtk_map = LdtkMap {
            project,
            tilesets: dependencies
                .iter()
                .map(|dep| (dep.0, load_context.load(dep.1.clone())))
                .collect(),
        };
        Ok(ldtk_map)
    }

    fn extensions(&self) -> &[&str] {
        static EXTENSIONS: &[&str] = &["ldtk"];
        EXTENSIONS
    }
}

pub fn process_loaded_tile_maps(
    mut commands: Commands,
    mut map_events: EventReader<AssetEvent<LdtkMap>>,
    maps: Res<Assets<LdtkMap>>,
    mut query: Query<(Entity, &Handle<LdtkMap>, &LdtkMapConfig)>,
    new_maps: Query<&Handle<LdtkMap>, Added<Handle<LdtkMap>>>,
) {
    let mut changed_maps = Vec::<AssetId<LdtkMap>>::default();
    for event in map_events.read() {
        match event {
            AssetEvent::Added { id } => {
                log::info!("Map added!");
                changed_maps.push(*id);
            }
            AssetEvent::Modified { id } => {
                log::info!("Map changed!");
                changed_maps.push(*id);
            }
            AssetEvent::Removed { id } => {
                log::info!("Map removed!");
                // if mesh was modified and removed in the same update, ignore the modification
                // events are ordered so future modification events are ok
                changed_maps.retain(|changed_handle| changed_handle == id);
            }
            _ => continue,
        }
    }

    // If we have new map entities, add them to the changed_maps list
    for new_map_handle in new_maps.iter() {
        changed_maps.push(new_map_handle.id());
    }

    for changed_map in changed_maps.iter() {
        for (entity, map_handle, map_config) in query.iter_mut() {
            // only deal with currently changed map
            if map_handle.id() != *changed_map {
                continue;
            }
            if let Some(ldtk_map) = maps.get(map_handle) {
                // Despawn all existing tilemaps for this LdtkMap
                commands.entity(entity).despawn_descendants();

                // Pull out tilesets and their definitions into a new hashmap
                let mut tilesets = HashMap::new();
                ldtk_map.project.defs.tilesets.iter().for_each(|tileset| {
                    tilesets.insert(
                        tileset.uid,
                        (
                            ldtk_map.tilesets.get(&tileset.uid).unwrap().clone(),
                            tileset,
                        ),
                    );
                });

                let default_grid_size = ldtk_map.project.default_grid_size;
                let level = &ldtk_map.project.levels[map_config.selected_level];

                let map_tile_count_x = (level.px_wid / default_grid_size) as u32;
                let map_tile_count_y = (level.px_hei / default_grid_size) as u32;

                let size = TilemapSize {
                    x: map_tile_count_x,
                    y: map_tile_count_y,
                };

                // We will create a tilemap for each layer in the following loop
                for (layer_id, layer) in level
                    .layer_instances
                    .as_ref()
                    .unwrap()
                    .iter()
                    .rev()
                    .enumerate()
                {
                    if let Some(uid) = layer.tileset_def_uid {
                        let (texture, tileset) = tilesets.get(&uid).unwrap().clone();

                        // Tileset-specific tilemap settings
                        let tile_size = TilemapTileSize {
                            x: tileset.tile_grid_size as f32,
                            y: tileset.tile_grid_size as f32,
                        };

                        // Pre-emptively create a map entity for tile creation
                        let map_entity = commands.spawn_empty().id();

                        // Create tiles for this layer from LDtk's grid_tiles and auto_layer_tiles
                        let mut storage = TileStorage::empty(size);

                        for tile in layer.grid_tiles.iter().chain(layer.auto_layer_tiles.iter()) {
                            let mut position = TilePos {
                                x: (tile.px[0] / default_grid_size) as u32,
                                y: (tile.px[1] / default_grid_size) as u32,
                            };

                            position.y = map_tile_count_y - position.y - 1;

                            let tile_entity = commands
                                .spawn(TileBundle {
                                    position,
                                    tilemap_id: TilemapId(map_entity),
                                    texture_index: TileTextureIndex(tile.t as u32),
                                    ..default()
                                })
                                .id();

                            storage.set(&position, tile_entity);
                        }

                        let grid_size = tile_size.into();
                        let map_type = TilemapType::default();

                        // Create the tilemap
                        commands.entity(map_entity).insert(TilemapBundle {
                            grid_size,
                            map_type,
                            size,
                            storage,
                            texture: TilemapTexture::Single(texture),
                            tile_size,
                            transform: get_tilemap_center_transform(
                                &size,
                                &grid_size,
                                &map_type,
                                layer_id as f32,
                            ),
                            ..default()
                        });
                    }
                }
            }
        }
    }
}