import MapData from '../model/data/MapData';
import { nextPowerOf2 } from '../util';

import Renderer from './renderer/Renderer';
import { SpriteCoords, SpriteView, SpriteViewBuilder } from './sprite';
import { loadImage, mkTexture } from './util/image';

interface Tileset {
	texture: WebGLTexture;
	tiles: SpriteCoords[];
}

function loadTiles(tiles: string[]): Promise<HTMLImageElement[]> {
	return Promise.all(tiles.map((t) => loadImage(`resources/sprite/tile/${t}.png`)));
}

function mkTileset(
	gl: WebGLRenderingContext,
	tiles: HTMLImageElement[],
): Tileset {
	const tileSize = 32;

	const canvasDim = nextPowerOf2(Math.sqrt(tiles.length));
	const canvasSize = canvasDim * tileSize;

	const canvas = document.createElement('canvas');
	canvas.width = canvas.height = canvasSize;

	let x = 0, y = 0;
	const tileCoords: SpriteCoords[] = [];
	const ctx = canvas.getContext('2d') as CanvasRenderingContext2D;

	for (const tile of tiles) {
		ctx.drawImage(tile, x * tileSize, y * tileSize);
		tileCoords.push([x / canvasDim, y / canvasDim, (x + 1) / canvasDim, (y + 1) / canvasDim]);

		x++;
		if (x === canvasDim) {
			x = 0;
			y++;
		}
	}

	return {
		texture: mkTexture(gl, canvas),
		tiles: tileCoords,
	};
}

function addSprite(builder: SpriteViewBuilder, tileset: Tileset, x: number, y: number, tile: number) {
	if (tile === 0)
		return;

	const tilePos = tileset.tiles[tile - 1];
	builder.addSprite([x, y, x + 1, y + 1], tilePos);
}

export async function loadMap(r: Renderer, map: MapData): Promise<SpriteView> {
	const tiles = await loadTiles(map.tiles);
	const tileset = mkTileset(r.getContext(), tiles);

	const builder = new SpriteViewBuilder(r, tileset.texture);

	for (const layer of map.layers)
		for (let x = 0; x < map.width; x++)
			for (let y = 0; y < map.height; y++)
				addSprite(builder, tileset, x, y, layer[y][x]);

	return builder.build();
}