import { copy } from "@std/fs";
import { createCanvas, loadImage } from "@gfx/canvas-wasm";
import { ENGINE_TEXTURE_DIR, load_and_check, load_order, LoadedMod } from "./tools/check_mods.ts";
import type { AtlasListing, ModData, ModListing } from "./common/mod_loader.ts";

// all overridable so tests can build somewhere else
const BUILD_FOLDER = Deno.env.get("BUILD_DIR") ?? "build";
const MODS_FOLDER = Deno.env.get("MODS_DIR") ?? "mods";
// server scripts go here instead of the served build folder, players never get them
const SERVER_MODS_FOLDER = Deno.env.get("SERVER_MODS_DIR") ?? "server_mods";

// what the server reads at startup, see server/main.ts
export interface ServerModIndex {
	atlas: AtlasListing;
	mods: { listing: ModListing; server?: string }[];
}

function clear_folder(folder: string) {
	try {
		Deno.removeSync(folder, { recursive: true });
	} catch (e) {
		if (!(e instanceof Deno.errors.NotFound)) throw e;
	}
	Deno.mkdirSync(folder, { recursive: true });
}

async function build_fonts() {
	// i used https://fonts.varg.dev/ to build the font, its confusing
	const canvas_size = 256;

	const font = await loadImage("assets/fonts/m6x11.png");
	const canvas = createCanvas(canvas_size, canvas_size);
	const ctx = canvas.getContext("2d");

	ctx.drawImage(font, 0, 0);
	const image_data = ctx.getImageData(0, 0, canvas_size, canvas_size);
	const data = image_data.data;
	for (let i = 0; i < data.length; i += 4) {
		const r = data[i];
		const g = data[i + 1];
		const b = data[i + 2];

		if (r === 0 && g === 0 && b === 0) {
			// black pixel, alpha = 0
			data[i + 3] = 0;
		} else {
			// force white white
			data[i] = 255;
			data[i + 1] = 255;
			data[i + 2] = 255;
			data[i + 3] = 255;
		}
	}
	ctx.putImageData(image_data, 0, 0);

	Deno.mkdirSync(`${BUILD_FOLDER}/assets/fonts`);
	Deno.writeFileSync(`${BUILD_FOLDER}/assets/fonts/m6x11.png`, canvas.toBuffer());
	await copy("assets/fonts/m6x11.fnt", `${BUILD_FOLDER}/assets/fonts/m6x11.fnt`);
}

function next_power_of_two(value: number): number {
	return Math.pow(2, Math.ceil(Math.log2(value)));
}

const SPRITE_SIZE = 16;

function calculate_atlas_size(count: number) {
	const raw_sprites_per_side = Math.ceil(Math.sqrt(count));
	const raw_size = raw_sprites_per_side * SPRITE_SIZE;
	const size = next_power_of_two(raw_size);

	return {
		sprites_per_side: size / SPRITE_SIZE,
		size,
	};
}

// one atlas with the engine's textures (engine:<file>) and every mod's (<mod>:<file>).
// named by its hash, so clients can cache it forever and download it from other origins
async function build_atlas(mods: LoadedMod[]): Promise<AtlasListing> {
	const textures = new Map<string, string>();
	for (const entry of Deno.readDirSync(ENGINE_TEXTURE_DIR)) {
		if (entry.isFile && entry.name.endsWith(".png")) {
			textures.set(`engine:${entry.name.replace(".png", "")}`, `${ENGINE_TEXTURE_DIR}/${entry.name}`);
		}
	}
	for (const mod of mods) {
		for (const [id, path] of mod.texture_files) {
			textures.set(id, path);
		}
	}

	// + 1 for the missing texture
	const atlas = calculate_atlas_size(textures.size + 1);

	const canvas = createCanvas(atlas.size, atlas.size);
	const ctx = canvas.getContext("2d");

	const atlas_info: Record<string, { x: number; y: number }> = {};

	// purple and black missing texture at x:0 y:0 wow !
	ctx.fillStyle = "magenta";
	ctx.fillRect(0, 0, 8, 8);
	ctx.fillRect(8, 8, 8, 8);
	ctx.fillStyle = "black";
	ctx.fillRect(8, 0, 8, 8);
	ctx.fillRect(0, 8, 8, 8);
	atlas_info["engine:missing"] = { x: 0, y: 0 };

	let index = 1;
	for (const [id, path] of [...textures].sort(([a], [b]) => a.localeCompare(b))) {
		const sprite = await loadImage(path);
		const row = Math.floor(index / atlas.sprites_per_side);
		const column = index % atlas.sprites_per_side;
		ctx.drawImage(sprite, column * SPRITE_SIZE, row * SPRITE_SIZE);
		index += 1;
		atlas_info[id] = { x: column, y: row };
	}

	const png = new Uint8Array(canvas.toBuffer());
	const json = new TextEncoder().encode(JSON.stringify(atlas_info));
	const hashes = { png: await sha256(png), json: await sha256(json) };
	const name = `assets/sprites/textures.${(hashes.png + hashes.json).slice(0, 12)}`;
	Deno.writeFileSync(`${BUILD_FOLDER}/${name}.png`, png);
	Deno.writeFileSync(`${BUILD_FOLDER}/${name}.json`, json);
	return { png: `${name}.png`, json: `${name}.json`, sha256: hashes };
}

async function build_sprites(mods: LoadedMod[]) {
	for (const entry of Deno.readDirSync("assets/sprites")) {
		if (entry.name.endsWith(".png")) {
			await copy(`assets/sprites/${entry.name}`, `${BUILD_FOLDER}/assets/sprites/${entry.name}`);
		}
	}
	return await build_atlas(mods);
}

async function build_assets(mods: LoadedMod[]): Promise<AtlasListing> {
	Deno.mkdirSync(`${BUILD_FOLDER}/assets`, { recursive: true });
	await copy("assets/ASSETS.md", `${BUILD_FOLDER}/assets/ASSETS.md`);

	await build_fonts();
	Deno.mkdirSync(`${BUILD_FOLDER}/assets/sprites`, { recursive: true });
	return await build_sprites(mods);
}

// every mod in mods/, checked and sorted so dependencies load first. a broken mod fails the whole build,
// the game never runs with some mods missing
function load_mods(): LoadedMod[] {
	const mods = load_and_check(MODS_FOLDER);
	const problems = mods.flatMap((mod) => mod.report.errors.map((error) => `  ${mod.id}: ${error}`));
	if (problems.length > 0) {
		throw new Error(`Mods have errors (deno task check-mods for details):\n${problems.join("\n")}`);
	}
	return load_order(mods);
}

async function bundle_script(path: string, platform: "browser" | "deno"): Promise<string> {
	const result = await Deno.bundle({ entrypoints: [path], platform, write: false, minify: false });
	if (!result.success || !result.outputFiles?.length) {
		throw new Error(`Couldn't bundle ${path}:\n${result.errors.map((e) => e.text).join("\n")}`);
	}
	return result.outputFiles[0].text();
}

async function sha256(bytes: Uint8Array<ArrayBuffer> | string) {
	const data = typeof bytes === "string" ? new TextEncoder().encode(bytes) : bytes;
	const digest = await crypto.subtle.digest("SHA-256", data);
	return [...new Uint8Array(digest)].map((b) => b.toString(16).padStart(2, "0")).join("");
}

async function short_hash(parts: string[]) {
	const digest = await crypto.subtle.digest("SHA-256", new TextEncoder().encode(parts.join("\0")));
	return [...new Uint8Array(digest)].slice(0, 6).map((b) => b.toString(16).padStart(2, "0")).join("");
}

// build/mods/<id>/<hash>/ gets what players download, server_mods/ the server scripts
async function build_mods(mods: LoadedMod[], atlas: AtlasListing) {
	clear_folder(SERVER_MODS_FOLDER);
	const index: ServerModIndex = { atlas, mods: [] };

	for (const mod of mods) {
		const manifest = mod.manifest as { name: string; version: string; scripts?: Record<string, string> };
		const scripts = manifest.scripts ?? {};

		const data: ModData = {
			blocks: mod.blocks.map((b) => b.json),
			items: mod.items.map((i) => i.json),
			recipes: mod.recipes.map((r) => r.json),
			ores: mod.ores.map((o) => o.json),
		};
		const data_json = JSON.stringify(data);
		const client = scripts.client ? await bundle_script(`${mod.dir}/${scripts.client}`, "browser") : undefined;
		const worldgen = scripts.worldgen
			? await bundle_script(`${mod.dir}/${scripts.worldgen}`, "browser")
			: undefined;
		const server = scripts.server ? await bundle_script(`${mod.dir}/${scripts.server}`, "deno") : undefined;

		const hash = await short_hash([data_json, client ?? "", worldgen ?? ""]);
		const public_dir = `mods/${mod.id}/${hash}`;
		Deno.mkdirSync(`${BUILD_FOLDER}/${public_dir}`, { recursive: true });

		const listing: ModListing = {
			id: mod.id,
			name: manifest.name,
			version: manifest.version,
			hash,
			data: `${public_dir}/data.json`,
			sha256: { data: await sha256(data_json) },
		};
		Deno.writeTextFileSync(`${BUILD_FOLDER}/${listing.data}`, data_json);
		if (client) {
			listing.client = `${public_dir}/client.js`;
			listing.sha256.client = await sha256(client);
			Deno.writeTextFileSync(`${BUILD_FOLDER}/${listing.client}`, client);
		}
		if (worldgen) {
			listing.worldgen = `${public_dir}/worldgen.js`;
			listing.sha256.worldgen = await sha256(worldgen);
			Deno.writeTextFileSync(`${BUILD_FOLDER}/${listing.worldgen}`, worldgen);
		}

		const entry: ServerModIndex["mods"][number] = { listing };
		if (server) {
			const server_dir = `${SERVER_MODS_FOLDER}/${mod.id}/${await short_hash([server])}`;
			Deno.mkdirSync(server_dir, { recursive: true });
			entry.server = `${server_dir}/server.js`;
			Deno.writeTextFileSync(entry.server, server);
		}
		index.mods.push(entry);
	}

	Deno.writeTextFileSync(`${SERVER_MODS_FOLDER}/index.json`, JSON.stringify(index, null, "\t"));
	console.log(`Mods: ${mods.map((m) => m.id).join(", ") || "none"}`);
}

async function build_client() {
	const _result = await Deno.bundle({
		entrypoints: ["./client/main.ts", "./client/workers/chunk_worker.ts"],
		outputDir: `${BUILD_FOLDER}/client`,
		platform: "browser",
		minify: false,
		keepNames: true,
	});
	await copy("./client/index.html", `${BUILD_FOLDER}/client/index.html`);
}

async function build() {
	try {
		const now = performance.now();
		clear_folder(BUILD_FOLDER);
		const mods = load_mods();
		const atlas = await build_assets(mods);
		await build_client();
		await build_mods(mods, atlas);
		console.log(`Built in ${(performance.now() - now).toFixed(2)}ms`);
	} catch (e) {
		// no index means the server refuses to start, instead of running without some mods
		try {
			Deno.removeSync(`${SERVER_MODS_FOLDER}/index.json`);
		} catch { /* wasn't there */ }
		console.log(e instanceof Error ? e.message : e);
		return false;
	}
	return true;
}

let last_build = 0;

if (import.meta.main) {
	const ok = await build();
	// deno task build --once, for scripts and ci
	if (Deno.args.includes("--once")) {
		Deno.exit(ok ? 0 : 1);
	}
	const watcher = Deno.watchFs(["assets", "client", "common", MODS_FOLDER], { recursive: true });
	for await (const event of watcher) {
		const now = performance.now();
		if (now - last_build < 500) {
			continue;
		}
		if (["create", "modify", "rename", "remove"].includes(event.kind)) {
			last_build = now;
			console.log("Rebuilding...");
			await build();
		}
	}
}