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 { pack_mod } from "./tools/pack_mod.ts";
import { BMOD_EXTENSION } from "./common/bmod.ts";
import { ENGINE_TEXTURES_INDEX } from "./server/host.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";
// where the server loads .bmod files from. the build puts every mod in mods/ there, next to any others
const SERVER_MODS_FOLDER = Deno.env.get("SERVER_MODS_DIR") ?? "server_mods";

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`);
}

async function build_sprites() {
	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}`);
		}
	}
}

// the engine's textures (engine:<file>), with a list of them. clients put them in the texture atlas with the mods'
function build_engine_textures() {
	const folder = `${BUILD_FOLDER}/assets/textures`;
	Deno.mkdirSync(folder, { recursive: true });
	const names: string[] = [];
	for (const entry of [...Deno.readDirSync(ENGINE_TEXTURE_DIR)].sort((a, b) => a.name.localeCompare(b.name))) {
		if (entry.isFile && entry.name.endsWith(".png")) {
			Deno.copyFileSync(`${ENGINE_TEXTURE_DIR}/${entry.name}`, `${folder}/${entry.name}`);
			names.push(entry.name.replace(/\.png$/, ""));
		}
	}
	Deno.writeTextFileSync(`${BUILD_FOLDER}/${ENGINE_TEXTURES_INDEX}`, JSON.stringify(names));
}

async function build_assets() {
	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 });
	await build_sprites();
	build_engine_textures();
}

// 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);
}

// every mod in mods/ into server_mods/<id>.bmod. other .bmod files there are left alone, they're other people's mods
async function build_mods(mods: LoadedMod[]) {
	Deno.mkdirSync(SERVER_MODS_FOLDER, { recursive: true });
	remove_old_format();
	for (const mod of mods) {
		Deno.writeFileSync(`${SERVER_MODS_FOLDER}/${mod.id}${BMOD_EXTENSION}`, await pack_mod(mod));
	}
	console.log(`Mods: ${mods.map((m) => m.id).join(", ") || "none"}`);
}

// builds before .bmod files put each mod's server script in a folder here with an index.json
function remove_old_format() {
	for (const entry of Deno.readDirSync(SERVER_MODS_FOLDER)) {
		if (entry.isDirectory || entry.name === "index.json") {
			Deno.removeSync(`${SERVER_MODS_FOLDER}/${entry.name}`, { recursive: true });
		}
	}
}

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);
		// checked first: a mod with errors stops the build before any .bmod is written
		const mods = load_mods();
		await build_assets();
		await build_client();
		await build_mods(mods);
		console.log(`Built in ${(performance.now() - now).toFixed(2)}ms`);
	} catch (e) {
		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();
		}
	}
}