const { spawnSync } = require("child_process");
const fs = require("fs");
const path = require("path");
const os = require("os");

const FFMPEG_REPO = "https://git.ffmpeg.org/ffmpeg.git";
const FFMPEG_TAG = "release/7.1"
const FFMPEG_SOURCE_DIR = path.join(__dirname, "_source/FFmpeg");
const FFMPEG_INSTALL_DIR = path.join(__dirname, "FFmpeg");

const isWindows = os.platform() == "win32";

function checkEnv() {
	if (!process.env.MSYSTEM_PREFIX) throw new Error("Please use msys2 environment to run this script");
	const bash = process.env.SHELL;
	if (!bash || !bash.endsWith("bash.exe")) throw new Error("bash.exe is not found in environments");
}

function download() {
	console.log("Downloading ffmpeg source...");
	if (0 != spawnSync("git", [
		"clone", FFMPEG_REPO,
		"-b", FFMPEG_TAG, FFMPEG_SOURCE_DIR
	], { stdio: "inherit" }).status) throw new Error("Failed to download ffmpeg");
}

function build() {
	//configure
	if (!fs.existsSync(path.join(FFMPEG_SOURCE_DIR, "ffbuild/config.mak"))) {
		console.log("Configuring ffmpeg...");
		const args = [
			`--prefix=${FFMPEG_INSTALL_DIR}`,
			"--enable-static",
			"--enable-small",
			"--disable-programs",
			"--disable-x86asm",
			...isWindows ? ["--toolchain=msvc"] : [],
		];
		const configureFile = path.join(FFMPEG_SOURCE_DIR, "configure");
		if (isWindows) args.unshift(configureFile);

		if (0 != spawnSync(isWindows ? process.env.SHELL : configureFile, args, { stdio: "inherit", cwd: FFMPEG_SOURCE_DIR }).status) throw new Error("Failed to configure ffmpeg");
	}
	//make
	if (0 != spawnSync("make", [
		"-j", os.cpus().length.toString(),
	], { stdio: "inherit" }).status) throw new Error("Failed to build ffmpeg");
	//install
	if (0 != spawnSync("make", [
		"install",
	], { stdio: "inherit", cwd: FFMPEG_SOURCE_DIR }).status) throw new Error("Failed to install ffmpeg");
}

function resolve() {
	console.log("Resolving ffmpeg ...");
	const libs = [];
	for (const file of fs.readdirSync(path.join(FFMPEG_INSTALL_DIR, "lib"))) {
		if (path.extname(file) == ".a") {
			const libName = file.replace(/\.a$/, "").replace(/^lib/, "");
			if (isWindows) fs.renameSync(path.join(FFMPEG_INSTALL_DIR, "lib", file), path.join(FFMPEG_INSTALL_DIR, "lib", libName + ".lib"));
			libs.push(libName);
		}
	}
	fs.writeFileSync(path.join(FFMPEG_INSTALL_DIR, "config.cmake"), [
		"set(FFMPEG_INCLUDE_DIR ${CMAKE_CURRENT_LIST_DIR}/include)",
		"set(FFMPEG_LIB_DIR ${CMAKE_CURRENT_LIST_DIR}/lib)",
		`set(FFMPEG_LIBS ${libs.join(" ")})`,
		"",
	].join("\n"));

}

async function main() {
	fs.mkdirSync(path.dirname(FFMPEG_SOURCE_DIR), { recursive: true });
	fs.mkdirSync(path.dirname(FFMPEG_INSTALL_DIR), { recursive: true });

	if (isWindows) checkEnv();

	if (!fs.existsSync(path.join(FFMPEG_SOURCE_DIR, "configure"))) download();
	if (!fs.existsSync(path.join(FFMPEG_INSTALL_DIR, "config.cmake"))) {
		build();
		resolve();
	}

	console.log(`FFmpeg build done !`);
}

main().catch(err => console.error(err.message));