const { Readable, PassThrough } = require("stream");
const { spawn } = require("child_process");

class FFMPEG {
	constructor(data) {
		this.data = data; // Can be Readable or Buffer
		this.isBuffer = data instanceof Buffer;
	}

	convert() {
		return new Promise((resolve, reject) => {
			const ffmpegArgs = [
				"-i",
				"pipe:0",
				"-c:v",
				"libx264",
				"-profile:v",
				"high",
				"-level",
				"4.1",
				"-c:a",
				"aac",
				"-crf",
				"26",
				"-preset",
				"medium",
				"-movflags",
				"+frag_keyframe+empty_moov+default_base_moof",
				"-f",
				"mp4",
				"pipe:1",
			];

			const ff = spawn("ffmpeg", ffmpegArgs);

			const inputStream = this.isBuffer ? Readable.from(this.data) : this.data;

			inputStream.pipe(ff.stdin);

			const output = new PassThrough();
			ff.stdout.pipe(output);

			let errData = "";
			ff.stderr.on("data", (chunk) => (errData += chunk.toString()));

			ff.on("close", (code) => {
				if (code !== 0) {
					reject(new Error(`FFMPEG exited with code ${code}\n${errData}`));
				}
			});

			ff.on("error", reject);

			resolve(output);
		});
	}
}

module.exports = FFMPEG;