import { ERROR_TERMINATED } from "./ffmpeg/package/dist/esm/errors.js";

export class VideoCompressor {
	constructor(progressBar) {
		this.progressBar = progressBar;
		this.ffmpeg = new FFmpegWASM.FFmpeg();
		this.inProgress = false;
	}

	async compress(file, filesizeBytes, duration) {
		this.progressBar.setStatus("Initializing...");
		this.inProgress = true;

		const progressCallback = event => this.progressBar.setProgress(event.progress);
		this.ffmpeg.on("progress", progressCallback);

		const filesizeKbit = filesizeBytes * 0.008;

		// Calculate target bitrate to create a video file with desired file size (https://trac.ffmpeg.org/wiki/Encode/H.264#twopass)
		let bitrate = filesizeKbit / duration;
		bitrate -= 128; // Subtract audio bitrate
		bitrate -= (bitrate / 100) * 5; // Subtract 5% to compensate for overhead
		bitrate = Math.floor(bitrate);

		if (bitrate <= 0) {
			this.inProgress = false;
			throw new Error("Selected file size is too low for this video");
		}

		console.debug("Target bitrate:", bitrate, "Video length:", duration);

		// Run compression
		try {
			await this.ffmpeg.load({ coreURL: "/assets/scripts/core/package/dist/umd/ffmpeg-core.js" });

			await this.ffmpeg.writeFile(file.name, await this.readFromBlob(file));

			await this.ffmpeg.exec(["-i", file.name, "-preset", "ultrafast", "-c:v", "libx264", "-b:v", bitrate + "k", "-c:a", "copy", "-b:a", "128k", "compressed.mp4"]);
		} catch (e) {
			// Ignore termination error
			if (e.message === ERROR_TERMINATED.message) {
				this.inProgress = false;
				return null;
			}

			throw e;
		}

		const video = await this.ffmpeg.readFile("compressed.mp4");
		const resultFile = new File([video.buffer], this.generateFileName(file.name), { type: "video/mp4" });

		// Clean up
		this.ffmpeg.off("progress", progressCallback);
		this.inProgress = false;

		return resultFile;
	}

	stop() {
		this.ffmpeg.terminate();
		this.inProgress = false;
	}

	generateFileName(filename) {
		let name = filename.replace(/\.\w+$/, "");

		if (/\s/.test(name)) name += " compressed";
		else name += "_compressed";

		return name + ".mp4";
	}

	// https://github.com/ffmpegwasm/ffmpeg.wasm/blob/main/packages/util/src/index.ts
	readFromBlob(blob) {
		return new Promise((resolve, reject) => {
			const fileReader = new FileReader();

			fileReader.onload = () => {
				const { result } = fileReader;
				if (result instanceof ArrayBuffer) {
					resolve(new Uint8Array(result));
				} else {
					resolve(new Uint8Array());
				}
			};

			fileReader.onerror = (event) => {
				reject(Error(`File could not be read! Code=${event?.target?.error?.code || -1}`));
			};

			fileReader.readAsArrayBuffer(blob);
		});
	}
}