const ws = new WebSocket(Deno.args[0])

export class TextLineStream extends TransformStream<string, string> {
    line = "";
    constructor() {
        super({
            transform: (chunk, controller) => {
                this.line += chunk;
                while (true) {
                    const newline = this.line.indexOf("\n");
                    if (newline === -1) break;
                    controller.enqueue(this.line.slice(0, newline));
                    this.line = this.line.slice(newline + 1);
                }
            },
            flush: (controller) => {
                if (this.line === "") return;
                controller.enqueue(this.line);
            },
        });
    }
}

function key_to_url(key: string): string {
    const [kind, id] = key.split(":", 2)
    if (kind == "youtube") return `https://youtube.com/watch?v=${id}`
    throw new Error("unknown kind");
}

async function do_download(key: string, output: string) {
    const url = key_to_url(key)
    await Deno.mkdir(output, { recursive: true })
    const child = new Deno.Command("yt-dlp", {
        args: [
            "--quiet",
            "--progress",
            "--progress-template", "%(progress)j",
            "--newline",
            "--download-archive", "archive",
            "-f", "bestvideo+bestaudio",
            "--embed-metadata",
            "--embed-thumbnail",
            "--embed-info-json",
            "--embed-subs",
            "--embed-chapters",
            "--ignore-no-formats",
            "--remux", "mkv",
            "-o", "%(id)s",
            url
        ],
        stdout: "piped",
        stderr: "inherit",
        cwd: output
    }).spawn()

    const lines = child.stdout.pipeThrough(new TextDecoderStream()).pipeThrough(new TextLineStream())
    for await (const line of lines) {
        if (!line.length) continue
        console.log(JSON.stringify(line));
        const k = JSON.parse(line)
        ws.send(JSON.stringify({
            t: "metadata", key, data: {
                progress: (k._percent ?? 0) / 100,
                status: k._default_template?.trim() ?? ""
            }
        }))
    }
    const status = await child.status
    if (!status.success) throw new Error("download failed");

    ws.send(JSON.stringify({ t: "complete", key }))
}

ws.onerror = () => console.error("ws error")
ws.onclose = () => console.error("ws closed")
ws.onopen = () => {
    console.log("ws open");
    ws.send(JSON.stringify({ t: "register", name: "yt-dlp video downloader", task_kinds: ["youtube"] }))
    ws.send(JSON.stringify({ t: "accept" }))
}
ws.onmessage = async ev => {
    if (typeof ev.data != "string") return
    const p = JSON.parse(ev.data)
    if (p.t == "error") console.error(`error: ${p.message}`);
    if (p.t == "work") {
        if (!p.data.output) throw new Error("no output");
        await do_download(p.key, p.data.output)
        ws.send(JSON.stringify({ t: "accept" }))
    }
}