import superjson from "superjson";
import { schema, type OutputType } from "./lyrics_POST.schema";

type LrclibResult = {
  plainLyrics?: string | null;
  syncedLyrics?: string | null;
  instrumental?: boolean;
};

function delay(ms: number) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

export async function handle(request: Request) {
  try {
    const input = schema.parse(superjson.parse(await request.text()));
    const params = new URLSearchParams({
      artist_name: input.artist,
      track_name: input.title,
    });
    if (input.album) params.set("album_name", input.album);
    if (input.durationMs) {
      params.set("duration", String(Math.round(input.durationMs / 1000)));
    }
    let response: Response | undefined;
    for (let attempt = 0; attempt < 2; attempt += 1) {
      response = await fetch(`https://lrclib.net/api/get?${params.toString()}`, {
        headers: { "User-Agent": "Aurora-SpotiRip/1.0" },
      });
      if (response.status !== 429 || attempt > 0) break;
      const retryAfter = Number(response.headers.get("retry-after") || 1);
      await delay(Math.min(5000, Math.max(500, retryAfter * 1000)));
    }
    if (!response) {
      throw new Error("Lyrics service did not respond.");
    }
    if (response.status === 404) {
      return new Response(superjson.stringify({} satisfies OutputType));
    }
    if (!response.ok) {
      return new Response(
        superjson.stringify({ error: `Lyrics service returned HTTP ${response.status}.` }),
        { status: 502 },
      );
    }
    const result = (await response.json()) as LrclibResult;
    const output: OutputType = {
      plain: result.plainLyrics || undefined,
      synced: result.syncedLyrics || undefined,
      instrumental: Boolean(result.instrumental),
    };
    return new Response(superjson.stringify(output));
  } catch (error) {
    const message = error instanceof Error ? error.message : "Unable to load lyrics.";
    return new Response(superjson.stringify({ error: message }), { status: 400 });
  }
}