import { createWriteStream, existsSync } from "node:fs";
import { mkdir, rename, rm } from "node:fs/promises";
import { resolve, join, dirname, extname } from "node:path";
import { Readable } from "node:stream";
import { pipeline } from "node:stream/promises";
import { randomUUID } from "node:crypto";
import Busboy from "busboy";
import { prisma } from "@/lib/db";
import { isAuthed } from "@/lib/auth";
import { searchReleaseGroup } from "@/lib/musicbrainz";

// Manually import an album (a ripped CD / files already on the PC): upload the audio (+ an
// optional cover) with artist/album/year, and Lyra writes it into the library. The web
// container bind-mounts /music, so it can write directly. A later library Scan MB-resolves it
// (cover art, canonical types) and re-probes quality.
//
// The body is STREAMED to disk with busboy rather than buffered via request.formData(), which
// caps out around ~15MB — real FLAC albums are hundreds of MB.

const AUDIO_EXT = new Set([".flac", ".mp3", ".m4a", ".opus", ".ogg", ".aac", ".wav"]);
const LOSSLESS_EXT = new Set([".flac", ".wav"]);
const ILLEGAL = /[<>:"/\\|?*]/g;

function safeName(s: string): string {
  const cleaned = s.replace(ILLEGAL, "_").trim().replace(/^\.+|\.+$/g, "").trim();
  return cleaned || "Unknown";
}

export async function POST(request: Request) {
  // This route is excluded from the auth middleware (to avoid the 10MB body cap), so it must
  // authenticate itself.
  if (!(await isAuthed(request))) {
    return Response.json({ error: "unauthorized" }, { status: 401 });
  }

  const ct = request.headers.get("content-type") ?? "";
  if (!ct.includes("multipart/form-data") || !request.body) {
    return Response.json({ error: "expected multipart form data" }, { status: 400 });
  }

  const root = resolve(process.env.LYRA_LIBRARY_ROOT ?? "/music");
  // stage under a hidden dir on the library filesystem so the final move is an atomic rename
  // (the scan skips dot-dirs). Cleaned up on any failure.
  const staging = join(root, `.import-${randomUUID()}`);
  await mkdir(staging, { recursive: true });

  const fields: Record<string, string> = {};
  const audioNames: string[] = [];
  let hasCover = false;

  try {
    await new Promise<void>((res, rej) => {
      const bb = Busboy({ headers: { "content-type": ct } });
      const writes: Promise<void>[] = [];
      bb.on("field", (name, val) => {
        fields[name] = val;
      });
      bb.on("file", (_name, stream, info) => {
        const ext = extname(info.filename).toLowerCase();
        if (AUDIO_EXT.has(ext)) {
          const safe = safeName(info.filename);
          audioNames.push(safe);
          writes.push(pipeline(stream, createWriteStream(join(staging, safe))));
        } else if (/\.(jpe?g|png)$/i.test(info.filename) && !hasCover) {
          hasCover = true;
          writes.push(pipeline(stream, createWriteStream(join(staging, "cover.jpg"))));
        } else {
          stream.resume(); // discard anything that isn't audio or a cover
        }
      });
      bb.on("error", rej);
      bb.on("close", () => Promise.all(writes).then(() => res(), rej));
      Readable.fromWeb(request.body as import("node:stream/web").ReadableStream).pipe(bb);
    });
  } catch {
    await rm(staging, { recursive: true, force: true });
    return Response.json({ error: "failed to write the upload to disk" }, { status: 500 });
  }

  const artist = (fields.artist ?? "").trim();
  const album = (fields.album ?? "").trim();
  const year = (fields.year ?? "").trim();
  const audio = audioNames.sort((a, b) => a.localeCompare(b));

  const bad =
    !artist || !album
      ? "artist and album are required"
      : audio.length === 0
        ? "no audio files provided"
        : year && !/^\d{4}$/.test(year)
          ? "year must be 4 digits"
          : null;
  if (bad) {
    await rm(staging, { recursive: true, force: true });
    return Response.json({ error: bad }, { status: 400 });
  }

  const albumFolder = year ? `${safeName(album)} (${year})` : safeName(album);
  const finalDir = join(root, safeName(artist), albumFolder);
  if (existsSync(finalDir) || (await prisma.libraryItem.findFirst({ where: { artist, album } }))) {
    await rm(staging, { recursive: true, force: true });
    return Response.json({ error: "this album is already in the library" }, { status: 409 });
  }

  await mkdir(dirname(finalDir), { recursive: true });
  await rename(staging, finalDir);

  // Resolve the release group so the album gets cover art immediately (best-effort — a
  // no-match just leaves rgMbid null; a later Scan can still match it). Uses the shared MB cache.
  let rgMbid: string | null = null;
  try {
    rgMbid = (await searchReleaseGroup(artist, album))?.rgMbid ?? null;
  } catch {
    /* MB unavailable — carry on without cover art */
  }

  const firstExt = extname(audio[0]).toLowerCase();
  await prisma.libraryItem.create({
    data: {
      artist,
      album,
      path: finalDir,
      source: "manual",
      format: firstExt.replace(".", "").toUpperCase(),
      // rough class from the extension (2 = CD-lossless, 1 = lossy); a later scan re-probes and
      // can upgrade a hi-res file to class 3.
      qualityClass: LOSSLESS_EXT.has(firstExt) ? 2 : 1,
      rgMbid,
      trackNames: audio,
    },
  });

  return Response.json({ ok: true, tracks: audio.length }, { status: 201 });
}