import { existsSync } from "node:fs";
import { mkdir, rename, rmdir } from "node:fs/promises";
import { dirname, resolve, sep } from "node:path";
import { Prisma } from "@prisma/client";
import { prisma } from "@/lib/db";
import { albumDir, yearFromPath } from "@/lib/library-path";
import { searchReleaseGroup } from "@/lib/musicbrainz";
import { removeLibraryItem } from "@/lib/library-ops";

function insideRoot(root: string, target: string): boolean {
  return target !== root && target.startsWith(root + sep);
}

// PATCH /api/library/[id] — fix an owned album's metadata: rename its folder to the canonical
// Artist/Album (Year) scheme on disk, update the LibraryItem, and re-resolve the MusicBrainz
// release-group (for cover art) when the artist/album changed. Does NOT rewrite the audio
// files' embedded tags — that's a worker (mutagen) job; Lyra reads from the folder + DB.
export async function PATCH(request: Request, { params }: { params: Promise<{ id: string }> }) {
  const { id } = await params;
  let body: unknown;
  try {
    body = await request.json();
  } catch {
    return Response.json({ error: "invalid JSON" }, { status: 400 });
  }
  const { artist, album, year } = (body ?? {}) as { artist?: unknown; album?: unknown; year?: unknown };
  const strOrUndef = (v: unknown) => (v === undefined ? undefined : typeof v === "string" ? v.trim() : null);
  const nextArtist = strOrUndef(artist);
  const nextAlbum = strOrUndef(album);
  const nextYear = strOrUndef(year); // "" clears the year; a 4-digit string sets it
  if (nextArtist === null || nextAlbum === null || nextYear === null) {
    return Response.json({ error: "artist, album, year must be strings" }, { status: 400 });
  }
  if (nextArtist === undefined && nextAlbum === undefined && nextYear === undefined) {
    return Response.json({ error: "nothing to update" }, { status: 400 });
  }
  if (nextArtist === "" || nextAlbum === "") {
    return Response.json({ error: "artist and album cannot be empty" }, { status: 400 });
  }
  if (nextYear && !/^\d{4}$/.test(nextYear)) {
    return Response.json({ error: "year must be a 4-digit year or blank" }, { status: 400 });
  }

  const item = await prisma.libraryItem.findUnique({ where: { id } });
  if (!item) return Response.json({ error: "not found" }, { status: 404 });

  const root = resolve(process.env.LYRA_LIBRARY_ROOT ?? "/music");
  const oldPath = resolve(item.path);
  if (!insideRoot(root, oldPath)) {
    return Response.json({ error: "refusing to touch a path outside the library" }, { status: 400 });
  }

  const finalArtist = nextArtist ?? item.artist;
  const finalAlbum = nextAlbum ?? item.album;
  // year isn't stored on LibraryItem; it lives only in the folder name. Keep the current
  // folder's year unless the caller passed one (empty string clears it).
  const finalYear = nextYear === undefined ? (yearFromPath(item.path) ?? undefined) : nextYear || undefined;
  const newPath = albumDir(root, finalArtist, finalAlbum, finalYear);

  if (newPath !== oldPath) {
    if (!insideRoot(root, newPath)) {
      return Response.json({ error: "refusing to write outside the library" }, { status: 400 });
    }
    if (existsSync(newPath)) {
      return Response.json({ error: "a folder for that artist/album/year already exists" }, { status: 409 });
    }
    try {
      await mkdir(dirname(newPath), { recursive: true });
      await rename(oldPath, newPath);
      const oldParent = dirname(oldPath);
      if (oldParent !== root && oldParent !== dirname(newPath)) await rmdir(oldParent).catch(() => {});
    } catch {
      return Response.json({ error: "failed to rename the album folder" }, { status: 500 });
    }
  }

  // Re-resolve the release-group when the artist/album changed (year alone doesn't change it).
  // Best-effort: on an MB outage, keep the existing rgMbid rather than dropping the cover art.
  let rgMbid = item.rgMbid;
  if (nextArtist !== undefined || nextAlbum !== undefined) {
    try {
      rgMbid = (await searchReleaseGroup(finalArtist, finalAlbum))?.rgMbid ?? null;
    } catch {
      /* keep existing rgMbid */
    }
  }

  try {
    const updated = await prisma.libraryItem.update({
      where: { id },
      data: { artist: finalArtist, album: finalAlbum, path: newPath, rgMbid },
    });
    return Response.json({ id: updated.id, artist: updated.artist, album: updated.album, path: updated.path, rgMbid: updated.rgMbid });
  } catch (e) {
    if (e instanceof Prisma.PrismaClientKnownRequestError && e.code === "P2002") {
      // moved the folder already; the (artist, album) row collides with another library item
      return Response.json({ error: "another library item already has that artist/album" }, { status: 409 });
    }
    throw e;
  }
}

// DELETE /api/library/[id] — remove an owned album: delete its folder on disk, drop the
// LibraryItem, and stop monitoring the matching release so the monitor doesn't re-grab it.
// DELETE /api/library/[id] — remove an owned album: delete its folder on disk, drop the
// LibraryItem, and stop monitoring the matching release so the monitor doesn't re-grab it.
export async function DELETE(_request: Request, { params }: { params: Promise<{ id: string }> }) {
  const { id } = await params;
  const r = await removeLibraryItem(id);
  return r.ok ? Response.json({ ok: true }) : Response.json({ error: r.error }, { status: r.status });
}