import "server-only";
import { randomUUID } from "node:crypto";
import { fetchImageBytes, cacheImageBytes } from "./image-byte-cache";
import { normalizeCanvasDownloadAsset } from "@/lib/canvas/photoshop-safe-download";
import { claimImageDownloadTask, saveImageDownloadAsset, getImageDownloadTasks } from "./image-archive-db";
import { uploadFile } from "./service";

export async function prepareImageArchiveDownload(id: string) {
  const task = await claimImageDownloadTask(id);
  if (!task?.targetUrl) return;
  try {
    const source = await fetchImageBytes(task.targetUrl);
    const asset = await normalizeCanvasDownloadAsset({
      item: { url: task.targetUrl }, index: 0, bytes: source.buffer,
      contentType: source.contentType, includeSequencePrefix: false,
    });
    if (!asset.ok) throw new Error(asset.error);
    // An already compatible PNG shares the original object; other formats get
    // one prepared PNG, without changing the original dimensions or transparency.
    const url = source.buffer.equals(asset.bytes) && asset.contentType === "image/png"
      ? task.targetUrl
      : (await uploadFile(`canvas-download-${randomUUID()}.${asset.filename.split(".").pop() || "png"}`, Uint8Array.from(asset.bytes).buffer)).url;
    await saveImageDownloadAsset(id, { status: "ready", url, bytes: asset.bytes.length,
      contentType: asset.contentType, preparedAt: new Date().toISOString() });
    await cacheImageBytes(`source::${url}`, { buffer: asset.bytes, contentType: asset.contentType });
  } catch {
    const attempts = Number((task.metadata as { downloadAsset?: { attempts?: number } } | null)?.downloadAsset?.attempts || 1);
    await saveImageDownloadAsset(id, { status: attempts >= 12 ? "abandoned" : "failed", attempts, retryAt: new Date(Date.now() + 10 * 60_000).toISOString() });
  }
}
export async function preparePendingImageDownloads() {
  const tasks = await getImageDownloadTasks();
  let cursor = 0;
  await Promise.all(Array.from({ length: Math.min(2, tasks.length) }, async () => {
    while (cursor < tasks.length) await prepareImageArchiveDownload(tasks[cursor++].id);
  }));
  return tasks.length;
}