import "server-only";
import { randomUUID } from "node:crypto";
import { mkdir, readFile, rename, rm, statfs, writeFile, readdir } from "node:fs/promises";
import { join } from "node:path";
import { downloadZipDirectory } from "./download-zip-stream";

export type ZipTask = {
  id: string; userId: string; folderName: string;
  files: Array<{ url: string; name?: string; prepared?: string; filename?: string; error?: string }>;
  totalCount: number; processedCount: number; successCount: number; failedCount: number;
  compressPercent: number; status: "pending" | "running" | "completed" | "failed";
  stage: string; error?: string; zipFile?: { path: string; bytes: number };
  contentDisposition?: string; cdnUrl?: string; cdnObject?: { storageConfigId: string; key: string };
  createdAt: number; updatedAt: number; expiresAt: number;
};
const validId = (id: string) => /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i.test(id);
export function zipTaskPath(id: string) {
  if (!validId(id)) throw new Error("无效的打包任务编号");
  return join(downloadZipDirectory, id);
}
export async function saveZipTask(task: ZipTask) {
  const dir = zipTaskPath(task.id);
  await mkdir(dir, { recursive: true, mode: 0o700 });
  const path = join(dir, `task-${randomUUID()}.partial`);
  // No cookies, storage credentials or provider keys are persisted.
  await writeFile(path, JSON.stringify(task), { mode: 0o600 });
  await rename(path, join(dir, "task.json"));
}
export async function loadZipTask(id: string, userId: string): Promise<ZipTask | null> {
  if (!validId(id)) return null;
  try {
    const task: ZipTask = JSON.parse(await readFile(join(zipTaskPath(id), "task.json"), "utf8"));
    if (task.userId !== userId || task.id !== id || task.expiresAt <= Date.now()) return null;
    return task;
  } catch { return null; }
}
export async function claimZipTask(id: string) {
  const dir = zipTaskPath(id); const lock = join(dir, "lock");
  await mkdir(dir, { recursive: true, mode: 0o700 });
  for (let attempt = 0; attempt < 2; attempt++) {
    try {
      await mkdir(lock, { mode: 0o700 });
      try { await writeFile(join(lock, "owner.json"), JSON.stringify({ pid: process.pid, createdAt: Date.now() }), { mode: 0o600 }); }
      catch (error) { await rm(lock, { recursive: true, force: true }); throw error; }
      return async () => { await rm(lock, { recursive: true, force: true }); };
    } catch (error) {
      if ((error as NodeJS.ErrnoException).code !== "EEXIST") throw error;
      try {
        const owner = JSON.parse(await readFile(join(lock, "owner.json"), "utf8"));
        // An older worker can finish even if a second web process handles a poll.
        try { process.kill(owner.pid, 0); return null; }
        catch (e) { if ((e as NodeJS.ErrnoException).code !== "ESRCH") return null; }
        await rm(lock, { recursive: true, force: true });
      } catch { return null; }
    }
  }
  return null;
}
export async function assertZipDiskSpace(bytes = 0) {
  const disk = await statfs(downloadZipDirectory);
  if (disk.bavail * disk.bsize < bytes + 1024 ** 3) throw new Error("服务器下载空间不足，请减少本次图片数量");
}

let cleanupAt = 0;
export async function cleanupZipTasks() {
  if (Date.now() - cleanupAt < 60_000) return;
  cleanupAt = Date.now();
  for (const id of await readdir(downloadZipDirectory).catch(() => [] as string[])) {
    if (!validId(id)) continue;
    const dir = zipTaskPath(id);
    try {
      const task: ZipTask = JSON.parse(await readFile(join(dir, "task.json"), "utf8"));
      if (task.expiresAt > Date.now()) continue;
      const release = await claimZipTask(id);
      if (!release) continue;
      try {
        if (task.cdnObject) {
          const { removeCanvasZipObject } = await import("@/lib/storage/canvas-zip-delivery");
          await removeCanvasZipObject(task.cdnObject).catch(() => undefined);
        }
        await rm(join(downloadZipDirectory, `${id}.zip`), { force: true });
        await rm(join(downloadZipDirectory, `${id}.zip.partial`), { force: true });
      } finally { await release(); }
      await rm(dir, { recursive: true, force: true });
    } catch { /* An incomplete manifest is never treated as another owner's task. */ }
  }
}
export async function assertZipTaskCapacity(userId: string) {
  let total = 0; let own = 0;
  for (const id of await readdir(downloadZipDirectory).catch(() => [] as string[])) {
    if (!validId(id)) continue;
    try {
      const task: ZipTask = JSON.parse(await readFile(join(zipTaskPath(id), "task.json"), "utf8"));
      if (task.expiresAt > Date.now() && ["pending", "running"].includes(task.status)) {
        total++; if (task.userId === userId) own++;
      }
    } catch { /* Ignore a concurrently created task until its atomic manifest exists. */ }
  }
  if (own >= 2 || total >= 8) throw new Error("正在准备的 ZIP 较多，请等待已有任务完成后再试");
}