import "server-only";
import { createReadStream, createWriteStream } from "node:fs";
import { mkdir, stat, statfs, unlink, readdir, rename } from "node:fs/promises";
import { join } from "node:path";
import { tmpdir } from "node:os";
import { pipeline } from "node:stream/promises";
import { Readable, Transform } from "node:stream";
import JSZip from "jszip";
export const downloadZipDirectory = process.env.CANVAS_DOWNLOAD_ZIP_DIR || join(tmpdir(), "canvas-download-zips-v2");
const directory = downloadZipDirectory;
export async function writeDownloadZip(zip: JSZip, id: string, progress: (percent: number) => void) {
  await mkdir(directory, { recursive: true, mode: 0o700 });
  // Remove abandoned files after restart as well as expired in-process tasks.
  for (const name of await readdir(directory)) {
    const path = join(directory, name);
    const info = await stat(path).catch(() => null);
    if (info?.isFile() && name.endsWith(".partial") && info.mtimeMs < Date.now() - 60 * 60_000) await unlink(path).catch(() => undefined);
  }
  const path = join(directory, `${id}.zip`);
  const temporary = `${path}.partial`;
  try {
    const reserve = 1024 ** 3 + 32 * 1024 ** 2;
    const initialDisk = await statfs(directory);
    if (initialDisk.bavail * initialDisk.bsize < reserve)
      throw new Error("服务器下载空间不足，请减少本次图片数量");
    let sinceCheck = 8 * 1024 ** 2;
    const guard = new Transform({ transform(chunk, _encoding, callback) {
      sinceCheck += chunk.length;
      if (sinceCheck < 8 * 1024 ** 2) { callback(null, chunk); return; }
      sinceCheck = 0;
      // Input files are released as their streams close, so available disk grows
      // while the ZIP is written. Check current space instead of a stale budget.
      void statfs(directory).then(disk => {
        callback(disk.bavail * disk.bsize < reserve ? new Error("服务器下载空间不足，请减少本次图片数量") : null, chunk);
      }, error => callback(error));
    } });
    await pipeline(zip.generateNodeStream({ type: "nodebuffer", streamFiles: true, compression: "STORE" },
      metadata => progress(metadata.percent)), guard, createWriteStream(temporary, { mode: 0o600 }));
    await rename(temporary, path);
    return { path, bytes: (await stat(path)).size };
  } catch (error) { await unlink(temporary).catch(() => undefined); throw error; }
}
export function readDownloadZip(path: string, range?: { start: number; end: number }) {
  return Readable.toWeb(createReadStream(path, range)) as ReadableStream<Uint8Array>;
}
export function streamDownloadZip(zip: JSZip) {
  return Readable.toWeb(zip.generateNodeStream({ type: "nodebuffer", streamFiles: true, compression: "STORE" }) as Readable) as ReadableStream<Uint8Array>;
}
export async function removeDownloadZip(path: string) { await unlink(path).catch(() => undefined); }