import { basename, extname } from "node:path";
import type { FilesDownloadQuery } from "@umt/contracts";
import type { Principal } from "../../http/auth.ts";
import { remote, remoteError } from "../../storage/vfs.ts";
import { FilesError, type FmDeps, isAdminSession, recheck, resolveIn } from "./common.ts";
import { audit } from "./ledger.ts";
import { kindOfName } from "./list.ts";
import { previewKindOf } from "./preview-parse.ts";

// GET /files/download(W5-A2):仅管理员会话;只下载 NFO/字幕/图片小文件(视频不经浏览器,规格 §1 边界);
// 路径守卫同其它接口(realpath 在根内、符号链接目标也须在根内,打开前再复核一次);
// 打开后按文件句柄再 stat,校验的就是要流出去的那个文件;流式返回,写审计。

const ALLOWED = new Set(["nfo", "subtitle", "image"]);

const MIME: Record<string, string> = {
  jpg: "image/jpeg",
  jpeg: "image/jpeg",
  png: "image/png",
  gif: "image/gif",
  webp: "image/webp",
  bmp: "image/bmp",
  avif: "image/avif",
  torrent: "application/x-bittorrent",
  nfo: "text/plain; charset=utf-8",
  xml: "text/plain; charset=utf-8",
  srt: "text/plain; charset=utf-8",
  ass: "text/plain; charset=utf-8",
  ssa: "text/plain; charset=utf-8",
  vtt: "text/plain; charset=utf-8",
  sub: "text/plain; charset=utf-8",
  sup: "application/octet-stream",
  idx: "text/plain; charset=utf-8",
};

/** RFC 6266 / 5987:ASCII 兜底名 + UTF-8 原名 */
function disposition(kind: "inline" | "attachment", name: string): string {
  const ascii = name.replace(/[^\x20-\x7e]|["\\]/g, "_");
  return `${kind}; filename="${ascii}"; filename*=UTF-8''${encodeURIComponent(name)}`;
}

export async function downloadFile(
  d: FmDeps,
  principal: Principal | undefined,
  q: FilesDownloadQuery,
): Promise<Response> {
  // 路由中间件已按 auth:"session" 拦截;这里同口径复核(纵深防御)
  if (!isAdminSession(principal))
    throw new FilesError("forbidden", "下载仅限控制台管理员会话，API Key / DEV key 不可用");
  const r = await resolveIn(d, q.root, q.path);
  if (r.rel === "" || r.lst?.isDirectory()) throw new FilesError("bad_request", "只能下载文件，不能下载目录");
  const name = basename(r.abs);
  const kind = kindOfName(name);
  // FM-2:可预览的文本类(txt/log/md/json…)、.torrent、avif/gif 也允许下载
  const pk = previewKindOf(name);
  if (!ALLOWED.has(kind) && !pk)
    throw new FilesError("forbidden", `只能下载 NFO、字幕、图片、文本和 .torrent，此文件类型为 ${kind}`);
  const real = await recheck(r.abs, r.rootReal);
  if (r.def.storageId) return downloadRemote(d, principal, q, r.rel, real, name, kind, pk);
  const file = await Deno.open(real, { read: true });
  let size: number;
  try {
    const st = await file.stat();
    if (!st.isFile) throw new FilesError("bad_request", "不是普通文件");
    size = st.size;
    if (size > d.options.downloadMaxBytes)
      throw new FilesError(
        "too_large",
        `文件 ${size} 字节，超过下载上限 ${d.options.downloadMaxBytes}(FILES_DOWNLOAD_MAX_BYTES)`,
      );
  } catch (e) {
    file.close();
    throw e;
  }
  const ext = extname(name).replace(/^\./, "").toLowerCase();
  // SVG 可带脚本:不内联、不给 image/svg+xml
  const inline = q.inline && (kind === "image" || pk === "image") && ext !== "svg";
  await audit(d, principal, "download", { root: q.root, path: r.rel, size, inline });
  return new Response(file.readable, {
    status: 200,
    headers: {
      "content-type": (ext !== "svg" && MIME[ext]) || "application/octet-stream",
      "content-length": String(size),
      "content-disposition": disposition(inline ? "inline" : "attachment", name),
      "x-content-type-options": "nosniff",
      "content-security-policy": "default-src 'none'; sandbox",
      "cache-control": "private, no-store",
    },
  });
}

/** Alist 文件:经服务端流式转发(不落本地盘,同一下载上限与类型限制;MP 是先下到临时目录再回传) */
async function downloadRemote(
  d: FmDeps,
  principal: Principal | undefined,
  q: FilesDownloadQuery,
  rel: string,
  abs: string,
  name: string,
  kind: string,
  pk: ReturnType<typeof previewKindOf>,
): Promise<Response> {
  const { v, client } = await remote(abs);
  let size: number;
  let res: Response;
  try {
    const o = await client.get(v.remote);
    if (o.isDir) throw new FilesError("bad_request", "只能下载文件，不能下载目录");
    size = o.size;
    if (size > d.options.downloadMaxBytes)
      throw new FilesError(
        "too_large",
        `文件 ${size} 字节，超过下载上限 ${d.options.downloadMaxBytes}(FILES_DOWNLOAD_MAX_BYTES)`,
      );
    res = await client.openRead(v.remote);
  } catch (e) {
    if (e instanceof FilesError) throw e;
    throw remoteError(e, abs);
  }
  const ext = extname(name).replace(/^\./, "").toLowerCase();
  const inline = q.inline && (kind === "image" || pk === "image") && ext !== "svg";
  await audit(d, principal, "download", { root: q.root, path: rel, size, inline });
  return new Response(res.body, {
    status: 200,
    headers: {
      "content-type": (ext !== "svg" && MIME[ext]) || "application/octet-stream",
      ...(size ? { "content-length": String(size) } : {}),
      "content-disposition": disposition(inline ? "inline" : "attachment", name),
      "x-content-type-options": "nosniff",
      "content-security-policy": "default-src 'none'; sandbox",
      "cache-control": "private, no-store",
    },
  });
}