// The qBittorrent API client — qbittorrent's own code, living in the module (novox/hq ADR 0039).
// Written against the WebUI API (/api/v2/...), self-contained so a change to it rebuilds only
// qbittorrent. Both this module's tools and its events entrypoint import it, and nothing outside
// qbittorrent does.
//
// The WebUI authenticates with a session cookie (SID) obtained by POSTing credentials, and guards
// against CSRF by checking the Referer header. Node's fetch keeps no cookie jar, so the SID is
// captured on login and carried by hand on every later call, with a single re-login on expiry.

import { readFileSync } from "node:fs";

export interface QbTransferInfo {
  dlSpeedBytesPerSec: number;
  upSpeedBytesPerSec: number;
  dlData: number;
  upData: number;
  connectionStatus: string;
}

export interface QbTorrent {
  hash: string;
  name: string;
  /** qBittorrent's state, e.g. "downloading", "stalledUP", "uploading", "pausedUP", "error". */
  state: string;
  /** 0..1 — 1 means the download is complete. */
  progress: number;
  sizeBytes: number;
  dlSpeed: number;
  upSpeed: number;
  category: string;
  ratio: number;
  savePath: string;
}

/** The settings-merged config the mesh delivers (novox/hq ADR 0046): { url, apiKey, token, password, user, ... }. */
function meshConfig(file?: string): Record<string, string> {
  if (!file) return {};
  try { return JSON.parse(readFileSync(file, "utf8")) as Record<string, string>; }
  catch { return {}; }
}

/** Read a secret the mesh mounted at a file path (an own-secret delivered by `secret accept`);
 *  absent or unreadable yields undefined so callers fall back rather than crash. */
function readSecret(file?: string): string | undefined {
  if (!file) return undefined;
  try { return readFileSync(file, "utf8").trim(); }
  catch { return undefined; }
}

export class QbittorrentClient {
  readonly baseUrl: string;
  private sid: string | null = null;

  constructor(
    baseUrl: string,
    private readonly user: string,
    private readonly password: string,
  ) {
    this.baseUrl = baseUrl.replace(/\/$/, "");
  }

  /**
   * Build from the module's resolved environment. URL and password are read from
   * MESH_QBITTORRENT_URL and MESH_QBITTORRENT_PASSWORD; both must be present — an unconfigured
   * qBittorrent throws rather than pretend to be reachable, so the tools/events simply do not load
   * (the harness treats the throw as "exposes nothing"). The user defaults to "admin".
   */
  static fromEnv(env: NodeJS.ProcessEnv = process.env): QbittorrentClient {
    const cfg = meshConfig(env.MESH_QBITTORRENT_CONFIG_FILE);
    const url = cfg.url ?? env.MESH_QBITTORRENT_URL;
    const password = cfg.password ?? readSecret(env.MESH_QBITTORRENT_PASSWORD_FILE) ?? env.MESH_QBITTORRENT_PASSWORD;
    if (!url || !password) {
      throw new Error("qBittorrent not configured — set MESH_QBITTORRENT_URL and MESH_QBITTORRENT_PASSWORD");
    }
    const user = cfg.user ?? env.MESH_QBITTORRENT_USER ?? "admin";
    return new QbittorrentClient(url, user, password);
  }

  private async login(): Promise<void> {
    const res = await fetch(`${this.baseUrl}/api/v2/auth/login`, {
      method: "POST",
      headers: { "Content-Type": "application/x-www-form-urlencoded", Referer: this.baseUrl },
      body: new URLSearchParams({ username: this.user, password: this.password }),
    });
    if (!res.ok) throw new Error(`qBittorrent login: ${res.status} ${await res.text()}`);
    if ((await res.text()).trim() !== "Ok.") {
      throw new Error("qBittorrent login rejected — check credentials");
    }
    const match = res.headers.get("set-cookie")?.match(/SID=([^;]+)/);
    if (!match) throw new Error("qBittorrent login returned no SID cookie");
    this.sid = match[1];
  }

  private async call(method: "GET" | "POST", path: string, form?: Record<string, string>): Promise<Response> {
    if (!this.sid) await this.login();
    const doFetch = (): Promise<Response> => {
      const headers: Record<string, string> = { Referer: this.baseUrl, Cookie: `SID=${this.sid}` };
      const init: RequestInit = { method, headers };
      if (form) {
        headers["Content-Type"] = "application/x-www-form-urlencoded";
        init.body = new URLSearchParams(form);
      }
      return fetch(`${this.baseUrl}/api/v2/${path}`, init);
    };
    let res = await doFetch();
    if (res.status === 403) {
      // The SID expired — re-authenticate once and retry, rather than fail a routine call.
      await this.login();
      res = await doFetch();
    }
    return res;
  }

  private async getJson<T>(path: string): Promise<T> {
    const res = await this.call("GET", path);
    if (!res.ok) throw new Error(`qBittorrent GET ${path}: ${res.status} ${await res.text()}`);
    return (await res.json()) as T;
  }

  async getVersion(): Promise<string> {
    const res = await this.call("GET", "app/version");
    if (!res.ok) throw new Error(`qBittorrent app/version: ${res.status}`);
    return (await res.text()).trim();
  }

  async getTransferInfo(): Promise<QbTransferInfo> {
    const d = await this.getJson<Record<string, any>>("transfer/info");
    return {
      dlSpeedBytesPerSec: Number(d.dl_info_speed ?? 0),
      upSpeedBytesPerSec: Number(d.up_info_speed ?? 0),
      dlData: Number(d.dl_info_data ?? 0),
      upData: Number(d.up_info_data ?? 0),
      connectionStatus: String(d.connection_status ?? "unknown"),
    };
  }

  async getTorrents(filter?: string): Promise<QbTorrent[]> {
    const path = filter ? `torrents/info?filter=${encodeURIComponent(filter)}` : "torrents/info";
    const list = await this.getJson<Record<string, any>[]>(path);
    return list.map((t) => ({
      hash: String(t.hash),
      name: String(t.name ?? "Unknown"),
      state: String(t.state ?? "unknown"),
      progress: Number(t.progress ?? 0),
      sizeBytes: Number(t.size ?? 0),
      dlSpeed: Number(t.dlspeed ?? 0),
      upSpeed: Number(t.upspeed ?? 0),
      category: String(t.category ?? ""),
      ratio: Number(t.ratio ?? 0),
      savePath: String(t.save_path ?? ""),
    }));
  }

  /** Add a torrent by magnet or http(s) .torrent URL, optionally into a category / save path. */
  async add(url: string, category = "", savepath = "", paused = false): Promise<void> {
    const form: Record<string, string> = { urls: url, paused: paused ? "true" : "false" };
    if (category) form.category = category;
    if (savepath) form.savepath = savepath;
    const res = await this.call("POST", "torrents/add", form);
    const text = (await res.text()).trim();
    if (!res.ok || text.toLowerCase() === "fails.") {
      throw new Error(`qBittorrent refused the torrent: ${res.status} ${text}`);
    }
  }

  // qBittorrent 5.x renamed pause/resume to stop/start; try the modern name and fall back to the
  // legacy one on a 404, so the client works against both.
  private async command(modern: string, legacy: string, hashes: string): Promise<void> {
    let res = await this.call("POST", `torrents/${modern}`, { hashes });
    if (res.status === 404) res = await this.call("POST", `torrents/${legacy}`, { hashes });
    if (!res.ok) throw new Error(`qBittorrent torrents/${modern}: ${res.status} ${await res.text()}`);
  }

  /** Pause torrents — a pipe-separated hash list, or "all" (the default). */
  async pause(hashes = "all"): Promise<void> {
    await this.command("stop", "pause", hashes);
  }

  /** Resume torrents — a pipe-separated hash list, or "all" (the default). */
  async resume(hashes = "all"): Promise<void> {
    await this.command("start", "resume", hashes);
  }

  async delete(hashes: string, deleteFiles = false): Promise<void> {
    const res = await this.call("POST", "torrents/delete", { hashes, deleteFiles: deleteFiles ? "true" : "false" });
    if (!res.ok) throw new Error(`qBittorrent torrents/delete: ${res.status} ${await res.text()}`);
  }
}