import { deserialize } from 'bson';
import type { TTSMod } from '@tts/shared';
import { ItemNotFoundError, NoFileError, SteamApiError } from './errors.js';

const STEAM_API_URL =
  'https://api.steampowered.com/ISteamRemoteStorage/GetPublishedFileDetails/v1/';

interface SteamPublishedFileDetails {
  publishedfileid: string;
  title: string;
  creator: string;
  preview_url: string;
  file_url?: string;
  description?: string;
  tags?: { tag: string }[];
  time_created?: number;
  time_updated?: number;
}

interface SteamResponse {
  response: {
    result: number;
    resultcount: number;
    publishedfiledetails?: SteamPublishedFileDetails[];
  };
}

/**
 * Fetch a full TTS save for a Workshop item and BSON-deserialize it.
 *
 * @param id Workshop item ID (digits only).
 * @param apiKey Steam Web API key.
 */
export async function fetchMod(id: string, apiKey: string): Promise<TTSMod> {
  const fileUrl = await getFileUrl(id, apiKey);
  return fetchModFromUrl(fileUrl);
}

/**
 * Download a TTS save from a direct URL and BSON-deserialize it.
 *
 * @param fileUrl Direct URL to the save file (e.g. from a search result).
 */
export async function fetchModFromUrl(fileUrl: string): Promise<TTSMod> {
  const buffer = await downloadSave(fileUrl);
  return deserialize(new Uint8Array(buffer)) as TTSMod;
}

/**
 * Derive a filename from a `content-disposition` header.
 * Parses `filename="..."`; falls back to the URL path, then a default.
 */
export function getFileName(url: string, disposition: string | null): string {
  if (disposition) {
    const match = disposition.match(/filename\*?=(?:"([^"]*)"|([^;\s]*))/i);
    const name = match?.[1] ?? match?.[2];
    if (name) {
      return name;
    }
  }
  return new URL(url).pathname.split('/').pop() || 'save.json';
}

/**
 * Fetch the raw save file bytes for a Workshop item.
 * Returns the bytes plus a derived filename.
 */
export async function fetchModFile(
  id: string,
  apiKey: string,
): Promise<{ data: ArrayBuffer; filename: string }> {
  const fileUrl = await getFileUrl(id, apiKey);
  return fetchModFileFromUrl(fileUrl);
}

/**
 * Fetch the raw save file bytes from a direct URL.
 * Returns the bytes plus a derived filename.
 */
export async function fetchModFileFromUrl(
  fileUrl: string,
): Promise<{ data: ArrayBuffer; filename: string }> {
  const data = await downloadSave(fileUrl);
  const filename = getFileName(fileUrl, null);
  return { data, filename };
}

/** Download a save file's bytes from a URL, throwing on failure. */
async function downloadSave(fileUrl: string): Promise<ArrayBuffer> {
  const res = await fetch(fileUrl);
  if (!res.ok) {
    throw new SteamApiError(
      `Failed to download save file (${res.status})`,
      502,
    );
  }
  return res.arrayBuffer();
}

/** Resolve the `file_url` for a Workshop item via the Steam API. */
async function getFileUrl(id: string, apiKey: string): Promise<string> {
  const params = new URLSearchParams();
  params.append('key', apiKey);
  params.append('itemcount', '1');
  params.append('publishedfileids[0]', id);

  const res = await fetch(STEAM_API_URL, {
    method: 'POST',
    body: params,
  });
  if (!res.ok) {
    throw new SteamApiError(`Steam API responded ${res.status}`, 502);
  }

  const json = (await res.json()) as SteamResponse;
  const details = json.response.publishedfiledetails?.[0];
  if (!details) {
    throw new ItemNotFoundError(id);
  }
  if (!details.file_url) {
    throw new NoFileError(id);
  }
  return details.file_url;
}

export * from './errors.js';