import { createHash } from 'crypto';
import fetch from 'node-fetch';

// Try multiple community-maintained rule sources in order
const RULES_URLS = [
  'https://raw.githubusercontent.com/rafa-9/dynamic-rules/main/rules.json',
  'https://raw.githubusercontent.com/datawhores/onlyfans-dynamic-rules/main/dynamicRules.json',
  'https://raw.githubusercontent.com/DATAHOARDERS/dynamic-rules/main/onlyfans.json',
];
const REFRESH_INTERVAL = 60 * 60 * 1000; // 1 hour

let rules = null;
let lastFetch = 0;

function normalizeRules(raw) {
  // Different sources use different key names — normalize them
  return {
    static_param: raw.static_param,
    checksum_indexes: raw.checksum_indexes,
    checksum_constant: raw.checksum_constant ?? 0,
    checksum_constants: raw.checksum_constants ?? null, // per-index constants (some sources)
    app_token: raw.app_token || raw['app-token'] || '33d57ade8c02dbc5a333db99ff9ae26a',
    prefix: raw.prefix || raw.format?.split(':')[0],
    suffix: raw.suffix || raw.format?.split(':').pop(),
    remove_headers: raw.remove_headers ?? [],
  };
}

async function fetchRules() {
  for (const url of RULES_URLS) {
    try {
      const res = await fetch(url);
      if (!res.ok) continue;
      const raw = await res.json();
      rules = normalizeRules(raw);
      lastFetch = Date.now();
      console.log(`[signing] Rules loaded from ${url} (prefix: ${rules.prefix})`);
      return rules;
    } catch (err) {
      console.warn(`[signing] Failed to fetch from ${url}: ${err.message}`);
    }
  }
  throw new Error('All dynamic rules sources failed');
}

export async function initRules() {
  await fetchRules();
}

export function getRules() {
  if (Date.now() - lastFetch > REFRESH_INTERVAL) {
    fetchRules().catch((err) => console.error('[signing] Failed to refresh rules:', err.message));
  }
  return rules;
}

export function createSignedHeaders(path, userId) {
  if (!rules) throw new Error('Signing rules not initialized');

  const timestamp = Date.now().toString();

  // Use "0" for userId when user-id is in remove_headers
  const signUserId = rules.remove_headers?.includes('user-id') ? '0' : userId;
  const message = [rules.static_param, timestamp, path, signUserId].join('\n');

  const sha1Hex = createHash('sha1').update(message).digest('hex');

  const hexBytes = Buffer.from(sha1Hex, 'ascii');
  let checksum = 0;
  for (let i = 0; i < rules.checksum_indexes.length; i++) {
    const byteVal = hexBytes[rules.checksum_indexes[i]];
    const perIndex = rules.checksum_constants?.[i] ?? 0;
    checksum += byteVal + perIndex;
  }
  checksum += rules.checksum_constant;

  const sign = `${rules.prefix}:${sha1Hex}:${Math.abs(checksum).toString(16)}:${rules.suffix}`;

  return {
    sign,
    time: timestamp,
    'app-token': rules.app_token,
  };
}