export const SEARCH_ERROR_CODES = Object.freeze({ CAPABILITY_DISABLED: 'CAPABILITY_DISABLED', INVALID_REQUEST: 'INVALID_REQUEST', PROVIDER_UNAVAILABLE: 'PROVIDER_UNAVAILABLE', UNSAFE_URL: 'UNSAFE_URL' });

export function validateSearchRequest(input = {}) {
  const query = String(input.query ?? '').trim();
  if (!query || query.length > 500) return { ok: false, code: SEARCH_ERROR_CODES.INVALID_REQUEST, message: 'query must be 1-500 characters' };
  const limit = Math.max(1, Math.min(20, Number(input.limit ?? 10) || 10));
  return { ok: true, value: { query, type: String(input.type ?? 'web'), limit } };
}

/** provider 返回的配图字段名不统一，统一取第一个安全的 https 地址。 */
function pickResultImage(result = {}) {
  for (const candidate of [result.image, result.img_src, result.thumbnail_src, result.thumbnail]) {
    const value = String(candidate ?? '').trim();
    if (value.startsWith('https://') && isSafeHttpUrl(value)) return value.slice(0, 1000);
  }
  return '';
}

export function normalizeSearchResult(result = {}, index = 0) {
  const image = pickResultImage(result);
  const publishedAt = String(result.publishedAt ?? result.publishedDate ?? '').trim().slice(0, 40);
  return {
    title: String(result.title ?? '').trim(),
    url: String(result.url ?? '').trim(),
    snippet: String(result.snippet ?? result.content ?? '').trim().slice(0, 2000),
    source: String(result.source ?? 'unknown'),
    rank: index + 1,
    ...(image ? { image } : {}),
    ...(publishedAt ? { publishedAt } : {}),
  };
}

export function buildCitations(results = []) {
  return results.filter((item) => item.url).map((item, index) => ({ id: `[${index + 1}]`, title: item.title, url: item.url, source: item.source }));
}

export function isSafeHttpUrl(value) {
  try { const url = new URL(value); return ['http:', 'https:'].includes(url.protocol) && !['localhost', '127.0.0.1', '::1'].includes(url.hostname); } catch { return false; }
}