#!/usr/bin/env node
import { writeFile } from 'node:fs/promises';

const DEFAULT_COUNT = 6;
const MAX_COUNT = 10;
const DEFAULT_TIMEOUT_MS = 9_000;
const DEFAULT_MAX_CHARS = 4_000;
const MAX_CHARS = 10_000;
const USER_AGENT = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123 Safari/537.36 ZhinianAssistant/0.1';

function parseArgs(argv) {
  const args = {
    query: '',
    count: DEFAULT_COUNT,
    fetchUrl: '',
    maxChars: DEFAULT_MAX_CHARS,
    output: '',
    language: 'zh-CN',
  };

  const positional = [];
  for (let index = 0; index < argv.length; index += 1) {
    const arg = argv[index];
    if (arg === '--count' || arg === '-n') {
      args.count = Number.parseInt(argv[++index] || '', 10);
    } else if (arg === '--fetch-url') {
      args.fetchUrl = argv[++index] || '';
    } else if (arg === '--max-chars') {
      args.maxChars = Number.parseInt(argv[++index] || '', 10);
    } else if (arg === '--output' || arg === '-o') {
      args.output = argv[++index] || '';
    } else if (arg === '--language' || arg === '--lang') {
      args.language = argv[++index] || args.language;
    } else if (arg === '--help' || arg === '-h') {
      printHelp();
      process.exit(0);
    } else {
      positional.push(arg);
    }
  }

  args.query = positional.join(' ').trim();
  args.count = Number.isFinite(args.count) ? Math.max(1, Math.min(MAX_COUNT, args.count)) : DEFAULT_COUNT;
  args.maxChars = Number.isFinite(args.maxChars) ? Math.max(500, Math.min(MAX_CHARS, args.maxChars)) : DEFAULT_MAX_CHARS;
  return args;
}

function printHelp() {
  process.stdout.write(`Usage:
  node search-web.mjs "<query>" [--count 6] [--output <file>]
  node search-web.mjs --fetch-url "<url>" [--max-chars 4000] [--output <file>]

Options:
  --count, -n     Number of search results to return, 1-${MAX_COUNT}.
  --fetch-url     Fetch and summarize a single page URL.
  --max-chars     Maximum returned text length in fetch mode, 500-${MAX_CHARS}.
  --output, -o    Write JSON result to a file in addition to stdout.
  --language      Accept-Language value. Default: zh-CN.
`);
}

function decodeHtml(value) {
  return String(value || '')
    .replace(/&quot;/g, '"')
    .replace(/&#34;/g, '"')
    .replace(/&#39;/g, "'")
    .replace(/&apos;/g, "'")
    .replace(/&nbsp;/g, ' ')
    .replace(/&amp;/g, '&')
    .replace(/&lt;/g, '<')
    .replace(/&gt;/g, '>');
}

function stripTags(value) {
  return decodeHtml(value)
    .replace(/<script[\s\S]*?<\/script>/gi, ' ')
    .replace(/<style[\s\S]*?<\/style>/gi, ' ')
    .replace(/<noscript[\s\S]*?<\/noscript>/gi, ' ')
    .replace(/<br\s*\/?>/gi, '\n')
    .replace(/<\/(p|div|li|h[1-6]|tr)>/gi, '\n')
    .replace(/<[^>]+>/g, ' ')
    .replace(/[ \t]+/g, ' ')
    .replace(/\n\s+/g, '\n')
    .replace(/\n{3,}/g, '\n\n')
    .trim();
}

function isHttpUrl(value) {
  try {
    const url = new URL(value);
    return url.protocol === 'http:' || url.protocol === 'https:';
  } catch {
    return false;
  }
}

function buildBingSearchUrl(query) {
  const url = new URL('https://www.bing.com/search');
  url.searchParams.set('q', query);
  url.searchParams.set('setlang', 'zh-CN');
  url.searchParams.set('mkt', 'zh-CN');
  return url.toString();
}

async function fetchText(url, language, timeoutMs = DEFAULT_TIMEOUT_MS) {
  const controller = new AbortController();
  const timer = setTimeout(() => controller.abort(), timeoutMs);
  try {
    const response = await fetch(url, {
      redirect: 'follow',
      signal: controller.signal,
      headers: {
        'User-Agent': USER_AGENT,
        'Accept': 'text/html,application/xhtml+xml,application/xml,application/json;q=0.9,text/plain;q=0.8,*/*;q=0.7',
        'Accept-Language': language || 'zh-CN',
      },
    });
    const contentType = response.headers.get('content-type') || '';
    const text = await response.text();
    if (!response.ok) {
      throw new Error(`HTTP ${response.status} ${response.statusText}`);
    }
    return { text, contentType, finalUrl: response.url, status: response.status };
  } finally {
    clearTimeout(timer);
  }
}

function normalizeBingUrl(rawUrl) {
  const url = decodeHtml(rawUrl).trim();
  if (!url) return '';
  try {
    const parsed = new URL(url);
    if (parsed.hostname.endsWith('bing.com') && parsed.pathname === '/ck/a') {
      const target = parsed.searchParams.get('u');
      if (target) {
        const decoded = target.startsWith('a1') ? Buffer.from(target.slice(2), 'base64').toString('utf8') : target;
        return isHttpUrl(decoded) ? decoded : url;
      }
    }
  } catch {
    return '';
  }
  return isHttpUrl(url) ? url : '';
}

function parseBingResults(html, count) {
  const results = [];
  const seen = new Set();
  const blocks = html.match(/<li class="b_algo"[\s\S]*?<\/li>/gi) || [];
  for (const block of blocks) {
    if (results.length >= count) break;
    const linkMatch = block.match(/<h2[^>]*>[\s\S]*?<a[^>]+href="([^"]+)"[^>]*>([\s\S]*?)<\/a>[\s\S]*?<\/h2>/i);
    if (!linkMatch) continue;
    const url = normalizeBingUrl(linkMatch[1]);
    if (!url || seen.has(url)) continue;
    seen.add(url);

    const title = stripTags(linkMatch[2]);
    const snippetMatch = block.match(/<p[^>]*>([\s\S]*?)<\/p>/i);
    const snippet = snippetMatch ? stripTags(snippetMatch[1]) : '';
    let sourceName = '';
    try {
      sourceName = new URL(url).hostname.replace(/^www\./, '');
    } catch {
      sourceName = '';
    }

    results.push({
      title,
      url,
      snippet,
      sourceName,
    });
  }
  return results;
}

function summarizeHtml(html, maxChars) {
  const titleMatch = html.match(/<title[^>]*>([\s\S]*?)<\/title>/i);
  const title = titleMatch ? stripTags(titleMatch[1]) : '';
  const text = stripTags(html).slice(0, maxChars);
  return { title, text, truncated: stripTags(html).length > maxChars };
}

async function search(args) {
  if (!args.query) {
    throw new Error('Search query is required.');
  }
  const url = buildBingSearchUrl(args.query);
  const fetched = await fetchText(url, args.language);
  return {
    status: 'ok',
    mode: 'search',
    query: args.query,
    provider: 'bing-html',
    fetchedAt: new Date().toISOString(),
    results: parseBingResults(fetched.text, args.count),
  };
}

async function fetchPage(args) {
  if (!isHttpUrl(args.fetchUrl)) {
    throw new Error('A valid http(s) --fetch-url is required.');
  }
  const fetched = await fetchText(args.fetchUrl, args.language);
  const lowerType = fetched.contentType.toLowerCase();
  const body = lowerType.includes('application/json')
    ? JSON.stringify(JSON.parse(fetched.text), null, 2).slice(0, args.maxChars)
    : lowerType.includes('text/plain')
      ? fetched.text.slice(0, args.maxChars)
      : summarizeHtml(fetched.text, args.maxChars).text;
  const htmlSummary = lowerType.includes('text/html') ? summarizeHtml(fetched.text, args.maxChars) : null;
  return {
    status: 'ok',
    mode: 'fetch',
    url: args.fetchUrl,
    finalUrl: fetched.finalUrl,
    httpStatus: fetched.status,
    contentType: fetched.contentType,
    title: htmlSummary?.title || '',
    fetchedAt: new Date().toISOString(),
    text: body,
    truncated: fetched.text.length > args.maxChars,
  };
}

async function main() {
  const args = parseArgs(process.argv.slice(2));
  const result = args.fetchUrl ? await fetchPage(args) : await search(args);
  const json = `${JSON.stringify(result, null, 2)}\n`;
  if (args.output) {
    await writeFile(args.output, json, 'utf8');
  }
  process.stdout.write(json);
}

main().catch((error) => {
  const json = `${JSON.stringify({
    status: 'error',
    error: error instanceof Error ? error.message : String(error),
    fetchedAt: new Date().toISOString(),
  }, null, 2)}\n`;
  process.stdout.write(json);
  process.exitCode = 1;
});