'use strict';

const fs = require('fs');
const path = require('path');
const vm = require('node:vm');

function stripHtml(value) {
  return String(value || '')
    .replace(/<br\s*\/?>/gi, '\n')
    .replace(/<[^>]+>/g, ' ')
    .replace(/&nbsp;/g, ' ')
    .replace(/&amp;/g, '&')
    .replace(/&lt;/g, '<')
    .replace(/&gt;/g, '>')
    .replace(/&quot;/g, '"')
    .replace(/\s+/g, ' ')
    .trim();
}

function extractFaqFromLdJson(html, max = 50) {
  const re = /<script[^>]*type=["']application\/ld\+json["'][^>]*>([\s\S]*?)<\/script>/gi;
  let m;
  while ((m = re.exec(String(html)))) {
    try {
      const data = JSON.parse(m[1].trim());
      const candidates = Array.isArray(data) ? data : [data];
      for (const item of candidates) {
        const main = item && (item.mainEntity || (item['@type'] === 'FAQPage' && item.mainEntity));
        if (!Array.isArray(main)) continue;
        const out = main
          .filter((q) => q && q.name && q.acceptedAnswer && q.acceptedAnswer.text)
          .map((q) => ({ q: stripHtml(q.name), a: stripHtml(q.acceptedAnswer.text) }))
          .filter((q) => q.q && q.a)
          .slice(0, max);
        if (out.length) return out;
      }
    } catch {
      // 非 JSON-LD 块忽略
    }
  }
  return [];
}

// Nuxt SSR 页面（如 dropshipping.yehwang.com）没有 FAQPage JSON-LD，
// FAQ 数据内嵌在 window.__NUXT__ 的 payload 里（data[].info.content = [{title, content(HTML)}]）。
// 在隔离 sandbox 里求值这段自执行脚本，只取回返回对象，不接触宿主全局。
function extractNuxtPayload(html) {
  const m = String(html || '').match(/__NUXT__=([\s\S]*?)<\/script>/);
  if (!m) return null;
  try {
    return vm.runInNewContext(m[1].replace(/;\s*$/, ''), Object.create(null), { timeout: 2000 });
  } catch {
    return null;
  }
}

function extractFaqFromNuxt(html, max = 50) {
  const payload = extractNuxtPayload(html);
  if (!payload || !payload.data) return [];
  const out = [];
  const seen = new Set();
  const walk = (node) => {
    if (out.length >= max) return;
    if (Array.isArray(node)) {
      for (const item of node) walk(item);
      return;
    }
    if (!node || typeof node !== 'object') return;
    if (typeof node.title === 'string' && typeof node.content === 'string') {
      const q = stripHtml(node.title);
      const a = stripHtml(node.content);
      if (q && a && !seen.has(q)) {
        seen.add(q);
        out.push({ q, a });
      }
    }
    for (const value of Object.values(node)) {
      if (value && typeof value === 'object') walk(value);
    }
  };
  walk(payload.data);
  return out;
}

function loadFaqConfig(file) {
  try {
    return JSON.parse(fs.readFileSync(file, 'utf8'));
  } catch {
    return { enabled: false, pages: [] };
  }
}

function createFaqFetcher(config = {}) {
  const pages = config.pages || [];
  const timeoutMs = config.timeoutMs || 15000;
  const max = config.maxFaqsPerPage || 50;

  async function fetchPage(page) {
    const res = await fetch(page.url, {
      headers: { 'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0 Safari/537.36', Accept: 'text/html,application/xhtml+xml' },
      signal: AbortSignal.timeout(timeoutMs),
    });
    if (!res.ok) throw new Error(`fetch ${page.url} failed: HTTP ${res.status}`);
    const html = await res.text();
    return page.extractor === 'nuxt' ? extractFaqFromNuxt(html, max) : extractFaqFromLdJson(html, max);
  }

  async function fetchAll() {
    const out = [];
    for (const page of pages) {
      try {
        const questions = await fetchPage(page);
        out.push({ ...page, questions });
      } catch (err) {
        out.push({ ...page, questions: [], error: err.message });
      }
    }
    return out;
  }

  return { fetchPage, fetchAll, pages };
}

module.exports = { createFaqFetcher, loadFaqConfig, extractFaqFromLdJson, extractFaqFromNuxt, extractNuxtPayload, stripHtml };