import 'dart:convert';

import 'school_navigation_policy.dart';

/// Only serialize recognized table fragments, never a login document.
const schoolPageProbeScript = r'''(() => {
  const trusted = value => {
    try {
      const u = new URL(value);
      return u.hostname === 'yjsjy.uestc.edu.cn' && !u.username && !u.password &&
        ((u.protocol === 'https:' && (!u.port || u.port === '443')) ||
         (u.protocol === 'http:' && (!u.port || u.port === '80'))) &&
        /^\/pyxx(?:\/|$)/.test(u.pathname);
    } catch (_) { return false; }
  };
  const topUrl = location.href;
  const result = {topUrl, authenticated: false, pages: []};
  if (!trusted(topUrl) || document.querySelector('input[type="password"]')) {
    return JSON.stringify(result);
  }
  const topOrigin = new URL(topUrl).origin;
  const home = /^\/pyxx\/home\/(?:index)?\/?$/.test(location.pathname);
  const chrome = document.querySelector('#navbar') && document.querySelector('#main-container');
  result.authenticated = typeof window.logout === 'function' && Boolean(chrome || home);
  const seen = new Set();
  const visit = (doc, depth) => {
    if (!doc || depth > 4 || seen.size >= 16 || seen.has(doc)) return;
    seen.add(doc);
    let url;
    try { url = doc.location.href; } catch (_) { return; }
    if (!trusted(url) || new URL(url).origin !== topOrigin ||
        doc.querySelector('input[type="password"]')) return;
    for (const [kind, tableId, termId] of [
      ['timetable', '#tbl', '#drpxq'], ['exams', '#sample-table-1', '#xqbh']
    ]) {
      const table = doc.querySelector(tableId), term = doc.querySelector(termId);
      if (!table || !term || !term.options || term.selectedIndex < 0) continue;
      const selected = term.cloneNode(true);
      Array.from(selected.options).forEach((option, index) => {
        if (index === term.selectedIndex) option.setAttribute('selected', 'selected');
        else option.removeAttribute('selected');
      });
      const html = selected.outerHTML + table.outerHTML;
      if (html.length <= 2 * 1024 * 1024) result.pages.push({kind, url, html});
    }
    for (const frame of doc.querySelectorAll('iframe,frame')) {
      try { visit(frame.contentDocument, depth + 1); } catch (_) {}
    }
  };
  visit(document, 0);
  return JSON.stringify(result);
})()''';

class SchoolTableFragment {
  const SchoolTableFragment(this.kind, this.url, this.html);
  final String kind;
  final Uri url;
  final String html;
}

class SchoolPageEvidence {
  const SchoolPageEvidence(this.authenticated, this.pages);
  final bool authenticated;
  final List<SchoolTableFragment> pages;

  static SchoolPageEvidence decode(Object raw, Uri current) {
    dynamic value = raw;
    for (var i = 0; i < 2 && value is String; i++) {
      value = jsonDecode(value);
    }
    if (value is! Map ||
        value['topUrl'] != current.toString() ||
        !SchoolNavigationPolicy.isGraduatePage(current)) {
      throw const FormatException('Untrusted school page evidence');
    }
    final pages = <SchoolTableFragment>[];
    final candidates = value['pages'];
    if (candidates is List && candidates.length <= 32) {
      for (final page in candidates) {
        if (page is! Map || page['url'] is! String || page['html'] is! String) {
          continue;
        }
        final uri = Uri.tryParse(page['url'] as String);
        final content = page['html'] as String;
        if (uri == null ||
            !SchoolNavigationPolicy.isGraduatePage(uri) ||
            uri.origin != current.origin ||
            utf8.encode(content).length > 2 * 1024 * 1024 ||
            !const ['timetable', 'exams'].contains(page['kind'])) {
          continue;
        }
        pages.add(SchoolTableFragment(page['kind'] as String, uri, content));
      }
    }
    return SchoolPageEvidence(value['authenticated'] == true, pages);
  }
}