feat(app): 完善播放协议搜索与空状态

lib/core/legal/legal_article_view.dart

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+// Author: fruit.com.cn
+
+import 'package:flutter/material.dart';
+import 'package:html/dom.dart' as dom;
+import 'package:html/parser.dart' as html_parser;
+
+import '../theme/app_colors.dart';
+
+const double _bodySize = 16;
+const double _headingSize = 18;
+const double _blockGap = 12;
+const double _lineHeight = 1.7;
+
+const TextStyle _bodyStyle = TextStyle(
+  color: AppColors.textPrimary,
+  fontSize: _bodySize,
+  height: _lineHeight,
+);
+
+/// 把协议页的 HTML 正文画成普通控件。
+class LegalArticleView extends StatelessWidget {
+  const LegalArticleView({super.key, required this.html});
+
+  final String html;
+
+  @override
+  Widget build(BuildContext context) {
+    final fragment = html_parser.parseFragment(html);
+    return Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        for (final node in fragment.nodes) _block(node),
+      ],
+    );
+  }
+}
+
+Widget _block(dom.Node node) {
+  if (node is! dom.Element) {
+    return _paragraph(node.text ?? '');
+  }
+  switch (node.localName) {
+    case 'h1':
+    case 'h2':
+    case 'h3':
+      return _heading(node.text);
+    case 'ul':
+    case 'ol':
+      return _list(node);
+    case 'pre':
+      return _paragraph(node.text);
+    case 'blockquote':
+      return _paragraph(node.text);
+    default:
+      return _paragraphSpan(node);
+  }
+}
+
+Widget _heading(String text) {
+  return Padding(
+    padding: const EdgeInsets.only(bottom: _blockGap),
+    child: Text(
+      text.trim(),
+      style: const TextStyle(
+        color: AppColors.textPrimary,
+        fontSize: _headingSize,
+        height: 1.4,
+        fontWeight: FontWeight.w700,
+      ),
+    ),
+  );
+}
+
+Widget _list(dom.Element element) {
+  final items = element.children.where((child) => child.localName == 'li');
+  return Padding(
+    padding: const EdgeInsets.only(bottom: _blockGap),
+    child: Column(
+      crossAxisAlignment: CrossAxisAlignment.start,
+      children: [
+        for (final item in items)
+          Padding(
+            padding: const EdgeInsets.only(bottom: 4),
+            child: Text('• ${item.text.trim()}', style: _bodyStyle),
+          ),
+      ],
+    ),
+  );
+}
+
+Widget _paragraph(String text) {
+  final value = text.trim();
+  if (value.isEmpty) return const SizedBox.shrink();
+  return Padding(
+    padding: const EdgeInsets.only(bottom: _blockGap),
+    child: Text(value, style: _bodyStyle),
+  );
+}
+
+Widget _paragraphSpan(dom.Element element) {
+  return Padding(
+    padding: const EdgeInsets.only(bottom: _blockGap),
+    child: Text.rich(TextSpan(style: _bodyStyle, children: _inlines(element))),
+  );
+}
+
+List<InlineSpan> _inlines(dom.Node node) {
+  if (node is dom.Text) {
+    return [TextSpan(text: node.text)];
+  }
+  if (node is! dom.Element) return const [];
+  final children = node.nodes.expand(_inlines).toList();
+  switch (node.localName) {
+    case 'strong':
+    case 'b':
+      return [TextSpan(style: const TextStyle(fontWeight: FontWeight.w700), children: children)];
+    case 'em':
+    case 'i':
+      return [TextSpan(style: const TextStyle(fontStyle: FontStyle.italic), children: children)];
+    case 'a':
+      return [TextSpan(style: const TextStyle(color: AppColors.blue), children: children)];
+    case 'br':
+      return const [TextSpan(text: '\n')];
+    default:
+      return children;
+  }
+}

lib/core/legal/legal_html.dart

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+// Author: fruit.com.cn
+
+import 'package:dio/dio.dart';
+
+import '../config/app_config.dart';
+
+final RegExp _articlePattern = RegExp(
+  '<article>([\\s\\S]*)</article>',
+  caseSensitive: false,
+);
+
+/// 从协议页里取出正文。没有 article 时退回整页。
+String legalArticle(String html) {
+  final match = _articlePattern.firstMatch(html);
+  final body = match?.group(1);
+  if (body == null || body.trim().isEmpty) return html;
+  return body.trim();
+}
+
+/// 拉取协议页 HTML。不走业务 JSON 包装。
+Future<String> fetchLegalArticle(String url) async {
+  final dio = Dio(
+    BaseOptions(
+      connectTimeout: AppConfig.requestTimeout,
+      receiveTimeout: AppConfig.requestTimeout,
+      responseType: ResponseType.plain,
+      validateStatus: (code) => code != null && code >= 200 && code < 300,
+    ),
+  );
+  final response = await dio.get<String>(url);
+  final body = response.data;
+  if (body == null || body.trim().isEmpty) {
+    throw StateError('empty legal page');
+  }
+  return legalArticle(body);
+}

lib/core/legal/legal_opener.dart

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+// Author: fruit.com.cn
+
+import 'package:flutter/material.dart';
+
+import 'legal_web_page.dart';
+
+/// 在当前 App 里打开协议地址。
+Future<void> openLegalUrlOrNotify(BuildContext context, String url) {
+  return Navigator.of(context).push<void>(
+    MaterialPageRoute<void>(builder: (_) => LegalWebPage(url: url)),
+  );
+}

lib/core/legal/legal_page.dart

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+// Author: fruit.com.cn
+
+import 'package:flutter/material.dart';
+
+import '../config/app_config.dart';
+
+/// 隐私协议公开路径，对应 `/privacy/{语言}`。
+const String legalPrivacyPath = 'privacy';
+
+/// 服务条款公开路径，对应 `/terms/{语言}`。
+const String legalTermsPath = 'terms';
+
+const Set<String> _legalLanguages = {'zh', 'en', 'id'};
+
+/// 界面语言落到协议页支持的三种语言。其余语言用英文。
+String legalLanguageCode(Locale locale) {
+  final code = locale.languageCode;
+  if (_legalLanguages.contains(code)) return code;
+  return 'en';
+}
+
+/// 拼出当前服务器上的协议页地址。
+String legalPageUrl(String path, Locale locale) {
+  final base = AppConfig.apiBaseUrl;
+  final root = base.endsWith('/') ? base.substring(0, base.length - 1) : base;
+  return '$root/$path/${legalLanguageCode(locale)}';
+}

lib/core/legal/legal_web_page.dart

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+// Author: fruit.com.cn
+
+import 'package:flutter/material.dart';
+import '../../l10n/app_localizations.dart';
+import '../theme/app_colors.dart';
+import '../widgets/plain_page_scaffold.dart';
+import 'legal_article_view.dart';
+import 'legal_html.dart';
+
+const double _pagePadding = 20;
+
+/// 在应用内展示协议页，不使用系统 WebView。
+class LegalWebPage extends StatefulWidget {
+  const LegalWebPage({super.key, required this.url, this.load});
+
+  final String url;
+
+  /// 测试时可替换网络请求。
+  final Future<String> Function(String url)? load;
+
+  @override
+  State<LegalWebPage> createState() => _LegalWebPageState();
+}
+
+class _LegalWebPageState extends State<LegalWebPage> {
+  String? _html;
+  var _failed = false;
+
+  @override
+  void initState() {
+    super.initState();
+    _load();
+  }
+
+  Future<void> _load() async {
+    setState(() {
+      _html = null;
+      _failed = false;
+    });
+    try {
+      final loader = widget.load ?? fetchLegalArticle;
+      final html = await loader(widget.url);
+      if (!mounted) return;
+      setState(() => _html = html);
+    } catch (_) {
+      if (!mounted) return;
+      setState(() => _failed = true);
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return PlainPageScaffold(
+      pageKey: const Key('legal-web-page'),
+      backKey: const Key('legal-web-back'),
+      title: '',
+      child: _body(context),
+    );
+  }
+
+  Widget _body(BuildContext context) {
+    final html = _html;
+    if (html != null) {
+      return ListView(
+        padding: const EdgeInsets.fromLTRB(_pagePadding, 8, _pagePadding, 28),
+        children: [
+          LegalArticleView(html: html),
+        ],
+      );
+    }
+    if (_failed) return _failure(context);
+    return const Center(
+      child: CircularProgressIndicator(
+        key: Key('legal-web-loading'),
+        color: AppColors.blue,
+      ),
+    );
+  }
+
+  Widget _failure(BuildContext context) {
+    final l10n = AppLocalizations.of(context)!;
+    return Center(
+      child: Column(
+        mainAxisSize: MainAxisSize.min,
+        children: [
+          Text(l10n.legalOpenFailed, style: const TextStyle(color: AppColors.muted)),
+          TextButton(
+            key: const Key('legal-web-retry'),
+            onPressed: _load,
+            child: Text(l10n.retry),
+          ),
+        ],
+      ),
+    );
+  }
+}