import 'dart:convert';

enum DeepLinkSource { push, appLink, universalLink, customScheme }

typedef DeepLinkNavigator = bool Function(String location);
typedef DeepLinkAuthGuard = bool Function(String location);

class DeepLinkEvent {
  const DeepLinkEvent({
    required this.raw,
    required this.source,
    required this.receivedAt,
    this.eventId,
  });

  final String raw;
  final DeepLinkSource source;
  final DateTime receivedAt;
  final String? eventId;
}

/// Source adapters feed one parser and a bounded FIFO. Navigation starts only
/// after GoRouter has a context and the auth guard accepts the target.
abstract final class DeepLinkService {
  static const maxPending = 20;
  static const expiry = Duration(minutes: 15);
  static const _environmentHosts = String.fromEnvironment(
    'JINZHI_DEEP_LINK_HOSTS',
  );

  static final List<DeepLinkEvent> _pending = [];
  static final Set<String> _pendingEventIds = {};
  static final Map<String, DateTime> _seenEventIds = {};
  static final Set<String> _configuredHttpsHosts = _normalizedHosts(
    _environmentHosts.split(','),
  );
  static Set<String> _trustedHttpsHosts = {..._configuredHttpsHosts};
  static DeepLinkNavigator? _navigator;
  static DeepLinkAuthGuard _authGuard = (_) => true;

  static int get pendingCount => _pending.length;

  static void handle(String raw) => enqueue(raw, source: DeepLinkSource.push);

  static void handleUri(Uri uri) => enqueue(
    uri.toString(),
    source: uri.scheme.toLowerCase() == 'jinzhi'
        ? DeepLinkSource.customScheme
        : DeepLinkSource.universalLink,
  );

  static void enqueue(
    String raw, {
    required DeepLinkSource source,
    DateTime? receivedAt,
  }) {
    final normalized = raw.trim();
    if (normalized.isEmpty) return;
    final event = DeepLinkEvent(
      raw: normalized,
      source: source,
      receivedAt: receivedAt ?? DateTime.now(),
      eventId: _eventId(normalized),
    );
    _discardExpired(event.receivedAt);
    _seenEventIds.removeWhere(
      (_, seenAt) => event.receivedAt.difference(seenAt) > expiry,
    );
    if (event.eventId case final id? when _seenEventIds.containsKey(id)) return;
    if (_pending.length == maxPending) _removeAt(0);
    _pending.add(event);
    if (event.eventId case final id?) {
      _pendingEventIds.add(id);
      _seenEventIds[id] = event.receivedAt;
    }
    _drain();
  }

  static void attachRouter(
    DeepLinkNavigator navigator, {
    DeepLinkAuthGuard? authGuard,
  }) {
    _navigator = navigator;
    _authGuard = authGuard ?? (_) => true;
    _drain();
  }

  static void notifyAuthChanged() => _drain();

  static void detachRouter() => _navigator = null;

  /// Universal/App Link domains are supplied by the release environment. An
  /// empty allowlist intentionally disables HTTPS deep links until the native
  /// association domain is confirmed.
  static void configureTrustedHttpsHosts(Iterable<String> hosts) {
    _trustedHttpsHosts = _normalizedHosts(hosts);
  }

  static void resetForTest() {
    _pending.clear();
    _pendingEventIds.clear();
    _seenEventIds.clear();
    _trustedHttpsHosts = {..._configuredHttpsHosts};
    _navigator = null;
    _authGuard = (_) => true;
  }

  static void _drain() {
    final navigator = _navigator;
    if (navigator == null) return;
    _discardExpired(DateTime.now());
    while (_pending.isNotEmpty) {
      final event = _pending.first;
      final target = _route(event.raw);
      if (target == null) {
        _removeAt(0);
        continue;
      }
      if (!_authGuard(target) || !navigator(target)) return;
      _removeAt(0);
    }
  }

  static void _discardExpired(DateTime now) {
    while (_pending.isNotEmpty &&
        now.difference(_pending.first.receivedAt) > expiry) {
      _removeAt(0);
    }
  }

  static void _removeAt(int index) {
    final removed = _pending.removeAt(index);
    if (removed.eventId case final id?) _pendingEventIds.remove(id);
  }

  static String? _eventId(String raw) {
    try {
      final decoded = jsonDecode(raw);
      if (decoded is Map) {
        final id = '${decoded['event_id'] ?? decoded['eventId'] ?? ''}'.trim();
        if (id.isNotEmpty) return id;
      }
    } catch (_) {}
    final uri = Uri.tryParse(raw);
    final id = uri?.queryParameters['event_id']?.trim();
    return id == null || id.isEmpty ? null : id;
  }

  static String? _route(String raw) {
    var source = raw.trim();
    try {
      final decoded = jsonDecode(source);
      if (decoded is Map) {
        source =
            '${decoded['deep_link'] ?? decoded['url'] ?? decoded['link'] ?? ''}';
      }
    } catch (_) {}
    final uri = Uri.tryParse(source);
    if (uri == null) return null;
    if (uri.scheme.toLowerCase() == 'jinzhi') {
      final path = uri.path.isNotEmpty
          ? uri.path
          : uri.host.isNotEmpty
          ? '/${uri.host}'
          : '/assets';
      return _allowed(path)
          ? '$path${uri.hasQuery ? '?${uri.query}' : ''}'
          : null;
    }
    if (uri.scheme.toLowerCase() == 'https' &&
        uri.port == 443 &&
        uri.userInfo.isEmpty &&
        _trustedHttpsHosts.contains(uri.host.toLowerCase()) &&
        _allowed(uri.path)) {
      return '${uri.path}${uri.hasQuery ? '?${uri.query}' : ''}';
    }
    return null;
  }

  static bool _allowed(String path) => const {
    '/assets',
    '/market',
    '/news',
    '/profile',
    '/settings',
  }.contains(path);

  static Set<String> _normalizedHosts(Iterable<String> hosts) => {
    for (final host in hosts)
      if (host.trim().isNotEmpty) host.trim().toLowerCase(),
  };
}