// HubService — singleton wrapper around fai_dart_sdk's HubClient.
//
// Centralises the gRPC connection so each page just imports
// `HubService.instance` instead of constructing its own client.
// Methods return UI-friendly types so pages stay free of
// protobuf imports.

import 'package:fai_dart_sdk/fai_dart_sdk.dart';
import 'package:shared_preferences/shared_preferences.dart';

class HubService {
  HubService._();
  static final HubService instance = HubService._();

  HubClient _client = HubClient();

  /// The endpoint string ("http://host:port") the connection
  /// targets. Shown in the navigation rail.
  String get endpointLabel => _client.endpoint.toString();

  HubEndpoint get currentEndpoint => _client.endpoint;

  static const _kHostKey = 'hub.host';
  static const _kPortKey = 'hub.port';
  static const _kSecureKey = 'hub.secure';

  /// Read persisted endpoint and reconnect if it differs from
  /// the default. Called once at app start.
  Future<void> loadPersistedEndpoint() async {
    final prefs = await SharedPreferences.getInstance();
    final host = prefs.getString(_kHostKey);
    final port = prefs.getInt(_kPortKey);
    final secure = prefs.getBool(_kSecureKey);
    if (host == null) return;
    final endpoint = HubEndpoint(
      host: host,
      port: port ?? 50051,
      secure: secure ?? false,
    );
    if (endpoint.toString() != _client.endpoint.toString()) {
      await reconnect(endpoint);
    }
  }

  /// Reconnect to a new endpoint and persist for next launch.
  Future<void> reconnect(HubEndpoint endpoint) async {
    await _client.close();
    _client = HubClient(endpoint: endpoint);
    final prefs = await SharedPreferences.getInstance();
    await prefs.setString(_kHostKey, endpoint.host);
    await prefs.setInt(_kPortKey, endpoint.port);
    await prefs.setBool(_kSecureKey, endpoint.secure);
  }

  Future<bool> healthy() => _client.healthy();

  Future<List<ModuleSummary>> listModules() async {
    final caps = await _client.listCapabilities();

    // Group capabilities by module so Studio's UI maps a card
    // to a module rather than a capability.
    final byModule = <String, List<CapabilityEntry>>{};
    for (final c in caps) {
      byModule.putIfAbsent(c.moduleName, () => []).add(c);
    }
    return byModule.entries.map((e) {
      final caps = e.value;
      return ModuleSummary(
        name: e.key,
        version: caps.first.moduleVersion,
        capabilities: caps
            .map((c) => '${c.capability}@${c.version}')
            .toList(),
      );
    }).toList()
      ..sort((a, b) => a.name.compareTo(b.name));
  }

  Future<List<AuditEvent>> recentEvents({
    int limit = 50,
    List<String> types = const [],
  }) async {
    final events = await _client.eventLog(limit: limit, types: types);
    return events
        .map(
          (e) => AuditEvent(
            eventId: e.eventId,
            timestamp: DateTime.tryParse(e.timestamp) ?? DateTime.now(),
            type: e.eventType,
            flowName: e.flowName.isEmpty ? null : e.flowName,
            stepId: e.stepId.isEmpty ? null : e.stepId,
            moduleName: e.moduleName.isEmpty ? null : e.moduleName,
            durationMs: e.durationMs == 0 ? null : e.durationMs.toInt(),
            error: e.error.isEmpty ? null : e.error,
          ),
        )
        .toList();
  }

  Future<List<PendingApproval>> pendingApprovals() async {
    final entries = await _client.listApprovals(statuses: ['pending']);
    return entries
        .map(
          (e) => PendingApproval(
            id: e.approvalId,
            flowName: e.flowName,
            stepId: e.stepId,
            prompt: e.prompt,
            showPreview: e.payloadPreview.isEmpty ? null : e.payloadPreview,
            createdAt: DateTime.tryParse(e.createdAt) ?? DateTime.now(),
            expiresAt: e.expiresAt.isEmpty
                ? null
                : DateTime.tryParse(e.expiresAt),
          ),
        )
        .toList();
  }

  Future<void> approve(String id, String reviewer) =>
      _client.approve(approvalId: id, reviewer: reviewer);

  Future<void> reject(String id, String reviewer, String reason) =>
      _client.reject(
        approvalId: id,
        reviewer: reviewer,
        reason: reason,
      );

  /// Composite "doctor" snapshot. One round-trip per piece, run
  /// in parallel so the page populates fast.
  Future<DoctorSnapshot> doctor() async {
    final results = await Future.wait([
      _client.listCapabilities().catchError((_) => <CapabilityEntry>[]),
      _client.listApprovals(statuses: const ['pending'])
          .catchError((_) => <PendingApprovalEntry>[]),
      _client.verifyEventChain().catchError(
            (_) => VerifyEventChainResponse(),
          ),
      _client.listServices().catchError((_) => <DeclaredService>[]),
    ]);

    final caps = results[0] as List<CapabilityEntry>;
    final approvals = results[1] as List<PendingApprovalEntry>;
    final chain = results[2] as VerifyEventChainResponse;
    final services = results[3] as List<DeclaredService>;

    // Module count = distinct module_name across capabilities.
    final moduleNames = <String>{for (final c in caps) c.moduleName};

    return DoctorSnapshot(
      moduleCount: moduleNames.length,
      capabilityCount: caps.length,
      pendingApprovals: approvals.length,
      eventChainTotal: chain.total.toInt(),
      eventChainVerified: chain.verified.toInt(),
      eventChainTamperedAt:
          chain.tamperedAt.isEmpty ? null : chain.tamperedAt,
      services: services
          .map(
            (s) => ServiceEntry(
              name: s.name,
              endpoint: s.endpoint,
              tags: s.tags,
            ),
          )
          .toList(),
    );
  }
}

class DoctorSnapshot {
  final int moduleCount;
  final int capabilityCount;
  final int pendingApprovals;
  final int eventChainTotal;
  final int eventChainVerified;
  final String? eventChainTamperedAt;
  final List<ServiceEntry> services;

  const DoctorSnapshot({
    required this.moduleCount,
    required this.capabilityCount,
    required this.pendingApprovals,
    required this.eventChainTotal,
    required this.eventChainVerified,
    required this.eventChainTamperedAt,
    required this.services,
  });

  bool get chainHealthy => eventChainTamperedAt == null;
}

class ServiceEntry {
  final String name;
  final String endpoint;
  final List<String> tags;

  const ServiceEntry({
    required this.name,
    required this.endpoint,
    required this.tags,
  });
}

/// UI-side type, decoupled from the proto wire type so pages
/// don't import protobuf packages.
class ModuleSummary {
  final String name;
  final String version;
  final List<String> capabilities;

  const ModuleSummary({
    required this.name,
    required this.version,
    required this.capabilities,
  });
}

class AuditEvent {
  final String eventId;
  final DateTime timestamp;
  final String type;
  final String? flowName;
  final String? stepId;
  final String? moduleName;
  final int? durationMs;
  final String? error;

  const AuditEvent({
    required this.eventId,
    required this.timestamp,
    required this.type,
    this.flowName,
    this.stepId,
    this.moduleName,
    this.durationMs,
    this.error,
  });
}

class PendingApproval {
  final String id;
  final String flowName;
  final String stepId;
  final String prompt;
  final String? showPreview;
  final DateTime createdAt;
  final DateTime? expiresAt;

  const PendingApproval({
    required this.id,
    required this.flowName,
    required this.stepId,
    required this.prompt,
    this.showPreview,
    required this.createdAt,
    this.expiresAt,
  });
}