import 'dart:developer' as developer;

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

import 'auth_state.dart';

part 'auth_provider.g.dart';

/// Provides authentication state and operations.
///
/// Note: Full OIDC implementation with flutter_appauth requires
/// native platform configuration. For now, this provides the
/// state management infrastructure.
@riverpod
class AuthNotifier extends _$AuthNotifier {
  static const _accessTokenKey = 'auth_access_token';
  static const _refreshTokenKey = 'auth_refresh_token';
  static const _expiresAtKey = 'auth_expires_at';
  static const _userIdKey = 'auth_user_id';
  static const _userNameKey = 'auth_user_name';
  static const _userEmailKey = 'auth_user_email';

  @override
  Future<AuthState> build() async {
    return _loadStoredAuth();
  }

  Future<AuthState> _loadStoredAuth() async {
    try {
      final prefs = await SharedPreferences.getInstance();

      final accessToken = prefs.getString(_accessTokenKey);
      if (accessToken == null) {
        return const AuthState();
      }

      final expiresAtMs = prefs.getInt(_expiresAtKey);
      final expiresAt = expiresAtMs != null
          ? DateTime.fromMillisecondsSinceEpoch(expiresAtMs)
          : null;

      final authState = AuthState(
        isAuthenticated: true,
        accessToken: accessToken,
        refreshToken: prefs.getString(_refreshTokenKey),
        expiresAt: expiresAt,
        userId: prefs.getString(_userIdKey),
        userName: prefs.getString(_userNameKey),
        userEmail: prefs.getString(_userEmailKey),
      );

      // Check if token is expired
      if (authState.isTokenExpired) {
        developer.log('Stored token expired, clearing auth', name: 'auth');
        await _clearStoredAuth();
        return const AuthState();
      }

      developer.log('Restored auth for ${authState.userName}', name: 'auth');
      return authState;
    } catch (e) {
      developer.log('Failed to load stored auth: $e', name: 'auth');
      return const AuthState();
    }
  }

  /// Sign in with OIDC (placeholder for flutter_appauth integration).
  Future<void> signIn() async {
    // TODO: Implement OIDC flow with flutter_appauth
    // For now, this is a placeholder that will be implemented
    // when native platform configuration is complete.
    developer.log('Sign in requested - OIDC not yet configured', name: 'auth');
  }

  /// Sign out and clear stored credentials.
  Future<void> signOut() async {
    await _clearStoredAuth();
    state = const AsyncData(AuthState());
    developer.log('Signed out', name: 'auth');
  }

  /// Update auth state (called after successful OIDC flow).
  Future<void> setAuthenticated({
    required String accessToken,
    String? refreshToken,
    DateTime? expiresAt,
    String? userId,
    String? userName,
    String? userEmail,
  }) async {
    final prefs = await SharedPreferences.getInstance();

    await prefs.setString(_accessTokenKey, accessToken);
    if (refreshToken != null) {
      await prefs.setString(_refreshTokenKey, refreshToken);
    }
    if (expiresAt != null) {
      await prefs.setInt(_expiresAtKey, expiresAt.millisecondsSinceEpoch);
    }
    if (userId != null) await prefs.setString(_userIdKey, userId);
    if (userName != null) await prefs.setString(_userNameKey, userName);
    if (userEmail != null) await prefs.setString(_userEmailKey, userEmail);

    state = AsyncData(AuthState(
      isAuthenticated: true,
      accessToken: accessToken,
      refreshToken: refreshToken,
      expiresAt: expiresAt,
      userId: userId,
      userName: userName,
      userEmail: userEmail,
    ));

    developer.log('Authenticated as $userName', name: 'auth');
  }

  Future<void> _clearStoredAuth() async {
    final prefs = await SharedPreferences.getInstance();
    await prefs.remove(_accessTokenKey);
    await prefs.remove(_refreshTokenKey);
    await prefs.remove(_expiresAtKey);
    await prefs.remove(_userIdKey);
    await prefs.remove(_userNameKey);
    await prefs.remove(_userEmailKey);
  }
}