/// Riverpod provider optimization utilities
///
/// Features:
/// - Granular rebuild prevention with .select()
/// - Provider caching strategies
/// - Debounced provider updates
/// - Performance-optimized provider patterns

import 'package:flutter/foundation.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'debouncer.dart';

/// Extension for optimized provider watching
extension ProviderOptimizationExtensions on WidgetRef {
  /// Watch only a specific field to minimize rebuilds
  ///
  /// Example:
  /// ```dart
  /// final name = ref.watchField(userProvider, (user) => user.name);
  /// ```
  T watchField<S, T>(ProviderListenable<S> provider, T Function(S) selector) {
    return watch(provider.select(selector));
  }

  /// Watch multiple fields efficiently
  ///
  /// Example:
  /// ```dart
  /// final (name, age) = ref.watchFields(
  ///   userProvider,
  ///   (user) => (user.name, user.age),
  /// );
  /// ```
  T watchFields<S, T>(ProviderListenable<S> provider, T Function(S) selector) {
    return watch(provider.select(selector));
  }

  /// Listen to provider only when condition is met
  ///
  /// Example:
  /// ```dart
  /// ref.listenWhen(
  ///   userProvider,
  ///   (prev, next) => prev?.id != next?.id,
  ///   (prev, next) {
  ///     // Handle change
  ///   },
  /// );
  /// ```
  void listenWhen<T>(
    ProviderListenable<T> provider,
    bool Function(T? previous, T next) condition,
    void Function(T? previous, T next) listener, {
    void Function(Object error, StackTrace stackTrace)? onError,
  }) {
    T? previous;
    listen<T>(
      provider,
      (prev, next) {
        if (condition(prev, next)) {
          listener(prev, next);
          previous = next;
        }
      },
      onError: onError,
    );
  }
}

/// Debounced state notifier for performance optimization
abstract class DebouncedStateNotifier<T> extends StateNotifier<T> {
  final Debouncer _debouncer;

  DebouncedStateNotifier(
    super.state, {
    int debounceDuration = 300,
  }) : _debouncer = Debouncer(milliseconds: debounceDuration);

  /// Update state with debouncing
  void updateDebounced(T newState) {
    _debouncer.run(() {
      if (mounted) {
        state = newState;
      }
    });
  }

  /// Update state immediately (bypass debouncing)
  void updateImmediate(T newState) {
    _debouncer.cancel();
    if (mounted) {
      state = newState;
    }
  }

  @override
  void dispose() {
    _debouncer.dispose();
    super.dispose();
  }
}

/// Cached async value to prevent unnecessary rebuilds
class CachedAsyncValue<T> {
  final AsyncValue<T> _value;
  final DateTime _timestamp;
  final Duration _cacheDuration;

  CachedAsyncValue(
    this._value, {
    Duration cacheDuration = const Duration(minutes: 5),
  })  : _timestamp = DateTime.now(),
        _cacheDuration = cacheDuration;

  AsyncValue<T> get value => _value;

  bool get isExpired {
    return DateTime.now().difference(_timestamp) > _cacheDuration;
  }

  bool get isValid {
    return !isExpired && _value is AsyncData<T>;
  }
}

/// Provider cache manager
class ProviderCacheManager {
  static final Map<String, CachedAsyncValue> _cache = {};

  /// Get cached value or compute new one
  static AsyncValue<T> getOrCompute<T>({
    required String key,
    required AsyncValue<T> Function() compute,
    Duration cacheDuration = const Duration(minutes: 5),
  }) {
    final cached = _cache[key] as CachedAsyncValue<T>?;

    if (cached != null && cached.isValid) {
      return cached.value;
    }

    final value = compute();
    _cache[key] = CachedAsyncValue(value, cacheDuration: cacheDuration);

    return value;
  }

  /// Invalidate specific cache entry
  static void invalidate(String key) {
    _cache.remove(key);
  }

  /// Clear all cache
  static void clear() {
    _cache.clear();
  }

  /// Clean expired cache entries
  static void cleanExpired() {
    _cache.removeWhere((key, value) => value.isExpired);
  }
}

/// Optimized family provider cache
class FamilyProviderCache<Arg, T> {
  final Map<Arg, T> _cache = {};
  final int _maxSize;

  FamilyProviderCache({int maxSize = 50}) : _maxSize = maxSize;

  T? get(Arg arg) => _cache[arg];

  void set(Arg arg, T value) {
    // Simple LRU: remove oldest if cache is full
    if (_cache.length >= _maxSize) {
      final firstKey = _cache.keys.first;
      _cache.remove(firstKey);
    }
    _cache[arg] = value;
  }

  void invalidate(Arg arg) {
    _cache.remove(arg);
  }

  void clear() {
    _cache.clear();
  }

  int get size => _cache.length;
}

/// Performance-optimized state notifier mixin
mixin PerformanceOptimizedNotifier<T> on StateNotifier<T> {
  /// Track rebuild count in debug mode
  int _rebuildCount = 0;

  @override
  set state(T value) {
    if (kDebugMode) {
      _rebuildCount++;
      if (_rebuildCount % 10 == 0) {
        debugPrint(
          '⚠️ ${runtimeType.toString()} has been rebuilt $_rebuildCount times',
        );
      }
    }
    super.state = value;
  }

  /// Update state only if changed
  void updateIfChanged(T newState) {
    if (state != newState) {
      state = newState;
    }
  }

  /// Update part of state efficiently
  void updatePart<S>(S Function(T) selector, S newValue) {
    if (selector(state) != newValue) {
      // This requires implementing proper state copying
      // Subclasses should override this
      throw UnimplementedError('updatePart must be implemented in subclass');
    }
  }
}

/// Selector helper for complex state
class StateSelector<T> {
  final T state;

  const StateSelector(this.state);

  /// Select a field from state
  S select<S>(S Function(T) selector) => selector(state);

  /// Select multiple fields
  R selectAll<R>(R Function(T) selector) => selector(state);
}

/// Optimized consumer for minimal rebuilds
///
/// Example:
/// ```dart
/// OptimizedConsumer<UserState>(
///   selector: (state) => state.name,
///   builder: (context, name, child) {
///     return Text(name);
///   },
/// )
/// ```
class OptimizedConsumer<T, S> extends ConsumerWidget {
  final ProviderListenable<T> provider;
  final S Function(T) selector;
  final Widget Function(BuildContext context, S value, Widget? child) builder;
  final Widget? child;

  const OptimizedConsumer({
    super.key,
    required this.provider,
    required this.selector,
    required this.builder,
    this.child,
  });

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final value = ref.watch(provider.select(selector));
    return builder(context, value, child);
  }
}

/// Batch state updates for performance
class BatchedStateUpdates<T> {
  final void Function(T) updateState;
  final List<void Function(T)> _pendingUpdates = [];
  final Debouncer _debouncer;

  BatchedStateUpdates(
    this.updateState, {
    int debounceDuration = 100,
  }) : _debouncer = Debouncer(milliseconds: debounceDuration);

  /// Queue an update
  void queueUpdate(void Function(T) update) {
    _pendingUpdates.add(update);
    _debouncer.run(_flushUpdates);
  }

  /// Flush all pending updates
  void _flushUpdates() {
    if (_pendingUpdates.isEmpty) return;

    // Apply all updates in batch
    for (final update in _pendingUpdates) {
      // Note: This would need proper implementation based on state type
      // updateState(update);
    }

    _pendingUpdates.clear();
  }

  /// Force flush immediately
  void flush() {
    _debouncer.cancel();
    _flushUpdates();
  }

  void dispose() {
    _debouncer.dispose();
    _pendingUpdates.clear();
  }
}