import 'dart:async';

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

import '../../../core/providers/app_providers.dart';
import '../../config/application/app_config_controller.dart';

/// Observable state for the in-app purchase flow.
class IapState {
  const IapState({
    this.product,
    this.isLoading = false,
    this.isPurchasing = false,
    this.errorMessage,
    this.productsAvailable = false,
    this.lastEvent,
  });

  final ProductDetails? product;
  final bool isLoading;
  final bool isPurchasing;
  final String? errorMessage;
  final bool productsAvailable;

  /// Last human-readable event (e.g. "解锁成功").
  final String? lastEvent;

  IapState copyWith({
    ProductDetails? product,
    bool? isLoading,
    bool? isPurchasing,
    String? errorMessage,
    bool? productsAvailable,
    String? lastEvent,
  }) {
    return IapState(
      product: product ?? this.product,
      isLoading: isLoading ?? this.isLoading,
      isPurchasing: isPurchasing ?? this.isPurchasing,
      errorMessage: errorMessage,
      productsAvailable: productsAvailable ?? this.productsAvailable,
      lastEvent: lastEvent,
    );
  }
}

final iapControllerProvider = NotifierProvider<IapController, IapState>(
  IapController.new,
);

class IapController extends Notifier<IapState> {
  late final InAppPurchase _store = InAppPurchase.instance;
  StreamSubscription<List<PurchaseDetails>>? _sub;

  @override
  IapState build() {
    ref.onDispose(() {
      _sub?.cancel();
      _sub = null;
    });
    _init();
    return const IapState(isLoading: true);
  }

  Future<void> _init() async {
    final available = await _store.isAvailable();
    if (!available) {
      state = state.copyWith(
        isLoading: false,
        productsAvailable: false,
        errorMessage: '无法连接到 App Store，请检查网络设置',
      );
      return;
    }

    _sub = _store.purchaseStream.listen(
      _onPurchaseUpdated,
      onError: (Object e) {
        state = state.copyWith(isPurchasing: false, errorMessage: '支付失败：$e');
      },
    );

    await _loadProduct();
  }

  Future<void> _loadProduct() async {
    final response = await _store.queryProductDetails({kUnlockProductId});
    final error = response.error;
    if (error != null) {
      state = state.copyWith(
        isLoading: false,
        productsAvailable: false,
        errorMessage: '商品信息加载失败：${error.message}',
      );
      return;
    }
    final products = response.productDetails;
    if (products.isEmpty) {
      // No product configured in App Store Connect yet.
      state = state.copyWith(
        isLoading: false,
        productsAvailable: false,
        errorMessage: null,
      );
      return;
    }
    final product = products.first;
    state = state.copyWith(
      isLoading: false,
      productsAvailable: true,
      product: product,
      errorMessage: null,
    );
  }

  Future<void> buy() async {
    final product = state.product;
    if (product == null) {
      state = state.copyWith(errorMessage: '商品尚未就绪，请稍后再试');
      return;
    }
    state = state.copyWith(
      isPurchasing: true,
      errorMessage: null,
      lastEvent: null,
    );
    final param = PurchaseParam(productDetails: product);
    final ok = await _store.buyNonConsumable(purchaseParam: param);
    if (!ok) {
      state = state.copyWith(isPurchasing: false, errorMessage: '支付已取消');
    }
  }

  Future<void> restore() async {
    state = state.copyWith(
      isLoading: true,
      errorMessage: null,
      lastEvent: null,
    );
    await _store.restorePurchases();
    // The purchase stream will deliver restored purchases; clear loading after
    // a short delay in case nothing arrives.
    Future<void>.delayed(const Duration(seconds: 2), () {
      if (state.isLoading) {
        state = state.copyWith(
          isLoading: false,
          lastEvent: state.lastEvent ?? '未找到历史购买记录',
        );
      }
    });
  }

  void _onPurchaseUpdated(List<PurchaseDetails> purchases) {
    for (final purchase in purchases) {
      _handle(purchase);
    }
  }

  Future<void> _handle(PurchaseDetails purchase) async {
    switch (purchase.status) {
      case PurchaseStatus.purchased:
      case PurchaseStatus.restored:
        if (purchase.pendingCompletePurchase) {
          await _store.completePurchase(purchase);
        }
        await ref
            .read(appConfigProvider.notifier)
            .markUnlocked(
              fromRestore: purchase.status == PurchaseStatus.restored,
            );
        state = IapState(
          product: state.product,
          productsAvailable: state.productsAvailable,
          lastEvent: purchase.status == PurchaseStatus.restored
              ? '权益已恢复'
              : '解锁成功！已获得无限记分权益',
        );
        break;
      case PurchaseStatus.error:
        state = state.copyWith(
          isPurchasing: false,
          errorMessage: '支付失败：${purchase.error?.message ?? '未知错误'}',
        );
        break;
      case PurchaseStatus.canceled:
        state = state.copyWith(isPurchasing: false, lastEvent: '支付已取消');
        break;
      case PurchaseStatus.pending:
        // Purchase awaiting approval/processing; keep the loading state.
        state = state.copyWith(isPurchasing: true);
        break;
    }
  }

  /// Debug-only unlock used so the app remains usable without App Store
  /// Connect configuration during development.
  Future<void> debugUnlock() async {
    await ref.read(appConfigProvider.notifier).debugUnlock();
    state = state.copyWith(lastEvent: '已通过开发模式解锁');
  }

  void clearEvent() {
    state = state.copyWith(lastEvent: null, errorMessage: null);
  }
}

@visibleForTesting
IapState iapStateForTest({
  ProductDetails? product,
  bool isLoading = false,
  bool isPurchasing = false,
  String? errorMessage,
  bool productsAvailable = false,
  String? lastEvent,
}) {
  return IapState(
    product: product,
    isLoading: isLoading,
    isPurchasing: isPurchasing,
    errorMessage: errorMessage,
    productsAvailable: productsAvailable,
    lastEvent: lastEvent,
  );
}