import 'dart:async';

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

import '../../app/theme.dart';
import '../settings/settings_screen.dart';

/// One-time "Support Nanga Kathai" amounts. Create these as consumable in-app products with the
/// same IDs in Play Console and App Store Connect; each store charges in the buyer's own
/// currency (₹, CA$, US$, AED, SAR…) and the app shows the price exactly as the store gives it.
const supportProductIds = {'nk_support_small', 'nk_support_medium', 'nk_support_large'};

/// Prices are set per country in the stores, e.g. India ₹300 / ₹500 / ₹1,000,
/// US and Canada $10 / $25 / $50 (see docs/support-payments.md).
const _labels = {
  'nk_support_small': ('Supporter', Icons.favorite_outline),
  'nk_support_medium': ('Friend of Nanga Kathai', Icons.music_note_outlined),
  'nk_support_large': ('Champion of Badaga music', Icons.favorite_rounded),
};

enum SupportStatus { loading, ready, unavailable, buying, thanks, failed }

class SupportState {
  const SupportState(this.status, [this.products = const []]);

  final SupportStatus status;
  final List<ProductDetails> products;

  SupportState copyWith(SupportStatus status) => SupportState(status, products);
}

/// Started at app launch, so a purchase that finishes while the app was closed is still
/// completed (Google refunds purchases that are never acknowledged).
class SupportPurchases extends Notifier<SupportState> {
  StreamSubscription<List<PurchaseDetails>>? _sub;

  @override
  SupportState build() {
    _sub = InAppPurchase.instance.purchaseStream.listen(_onPurchases, onError: (_) {
      state = state.copyWith(SupportStatus.failed);
    });
    ref.onDispose(() => _sub?.cancel());
    return const SupportState(SupportStatus.loading);
  }

  Future<void> loadProducts() async {
    if (state.products.isNotEmpty) return;
    state = const SupportState(SupportStatus.loading);
    try {
      if (!await InAppPurchase.instance.isAvailable()) {
        state = const SupportState(SupportStatus.unavailable);
        return;
      }
      final res = await InAppPurchase.instance.queryProductDetails(supportProductIds);
      final products = [...res.productDetails]..sort((a, b) => a.rawPrice.compareTo(b.rawPrice));
      state = SupportState(products.isEmpty ? SupportStatus.unavailable : SupportStatus.ready, products);
    } catch (_) {
      state = const SupportState(SupportStatus.unavailable);
    }
  }

  Future<void> buy(ProductDetails product) async {
    state = state.copyWith(SupportStatus.buying);
    try {
      await InAppPurchase.instance.buyConsumable(purchaseParam: PurchaseParam(productDetails: product));
    } catch (_) {
      state = state.copyWith(SupportStatus.failed);
    }
  }

  void reset() => state = state.copyWith(state.products.isEmpty ? SupportStatus.loading : SupportStatus.ready);

  Future<void> _onPurchases(List<PurchaseDetails> purchases) async {
    for (final p in purchases) {
      switch (p.status) {
        case PurchaseStatus.purchased || PurchaseStatus.restored:
          state = state.copyWith(SupportStatus.thanks);
        case PurchaseStatus.error:
          state = state.copyWith(SupportStatus.failed);
        case PurchaseStatus.canceled:
          state = state.copyWith(SupportStatus.ready);
        case PurchaseStatus.pending:
          break;
      }
      if (p.pendingCompletePurchase) await InAppPurchase.instance.completePurchase(p);
    }
  }
}

final supportProvider = NotifierProvider<SupportPurchases, SupportState>(SupportPurchases.new);

class SupportScreen extends ConsumerStatefulWidget {
  const SupportScreen({super.key});

  @override
  ConsumerState<SupportScreen> createState() => _SupportScreenState();
}

class _SupportScreenState extends ConsumerState<SupportScreen> {
  @override
  void initState() {
    super.initState();
    Future.microtask(() => ref.read(supportProvider.notifier).loadProducts());
  }

  @override
  Widget build(BuildContext context) {
    final text = Theme.of(context).textTheme;
    final support = ref.watch(supportProvider);
    final notifier = ref.read(supportProvider.notifier);

    if (support.status == SupportStatus.thanks) {
      return Scaffold(
        appBar: AppBar(),
        body: Padding(
          padding: const EdgeInsets.all(24),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              const Icon(Icons.favorite_rounded, color: NkColors.sun, size: 64),
              const SizedBox(height: 16),
              Text('Thank you!', textAlign: TextAlign.center, style: text.headlineMedium),
              const SizedBox(height: 8),
              const Text(
                'Your support keeps Badaga music free for everyone and helps us bring more artists to Nanga Kathai.',
                textAlign: TextAlign.center,
                style: TextStyle(color: NkColors.muted, height: 1.5),
              ),
              const SizedBox(height: 24),
              FilledButton(
                onPressed: () {
                  notifier.reset();
                  Navigator.of(context).maybePop();
                },
                child: const Text('Done'),
              ),
            ],
          ),
        ),
      );
    }

    return Scaffold(
      appBar: AppBar(title: const Text('Support Nanga Kathai')),
      body: ListView(
        padding: const EdgeInsets.fromLTRB(20, 0, 20, 32),
        children: [
          Text('Help keep Badaga music free', style: text.headlineSmall),
          const SizedBox(height: 8),
          const Text(
            'Nanga Kathai is free, with no ads. If it brings you joy, a one-time gift helps us pay for the servers, '
            'restore old recordings and build the tools that will let singers earn from their songs.',
            style: TextStyle(color: NkColors.muted, height: 1.5),
          ),
          const SizedBox(height: 20),
          switch (support.status) {
            SupportStatus.loading => const Padding(
                padding: EdgeInsets.all(32),
                child: Center(child: CircularProgressIndicator()),
              ),
            SupportStatus.unavailable => const Card(
                color: NkColors.surface,
                child: Padding(
                  padding: EdgeInsets.all(16),
                  child: Text(
                    'Support is not available on this phone right now. Please check that you are signed in to '
                    'Google Play or the App Store, and try again later.',
                    style: TextStyle(color: NkColors.muted, height: 1.5),
                  ),
                ),
              ),
            _ => Column(
                children: [
                  for (final p in support.products)
                    Card(
                      color: NkColors.surface,
                      child: ListTile(
                        leading: Icon(_labels[p.id]?.$2 ?? Icons.favorite_outline, color: NkColors.sun),
                        title: Text(_labels[p.id]?.$1 ?? p.title,
                            style: const TextStyle(fontWeight: FontWeight.w700)),
                        trailing: FilledButton(
                          onPressed: support.status == SupportStatus.buying ? null : () => notifier.buy(p),
                          child: Text(p.price),
                        ),
                      ),
                    ),
                  if (support.status == SupportStatus.failed)
                    const Padding(
                      padding: EdgeInsets.only(top: 8),
                      child: Text('The payment did not go through. You have not been charged.',
                          style: TextStyle(color: NkColors.muted)),
                    ),
                ],
              ),
          },
          const SizedBox(height: 8),
          ListTile(
            contentPadding: EdgeInsets.zero,
            leading: const Icon(Icons.volunteer_activism_outlined, color: NkColors.sun),
            title: const Text('Want to give more, or sponsor an album?'),
            subtitle: const Text('Write to us at $supportEmail', style: TextStyle(color: NkColors.muted)),
            onTap: () => contactSupport(subject: 'Supporting Nanga Kathai'),
          ),
          const SizedBox(height: 8),
          const Text(
            'One-time payment through Google Play or the App Store, in your local currency. '
            'Nothing renews and nothing is unlocked: every song stays free for everyone.',
            style: TextStyle(color: NkColors.muted, fontSize: 12, height: 1.5),
          ),
        ],
      ),
    );
  }
}