// purchase_page.dart — 购买套餐(三档 pro:月/季/年,pay v2 通道)。
// 档位数据来自 GET /v1/pay/catalog(server 单源);金额仅展示,扣款以 pay 为准。
// 支付渠道即币种即方式(USDT→加密货币 默认 / 人民币→支付宝),顶部 SegSwitch 选定,
// 套餐价随渠道币种刷新;点「立即购买」直接下单进支付页(不再底部弹窗选方式)。
import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';

import '../l10n/app_text.dart';
import '../models/payment.dart';
import '../pangolin_theme.dart';
import '../state/payment_provider.dart';
import '../widgets/page_body.dart';
import '../widgets/pangolin_icons.dart';
import '../widgets/sub_scaffold.dart';
import '../widgets/pangolin_toast.dart';
import '../widgets/plan_card.dart';
import '../widgets/seg_switch.dart';

/// 手写 firstWhere-or-null(避免仅为一次查找引入 package:collection 依赖)。
T? _firstWhereOrNull<T>(List<T> items, bool Function(T) test) {
  for (final it in items) {
    if (test(it)) return it;
  }
  return null;
}

class PurchaseScreen extends ConsumerStatefulWidget {
  const PurchaseScreen({super.key, required this.t, this.onBack, this.onOrderCreated, this.embedded = false});

  final AppText t;
  final VoidCallback? onBack;
  /// 下单成功(进入 awaitingPayment)后由壳导航到支付页。
  final VoidCallback? onOrderCreated;
  final bool embedded;

  @override
  ConsumerState<PurchaseScreen> createState() => _PurchaseScreenState();
}

class _PurchaseScreenState extends ConsumerState<PurchaseScreen> {
  AppText get t => widget.t;
  bool get _zh => t.lang == AppLang.zh;

  // 支付渠道:默认 USDT·加密货币。切换即刷新套餐卡显价币种。
  PayChannel _channel = PayChannel.usdt;

  String _name(String sku) => switch (sku) {
        'pro_month' => t.proMonthly,
        'pro_quarter' => t.proQuarterly,
        'pro_year' => t.proYearly,
        _ => sku,
      };

  Future<void> _buy(PayCatalogItem item) async {
    await ref.read(paymentFlowProvider.notifier).start(item, _channel.method);
    if (!mounted) return;
    final st = ref.read(paymentFlowProvider);
    if (st.phase == PaymentPhase.awaitingPayment) {
      widget.onOrderCreated?.call();
    } else if (st.phase == PaymentPhase.failed) {
      // 下单失败给可见 toast,别让用户以为「点了没反应」。
      showPangolinToast(
        context,
        (_zh ? st.errorZh : st.errorEn) ?? t.orderCreateFailed,
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    final c = context.pangolin;
    final catalog = ref.watch(payCatalogProvider);

    final body = PageBody(wide: true, child: catalog.when(
      loading: () => const Center(
          child: Padding(padding: EdgeInsets.all(40), child: CircularProgressIndicator())),
      error: (_, __) => Center(
        child: Padding(
          padding: const EdgeInsets.all(40),
          child: Text(t.lang.loadFailedRetry, style: PangolinText.body.copyWith(color: c.fg3)),
        ),
      ),
      data: (items) {
        final promoItem = _firstWhereOrNull(items, (i) => i.promo);
        final planItems = items.where((i) => !i.promo).toList();
        final originalItem = _firstWhereOrNull(items, (i) => i.sku == 'pro_month');
        return ListView(
          padding: const EdgeInsets.fromLTRB(20, 14, 20, 24),
          children: [
            // 支付渠道 SegSwitch(默认 USDT;人民币走支付宝)→ 套餐价随之刷新
            Padding(
              padding: const EdgeInsets.only(left: 2, bottom: 8),
              child: Text(t.payChannel.toUpperCase(),
                  style: PangolinText.caption.copyWith(
                      color: c.fg3, fontWeight: FontWeight.w700, letterSpacing: 0.6)),
            ),
            SegSwitch(
              options: [
                (icon: PangolinIcons.globe, label: t.payChannelUsdt),
                (icon: PangolinIcons.creditCard, label: t.payChannelCny),
              ],
              selectedIndex: _channel == PayChannel.usdt ? 0 : 1,
              onChanged: (i) => setState(
                  () => _channel = i == 0 ? PayChannel.usdt : PayChannel.cny),
            ),
            const SizedBox(height: 18),
            if (promoItem != null)
              Padding(
                padding: const EdgeInsets.only(bottom: 14),
                child: _PromoCard(
                  t: t,
                  channel: _channel,
                  item: promoItem,
                  originalItem: originalItem,
                  onPressed: () => _buy(promoItem),
                ),
              ),
            for (final it in planItems)
              Padding(
                padding: EdgeInsets.only(bottom: 14, top: it.sku == 'pro_year' ? 12 : 0),
                child: PlanCard(
                  name: _name(it.sku),
                  price: it.priceLabel(_channel),
                  period: '${it.perMonthLabel(_channel)}${t.perMonthSuffix}',
                  features: t.featsPro,
                  ctaLabel: t.buyNow,
                  featured: it.sku == 'pro_year',
                  popularLabel: it.sku == 'pro_year' ? t.mostPopular : null,
                  onPressed: () => _buy(it),
                ),
              ),
          ],
        );
      },
    ));

    return SubScaffold(
      title: t.purchaseTitle,
      onBack: widget.onBack,
      embedded: widget.embedded,
      child: body,
    );
  }
}

/// _PromoCard — 全员优惠月付特殊卡片(横幅式,视觉上与普通 PlanCard 拉开层次)。
/// 徽章 + 大号现价(随渠道 ¥/$ 联动)+ 可选原价划线(以 pro_month 为参照)。
class _PromoCard extends StatelessWidget {
  const _PromoCard({
    required this.t,
    required this.channel,
    required this.item,
    required this.originalItem,
    required this.onPressed,
  });

  final AppText t;
  final PayChannel channel;
  final PayCatalogItem item;
  final PayCatalogItem? originalItem;
  final VoidCallback onPressed;

  @override
  Widget build(BuildContext context) {
    final originalLabel = originalItem?.priceLabel(channel);

    return Container(
      padding: const EdgeInsets.fromLTRB(18, 16, 18, 16),
      decoration: BoxDecoration(
        gradient: const LinearGradient(
          begin: Alignment.topLeft,
          end: Alignment.bottomRight,
          colors: [PangolinColors.clay500, PangolinColors.clay700],
        ),
        borderRadius: BorderRadius.circular(PangolinRadius.xl),
        boxShadow: PangolinShadow.md,
      ),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        mainAxisSize: MainAxisSize.min,
        children: [
          Container(
            padding: const EdgeInsets.symmetric(horizontal: 9, vertical: 4),
            decoration: BoxDecoration(
              color: PangolinColors.white.withValues(alpha: 0.22),
              borderRadius: BorderRadius.circular(PangolinRadius.full),
            ),
            child: Row(mainAxisSize: MainAxisSize.min, children: [
              Icon(PangolinIcons.zap, size: 13, color: PangolinColors.white),
              const SizedBox(width: 4),
              Text(t.promoBadge,
                  style: PangolinText.caption.copyWith(
                      color: PangolinColors.white, fontWeight: FontWeight.w700, fontSize: 11)),
            ]),
          ),
          const SizedBox(height: 12),
          Text(t.proMonthly,
              style: PangolinText.sm.copyWith(
                  color: PangolinColors.white.withValues(alpha: 0.85), fontWeight: FontWeight.w600)),
          const SizedBox(height: 6),
          Row(
            crossAxisAlignment: CrossAxisAlignment.baseline,
            textBaseline: TextBaseline.alphabetic,
            children: [
              Text(item.priceLabel(channel),
                  style: PangolinText.display.copyWith(color: PangolinColors.white, fontSize: 30)),
              Text(t.perMonthSuffix,
                  style: PangolinText.caption.copyWith(
                      color: PangolinColors.white.withValues(alpha: 0.85), fontSize: 13)),
              if (originalLabel != null) ...[
                const SizedBox(width: 8),
                Text(originalLabel,
                    style: PangolinText.sm.copyWith(
                      color: PangolinColors.white.withValues(alpha: 0.62),
                      fontSize: 14,
                      decoration: TextDecoration.lineThrough,
                    )),
              ],
            ],
          ),
          const SizedBox(height: 16),
          SizedBox(
            width: double.infinity,
            child: Material(
              color: PangolinColors.white,
              shape: const StadiumBorder(),
              clipBehavior: Clip.antiAlias,
              child: InkWell(
                onTap: onPressed,
                child: Padding(
                  padding: const EdgeInsets.symmetric(vertical: 12),
                  child: Center(
                    child: Text(t.buyNow,
                        style: PangolinText.sm.copyWith(
                            fontWeight: FontWeight.w700, fontSize: 14, color: PangolinColors.clay700)),
                  ),
                ),
              ),
            ),
          ),
        ],
      ),
    );
  }
}