import 'package:flutter/material.dart';
import 'package:shadcn_ui/shadcn_ui.dart';
import 'package:provider/provider.dart';
import '../../../core/theme/app_spacing.dart';
import '../../../core/theme/app_theme_extension.dart';
import '../../../data/models/coin.dart';
import '../../../providers/market_provider.dart';
import '../../../providers/asset_provider.dart';
import '../../../data/services/trade_service.dart';
import '../../components/neon_glow.dart';
import 'components/coin_selector.dart';
import 'components/price_card.dart';
import 'components/placeholder_card.dart';
import 'components/trade_form_card.dart';
import 'components/trade_button.dart';
import 'components/confirm_dialog.dart';

/// 交易頁面
///
/// 設計稿 Trade 頁面，佈局結構：
/// - 幣種選擇器卡片（Coin Selector Card）
/// - 價格卡片（Price Card）：大號價格 + 漲跌幅徽章 + 副標題
/// - 買入/賣出切換（Buy/Sell Toggle）
/// - 交易表單卡片（Trade Form Card）：金額輸入 + 快捷比例 + 計算數量
/// - CTA 買入/賣出按鈕（Buy/Sell Button）
class TradePage extends StatefulWidget {
  final String? initialCoinCode;

  const TradePage({super.key, this.initialCoinCode});

  @override
  State<TradePage> createState() => _TradePageState();
}

class _TradePageState extends State<TradePage>
    with AutomaticKeepAliveClientMixin {
  int _tradeType = 0; // 0=買入, 1=賣出
  Coin? _selectedCoin;
  final _amountController = TextEditingController();
  bool _isSubmitting = false;

  @override
  bool get wantKeepAlive => true;

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) => _loadData());
  }

  void _loadData() {
    final marketProvider = context.read<MarketProvider>();
    marketProvider.loadCoins().then((_) {
      if (widget.initialCoinCode != null && _selectedCoin == null) {
        final coins = marketProvider.allCoins;
        final coin = coins.firstWhere(
          (c) =>
              c.code.toUpperCase() == widget.initialCoinCode!.toUpperCase(),
          orElse: () =>
              coins.isNotEmpty ? coins.first : throw Exception('No coins'),
        );
        if (mounted) setState(() => _selectedCoin = coin);
      }
    });
    context.read<AssetProvider>().refreshAll(force: true);
  }

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

  /// 獲取交易賬戶中 USDT 可用餘額
  String get _availableUsdt {
    final holdings = context.read<AssetProvider>().holdings;
    final usdt = holdings.where((h) => h.coinCode == 'USDT').firstOrNull;
    return usdt?.quantity ?? '0';
  }

  /// 獲取交易賬戶中當前幣種的持倉數量
  String get _availableCoinQty {
    if (_selectedCoin == null) return '0';
    final holdings = context.read<AssetProvider>().holdings;
    final pos = holdings
        .where((h) => h.coinCode == _selectedCoin!.code)
        .firstOrNull;
    return pos?.quantity ?? '0';
  }

  /// 計算可買入/賣出的最大 USDT 金額
  String get _maxAmount {
    if (_selectedCoin == null) return '0';
    final price = _selectedCoin!.price;
    if (price <= 0) return '0';

    if (_tradeType == 0) {
      return _availableUsdt;
    } else {
      final qty = double.tryParse(_availableCoinQty) ?? 0;
      return (qty * price).toStringAsFixed(2);
    }
  }

  /// 計算數量
  String get _calculatedQuantity {
    final amount = double.tryParse(_amountController.text) ?? 0;
    final price = _selectedCoin?.price ?? 0;
    if (price <= 0 || amount <= 0) return '0';
    // 向下截斷到4位小數，避免回算超出金額
    final qty = amount / price;
    return ((qty * 10000).truncateToDouble() / 10000).toStringAsFixed(4);
  }

  @override
  Widget build(BuildContext context) {
    super.build(context);

    return Scaffold(
      backgroundColor: context.colors.background,
      body: Consumer2<MarketProvider, AssetProvider>(
        builder: (context, market, asset, _) {
          return SafeArea(
            child: SingleChildScrollView(
              padding: const EdgeInsets.fromLTRB(
                AppSpacing.md, AppSpacing.md, AppSpacing.md, AppSpacing.xl + AppSpacing.sm, // 添加頂部間距
              ),
              child: Column(
                children: [
                  // 幣種選擇器卡片
                  CoinSelector(
                    selectedCoin: _selectedCoin,
                    coins: market.allCoins
                        .where((c) =>
                            c.code != 'USDT' &&
                            c.code != 'BTC' &&
                            c.code != 'ETH')
                        .toList(),
                    onCoinSelected: (coin) {
                      setState(() {
                        _selectedCoin = coin;
                        _amountController.clear();
                      });
                    },
                  ),
                  const SizedBox(height: AppSpacing.md),

                  // 價格卡片
                  if (_selectedCoin != null)
                    PriceCard(coin: _selectedCoin!)
                  else
                    PlaceholderCard(
                      message: '請先選擇交易幣種',
                    ),
                  const SizedBox(height: AppSpacing.md),

                  // 交易表單卡片（內含買入/賣出切換 + 表單）
                  TradeFormCard(
                    tradeType: _tradeType,
                    selectedCoin: _selectedCoin,
                    amountController: _amountController,
                    availableUsdt: _availableUsdt,
                    availableCoinQty: _availableCoinQty,
                    calculatedQuantity: _calculatedQuantity,
                    maxAmount: _maxAmount,
                    onTradeTypeChanged: (type) => setState(() {
                      _tradeType = type;
                      _amountController.clear();
                    }),
                    onAmountChanged: () => setState(() {}),
                    onFillPercent: (pct) => _fillPercent(pct),
                  ),
                  const SizedBox(height: AppSpacing.md),

                  // CTA 買入/賣出按鈕
                  SizedBox(
                    width: double.infinity,
                    height: 48,
                    child: TradeButton(
                      isBuy: _tradeType == 0,
                      coinCode: _selectedCoin?.code,
                      enabled: _canTrade() && !_isSubmitting,
                      isLoading: _isSubmitting,
                      onPressed: _executeTrade,
                    ),
                  ),
                ],
              ),
            ),
          );
        },
      ),
    );
  }

  bool _canTrade() {
    if (_selectedCoin == null) return false;
    final amount = double.tryParse(_amountController.text) ?? 0;
    if (amount <= 0) return false;
    // 買入時校驗不超過可用USDT
    if (_tradeType == 0) {
      final available = double.tryParse(_availableUsdt) ?? 0;
      if (amount > available) return false;
    }
    return true;
  }

  void _fillPercent(double pct) {
    final max = double.tryParse(_maxAmount) ?? 0;
    final value = max * pct;
    // 向下截斷到2位小數，避免四捨五入超出可用餘額
    // 向下截斷到2位小數，再減0.01作為安全緩衝，避免精度問題導致餘額不足
    final truncated = ((value * 100).truncateToDouble() / 100);
    final safe = truncated > 0.01 ? truncated - 0.01 : truncated;
    _amountController.text = safe.toStringAsFixed(2);
    setState(() {});
  }

  void _executeTrade() async {
    final isBuy = _tradeType == 0;
    final amount = _amountController.text;
    final quantity = _calculatedQuantity;
    final price = _selectedCoin!.price.toStringAsFixed(2);
    final coinCode = _selectedCoin!.code;

    final confirmed = await showDialog<bool>(
      context: context,
      builder: (ctx) => ConfirmDialog(
        isBuy: isBuy,
        coinCode: coinCode,
        price: price,
        quantity: quantity,
        amount: amount,
      ),
    );

    if (confirmed != true) return;

    setState(() => _isSubmitting = true);

    try {
      final tradeService = context.read<TradeService>();
      final response = isBuy
          ? await tradeService.buy(
              coinCode: coinCode, price: price, quantity: quantity)
          : await tradeService.sell(
              coinCode: coinCode, price: price, quantity: quantity);

      if (!mounted) return;

      if (response.success) {
        _amountController.clear();
        // 刷新資產數據
        context.read<AssetProvider>().refreshAll(force: true);
        _showResultDialog(true, '${isBuy ? '買入' : '賣出'}成功',
            '$quantity $coinCode @ $price USDT');
      } else {
        _showResultDialog(false, '交易失敗', response.message ?? '請稍後重試');
      }
    } catch (e) {
      if (mounted) {
        _showResultDialog(false, '交易失敗', e.toString());
      }
    } finally {
      if (mounted) setState(() => _isSubmitting = false);
    }
  }

  void _showResultDialog(bool success, String title, String message) {
    showShadDialog(
      context: context,
      builder: (ctx) => ShadDialog.alert(
        title: Row(
          children: [
            NeonIcon(
              icon: success ? Icons.check_circle : Icons.error,
              color: success
                  ? ctx.appColors.up
                  : ctx.colors.error,
              size: 24,
            ),
            SizedBox(width: AppSpacing.sm),
            Text(title),
          ],
        ),
        description: Text(message),
        actions: [
          ShadButton(
            child: const Text('確定'),
            onPressed: () => Navigator.of(ctx).pop(),
          ),
        ],
      ),
    );
  }
}