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

import '../../core/network/api_exception.dart';
import '../../models/bill.dart';
import '../../models/statistics_response.dart';
import '../../providers/bill_provider.dart';
import '../../providers/bill_refresh.dart';
import '../../providers/budget_provider.dart';
import '../../utils/amount_util.dart';
import '../../utils/bill_grouping.dart';
import '../../utils/date_util.dart';
import '../../widgets/state_views.dart';
import '../bill/bill_edit_page.dart';
import 'widgets/bill_group_card.dart';
import 'widgets/budget_card.dart';
import 'widgets/month_switcher.dart';

/// 首页：月份切换 + 本月汇总 + 预算环 + 按日期分组的账单列表
class HomePage extends ConsumerWidget {
  const HomePage({super.key});

  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final anchor = ref.watch(monthAnchorProvider);
    final billsAsync = ref.watch(billsProvider(anchor));
    final statsAsync = ref.watch(monthlyStatisticsProvider(anchor));
    final budgetAsync = ref.watch(budgetProvider);
    final isCurrentMonth = isSameMonth(anchor, DateTime.now());

    return Scaffold(
      body: Container(
        width: double.infinity,
        height: double.infinity,
        decoration: const BoxDecoration(
          gradient: LinearGradient(
            begin: Alignment.topLeft,
            end: Alignment.bottomRight,
            colors: [Color(0xFFFFE5CC), Color(0xFFFFD4A8), Color(0xFFFFC08A)],
          ),
        ),
        child: SafeArea(
          child: RefreshIndicator(
            color: const Color(0xFFC8956E),
            onRefresh: () => _onRefresh(ref),
            child: ListView(
              // 内容不足一屏时也要能下拉刷新
              physics: const AlwaysScrollableScrollPhysics(),
              padding: const EdgeInsets.fromLTRB(16, 12, 16, 0),
              children: [
                _header(anchor),
                const SizedBox(height: 14),
                _summaryCard(anchor, statsAsync),
                const SizedBox(height: 12),
                // 后端预算接口只提供当月数据，历史月份不展示，避免串数据
                if (isCurrentMonth)
                  BudgetCard(budget: budgetAsync)
                else
                  _budgetUnavailableTip(),
                const SizedBox(height: 16),
                ..._billSection(context, ref, billsAsync),
                const SizedBox(height: 90), // 底部导航避让
              ],
            ),
          ),
        ),
      ),
    );
  }

  // ---- 顶部标题 + 月份切换 ----
  Widget _header(DateTime anchor) {
    return Row(
      children: [
        const Text(
          '我的账单',
          style: TextStyle(
            fontSize: 20,
            fontWeight: FontWeight.bold,
            color: Color(0xFF5D4037),
          ),
        ),
        const Spacer(),
        const MonthSwitcher(),
      ],
    );
  }

  // ---- 本月汇总 ----
  Widget _summaryCard(DateTime anchor, AsyncValue<StatisticsResponse> statsAsync) {
    final stats = statsAsync.value;
    return Container(
      padding: const EdgeInsets.symmetric(vertical: 16),
      decoration: BoxDecoration(
        color: Colors.white,
        borderRadius: BorderRadius.circular(16),
      ),
      child: Row(
        children: [
          _summaryItem('${anchor.month}月收入', stats?.totalIncome, const Color(0xFF19BE6B)),
          _vDivider(),
          _summaryItem('${anchor.month}月支出', stats?.totalExpense, const Color(0xFFFA3534)),
          _vDivider(),
          _summaryItem('结余', stats?.balance, const Color(0xFF5D4037)),
        ],
      ),
    );
  }

  Widget _summaryItem(String label, double? amount, Color color) {
    return Expanded(
      child: Column(
        children: [
          Text(label, style: const TextStyle(fontSize: 12, color: Color(0xFF8D6E63))),
          const SizedBox(height: 6),
          Text(
            // 统计未加载完时显示占位，避免整块转圈导致头部抖动
            amount == null ? '--' : '¥${formatAmount(amount)}',
            style: TextStyle(fontSize: 15, fontWeight: FontWeight.bold, color: color),
          ),
        ],
      ),
    );
  }

  Widget _vDivider() => Container(width: 1, height: 28, color: const Color(0xFFF0E6D8));

  Widget _budgetUnavailableTip() {
    return Container(
      padding: const EdgeInsets.symmetric(vertical: 14),
      decoration: BoxDecoration(
        color: Colors.white.withValues(alpha: 0.7),
        borderRadius: BorderRadius.circular(16),
      ),
      child: const Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Text('🎯 ', style: TextStyle(fontSize: 14)),
          Text(
            '仅可查看本月预算',
            style: TextStyle(fontSize: 13, color: Color(0xFF8D6E63)),
          ),
        ],
      ),
    );
  }

  // ---- 账单列表 ----
  List<Widget> _billSection(
    BuildContext context,
    WidgetRef ref,
    AsyncValue<List<Bill>> billsAsync,
  ) {
    return [
      billsAsync.when(
        loading: () => const LoadingView(),
        error: (e, _) => ErrorView(
          message: asApiException(e).message,
          onRetry: () => ref.invalidate(billsProvider),
        ),
        data: (bills) {
          if (bills.isEmpty) {
            return const EmptyView(
              title: '本月暂无账单记录',
              tip: '点击底部「记账」添加，或用 OCR 识别小票',
            );
          }
          return Column(
            children: groupBillsByDate(bills)
                .map((group) => BillGroupCard(
                      group: group,
                      onTapBill: (bill) => Navigator.of(context).push(
                        MaterialPageRoute(builder: (_) => BillEditPage(billId: bill.id)),
                      ),
                    ))
                .toList(),
          );
        },
      ),
    ];
  }

  // ---- 下拉刷新 ----
  Future<void> _onRefresh(WidgetRef ref) async {
    final anchor = ref.read(monthAnchorProvider);
    invalidateBillDataFromWidget(ref);
    // 等三个请求结束再收起下拉动画；异常吞掉，由各自的 AsyncValue 渲染错误态
    await Future.wait<void>([
      _silent(ref.read(billsProvider(anchor).future)),
      _silent(ref.read(monthlyStatisticsProvider(anchor).future)),
      _silent(ref.read(budgetProvider.future)),
    ]);
  }

  Future<void> _silent(Future<Object?> future) =>
      future.then<void>((_) {}, onError: (_, _) {});
}