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

import '../../api/health_api.dart';
import '../../providers/health_provider.dart';
import '../../utils/toast.dart';

/// 设置减重目标 + 展示「每周该减多少」。
///
/// 这个页面的核心价值是第二块：把「三个月减 7kg」翻译成「每周 0.54kg」——
/// 前者没有可执行性，后者才有。
class GoalSetupPage extends ConsumerStatefulWidget {
  const GoalSetupPage({super.key});

  @override
  ConsumerState<GoalSetupPage> createState() => _GoalSetupPageState();
}

class _GoalSetupPageState extends ConsumerState<GoalSetupPage> {
  final _startCtrl = TextEditingController();
  final _targetCtrl = TextEditingController();

  DateTime _startDate = DateTime.now();
  DateTime _targetDate = DateTime.now().add(const Duration(days: 90));

  bool _saving = false;
  bool _loaded = false;

  @override
  void initState() {
    super.initState();
    // 已有目标就预填，让「想改一改」不用重敲
    Future.microtask(() async {
      try {
        final goal = await ref.read(healthApiProvider).goal();
        if (!mounted) return;
        if (goal.hasGoal) {
          setState(() {
            _startCtrl.text = _num(goal.startWeight);
            _targetCtrl.text = _num(goal.targetWeight);
            _startDate = goal.startDate ?? _startDate;
            _targetDate = goal.targetDate ?? _targetDate;
          });
        } else {
          // 没设过目标时，用最近一次体重当起始值
          final chart = await ref.read(healthApiProvider).weightChart();
          if (!mounted) return;
          final current = chart.currentWeight;
          if (current != null) {
            setState(() => _startCtrl.text = _num(current));
          }
        }
      } catch (_) {
        // 拿不到就不预填，用户手填即可
      } finally {
        if (mounted) setState(() => _loaded = true);
      }
    });
  }

  @override
  void dispose() {
    _startCtrl.dispose();
    _targetCtrl.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: const Color(0xFFF7F4F1),
      appBar: AppBar(
        title: const Text('减重目标'),
        backgroundColor: const Color(0xFFF7F4F1),
        elevation: 0,
        scrolledUnderElevation: 0,
        foregroundColor: const Color(0xFF5D4037),
      ),
      body: !_loaded
          ? const Center(
              child: CircularProgressIndicator(color: Color(0xFFC8956E)),
            )
          : ListView(
              padding: const EdgeInsets.fromLTRB(14, 6, 14, 24),
              children: [
                _formCard(),
                const SizedBox(height: 12),
                _planCard(),
                const SizedBox(height: 12),
                _weeklyTableCard(),
                const SizedBox(height: 20),
                _saveButton(),
              ],
            ),
    );
  }

  // ---------------- 输入区 ----------------

  Widget _formCard() {
    return Container(
      padding: const EdgeInsets.fromLTRB(16, 16, 16, 8),
      decoration: BoxDecoration(
        color: Colors.white,
        borderRadius: BorderRadius.circular(16),
      ),
      child: Column(
        children: [
          Row(
            children: [
              Expanded(
                child: _numberField(
                  controller: _startCtrl,
                  label: '起始体重',
                  hint: '65.0',
                ),
              ),
              const SizedBox(width: 14),
              Expanded(
                child: _numberField(
                  controller: _targetCtrl,
                  label: '目标体重',
                  hint: '58.0',
                ),
              ),
            ],
          ),
          const SizedBox(height: 4),
          _dateRow('开始日期', _startDate,
              (d) => setState(() => _startDate = d)),
          _dateRow('目标日期', _targetDate,
              (d) => setState(() => _targetDate = d)),
          const SizedBox(height: 4),
        ],
      ),
    );
  }

  Widget _numberField({
    required TextEditingController controller,
    required String label,
    required String hint,
  }) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        Text(label,
            style: const TextStyle(fontSize: 12, color: Color(0xFF8D6E63))),
        const SizedBox(height: 4),
        TextField(
          controller: controller,
          keyboardType: const TextInputType.numberWithOptions(decimal: true),
          onChanged: (_) => setState(() {}),
          style: const TextStyle(
              fontSize: 20,
              fontWeight: FontWeight.bold,
              color: Color(0xFF5D4037)),
          decoration: InputDecoration(
            hintText: hint,
            hintStyle: const TextStyle(
                fontSize: 20,
                fontWeight: FontWeight.bold,
                color: Color(0xFFD7CCC8)),
            suffixText: 'kg',
            suffixStyle:
                const TextStyle(fontSize: 12, color: Color(0xFF8D6E63)),
            isDense: true,
            contentPadding: const EdgeInsets.symmetric(vertical: 6),
            enabledBorder: const UnderlineInputBorder(
              borderSide: BorderSide(color: Color(0xFFE0D5CC)),
            ),
            focusedBorder: const UnderlineInputBorder(
              borderSide: BorderSide(color: Color(0xFFC8956E), width: 1.6),
            ),
          ),
        ),
      ],
    );
  }

  Widget _dateRow(String label, DateTime value, ValueChanged<DateTime> onPick) {
    return InkWell(
      onTap: () => _pickDate(value, onPick),
      child: Padding(
        padding: const EdgeInsets.symmetric(vertical: 13),
        child: Row(
          children: [
            Text(label,
                style: const TextStyle(
                    fontSize: 13, color: Color(0xFF8D6E63))),
            const Spacer(),
            Text(
              _dateText(value),
              style: const TextStyle(
                fontSize: 14,
                fontWeight: FontWeight.w600,
                color: Color(0xFF5D4037),
              ),
            ),
            const SizedBox(width: 4),
            const Icon(Icons.chevron_right,
                size: 18, color: Color(0xFFBCAAA4)),
          ],
        ),
      ),
    );
  }

  Future<void> _pickDate(
      DateTime initial, ValueChanged<DateTime> onPick) async {
    final picked = await showDatePicker(
      context: context,
      initialDate: initial,
      firstDate: DateTime(2020),
      lastDate: DateTime(2035),
    );
    if (picked != null) onPick(picked);
  }

  // ---------------- 计划预览 ----------------

  /// 本地先算一遍计划，让用户改数字时立刻看到「每周该减多少」，
  /// 不用等保存。算法和后端一致（总周数向上取整）。
  ({int weeks, double weeklyLoss, bool valid}) _computePlan() {
    final start = double.tryParse(_startCtrl.text.trim());
    final target = double.tryParse(_targetCtrl.text.trim());
    if (start == null || target == null || start <= target) {
      return (weeks: 0, weeklyLoss: 0, valid: false);
    }
    final days = _targetDate.difference(_startDate).inDays;
    if (days <= 0) return (weeks: 0, weeklyLoss: 0, valid: false);

    final weeks = (days / 7).ceil();
    final weekly = (start - target) / weeks;
    return (weeks: weeks, weeklyLoss: weekly, valid: true);
  }

  Widget _planCard() {
    final plan = _computePlan();

    return Container(
      padding: const EdgeInsets.all(16),
      decoration: BoxDecoration(
        color: Colors.white,
        borderRadius: BorderRadius.circular(16),
      ),
      child: !plan.valid
          ? const Text(
              '填好起始体重和目标体重\n（目标要低于起始）就能算出每周该减多少',
              style: TextStyle(
                  fontSize: 13, height: 1.7, color: Color(0xFFBCAAA4)),
            )
          : Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: [
                const Text('按这个目标',
                    style: TextStyle(
                        fontSize: 12, color: Color(0xFF8D6E63))),
                const SizedBox(height: 8),
                Row(
                  crossAxisAlignment: CrossAxisAlignment.baseline,
                  textBaseline: TextBaseline.alphabetic,
                  children: [
                    Text(
                      '每周 ${plan.weeklyLoss.toStringAsFixed(2)}',
                      style: const TextStyle(
                        fontSize: 26,
                        fontWeight: FontWeight.bold,
                        color: Color(0xFFC8956E),
                      ),
                    ),
                    const SizedBox(width: 4),
                    const Text('kg',
                        style: TextStyle(
                            fontSize: 14, color: Color(0xFF8D6E63))),
                    const Spacer(),
                    Text(
                      '共 ${plan.weeks} 周',
                      style: const TextStyle(
                          fontSize: 12.5, color: Color(0xFF8D6E63)),
                    ),
                  ],
                ),
                if (plan.weeklyLoss > 1) ...[
                  const SizedBox(height: 12),
                  Container(
                    padding: const EdgeInsets.symmetric(
                        horizontal: 10, vertical: 8),
                    decoration: BoxDecoration(
                      color: const Color(0xFFF8ECD2),
                      borderRadius: BorderRadius.circular(8),
                    ),
                    child: const Row(
                      children: [
                        Icon(Icons.info_outline,
                            size: 14, color: Color(0xFFD9A93C)),
                        SizedBox(width: 6),
                        Expanded(
                          child: Text(
                            '每周超过 1kg 通常掉的是肌肉和水分，'
                            '建议把目标日期往后放一放',
                            style: TextStyle(
                                fontSize: 11.5,
                                height: 1.5,
                                color: Color(0xFF8D6E63)),
                          ),
                        ),
                      ],
                    ),
                  ),
                ],
              ],
            ),
    );
  }

  /// 每周目标体重表 —— 让「每周 0.54kg」变成一串能对照的数字
  Widget _weeklyTableCard() {
    final plan = _computePlan();
    if (!plan.valid) return const SizedBox.shrink();

    final start = double.parse(_startCtrl.text.trim());

    return Container(
      padding: const EdgeInsets.fromLTRB(16, 16, 16, 6),
      decoration: BoxDecoration(
        color: Colors.white,
        borderRadius: BorderRadius.circular(16),
      ),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          const Text(
            '每周目标体重',
            style: TextStyle(
              fontSize: 15,
              fontWeight: FontWeight.w600,
              color: Color(0xFF5D4037),
            ),
          ),
          const SizedBox(height: 4),
          const Text(
            '对照着看，就能知道自己落后了还是超前了',
            style: TextStyle(fontSize: 11.5, color: Color(0xFFBCAAA4)),
          ),
          const SizedBox(height: 10),
          // 只列前 8 周和最后一周：全列出来（13 周以上）会很长且没人看
          ..._weekRows(start, plan.weeks, plan.weeklyLoss),
        ],
      ),
    );
  }

  List<Widget> _weekRows(double start, int weeks, double weekly) {
    final rows = <Widget>[];
    final showAll = weeks <= 8;
    final indices = showAll
        ? List<int>.generate(weeks, (i) => i + 1)
        : [1, 2, 3, 4, 5, 6, 7, 8, weeks];

    int? previous;
    for (final week in indices) {
      // 中间省略时插一行省略号
      if (previous != null && week != previous + 1) {
        rows.add(const Padding(
          padding: EdgeInsets.symmetric(vertical: 6),
          child: Center(
            child: Text('···',
                style: TextStyle(color: Color(0xFFBCAAA4), fontSize: 13)),
          ),
        ));
      }
      previous = week;

      final ideal = start - weekly * week;

      rows.add(
        Padding(
          padding: const EdgeInsets.only(bottom: 9),
          child: Row(
            children: [
              SizedBox(
                width: 62,
                child: Text(
                  '第 $week 周',
                  style: const TextStyle(
                      fontSize: 12.5, color: Color(0xFF8D6E63)),
                ),
              ),
              Expanded(
                child: Text(
                  '${ideal.toStringAsFixed(1)} kg',
                  style: const TextStyle(
                    fontSize: 13,
                    fontWeight: FontWeight.w600,
                    color: Color(0xFF5D4037),
                  ),
                ),
              ),
              Text(
                '累计减 ${(weekly * week).toStringAsFixed(1)} kg',
                style: const TextStyle(
                    fontSize: 11.5, color: Color(0xFFBCAAA4)),
              ),
            ],
          ),
        ),
      );
    }
    return rows;
  }

  // ---------------- 保存 ----------------

  Widget _saveButton() {
    return SizedBox(
      width: double.infinity,
      child: ElevatedButton(
        onPressed: _saving ? null : _save,
        style: ElevatedButton.styleFrom(
          backgroundColor: const Color(0xFFC8956E),
          foregroundColor: Colors.white,
          padding: const EdgeInsets.symmetric(vertical: 14),
          shape: RoundedRectangleBorder(
            borderRadius: BorderRadius.circular(24),
          ),
        ),
        child: Text(
          _saving ? '保存中…' : '保存目标',
          style: const TextStyle(fontSize: 15, fontWeight: FontWeight.w600),
        ),
      ),
    );
  }

  Future<void> _save() async {
    final start = double.tryParse(_startCtrl.text.trim());
    final target = double.tryParse(_targetCtrl.text.trim());

    if (start == null || target == null) {
      showToast(context, '请填写起始体重和目标体重', error: true);
      return;
    }
    if (start < 20 || start > 300 || target < 20 || target > 300) {
      showToast(context, '体重需在 20 ~ 300 kg 之间', error: true);
      return;
    }
    if (target >= start) {
      showToast(context, '目标体重要低于起始体重', error: true);
      return;
    }
    if (!_targetDate.isAfter(_startDate)) {
      showToast(context, '目标日期要晚于开始日期', error: true);
      return;
    }

    setState(() => _saving = true);
    try {
      await ref.read(healthApiProvider).saveGoal(
            startWeight: start,
            targetWeight: target,
            startDate: _startDate,
            targetDate: _targetDate,
          );
      if (!mounted) return;
      ref.invalidate(weightGoalProvider);
      ref.invalidate(weightChartProvider);
      showToast(context, '目标已保存', icon: 'check');
      Navigator.of(context).pop();
    } catch (e) {
      if (!mounted) return;
      showToast(context, e.toString(), error: true);
    } finally {
      if (mounted) setState(() => _saving = false);
    }
  }
}

String _num(num value) {
  if (value == value.roundToDouble()) return value.round().toString();
  return value.toStringAsFixed(1);
}

String _dateText(DateTime date) {
  final m = date.month.toString().padLeft(2, '0');
  final d = date.day.toString().padLeft(2, '0');
  return '${date.year}-$m-$d';
}