import DateTimePicker from '@react-native-community/datetimepicker';
import { useRouter } from 'expo-router';
import React, { useEffect, useMemo, useState } from 'react';
import { Modal, Platform, Pressable, SafeAreaView, ScrollView, StyleSheet, TextInput, View } from 'react-native';

import { ThemedText } from '@/components/ThemedText';
import { ThemedView } from '@/components/ThemedView';
import { HeaderBar } from '@/components/ui/HeaderBar';
import { palette } from '@/constants/Colors';
import { useAppDispatch, useAppSelector } from '@/hooks/redux';
import {
  clearError,
  loadPlans,
  saveDraftAsPlan,
  setGoal,
  setMode,
  setName,
  setPreferredTime,
  setSessionsPerWeek,
  setStartDate,
  setStartDateNextMonday,
  setStartWeight,
  toggleDayOfWeek,
  type PlanGoal
} from '@/store/trainingPlanSlice';

const WEEK_DAYS = ['日', '一', '二', '三', '四', '五', '六'];
const GOALS: { key: PlanGoal; title: string; desc: string }[] = [
  { key: 'postpartum_recovery', title: '产后恢复', desc: '温和激活，核心重建' },
  { key: 'posture_correction', title: '体态矫正', desc: '打开胸肩，改善圆肩驼背' },
  { key: 'fat_loss', title: '减脂塑形', desc: '全身燃脂，线条雕刻' },
  { key: 'core_strength', title: '核心力量', desc: '核心稳定，提升运动表现' },
  { key: 'flexibility', title: '柔韧灵活', desc: '拉伸延展，释放紧张' },
  { key: 'rehab', title: '康复保健', desc: '循序渐进，科学修复' },
  { key: 'stress_relief', title: '释压放松', desc: '舒缓身心，改善睡眠' },
];

export default function TrainingPlanCreateScreen() {
  const router = useRouter();
  const dispatch = useAppDispatch();
  const { draft, loading, error } = useAppSelector((s) => s.trainingPlan);
  const [weightInput, setWeightInput] = useState<string>('');
  const [datePickerVisible, setDatePickerVisible] = useState(false);
  const [pickerDate, setPickerDate] = useState<Date>(new Date());

  useEffect(() => {
    dispatch(loadPlans());
  }, [dispatch]);

  useEffect(() => {
    if (draft.startWeightKg && !weightInput) setWeightInput(String(draft.startWeightKg));
  }, [draft.startWeightKg]);

  const selectedCount = draft.mode === 'daysOfWeek' ? draft.daysOfWeek.length : draft.sessionsPerWeek;

  const canSave = useMemo(() => {
    if (!draft.goal) return false;
    if (draft.mode === 'daysOfWeek' && draft.daysOfWeek.length === 0) return false;
    if (draft.mode === 'sessionsPerWeek' && draft.sessionsPerWeek <= 0) return false;
    return true;
  }, [draft]);

  const formattedStartDate = useMemo(() => {
    const d = new Date(draft.startDate);
    try {
      return new Intl.DateTimeFormat('zh-CN', {
        year: 'numeric',
        month: 'long',
        day: 'numeric',
        weekday: 'short',
      }).format(d);
    } catch {
      return d.toLocaleDateString('zh-CN');
    }
  }, [draft.startDate]);

  const handleSave = async () => {
    try {
      await dispatch(saveDraftAsPlan()).unwrap();
      router.back();
    } catch (error) {
      // 错误已经在Redux中处理，这里可以显示额外的用户反馈
      console.error('保存训练计划失败:', error);
    }
  };

  useEffect(() => {
    if (error) {
      // 3秒后自动清除错误
      const timer = setTimeout(() => {
        dispatch(clearError());
      }, 3000);
      return () => clearTimeout(timer);
    }
  }, [error, dispatch]);

  const openDatePicker = () => {
    const base = draft.startDate ? new Date(draft.startDate) : new Date();
    base.setHours(0, 0, 0, 0);
    setPickerDate(base);
    setDatePickerVisible(true);
  };
  const closeDatePicker = () => setDatePickerVisible(false);
  const onConfirmDate = (date: Date) => {
    const today = new Date();
    today.setHours(0, 0, 0, 0);
    const picked = new Date(date);
    picked.setHours(0, 0, 0, 0);
    const finalDate = picked < today ? today : picked;
    dispatch(setStartDate(finalDate.toISOString()));
    closeDatePicker();
  };

  return (
    <SafeAreaView style={styles.safeArea}>
      <ThemedView style={styles.container}>
        <HeaderBar title="新建训练计划" onBack={() => router.back()} withSafeTop={false} transparent />
        <ScrollView showsVerticalScrollIndicator={false} contentContainerStyle={styles.content}>
          <ThemedText style={styles.title}>制定你的训练计划</ThemedText>
          <ThemedText style={styles.subtitle}>选择你的训练节奏与目标，我们将为你生成合适的普拉提安排。</ThemedText>

          {error && (
            <View style={styles.errorContainer}>
              <ThemedText style={styles.errorText}>⚠️ {error}</ThemedText>
            </View>
          )}

          <View style={styles.card}>
            <ThemedText style={styles.cardTitle}>计划名称</ThemedText>
            <TextInput
              placeholder="为你的训练计划起个名字（可选）"
              value={draft.name || ''}
              onChangeText={(text) => dispatch(setName(text))}
              style={styles.nameInput}
              maxLength={50}
            />
          </View>

          <View style={styles.card}>
            <ThemedText style={styles.cardTitle}>训练频率</ThemedText>
            <View style={styles.segment}>
              <Pressable
                onPress={() => dispatch(setMode('daysOfWeek'))}
                style={[styles.segmentItem, draft.mode === 'daysOfWeek' && styles.segmentItemActive]}
              >
                <ThemedText style={[styles.segmentText, draft.mode === 'daysOfWeek' && styles.segmentTextActive]}>按星期选择</ThemedText>
              </Pressable>
              <Pressable
                onPress={() => dispatch(setMode('sessionsPerWeek'))}
                style={[styles.segmentItem, draft.mode === 'sessionsPerWeek' && styles.segmentItemActive]}
              >
                <ThemedText style={[styles.segmentText, draft.mode === 'sessionsPerWeek' && styles.segmentTextActive]}>每周次数</ThemedText>
              </Pressable>
            </View>

            {draft.mode === 'daysOfWeek' ? (
              <View style={styles.weekRow}>
                {WEEK_DAYS.map((d, i) => {
                  const active = draft.daysOfWeek.includes(i);
                  return (
                    <Pressable key={i} onPress={() => dispatch(toggleDayOfWeek(i))} style={[styles.dayChip, active && styles.dayChipActive]}>
                      <ThemedText style={[styles.dayChipText, active && styles.dayChipTextActive]}>{d}</ThemedText>
                    </Pressable>
                  );
                })}
              </View>
            ) : (
              <View style={styles.sliderRow}>
                <ThemedText style={styles.sliderLabel}>每周训练</ThemedText>
                <View style={styles.counter}>
                  <Pressable onPress={() => dispatch(setSessionsPerWeek(Math.max(1, draft.sessionsPerWeek - 1)))} style={styles.counterBtn}>
                    <ThemedText style={styles.counterBtnText}>-</ThemedText>
                  </Pressable>
                  <ThemedText style={styles.counterValue}>{draft.sessionsPerWeek}</ThemedText>
                  <Pressable onPress={() => dispatch(setSessionsPerWeek(Math.min(7, draft.sessionsPerWeek + 1)))} style={styles.counterBtn}>
                    <ThemedText style={styles.counterBtnText}>+</ThemedText>
                  </Pressable>
                </View>
                <ThemedText style={styles.sliderSuffix}>次</ThemedText>
              </View>
            )}

            <ThemedText style={styles.helper}>已选择：{selectedCount} 次/周</ThemedText>
          </View>

          <View style={styles.card}>
            <ThemedText style={styles.cardTitle}>训练目标</ThemedText>
            <View style={styles.goalGrid}>
              {GOALS.map((g) => {
                const active = draft.goal === g.key;
                return (
                  <Pressable key={g.key} onPress={() => dispatch(setGoal(g.key))} style={[styles.goalItem, active && styles.goalItemActive]}>
                    <ThemedText style={[styles.goalTitle, active && styles.goalTitleActive]}>{g.title}</ThemedText>
                    <ThemedText style={styles.goalDesc}>{g.desc}</ThemedText>
                  </Pressable>
                );
              })}
            </View>
          </View>

          <View style={styles.card}>
            <ThemedText style={styles.cardTitle}>更多选项</ThemedText>
            <View style={styles.rowBetween}>
              <ThemedText style={styles.label}>开始日期</ThemedText>
              <View style={styles.rowRight}>
                <Pressable onPress={openDatePicker} style={styles.linkBtn}>
                  <ThemedText style={styles.linkText}>选择日期</ThemedText>
                </Pressable>
                <Pressable onPress={() => dispatch(setStartDateNextMonday())} style={[styles.linkBtn, { marginLeft: 8 }]}>
                  <ThemedText style={styles.linkText}>下周一</ThemedText>
                </Pressable>
              </View>
            </View>
            <ThemedText style={styles.dateHint}>{formattedStartDate}</ThemedText>

            <View style={styles.rowBetween}>
              <ThemedText style={styles.label}>开始体重 (kg)</ThemedText>
              <TextInput
                keyboardType="numeric"
                placeholder="可选"
                value={weightInput}
                onChangeText={(t) => {
                  setWeightInput(t);
                  const v = Number(t);
                  dispatch(setStartWeight(Number.isFinite(v) ? v : undefined));
                }}
                style={styles.input}
              />
            </View>

            <View style={[styles.rowBetween, { marginTop: 12 }]}>
              <ThemedText style={styles.label}>偏好时间段</ThemedText>
              <View style={styles.segmentSmall}>
                {(['morning', 'noon', 'evening', ''] as const).map((k) => (
                  <Pressable key={k || 'none'} onPress={() => dispatch(setPreferredTime(k))} style={[styles.segmentItemSmall, draft.preferredTimeOfDay === k && styles.segmentItemActiveSmall]}>
                    <ThemedText style={[styles.segmentTextSmall, draft.preferredTimeOfDay === k && styles.segmentTextActiveSmall]}>{k === 'morning' ? '晨练' : k === 'noon' ? '午间' : k === 'evening' ? '晚间' : '不限'}</ThemedText>
                  </Pressable>
                ))}
              </View>
            </View>
          </View>

          <Pressable disabled={!canSave || loading} onPress={handleSave} style={[styles.primaryBtn, (!canSave || loading) && styles.primaryBtnDisabled]}>
            <ThemedText style={styles.primaryBtnText}>
              {loading ? '创建中...' : canSave ? '生成计划' : '请先选择目标/频率'}
            </ThemedText>
          </Pressable>

          <View style={{ height: 32 }} />
        </ScrollView>
      </ThemedView>
      <Modal
        visible={datePickerVisible}
        transparent
        animationType="fade"
        onRequestClose={closeDatePicker}
      >
        <Pressable style={styles.modalBackdrop} onPress={closeDatePicker} />
        <View style={styles.modalSheet}>
          <DateTimePicker
            value={pickerDate}
            mode="date"
            display={Platform.OS === 'ios' ? 'inline' : 'calendar'}
            minimumDate={new Date()}
            {...(Platform.OS === 'ios' ? { locale: 'zh-CN' } : {})}
            onChange={(event, date) => {
              if (Platform.OS === 'ios') {
                if (date) setPickerDate(date);
              } else {
                if (event.type === 'set' && date) {
                  onConfirmDate(date);
                } else {
                  closeDatePicker();
                }
              }
            }}
          />
          {Platform.OS === 'ios' && (
            <View style={styles.modalActions}>
              <Pressable onPress={closeDatePicker} style={[styles.modalBtn]}>
                <ThemedText style={styles.modalBtnText}>取消</ThemedText>
              </Pressable>
              <Pressable onPress={() => { onConfirmDate(pickerDate); }} style={[styles.modalBtn, styles.modalBtnPrimary]}>
                <ThemedText style={[styles.modalBtnText, styles.modalBtnTextPrimary]}>确定</ThemedText>
              </Pressable>
            </View>
          )}
        </View>
      </Modal>
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  safeArea: {
    flex: 1,
    backgroundColor: '#F7F8FA',
  },
  container: {
    flex: 1,
    backgroundColor: '#F7F8FA',
  },
  content: {
    paddingHorizontal: 20,
    paddingTop: 16,
  },
  title: {
    fontSize: 28,
    fontWeight: '800',
    color: '#1A1A1A',
    lineHeight: 36,
  },
  subtitle: {
    fontSize: 14,
    color: '#5E6468',
    marginTop: 6,
    marginBottom: 16,
    lineHeight: 20,
  },
  card: {
    backgroundColor: '#FFFFFF',
    borderRadius: 16,
    padding: 16,
    marginTop: 14,
    shadowColor: '#000',
    shadowOpacity: 0.06,
    shadowRadius: 12,
    shadowOffset: { width: 0, height: 6 },
    elevation: 3,
  },
  cardTitle: {
    fontSize: 18,
    fontWeight: '700',
    color: '#0F172A',
    marginBottom: 12,
  },
  segment: {
    flexDirection: 'row',
    backgroundColor: '#F1F5F9',
    padding: 4,
    borderRadius: 999,
  },
  segmentItem: {
    flex: 1,
    borderRadius: 999,
    paddingVertical: 10,
    alignItems: 'center',
  },
  segmentItemActive: {
    backgroundColor: palette.primary,
  },
  segmentText: {
    fontSize: 14,
    color: '#475569',
    fontWeight: '600',
  },
  segmentTextActive: {
    color: palette.ink,
  },
  weekRow: {
    flexDirection: 'row',
    justifyContent: 'space-between',
    marginTop: 14,
  },
  dayChip: {
    width: 44,
    height: 44,
    borderRadius: 12,
    backgroundColor: '#F1F5F9',
    alignItems: 'center',
    justifyContent: 'center',
  },
  dayChipActive: {
    backgroundColor: '#E0F8A2',
    borderWidth: 2,
    borderColor: palette.primary,
  },
  dayChipText: {
    fontSize: 16,
    color: '#334155',
    fontWeight: '700',
  },
  dayChipTextActive: {
    color: '#0F172A',
  },
  sliderRow: {
    flexDirection: 'row',
    alignItems: 'center',
    marginTop: 16,
  },
  sliderLabel: {
    fontSize: 16,
    color: '#334155',
    fontWeight: '700',
  },
  counter: {
    flexDirection: 'row',
    alignItems: 'center',
    marginLeft: 12,
  },
  counterBtn: {
    width: 36,
    height: 36,
    borderRadius: 999,
    backgroundColor: '#F1F5F9',
    alignItems: 'center',
    justifyContent: 'center',
  },
  counterBtnText: {
    fontSize: 18,
    fontWeight: '800',
    color: '#0F172A',
  },
  counterValue: {
    width: 44,
    textAlign: 'center',
    fontSize: 18,
    fontWeight: '800',
    color: '#0F172A',
  },
  sliderSuffix: {
    marginLeft: 8,
    color: '#475569',
  },
  helper: {
    marginTop: 10,
    color: '#5E6468',
  },
  goalGrid: {
    flexDirection: 'row',
    flexWrap: 'wrap',
    justifyContent: 'space-between',
  },
  goalItem: {
    width: '48%',
    backgroundColor: '#F8FAFC',
    borderRadius: 14,
    padding: 12,
    marginBottom: 12,
  },
  goalItemActive: {
    backgroundColor: '#E0F8A2',
    borderColor: palette.primary,
    borderWidth: 2,
  },
  goalTitle: {
    fontSize: 16,
    fontWeight: '800',
    color: '#0F172A',
  },
  goalTitleActive: {
    color: '#0F172A',
  },
  goalDesc: {
    marginTop: 6,
    fontSize: 12,
    color: '#5E6468',
    lineHeight: 16,
  },
  rowBetween: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
    marginTop: 6,
  },
  rowRight: {
    flexDirection: 'row',
    alignItems: 'center',
  },
  label: {
    fontSize: 14,
    color: '#0F172A',
    fontWeight: '700',
  },
  linkBtn: {
    paddingHorizontal: 10,
    paddingVertical: 6,
    borderRadius: 999,
    backgroundColor: '#F1F5F9',
  },
  linkText: {
    color: '#334155',
    fontWeight: '700',
  },
  dateHint: {
    marginTop: 6,
    color: '#5E6468',
  },
  input: {
    marginLeft: 12,
    backgroundColor: '#F1F5F9',
    paddingHorizontal: 10,
    paddingVertical: 8,
    borderRadius: 8,
    minWidth: 88,
    textAlign: 'right',
    color: '#0F172A',
  },
  segmentSmall: {
    flexDirection: 'row',
    backgroundColor: '#F1F5F9',
    padding: 3,
    borderRadius: 999,
  },
  segmentItemSmall: {
    borderRadius: 999,
    paddingVertical: 6,
    paddingHorizontal: 10,
    marginHorizontal: 3,
  },
  segmentItemActiveSmall: {
    backgroundColor: palette.primary,
  },
  segmentTextSmall: {
    fontSize: 12,
    color: '#475569',
    fontWeight: '700',
  },
  segmentTextActiveSmall: {
    color: palette.ink,
  },
  primaryBtn: {
    marginTop: 18,
    backgroundColor: palette.primary,
    paddingVertical: 14,
    borderRadius: 14,
    alignItems: 'center',
  },
  primaryBtnDisabled: {
    opacity: 0.5,
  },
  primaryBtnText: {
    color: palette.ink,
    fontSize: 16,
    fontWeight: '800',
  },
  modalBackdrop: {
    ...StyleSheet.absoluteFillObject,
    backgroundColor: 'rgba(0,0,0,0.35)',
  },
  modalSheet: {
    position: 'absolute',
    left: 0,
    right: 0,
    bottom: 0,
    padding: 16,
    backgroundColor: '#FFFFFF',
    borderTopLeftRadius: 16,
    borderTopRightRadius: 16,
  },
  modalActions: {
    flexDirection: 'row',
    justifyContent: 'flex-end',
    marginTop: 8,
    gap: 12,
  },
  modalBtn: {
    paddingHorizontal: 14,
    paddingVertical: 10,
    borderRadius: 10,
    backgroundColor: '#F1F5F9',
  },
  modalBtnPrimary: {
    backgroundColor: palette.primary,
  },
  modalBtnText: {
    color: '#334155',
    fontWeight: '700',
  },
  modalBtnTextPrimary: {
    color: palette.ink,
  },

  // 计划名称输入框
  nameInput: {
    backgroundColor: '#F1F5F9',
    paddingHorizontal: 12,
    paddingVertical: 12,
    borderRadius: 8,
    fontSize: 16,
    color: '#0F172A',
    marginTop: 8,
  },

  // 错误状态
  errorContainer: {
    backgroundColor: 'rgba(237,71,71,0.1)',
    borderRadius: 12,
    padding: 16,
    marginTop: 16,
    borderWidth: 1,
    borderColor: 'rgba(237,71,71,0.2)',
  },
  errorText: {
    fontSize: 14,
    color: '#ED4747',
    fontWeight: '600',
    textAlign: 'center',
  },
});