/**
 * 报表页（plan.md「5.2 图表与可视化」+「5.3 年度报告」；P4 spec §7.3 重写）。
 *
 * 功能：
 * - 单一 anchor 日期 + 周期（周/月/年）统一导航（periodNav），替代三套独立切换器
 * - 收支看板/分类占比/日历/净资产趋势/年度报告
 * - ⋯ 菜单：AI 月度总结、导出报表为图片（react-native-view-shot）
 */
import React, { useMemo, useRef, useState } from 'react';
import { Alert, Modal, Pressable, ScrollView, StyleSheet, Text, View } from 'react-native';
import { SafeAreaView } from 'react-native-safe-area-context';
import { useRouter } from 'expo-router';
import { Ionicons } from '@expo/vector-icons';
import { captureRef } from 'react-native-view-shot';
import * as Sharing from 'expo-sharing';
import { useLedgerStore } from '../../store/ledgerStore';
import { useSettingsStore } from '../../store/settingsStore';
import { useTheme, createCommonStyles } from '../../theme';
import { useT } from '../../i18n';
import { Card } from '../../components/Card';
import { Button } from '../../components/Button';
import { BottomSheet } from '../../components/BottomSheet';
import { CategoryPie } from '../../components/charts/CategoryPie';
import { CalendarView } from '../../components/CalendarView';
import { TransactionCard } from '../../components/TransactionCard';
import { NetWorthChart } from '../../components/charts/NetWorthChart';
import { AnnualReport } from '../../components/charts/AnnualReport';
import { calculateMonthlyStats, generatePlainTextSummary, generateMonthlySummary } from '../../ai/monthlySummary';
import { BaseOpenAIProvider } from '../../domain/ai';
import { addDecimals, negateDecimal, toDateString } from '../../domain/decimal';
import { periodRange, shiftAnchor, isoWeekNumber, type ReportPeriod } from '../../domain/periodNav';

export default function ReportScreen() {
  const { theme } = useTheme();
  const commonStyles = useMemo(() => createCommonStyles(theme), [theme]);
  const t = useT();
  const router = useRouter();
  const ledger = useLedgerStore(s => s.ledger);
  const aiEnabled = useSettingsStore(s => s.aiEnabled);
  const aiApiKey = useSettingsStore(s => s.aiApiKey);
  const aiBaseUrl = useSettingsStore(s => s.aiBaseUrl);
  const aiModel = useSettingsStore(s => s.aiModel);

  // 周期 + 单一 anchor 日期（P4：替代旧版年/月/周三套独立切换状态）
  const [period, setPeriod] = useState<ReportPeriod>('monthly');
  const [anchor, setAnchor] = useState(() => toDateString(new Date()));

  // ⋯ 菜单
  const [menuOpen, setMenuOpen] = useState(false);

  // 日历选中日期用于明细展开
  const [selectedReportDate, setSelectedReportDate] = useState<string | null>(null);

  // AI 总结弹窗
  const [summaryModal, setSummaryModal] = useState(false);
  const [summaryText, setSummaryText] = useState('');

  // 截图 ref
  const scrollRef = useRef<ScrollView>(null);

  const transactions = useMemo(() => ledger?.transactions ?? [], [ledger]);

  // anchor 所在周期的起止日期与周期内交易
  const range = useMemo(() => periodRange(anchor, period), [anchor, period]);
  const rangeTxs = useMemo(
    () => transactions.filter(tx => tx.date >= range.start && tx.date <= range.end),
    [transactions, range],
  );

  // 周期收支统计（Income 腿取负、Expenses 腿原值，与旧 weeklyStats/monthlyStats 同算法）
  const rangeStats = useMemo(() => {
    const incomeAmounts: string[] = [];
    const expenseAmounts: string[] = [];
    for (const tx of rangeTxs) {
      for (const p of tx.postings) {
        if (!p.amount) continue;
        if (p.account.startsWith('Income')) incomeAmounts.push(negateDecimal(p.amount));
        if (p.account.startsWith('Expenses')) expenseAmounts.push(p.amount);
      }
    }
    const income = parseFloat(addDecimals(incomeAmounts.length ? incomeAmounts : ['0']));
    const expense = parseFloat(addDecimals(expenseAmounts.length ? expenseAmounts : ['0']));
    return { income, expense, net: income - expense, count: rangeTxs.length };
  }, [rangeTxs]);

  // 周期切换器 label
  const periodLabel = useMemo(() => {
    if (period === 'weekly') {
      const monday = range.start;
      const sunday = range.end;
      return `${anchor.slice(0, 4)}年第${isoWeekNumber(anchor)}周 (${Number(monday.slice(5, 7))}/${Number(monday.slice(8))} ~ ${Number(sunday.slice(5, 7))}/${Number(sunday.slice(8))})`;
    }
    if (period === 'monthly') return anchor.slice(0, 7);
    return `${anchor.slice(0, 4)}年`;
  }, [period, anchor, range]);

  // 净资产趋势的日期序列（基于 anchor 所在月，往前 6 个月）
  const netWorthDates = useMemo(() => {
    const dates: string[] = [];
    for (let i = 5; i >= 0; i--) {
      const d = new Date(Number(anchor.slice(0, 4)), Number(anchor.slice(5, 7)) - 1 - i, 1);
      dates.push(toDateString(d));
    }
    return dates;
  }, [anchor]);

  const shift = (delta: number) => {
    setSelectedReportDate(null);
    setAnchor(a => shiftAnchor(a, period, delta));
  };

  // 选中日期的交易明细
  const selectedDayTxs = useMemo(() => {
    if (!selectedReportDate) return [];
    return rangeTxs.filter(tx => tx.date.slice(0, 10) === selectedReportDate);
  }, [rangeTxs, selectedReportDate]);

  // 千分位格式化金额
  const fmtAmount = (num: number) => {
    const formatted = num.toLocaleString('zh-CN', { minimumFractionDigits: 2, maximumFractionDigits: 2 });
    return num >= 0 ? `¥${formatted}` : `-¥${Math.abs(num).toLocaleString('zh-CN', { minimumFractionDigits: 2, maximumFractionDigits: 2 })}`;
  };

  // 导出报表为图片
  const handleExportImage = async () => {
    try {
      if (!scrollRef.current) return;
      const uri = await captureRef(scrollRef, { format: 'png', quality: 0.9 });
      if (await Sharing.isAvailableAsync()) {
        await Sharing.shareAsync(uri, { mimeType: 'image/png', dialogTitle: t('report.shareTitle') });
      } else {
        Alert.alert(t('report.exportSuccess'), uri);
      }
    } catch (e) {
      Alert.alert(t('report.exportFail'), String(e));
    }
  };

  // AI / 纯文本月度总结（基于 anchor 所在月）
  const handleMonthlySummary = async () => {
    const year = Number(anchor.slice(0, 4));
    const month = Number(anchor.slice(5, 7));
    const stats = calculateMonthlyStats(transactions, year, month);
    if (aiEnabled && aiApiKey && aiBaseUrl) {
      try {
        const provider = new (class extends BaseOpenAIProvider {})({
          id: 'report-summary',
          name: 'Report Summary',
          apiKey: aiApiKey,
          baseUrl: aiBaseUrl,
          model: aiModel || 'glm-4-flash',
        });
        const result = await generateMonthlySummary(transactions, year, month, provider);
        setSummaryText(result.summary || generatePlainTextSummary(stats));
      } catch {
        setSummaryText(generatePlainTextSummary(stats));
      }
    } else {
      setSummaryText(generatePlainTextSummary(stats));
    }
    setSummaryModal(true);
  };

  const monthLabel = anchor.slice(0, 7);
  const anchorYear = Number(anchor.slice(0, 4));
  const anchorMonth = Number(anchor.slice(5, 7));

  return (
    <SafeAreaView style={[styles.page, { backgroundColor: theme.colors.bgPrimary }]} edges={['top']}>
      <View style={styles.header}>
        <Text style={[theme.typography.h1, { color: theme.colors.fgPrimary }]}>{t('tab.report')}</Text>
        <Pressable
          onPress={() => setMenuOpen(true)}
          style={({ pressed }) => [styles.iconBtn, { opacity: pressed ? 0.6 : 1 }]}
          accessibilityRole="button"
          accessibilityLabel={t('report.menu')}
        >
          <Ionicons name="ellipsis-horizontal" size={22} color={theme.colors.accent} />
        </Pressable>
      </View>

      {/* Tab 选择切换栏 */}
      <View style={[styles.tabContainer, { borderBottomColor: theme.colors.divider }]}>
        {([
          { key: 'weekly', label: t('report.tabWeekly') },
          { key: 'monthly', label: t('report.tabMonthly') },
          { key: 'annual', label: t('report.tabAnnual') }
        ] as const).map(tab => (
          <Pressable
            key={tab.key}
            onPress={() => {
              setPeriod(tab.key);
              setSelectedReportDate(null);
            }}
            style={[
              styles.tabBtn,
              period === tab.key && { borderBottomColor: theme.colors.accent }
            ]}
          >
            <Text
              style={[
                theme.typography.body,
                {
                  color: period === tab.key ? theme.colors.accent : theme.colors.fgSecondary,
                  fontWeight: period === tab.key ? '700' : '400',
                  paddingVertical: 10
                }
              ]}
            >
              {tab.label}
            </Text>
          </Pressable>
        ))}
      </View>

      {/* 统一周期切换器 */}
      <View style={styles.monthSwitcher}>
        <Pressable onPress={() => shift(-1)} style={({ pressed }) => [styles.monthBtn, { borderColor: theme.colors.border, opacity: pressed ? 0.6 : 1 }]}>
          <Ionicons name="chevron-back" size={18} color={theme.colors.fgPrimary} />
        </Pressable>
        <Text style={[theme.typography.h3, { color: theme.colors.fgPrimary }]}>
          {periodLabel}
        </Text>
        <Pressable onPress={() => shift(1)} style={({ pressed }) => [styles.monthBtn, { borderColor: theme.colors.border, opacity: pressed ? 0.6 : 1 }]}>
          <Ionicons name="chevron-forward" size={18} color={theme.colors.fgPrimary} />
        </Pressable>
      </View>

      <ScrollView
        ref={scrollRef}
        contentContainerStyle={[styles.content, { gap: theme.spacing.md }]}
      >
        {/* 数据空值判断 */}
        {rangeTxs.length === 0 ? (
          <Card title={t('report.title')}>
            <Text style={[theme.typography.body, { color: theme.colors.fgSecondary }]}>
              {t('report.empty')}
            </Text>
          </Card>
        ) : (
          <>
            {/* 周/月收支看板 */}
            {period !== 'annual' && (
              <>
                <Card title={t(period === 'weekly' ? 'report.weeklyTitle' : 'report.monthlyTitle')}>
                  <View style={styles.statsRow}>
                    <View style={styles.statItem}>
                      <Text style={[theme.typography.caption, { color: theme.colors.fgSecondary }]}>{t(period === 'weekly' ? 'report.weeklyIncome' : 'report.monthlyIncome')}</Text>
                      <Text style={[theme.typography.h3, { color: theme.colors.financial.income, fontVariant: ['tabular-nums'], fontWeight: '700' }]}>{fmtAmount(rangeStats.income)}</Text>
                    </View>
                    <View style={styles.statItem}>
                      <Text style={[theme.typography.caption, { color: theme.colors.fgSecondary }]}>{t(period === 'weekly' ? 'report.weeklyExpense' : 'report.monthlyExpense')}</Text>
                      <Text style={[theme.typography.h3, { color: theme.colors.financial.expense, fontVariant: ['tabular-nums'], fontWeight: '700' }]}>{fmtAmount(-rangeStats.expense)}</Text>
                    </View>
                    <View style={styles.statItem}>
                      <Text style={[theme.typography.caption, { color: theme.colors.fgSecondary }]}>{t(period === 'weekly' ? 'report.weeklyNet' : 'report.monthlyNet')}</Text>
                      <Text style={[theme.typography.h3, { color: theme.colors.accent, fontVariant: ['tabular-nums'], fontWeight: '700' }]}>{fmtAmount(rangeStats.net)}</Text>
                    </View>
                  </View>
                  <Text style={[theme.typography.caption, { color: theme.colors.fgSecondary, textAlign: 'center', marginTop: 8 }]}>
                    {t(period === 'weekly' ? 'report.weeklyStats' : 'report.monthlyStats', { count: rangeStats.count })}
                  </Text>
                </Card>

                <CategoryPie transactions={rangeTxs} />

                {/* 月 Tab 专属：日历 + 选中日期明细 + 净资产趋势 */}
                {period === 'monthly' && (
                  <>
                    <CalendarView
                      transactions={transactions}
                      year={anchorYear}
                      month={anchorMonth}
                      onDayPress={setSelectedReportDate}
                    />

                    {selectedReportDate && selectedReportDate.startsWith(monthLabel) && (
                      <Card title={`${selectedReportDate} 交易明细 (${selectedDayTxs.length})`}>
                        {selectedDayTxs.map(tx => (
                          <TransactionCard
                            key={tx.id}
                            transaction={tx}
                            onPress={() => router.push(`/transaction/${tx.id}`)}
                          />
                        ))}
                        {selectedDayTxs.length === 0 && (
                          <Text style={[theme.typography.caption, { color: theme.colors.fgSecondary, textAlign: 'center', marginVertical: 8 }]}>
                            {t('calendar.noDayTx')}
                          </Text>
                        )}
                      </Card>
                    )}

                    <NetWorthChart transactions={transactions} dates={netWorthDates} />
                  </>
                )}
              </>
            )}

            {/* 年度报表看板 */}
            {period === 'annual' && (
              <AnnualReport transactions={transactions} year={anchorYear} />
            )}
          </>
        )}
      </ScrollView>

      {/* ⋯ 菜单 */}
      <BottomSheet visible={menuOpen} onClose={() => setMenuOpen(false)} title={t('report.menu')}>
        <Pressable
          style={({ pressed }) => [styles.menuRow, { opacity: pressed ? 0.6 : 1 }]}
          onPress={() => { setMenuOpen(false); handleMonthlySummary(); }}
          accessibilityRole="button"
          accessibilityLabel={t('report.aiSummary')}
        >
          <Ionicons name="sparkles-outline" size={20} color={theme.colors.accent} />
          <Text style={[theme.typography.body, { color: theme.colors.fgPrimary }]}>{t('report.aiSummary')}</Text>
        </Pressable>
        <Pressable
          style={({ pressed }) => [styles.menuRow, { opacity: pressed ? 0.6 : 1 }]}
          onPress={() => { setMenuOpen(false); handleExportImage(); }}
          accessibilityRole="button"
          accessibilityLabel={t('report.exportImage')}
        >
          <Ionicons name="share-outline" size={20} color={theme.colors.accent} />
          <Text style={[theme.typography.body, { color: theme.colors.fgPrimary }]}>{t('report.exportImage')}</Text>
        </Pressable>
      </BottomSheet>

      {/* AI 总结弹窗 */}
      <Modal visible={summaryModal} animationType="slide" transparent onRequestClose={() => setSummaryModal(false)}>
        <View style={commonStyles.modalOverlay}>
          <View style={commonStyles.modalCard}>
            <Text style={[theme.typography.h3, { color: theme.colors.fgPrimary, marginBottom: 12 }]}>
              {monthLabel} {t('report.aiSummary')}
            </Text>
            <ScrollView style={{ maxHeight: 400 }}>
              <Text style={[theme.typography.body, { color: theme.colors.fgPrimary, lineHeight: 22 }]}>
                {summaryText}
              </Text>
            </ScrollView>
            <View style={{ marginTop: 16 }}>
              <Button label={t('common.confirm')} onPress={() => setSummaryModal(false)} />
            </View>
          </View>
        </View>
      </Modal>
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  page: { flex: 1 },
  header: { flexDirection: 'row', alignItems: 'center', justifyContent: 'space-between', paddingHorizontal: 16, paddingTop: 8, paddingBottom: 8 },
  iconBtn: { padding: 4 },
  monthSwitcher: { flexDirection: 'row', alignItems: 'center', justifyContent: 'center', gap: 20, paddingBottom: 12 },
  monthBtn: { width: 32, height: 32, borderRadius: 16, borderWidth: StyleSheet.hairlineWidth, alignItems: 'center', justifyContent: 'center' },
  content: { padding: 16, paddingBottom: 96 },
  tabContainer: { flexDirection: 'row', justifyContent: 'space-around', borderBottomWidth: StyleSheet.hairlineWidth, paddingHorizontal: 16, marginBottom: 8 },
  tabBtn: { flex: 1, alignItems: 'center', borderBottomWidth: 2, borderBottomColor: 'transparent' },
  statsRow: { flexDirection: 'row', justifyContent: 'space-around', marginVertical: 8, width: '100%' },
  statItem: { alignItems: 'center', gap: 4 },
  menuRow: { flexDirection: 'row', alignItems: 'center', gap: 12, paddingVertical: 14 },
});