import { Ionicons } from '@expo/vector-icons';
import * as AppleAuthentication from 'expo-apple-authentication';
import { useRouter } from 'expo-router';
import React, { useCallback, useEffect, useMemo, useState } from 'react';
import { Alert, Pressable, ScrollView, StyleSheet, Text, TouchableOpacity, View } from 'react-native';
import { SafeAreaView } from 'react-native-safe-area-context';

import { ThemedText } from '@/components/ThemedText';
import { ThemedView } from '@/components/ThemedView';
import { Colors } from '@/constants/Colors';
import { useAppDispatch } from '@/hooks/redux';
import { useColorScheme } from '@/hooks/useColorScheme';
import { login } from '@/store/userSlice';

export default function LoginScreen() {
  const router = useRouter();
  const scheme = (useColorScheme() ?? 'light') as 'light' | 'dark';
  const color = Colors[scheme];
  const dispatch = useAppDispatch();

  const [hasAgreed, setHasAgreed] = useState<boolean>(false);
  const [appleAvailable, setAppleAvailable] = useState<boolean>(false);
  const [loading, setLoading] = useState<boolean>(false);

  useEffect(() => {
    AppleAuthentication.isAvailableAsync().then(setAppleAvailable).catch(() => setAppleAvailable(false));
  }, []);

  const guardAgreement = useCallback((action: () => void) => {
    if (!hasAgreed) {
      Alert.alert('请先阅读并同意', '勾选“我已阅读并同意用户协议与隐私政策”后才可继续登录');
      return;
    }
    action();
  }, [hasAgreed]);

  const onAppleLogin = useCallback(async () => {
    if (!appleAvailable) return;
    try {
      setLoading(true);
      const credential = await AppleAuthentication.signInAsync({
        requestedScopes: [
          AppleAuthentication.AppleAuthenticationScope.FULL_NAME,
          AppleAuthentication.AppleAuthenticationScope.EMAIL,
        ],
      });
      const identityToken = (credential as any)?.identityToken;
      await dispatch(login({ appleIdentityToken: identityToken })).unwrap();
      router.back();
    } catch (err: any) {
      if (err?.code === 'ERR_CANCELED') return;
      const message = err?.message || '登录失败，请稍后再试';
      Alert.alert('登录失败', message);
    } finally {
      setLoading(false);
    }
  }, [appleAvailable, router]);

  const onGuestLogin = useCallback(() => {
    // TODO: 标记为游客身份，可在此写入本地状态/上报统计
    router.back();
  }, [router]);

  const disabledStyle = useMemo(() => ({ opacity: hasAgreed ? 1 : 0.5 }), [hasAgreed]);

  return (
    <SafeAreaView edges={['top']} style={[styles.safeArea, { backgroundColor: color.background }]}>
      <ThemedView style={styles.container}>
        {/* 自定义头部，与其它页面风格一致 */}
        <View style={styles.header}>
          <TouchableOpacity accessibilityRole="button" onPress={() => router.back()} style={styles.backButton}>
            <Ionicons name="chevron-back" size={24} color={scheme === 'dark' ? '#ECEDEE' : '#192126'} />
          </TouchableOpacity>
          <Text style={[styles.headerTitle, { color: color.text }]}>登录</Text>
          <View style={{ width: 32 }} />
        </View>

        <ScrollView contentContainerStyle={styles.content} showsVerticalScrollIndicator={false}>
          <View style={styles.headerWrap}>
            <ThemedText style={[styles.title, { color: color.text }]}>数字普拉提</ThemedText>
            <ThemedText style={[styles.subtitle, { color: color.textMuted }]}>欢迎登录</ThemedText>
          </View>

          {/* Apple 登录 */}
          {appleAvailable && (
            <Pressable
              accessibilityRole="button"
              onPress={() => guardAgreement(onAppleLogin)}
              disabled={!hasAgreed || loading}
              style={({ pressed }) => [
                styles.appleButton,
                { backgroundColor: '#000000' },
                disabledStyle,
                pressed && { transform: [{ scale: 0.98 }] },
              ]}
            >
              <Ionicons name="logo-apple" size={22} color="#FFFFFF" style={{ marginRight: 10 }} />
              <Text style={styles.appleText}>使用 Apple 登录</Text>
            </Pressable>
          )}

          {/* 游客登录（弱化样式） */}
          <Pressable
            accessibilityRole="button"
            onPress={() => guardAgreement(onGuestLogin)}
            disabled={!hasAgreed || loading}
            style={({ pressed }) => [
              styles.guestButton,
              { borderColor: color.border, backgroundColor: color.surface },
              disabledStyle,
              pressed && { transform: [{ scale: 0.98 }] },
            ]}
          >
            <Ionicons name="person-circle-outline" size={22} color={Colors.light.neutral200} style={{ marginRight: 8 }} />
            <Text style={[styles.guestText, { color: Colors.light.neutral200 }]}>以游客身份继续</Text>
          </Pressable>

          {/* 协议勾选 */}
          <View style={styles.agreementRow}>
            <Pressable onPress={() => setHasAgreed((v) => !v)} style={styles.checkboxWrap} accessibilityRole="checkbox" accessibilityState={{ checked: hasAgreed }}>
              <View
                style={[styles.checkbox, {
                  backgroundColor: hasAgreed ? color.primary : 'transparent',
                  borderColor: hasAgreed ? color.primary : color.border,
                }]}
              >
                {hasAgreed && <Ionicons name="checkmark" size={14} color={color.onPrimary} />}
              </View>
            </Pressable>
            <Text style={[styles.agreementText, { color: color.textMuted }]}>我已阅读并同意</Text>
            <Pressable onPress={() => router.push('/legal/privacy-policy')}>
              <Text style={[styles.link, { color: color.primary }]}>《隐私政策》</Text>
            </Pressable>
            <Text style={[styles.agreementText, { color: color.textMuted }]}>和</Text>
            <Pressable onPress={() => router.push('/legal/user-agreement')}>
              <Text style={[styles.link, { color: color.primary }]}>《用户协议》</Text>
            </Pressable>
          </View>

          {/* 占位底部间距 */}
          <View style={{ height: 40 }} />
        </ScrollView>
      </ThemedView>
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  safeArea: { flex: 1 },
  container: { flex: 1 },
  content: {
    flexGrow: 1,
    paddingHorizontal: 24,
    justifyContent: 'center',
  },
  header: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
    paddingHorizontal: 16,
    paddingTop: 4,
    paddingBottom: 8,
  },
  backButton: { width: 32, height: 32, alignItems: 'center', justifyContent: 'center' },
  headerTitle: { fontSize: 18, fontWeight: '700' },
  headerWrap: {
    marginBottom: 36,
  },
  title: {
    fontSize: 32,
    fontWeight: '500',
    letterSpacing: 0.5,
  },
  subtitle: {
    marginTop: 8,
    fontSize: 14,
    fontWeight: '500',
  },
  appleButton: {
    height: 56,
    borderRadius: 28,
    alignItems: 'center',
    justifyContent: 'center',
    flexDirection: 'row',
    marginBottom: 16,
    shadowColor: '#000',
    shadowOffset: { width: 0, height: 8 },
    shadowOpacity: 0.15,
    shadowRadius: 12,
    elevation: 2,
  },
  appleText: {
    fontSize: 16,
    color: '#FFFFFF',
    fontWeight: '600',
  },
  guestButton: {
    height: 52,
    borderRadius: 26,
    alignItems: 'center',
    justifyContent: 'center',
    flexDirection: 'row',
    borderWidth: 1,
    marginTop: 6,
  },
  guestText: {
    fontSize: 15,
    fontWeight: '500',
  },
  agreementRow: {
    flexDirection: 'row',
    alignItems: 'center',
    flexWrap: 'wrap',
    marginTop: 24,
  },
  checkboxWrap: { marginRight: 8 },
  checkbox: {
    width: 18,
    height: 18,
    borderRadius: 5,
    borderWidth: 1,
    alignItems: 'center',
    justifyContent: 'center',
  },
  agreementText: { fontSize: 12 },
  link: { fontSize: 12, fontWeight: '600' },
  footerHint: { marginTop: 24 },
  hintText: { fontSize: 12 },
});