import React, { useEffect, useMemo, useState } from 'react';
import {
  View,
  Text,
  StyleSheet,
  TouchableOpacity,
  Alert,
  Modal,
  Dimensions,
} from 'react-native';
import { CameraView, useCameraPermissions } from 'expo-camera';
import { useRouter } from 'expo-router';
import { MaterialCommunityIcons } from '@expo/vector-icons';
import * as hrefs from '../../navigation/hrefs';
import { spacing, fontSizes, borderRadius, useAppColors, type AppColors } from '../../theme';

const { width, height } = Dimensions.get('window');

interface QRCodeScannerProps {
  visible: boolean;
  onClose: () => void;
}

function createQrScannerStyles(colors: AppColors) {
  return StyleSheet.create({
    container: {
      flex: 1,
      backgroundColor: '#000',
    },
    camera: {
      flex: 1,
    },
    overlay: {
      flex: 1,
      backgroundColor: 'rgba(0,0,0,0.5)',
    },
    header: {
      flexDirection: 'row',
      alignItems: 'center',
      justifyContent: 'space-between',
      paddingHorizontal: spacing.md,
      paddingTop: spacing.xl,
      paddingBottom: spacing.md,
    },
    closeButton: {
      padding: spacing.sm,
    },
    headerTitle: {
      fontSize: fontSizes.lg,
      fontWeight: '600',
      color: '#fff',
    },
    placeholder: {
      width: 40,
    },
    scanArea: {
      flex: 1,
      justifyContent: 'center',
      alignItems: 'center',
    },
    scanFrame: {
      width: width * 0.7,
      height: width * 0.7,
      position: 'relative',
    },
    corner: {
      position: 'absolute',
      width: 20,
      height: 20,
      borderColor: colors.primary.main,
      borderWidth: 3,
    },
    topLeft: {
      top: 0,
      left: 0,
      borderRightWidth: 0,
      borderBottomWidth: 0,
    },
    topRight: {
      top: 0,
      right: 0,
      borderLeftWidth: 0,
      borderBottomWidth: 0,
    },
    bottomLeft: {
      bottom: 0,
      left: 0,
      borderRightWidth: 0,
      borderTopWidth: 0,
    },
    bottomRight: {
      bottom: 0,
      right: 0,
      borderLeftWidth: 0,
      borderTopWidth: 0,
    },
    scanText: {
      marginTop: spacing.lg,
      fontSize: fontSizes.md,
      color: '#fff',
      textAlign: 'center',
    },
    footer: {
      padding: spacing.xl,
      alignItems: 'center',
    },
    flashButton: {
      padding: spacing.md,
      backgroundColor: 'rgba(255,255,255,0.2)',
      borderRadius: borderRadius.full,
    },
    permissionContainer: {
      flex: 1,
      justifyContent: 'center',
      alignItems: 'center',
      padding: spacing.xl,
    },
    permissionText: {
      marginTop: spacing.lg,
      fontSize: fontSizes.md,
      color: 'rgba(255,255,255,0.72)',
      textAlign: 'center',
    },
    permissionButton: {
      marginTop: spacing.xl,
      paddingVertical: spacing.md,
      paddingHorizontal: spacing.xl,
      backgroundColor: colors.primary.main,
      borderRadius: borderRadius.md,
    },
    permissionButtonText: {
      color: '#fff',
      fontSize: fontSizes.md,
      fontWeight: '600',
    },
  });
}

export const QRCodeScanner: React.FC<QRCodeScannerProps> = ({ visible, onClose }) => {
  const router = useRouter();
  const themeColors = useAppColors();
  const styles = useMemo(() => createQrScannerStyles(themeColors), [themeColors]);
  const [permission, requestPermission] = useCameraPermissions();
  const [scanned, setScanned] = useState(false);

  useEffect(() => {
    if (visible) {
      setScanned(false);
      if (!permission?.granted) {
        requestPermission();
      }
    }
  }, [visible]);

  const handleBarCodeScanned = ({ type, data }: { type: string; data: string }) => {
    if (scanned) return;
    setScanned(true);
    onClose();

    if (data.startsWith('carrotbbs://qrcode/login')) {
      const sessionId = extractSessionId(data);
      if (sessionId) {
        router.push(hrefs.hrefQrLoginConfirm(sessionId));
      } else {
        Alert.alert('无效的二维码', '无法识别该二维码');
      }
    } else {
      Alert.alert('无效的二维码', '请扫描网页端的登录二维码');
    }
  };

  const extractSessionId = (url: string): string | null => {
    try {
      const sessionIdMatch = url.match(/session_id=([^&]+)/);
      return sessionIdMatch ? sessionIdMatch[1] : null;
    } catch {
      return null;
    }
  };

  if (!permission?.granted) {
    return (
      <Modal visible={visible} animationType="slide" onRequestClose={onClose}>
        <View style={styles.container}>
          <View style={styles.header}>
            <TouchableOpacity onPress={onClose} style={styles.closeButton}>
              <MaterialCommunityIcons name="close" size={24} color="#fff" />
            </TouchableOpacity>
            <Text style={styles.headerTitle}>扫码登录</Text>
            <View style={styles.placeholder} />
          </View>
          <View style={styles.permissionContainer}>
            <MaterialCommunityIcons name="camera-off" size={64} color="rgba(255,255,255,0.5)" />
            <Text style={styles.permissionText}>需要相机权限才能扫码</Text>
            <TouchableOpacity style={styles.permissionButton} onPress={requestPermission}>
              <Text style={styles.permissionButtonText}>授予权限</Text>
            </TouchableOpacity>
          </View>
        </View>
      </Modal>
    );
  }

  return (
    <Modal visible={visible} animationType="slide" onRequestClose={onClose}>
      <View style={styles.container}>
        <CameraView
          style={styles.camera}
          facing="back"
          onBarcodeScanned={scanned ? undefined : handleBarCodeScanned}
          barcodeScannerSettings={{
            barcodeTypes: ['qr'],
          }}
        >
          <View style={styles.overlay}>
            <View style={styles.header}>
              <TouchableOpacity onPress={onClose} style={styles.closeButton}>
                <MaterialCommunityIcons name="close" size={24} color="#fff" />
              </TouchableOpacity>
              <Text style={styles.headerTitle}>扫码登录</Text>
              <View style={styles.placeholder} />
            </View>

            <View style={styles.scanArea}>
              <View style={styles.scanFrame}>
                <View style={[styles.corner, styles.topLeft]} />
                <View style={[styles.corner, styles.topRight]} />
                <View style={[styles.corner, styles.bottomLeft]} />
                <View style={[styles.corner, styles.bottomRight]} />
              </View>
              <Text style={styles.scanText}>将二维码放入框内即可扫描</Text>
            </View>

            <View style={styles.footer}>
              <TouchableOpacity style={styles.flashButton} onPress={() => {}}>
                <MaterialCommunityIcons name="flashlight" size={24} color="#fff" />
              </TouchableOpacity>
            </View>
          </View>
        </CameraView>
      </View>
    </Modal>
  );
};

export default QRCodeScanner;