import React, { useState, useEffect, useCallback } from 'react';
import {
  View,
  Text,
  StyleSheet,
  TouchableOpacity,
  ActivityIndicator,
  Alert,
} from 'react-native';
import { SafeAreaView } from 'react-native-safe-area-context';
import { router, useLocalSearchParams } from 'expo-router';
import { Ionicons } from '@expo/vector-icons';
import { usePaymentSheet } from '@stripe/stripe-react-native';
import { AppColors, Spacing, BorderRadius, FontSizes, FontWeights, Shadows } from '@/constants/theme';
import { useAuth } from '@/contexts/AuthContext';
import { api } from '@/services/api';
import { LoadingSpinner } from '@/components/ui/LoadingSpinner';
import { hasBeneficiaryDevices } from '@/services/BeneficiaryDetailController';

const STRIPE_API_URL = 'https://wellnuo.smartlaunchhub.com/api/stripe';

const STARTER_KIT = {
  name: 'WellNuo Starter Kit',
  price: '$399',
  priceValue: 399,
};

export default function PurchaseScreen() {
  const params = useLocalSearchParams<{ lovedOneName?: string; beneficiaryId?: string }>();
  const lovedOneName = params.lovedOneName || '';
  const beneficiaryId = params.beneficiaryId;

  const [isProcessing, setIsProcessing] = useState(false);
  const [isLoading, setIsLoading] = useState(true);
  const [step, setStep] = useState<'purchase' | 'order_placed'>('purchase');
  const { user } = useAuth();

  const { initPaymentSheet, presentPaymentSheet } = usePaymentSheet();

  // Check if equipment is already ordered - redirect to equipment-status
  const checkEquipmentStatus = useCallback(async () => {
    if (!beneficiaryId) {
      setIsLoading(false);
      return;
    }

    try {
      const response = await api.getWellNuoBeneficiary(parseInt(beneficiaryId, 10));
      if (response.ok && response.data) {
        // If user already has devices - go to main screen
        if (hasBeneficiaryDevices(response.data)) {
          router.replace(`/(tabs)/beneficiaries/${beneficiaryId}`);
          return;
        }

        // If equipment is ordered/shipped/delivered - go to equipment-status
        const status = response.data.equipmentStatus;
        if (status && ['ordered', 'shipped', 'delivered'].includes(status)) {
          router.replace(`/(tabs)/beneficiaries/${beneficiaryId}/equipment-status`);
          return;
        }
      }
    } catch (error) {
      // Failed to check equipment status
    }

    setIsLoading(false);
  }, [beneficiaryId]);

  useEffect(() => {
    checkEquipmentStatus();
  }, [checkEquipmentStatus]);

  const handlePurchase = async () => {
    setIsProcessing(true);

    try {
      const userId = user?.user_id;
      if (!userId) {
        Alert.alert('Error', 'User not authenticated. Please log in again.');
        setIsProcessing(false);
        return;
      }

      if (!beneficiaryId) {
        Alert.alert('Error', 'Beneficiary not found. Please try again.');
        setIsProcessing(false);
        return;
      }

      const token = await api.getToken();
      if (!token) {
        Alert.alert('Error', 'Please log in again');
        setIsProcessing(false);
        return;
      }

      const response = await fetch(`${STRIPE_API_URL}/create-payment-sheet`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${token}`,
        },
        body: JSON.stringify({
          email: user?.email,
          amount: STARTER_KIT.priceValue * 100,
          metadata: {
            userId: String(userId),
            beneficiaryId: String(beneficiaryId),
            beneficiaryName: lovedOneName || 'To be configured',
            orderType: 'starter_kit',
          },
        }),
      });

      const data = await response.json();

      if (!data.paymentIntent) {
        throw new Error(data.error || 'Failed to create payment sheet');
      }

      const { error: initError } = await initPaymentSheet({
        merchantDisplayName: 'WellNuo',
        paymentIntentClientSecret: data.paymentIntent,
        customerId: data.customer,
        customerEphemeralKeySecret: data.ephemeralKey,
        defaultBillingDetails: {
          email: user?.email || '',
        },
        returnURL: 'wellnuo://stripe-redirect',
        applePay: {
          merchantCountryCode: 'US',
        },
        googlePay: {
          merchantCountryCode: 'US',
          testEnv: true,
        },
      });

      if (initError) {
        throw new Error(initError.message);
      }

      const { error: presentError } = await presentPaymentSheet();

      if (presentError) {
        if (presentError.code === 'Canceled') {
          setIsProcessing(false);
          return;
        }
        throw new Error(presentError.message);
      }

      await api.updateBeneficiaryEquipmentStatus(
        parseInt(beneficiaryId, 10),
        'ordered'
      );

      await api.setOnboardingCompleted(true);

      // Redirect directly to equipment-status page (skip order_placed screen)
      router.replace(`/(tabs)/beneficiaries/${beneficiaryId}/equipment-status`);
    } catch (error) {
      Alert.alert(
        'Payment Failed',
        error instanceof Error ? error.message : 'Something went wrong. Please try again.'
      );
    }

    setIsProcessing(false);
  };

  const handleAlreadyHaveSensors = () => {
    router.replace({
      pathname: '/(auth)/activate',
      params: { beneficiaryId, lovedOneName },
    });
  };

  const handleGoToEquipmentStatus = () => {
    if (beneficiaryId) {
      router.replace(`/(tabs)/beneficiaries/${beneficiaryId}/equipment-status`);
    } else {
      router.replace('/(tabs)');
    }
  };

  // Loading state - checking equipment status
  if (isLoading) {
    return <LoadingSpinner fullScreen message="Loading..." />;
  }

  // Order Placed Screen
  if (step === 'order_placed') {
    return (
      <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
        <View style={styles.orderPlacedContainer}>
          <View style={styles.successIcon}>
            <Ionicons name="checkmark" size={64} color={AppColors.white} />
          </View>

          <Text style={styles.orderPlacedTitle}>Order Placed!</Text>
          <Text style={styles.orderPlacedSubtitle}>
            Thank you for your purchase
          </Text>

          <View style={styles.orderInfoCard}>
            <View style={styles.orderInfoRow}>
              <Text style={styles.orderInfoLabel}>Item</Text>
              <Text style={styles.orderInfoValue}>{STARTER_KIT.name}</Text>
            </View>
            <View style={styles.orderInfoRow}>
              <Text style={styles.orderInfoLabel}>For</Text>
              <Text style={styles.orderInfoValue}>{lovedOneName || 'Your loved one'}</Text>
            </View>
            <View style={[styles.orderInfoRow, { borderBottomWidth: 0 }]}>
              <Text style={styles.orderInfoLabel}>Total</Text>
              <Text style={[styles.orderInfoValue, styles.orderInfoPrice]}>{STARTER_KIT.price}</Text>
            </View>
          </View>

          <TouchableOpacity style={styles.primaryButton} onPress={handleGoToEquipmentStatus}>
            <Text style={styles.primaryButtonText}>Track My Order</Text>
          </TouchableOpacity>
        </View>
      </SafeAreaView>
    );
  }

  return (
    <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
      <View style={styles.content}>
        {/* Header */}
        <View style={styles.header}>
          <TouchableOpacity
            style={styles.backButton}
            onPress={() => router.canGoBack() ? router.back() : router.replace('/(tabs)')}
          >
            <Ionicons name="arrow-back" size={24} color={AppColors.textPrimary} />
          </TouchableOpacity>
          <Text style={styles.title}>Get Started</Text>
          <View style={styles.placeholder} />
        </View>

        {/* Product Card */}
        <View style={styles.productCard}>
          <View style={styles.productIcon}>
            <Ionicons name="hardware-chip" size={48} color={AppColors.primary} />
          </View>

          <Text style={styles.productName}>{STARTER_KIT.name}</Text>
          <Text style={styles.productPrice}>{STARTER_KIT.price}</Text>

          <Text style={styles.productDescription}>
            5 smart sensors that easily plug into any outlet and set up through the app in minutes
          </Text>

          {/* Security Badge */}
          <View style={styles.securityBadge}>
            <Ionicons name="shield-checkmark" size={16} color={AppColors.success} />
            <Text style={styles.securityText}>Secure payment powered by Stripe</Text>
          </View>
        </View>

        {/* Bottom Actions */}
        <View style={styles.bottomActions}>
          <TouchableOpacity
            style={[styles.purchaseButton, isProcessing && styles.buttonDisabled]}
            onPress={handlePurchase}
            disabled={isProcessing}
          >
            {isProcessing ? (
              <ActivityIndicator color={AppColors.white} />
            ) : (
              <>
                <Ionicons name="card" size={20} color={AppColors.white} />
                <Text style={styles.purchaseButtonText}>Buy Now</Text>
              </>
            )}
          </TouchableOpacity>

          <TouchableOpacity style={styles.skipButton} onPress={handleAlreadyHaveSensors}>
            <Text style={styles.skipButtonText}>I already have sensors</Text>
          </TouchableOpacity>
        </View>
      </View>
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: AppColors.background,
  },
  content: {
    flex: 1,
    padding: Spacing.lg,
    justifyContent: 'space-between',
  },
  header: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
  },
  backButton: {
    padding: Spacing.sm,
    marginLeft: -Spacing.sm,
  },
  title: {
    fontSize: FontSizes.xl,
    fontWeight: FontWeights.bold,
    color: AppColors.textPrimary,
  },
  placeholder: {
    width: 40,
  },
  productCard: {
    backgroundColor: AppColors.white,
    borderRadius: BorderRadius.xl,
    padding: Spacing.xl,
    alignItems: 'center',
    borderWidth: 2,
    borderColor: AppColors.primary,
    ...Shadows.md,
  },
  productIcon: {
    width: 80,
    height: 80,
    borderRadius: 40,
    backgroundColor: `${AppColors.primary}15`,
    alignItems: 'center',
    justifyContent: 'center',
    marginBottom: Spacing.lg,
  },
  productName: {
    fontSize: FontSizes.xl,
    fontWeight: FontWeights.bold,
    color: AppColors.textPrimary,
    textAlign: 'center',
    marginBottom: Spacing.xs,
  },
  productPrice: {
    fontSize: FontSizes['3xl'],
    fontWeight: FontWeights.bold,
    color: AppColors.primary,
    marginBottom: Spacing.lg,
  },
  productDescription: {
    fontSize: FontSizes.base,
    color: AppColors.textSecondary,
    textAlign: 'center',
    lineHeight: 22,
    marginBottom: Spacing.lg,
  },
  securityBadge: {
    flexDirection: 'row',
    alignItems: 'center',
    gap: Spacing.xs,
    paddingVertical: Spacing.sm,
    paddingHorizontal: Spacing.md,
    backgroundColor: `${AppColors.success}10`,
    borderRadius: BorderRadius.lg,
  },
  securityText: {
    fontSize: FontSizes.sm,
    color: AppColors.success,
  },
  bottomActions: {
    gap: Spacing.md,
  },
  purchaseButton: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'center',
    gap: Spacing.sm,
    backgroundColor: AppColors.primary,
    paddingVertical: Spacing.lg,
    borderRadius: BorderRadius.lg,
    ...Shadows.primary,
  },
  buttonDisabled: {
    opacity: 0.7,
  },
  purchaseButtonText: {
    fontSize: FontSizes.lg,
    fontWeight: FontWeights.semibold,
    color: AppColors.white,
  },
  skipButton: {
    alignItems: 'center',
    paddingVertical: Spacing.sm,
  },
  skipButtonText: {
    fontSize: FontSizes.base,
    color: AppColors.textSecondary,
    textDecorationLine: 'underline',
  },
  // Order Placed Screen
  orderPlacedContainer: {
    flex: 1,
    padding: Spacing.lg,
    alignItems: 'center',
    justifyContent: 'center',
  },
  successIcon: {
    width: 100,
    height: 100,
    borderRadius: 50,
    backgroundColor: AppColors.success,
    alignItems: 'center',
    justifyContent: 'center',
    marginBottom: Spacing.xl,
    ...Shadows.lg,
  },
  orderPlacedTitle: {
    fontSize: FontSizes['2xl'],
    fontWeight: FontWeights.bold,
    color: AppColors.textPrimary,
    marginBottom: Spacing.xs,
  },
  orderPlacedSubtitle: {
    fontSize: FontSizes.base,
    color: AppColors.textSecondary,
    marginBottom: Spacing.xl,
  },
  orderInfoCard: {
    width: '100%',
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.lg,
    padding: Spacing.lg,
    marginBottom: Spacing.xl,
    ...Shadows.sm,
  },
  orderInfoRow: {
    flexDirection: 'row',
    justifyContent: 'space-between',
    alignItems: 'center',
    paddingVertical: Spacing.sm,
    borderBottomWidth: 1,
    borderBottomColor: AppColors.border,
  },
  orderInfoLabel: {
    fontSize: FontSizes.sm,
    color: AppColors.textSecondary,
  },
  orderInfoValue: {
    fontSize: FontSizes.base,
    fontWeight: FontWeights.medium,
    color: AppColors.textPrimary,
  },
  orderInfoPrice: {
    color: AppColors.primary,
    fontWeight: FontWeights.bold,
  },
  primaryButton: {
    width: '100%',
    backgroundColor: AppColors.primary,
    paddingVertical: Spacing.lg,
    borderRadius: BorderRadius.lg,
    alignItems: 'center',
    ...Shadows.primary,
  },
  primaryButtonText: {
    fontSize: FontSizes.base,
    fontWeight: FontWeights.semibold,
    color: AppColors.white,
  },
});