import React, { useState, useEffect, useCallback } from 'react';
import {
  View,
  Text,
  StyleSheet,
  ScrollView,
  TouchableOpacity,
  ActivityIndicator,
} from 'react-native';
import { Ionicons } from '@expo/vector-icons';
import { SafeAreaView } from 'react-native-safe-area-context';
import { router, useLocalSearchParams } from 'expo-router';
import { usePaymentSheet } from '@stripe/stripe-react-native';
import { api } from '@/services/api';
import { useBeneficiary } from '@/contexts/BeneficiaryContext';
import { useAuth } from '@/contexts/AuthContext';
import { useToast } from '@/components/ui/Toast';
import { LoadingSpinner } from '@/components/ui/LoadingSpinner';
import { FullScreenError } from '@/components/ui/ErrorMessage';
import {
  AppColors,
  BorderRadius,
  FontSizes,
  FontWeights,
  Spacing,
  Shadows,
} from '@/constants/theme';
import type { Beneficiary } from '@/types';
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,
  description: '5 smart sensors that easily plug into any outlet and set up through the app in minutes',
};

export default function PurchaseScreen() {
  const { id } = useLocalSearchParams<{ id: string }>();
  const { user } = useAuth();
  const toast = useToast();

  const [beneficiary, setBeneficiary] = useState<Beneficiary | null>(null);
  const [isLoading, setIsLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);
  const [isProcessing, setIsProcessing] = useState(false);

  const { initPaymentSheet, presentPaymentSheet } = usePaymentSheet();

  const loadBeneficiary = useCallback(async () => {
    if (!id) return;

    setIsLoading(true);
    setError(null);

    try {
      const response = await api.getWellNuoBeneficiary(parseInt(id, 10));
      if (response.ok && response.data) {
        setBeneficiary(response.data);

        // Redirect if user already has devices - shouldn't be on purchase page
        if (hasBeneficiaryDevices(response.data)) {
          router.replace(`/(tabs)/beneficiaries/${id}`);
          return;
        }

        // Redirect if equipment is ordered/shipped/delivered
        const status = response.data.equipmentStatus;
        if (status && ['ordered', 'shipped', 'delivered'].includes(status)) {
          router.replace(`/(tabs)/beneficiaries/${id}/equipment-status`);
          return;
        }
      } else {
        setError(response.error?.message || 'Failed to load beneficiary');
      }
    } catch (err) {
      setError(err instanceof Error ? err.message : 'An error occurred');
    } finally {
      setIsLoading(false);
    }
  }, [id]);

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

  const handlePurchase = async () => {
    if (!beneficiary) return;

    setIsProcessing(true);

    try {
      const response = await fetch(`${STRIPE_API_URL}/create-payment-sheet`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({
          email: user?.email || 'guest@wellnuo.com',
          amount: STARTER_KIT.priceValue * 100,
          metadata: {
            userId: user?.user_id || 'guest',
            beneficiaryName: beneficiary.displayName,
            beneficiaryId: id,
            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);
      }

      // Payment successful - update equipment status to 'ordered'
      const statusResponse = await api.updateBeneficiaryEquipmentStatus(
        parseInt(id, 10),
        'ordered'
      );

      if (!statusResponse.ok) {
        // Failed to update equipment status, but continue anyway - payment was successful
      }

      // Show success and navigate to equipment tracking
      toast.success('Order Placed!', 'Your WellNuo Starter Kit is on its way.');
      router.replace(`/(tabs)/beneficiaries/${id}/equipment-status`);
    } catch (error) {
      toast.error(
        'Payment Failed',
        error instanceof Error ? error.message : 'Something went wrong. Please try again.'
      );
    } finally {
      setIsProcessing(false);
    }
  };

  const handleAlreadyHaveSensors = () => {
    router.push({
      pathname: '/(auth)/activate',
      params: { beneficiaryId: id, lovedOneName: beneficiary?.displayName },
    });
  };

  if (isLoading) {
    return <LoadingSpinner fullScreen message="Loading..." />;
  }

  if (error || !beneficiary) {
    return (
      <FullScreenError
        message={error || 'Beneficiary not found'}
        onRetry={loadBeneficiary}
      />
    );
  }

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

      <ScrollView
        style={styles.content}
        contentContainerStyle={styles.scrollContent}
        showsVerticalScrollIndicator={false}
      >
        {/* Icon */}
        <View style={styles.iconContainer}>
          <Ionicons name="hardware-chip-outline" size={64} color={AppColors.primary} />
        </View>

        {/* Title */}
        <Text style={styles.title}>Start Monitoring {beneficiary.displayName}</Text>
        <Text style={styles.subtitle}>
          To monitor wellness, you need WellNuo sensors installed in their home.
        </Text>

        {/* Kit Card */}
        <View style={styles.kitCard}>
          <Text style={styles.kitName}>{STARTER_KIT.name}</Text>
          <Text style={styles.kitPrice}>{STARTER_KIT.price}</Text>

          <Text style={styles.kitDescription}>{STARTER_KIT.description}</Text>

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

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

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

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: AppColors.background,
  },
  header: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
    paddingHorizontal: Spacing.md,
    paddingVertical: Spacing.sm,
    borderBottomWidth: 1,
    borderBottomColor: AppColors.border,
  },
  backButton: {
    padding: Spacing.xs,
  },
  headerTitle: {
    fontSize: FontSizes.lg,
    fontWeight: FontWeights.semibold,
    color: AppColors.textPrimary,
  },
  placeholder: {
    width: 32,
  },
  content: {
    flex: 1,
  },
  scrollContent: {
    padding: Spacing.lg,
    paddingBottom: Spacing.xxl,
  },
  iconContainer: {
    width: 120,
    height: 120,
    borderRadius: 60,
    backgroundColor: AppColors.primaryLighter,
    justifyContent: 'center',
    alignItems: 'center',
    alignSelf: 'center',
    marginBottom: Spacing.lg,
  },
  title: {
    fontSize: FontSizes['2xl'],
    fontWeight: FontWeights.bold,
    color: AppColors.textPrimary,
    textAlign: 'center',
    marginBottom: Spacing.sm,
  },
  subtitle: {
    fontSize: FontSizes.base,
    color: AppColors.textSecondary,
    textAlign: 'center',
    marginBottom: Spacing.xl,
    lineHeight: 22,
  },
  kitCard: {
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.xl,
    padding: Spacing.lg,
    marginBottom: Spacing.lg,
    ...Shadows.md,
  },
  kitName: {
    fontSize: FontSizes.lg,
    fontWeight: FontWeights.bold,
    color: AppColors.textPrimary,
    textAlign: 'center',
  },
  kitPrice: {
    fontSize: FontSizes['3xl'],
    fontWeight: FontWeights.bold,
    color: AppColors.primary,
    textAlign: 'center',
    marginVertical: Spacing.md,
  },
  kitDescription: {
    fontSize: FontSizes.base,
    color: AppColors.textSecondary,
    textAlign: 'center',
    lineHeight: 22,
  },
  actionsSection: {
    gap: Spacing.md,
  },
  buyButton: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'center',
    backgroundColor: AppColors.primary,
    paddingVertical: Spacing.md,
    borderRadius: BorderRadius.lg,
    gap: Spacing.sm,
  },
  buyButtonDisabled: {
    opacity: 0.7,
  },
  buyButtonText: {
    fontSize: FontSizes.base,
    fontWeight: FontWeights.semibold,
    color: AppColors.white,
  },
  securityBadge: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'center',
    marginTop: Spacing.md,
    gap: Spacing.xs,
  },
  securityText: {
    fontSize: FontSizes.xs,
    color: AppColors.success,
  },
  alreadyHaveButton: {
    alignItems: 'center',
    paddingVertical: Spacing.sm,
  },
  alreadyHaveText: {
    fontSize: FontSizes.base,
    color: AppColors.textSecondary,
    textDecorationLine: 'underline',
  },
});