import React, { useState, useEffect, useRef } from 'react';
import {
  View,
  Text,
  StyleSheet,
  TouchableOpacity,
  Alert,
  ActivityIndicator,
  Modal,
  ScrollView,
  Linking,
} 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 { AppColors, BorderRadius, FontSizes, FontWeights, Spacing, Shadows } from '@/constants/theme';
import { useAuth } from '@/contexts/AuthContext';
import { api } from '@/services/api';
import { BeneficiaryMenu } from '@/components/ui/BeneficiaryMenu';
import type { Beneficiary } from '@/types';

const STRIPE_API_URL = 'https://wellnuo.smartlaunchhub.com/api/stripe';
const SUBSCRIPTION_PRICE = 49;

type SubscriptionState = 'active' | 'canceling' | 'none';

export default function SubscriptionScreen() {
  const { id } = useLocalSearchParams<{ id: string }>();
  const [isProcessing, setIsProcessing] = useState(false);
  const [isCanceling, setIsCanceling] = useState(false);
  const [beneficiary, setBeneficiary] = useState<Beneficiary | null>(null);
  const [isLoading, setIsLoading] = useState(true);
  const [showSuccessModal, setShowSuccessModal] = useState(false);
  const [justSubscribed, setJustSubscribed] = useState(false);
  const [transactions, setTransactions] = useState<Array<{
    id: string;
    type: 'subscription' | 'one_time';
    amount: number;
    currency: string;
    status: string;
    date: string;
    description: string;
    invoicePdf?: string;
    hostedUrl?: string;
    receiptUrl?: string;
  }>>([]);
  const [isLoadingTransactions, setIsLoadingTransactions] = useState(false);

  const { initPaymentSheet, presentPaymentSheet } = usePaymentSheet();
  const { user } = useAuth();

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

  const loadTransactions = async () => {
    if (!id) return;
    setIsLoadingTransactions(true);
    try {
      const response = await api.getTransactionHistory(parseInt(id, 10));
      if (response.ok && response.data) {
        setTransactions(response.data.transactions);
      }
    } catch (error) {
      // Silently ignore
    } finally {
      setIsLoadingTransactions(false);
    }
  };

  const loadBeneficiary = async () => {
    if (!id) return;
    try {
      const response = await api.getWellNuoBeneficiary(parseInt(id, 10));
      if (response.ok && response.data) {
        setBeneficiary(response.data);
      }
    } catch (error) {
      // Silently ignore
    } finally {
      setIsLoading(false);
    }
  };

  const subscription = beneficiary?.subscription;

  // Determine subscription state
  const getSubscriptionState = (): SubscriptionState => {
    if (!subscription) return 'none';

    const isStatusActive = subscription.status === 'active' || subscription.status === 'trialing';
    const isNotExpired = !subscription.endDate || new Date(subscription.endDate) > new Date();

    if (isStatusActive && isNotExpired) {
      return subscription.cancelAtPeriodEnd ? 'canceling' : 'active';
    }
    return 'none';
  };

  const subscriptionState = getSubscriptionState();


  const handleSubscribe = async () => {
    if (!beneficiary) {
      Alert.alert('Error', 'Beneficiary data not loaded.');
      return;
    }

    setIsProcessing(true);

    try {
      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-subscription-payment-sheet`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${token}`,
        },
        body: JSON.stringify({ beneficiaryId: beneficiary.id }),
      });

      if (!response.ok) {
        const errorText = await response.text();
        let errorMessage = 'Failed to create payment';
        try {
          const errorJson = JSON.parse(errorText);
          errorMessage = errorJson.error || errorJson.message || errorMessage;
        } catch {
          errorMessage = `Server error (${response.status})`;
        }
        throw new Error(errorMessage);
      }

      const data = await response.json();

      if (data.alreadySubscribed) {
        Alert.alert('Already Subscribed!', `${beneficiary.displayName} already has an active subscription.`);
        await loadBeneficiary();
        return;
      }

      if (!data.clientSecret) {
        throw new Error(data.error || 'Failed to create subscription - no clientSecret');
      }

      const isSetupIntent = data.clientSecret.startsWith('seti_');

      // Build payment sheet params based on intent type
      const baseParams = {
        merchantDisplayName: 'WellNuo',
        customerId: data.customer,
        ...(data.customerSessionClientSecret
          ? { customerSessionClientSecret: data.customerSessionClientSecret }
          : { customerEphemeralKeySecret: data.ephemeralKey }),
        returnURL: 'wellnuo://stripe-redirect',
        applePay: { merchantCountryCode: 'US' },
        googlePay: { merchantCountryCode: 'US', testEnv: true },
      };

      const paymentSheetParams = isSetupIntent
        ? { ...baseParams, setupIntentClientSecret: data.clientSecret }
        : { ...baseParams, paymentIntentClientSecret: data.clientSecret };

      // eslint-disable-next-line @typescript-eslint/no-explicit-any
      const { error: initError } = await initPaymentSheet(paymentSheetParams as any);
      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);
      }

      // For PaymentIntent (subscription with immediate payment), the subscription
      // is automatically activated via Stripe webhook when payment succeeds.
      // No need to call confirm endpoint for PaymentIntent.

      if (isSetupIntent && data.subscriptionId) {
        // Only for SetupIntent flow (future payment), we need to confirm
        const confirmResponse = await fetch(`${STRIPE_API_URL}/confirm-subscription-payment`, {
          method: 'POST',
          headers: {
            'Authorization': `Bearer ${token}`,
            'Content-Type': 'application/json',
          },
          body: JSON.stringify({
            subscriptionId: data.subscriptionId,
            beneficiaryId: beneficiary.id,
          }),
        });
        const confirmData = await confirmResponse.json();

        if (!confirmResponse.ok || confirmData.error) {
          throw new Error(confirmData.error || 'Failed to confirm subscription');
        }
      }

      // Wait a moment for webhook to process
      await new Promise(resolve => setTimeout(resolve, 2000));

      setJustSubscribed(true);
      await loadBeneficiary();
      setShowSuccessModal(true);
    } catch (error) {
      const errorMsg = error instanceof Error ? error.message : 'Something went wrong';
      Alert.alert('Payment Failed', errorMsg);
    } finally {
      setIsProcessing(false);
    }
  };

  const handleCancelSubscription = () => {
    if (!beneficiary) return;

    Alert.alert(
      'Cancel Subscription?',
      `Your subscription will remain active until ${subscription?.endDate ? formatDate(new Date(subscription.endDate)) : 'the end of your billing period'}. You can reactivate anytime before then.`,
      [
        { text: 'Keep Subscription', style: 'cancel' },
        { text: 'Cancel', style: 'destructive', onPress: confirmCancelSubscription },
      ]
    );
  };

  const confirmCancelSubscription = async () => {
    if (!beneficiary) return;
    setIsCanceling(true);

    try {
      const response = await api.cancelSubscription(beneficiary.id);
      if (!response.ok) throw new Error(response.error?.message || 'Failed to cancel subscription');
      await loadBeneficiary();
      Alert.alert('Subscription Canceled', 'You can reactivate anytime before the period ends.');
    } catch (error) {
      Alert.alert('Error', error instanceof Error ? error.message : 'Something went wrong.');
    } finally {
      setIsCanceling(false);
    }
  };

  const handleReactivateSubscription = async () => {
    if (!beneficiary) return;
    setIsProcessing(true);

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

      const response = await fetch(`${STRIPE_API_URL}/reactivate-subscription`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${token}`,
        },
        body: JSON.stringify({ beneficiaryId: beneficiary.id }),
      });

      const data = await response.json();
      if (!response.ok || data.error) {
        throw new Error(data.error || 'Failed to reactivate subscription');
      }

      await loadBeneficiary();
      Alert.alert('Reactivated!', 'Your subscription will continue to renew automatically.');
    } catch (error) {
      Alert.alert('Error', error instanceof Error ? error.message : 'Something went wrong.');
    } finally {
      setIsProcessing(false);
    }
  };

  const formatDate = (date: Date) => {
    return date.toLocaleDateString('en-US', { month: 'short', day: 'numeric', year: 'numeric' });
  };

  const openReceipt = (url?: string) => {
    if (url) Linking.openURL(url);
  };

  const handleSuccessModalClose = () => {
    setShowSuccessModal(false);
    router.replace(`/(tabs)/beneficiaries/${id}`);
  };

  // Loading state
  if (isLoading) {
    return (
      <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
        <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}>Subscription</Text>
          <View style={styles.placeholder} />
        </View>
        <View style={styles.centerContainer}>
          <ActivityIndicator size="large" color={AppColors.primary} />
        </View>
      </SafeAreaView>
    );
  }

  if (!beneficiary) {
    return (
      <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
        <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}>Subscription</Text>
          <View style={styles.placeholder} />
        </View>
        <View style={styles.centerContainer}>
          <Text style={styles.errorText}>Unable to load beneficiary</Text>
        </View>
      </SafeAreaView>
    );
  }

  // Render subscription status card based on state
  const renderStatusCard = () => {
    switch (subscriptionState) {
      case 'active':
        return (
          <View style={styles.statusCard}>
            <View style={styles.statusIconActive}>
              <Ionicons name="checkmark-circle" size={32} color={AppColors.white} />
            </View>
            <Text style={styles.statusTitle}>Active Subscription</Text>
            <Text style={styles.statusSubtitle}>
              {subscription?.endDate
                ? `Renews ${formatDate(new Date(subscription.endDate))}`
                : 'Renews monthly'}
            </Text>
            <View style={styles.priceRow}>
              <Text style={styles.priceAmount}>${SUBSCRIPTION_PRICE}</Text>
              <Text style={styles.pricePeriod}>/month</Text>
            </View>
          </View>
        );

      case 'canceling':
        return (
          <View style={[styles.statusCard, styles.statusCardCanceling]}>
            <View style={styles.statusIconCanceling}>
              <Ionicons name="time" size={32} color={AppColors.white} />
            </View>
            <Text style={styles.statusTitle}>Subscription Ending</Text>
            <Text style={styles.statusSubtitleCanceling}>
              Access until {subscription?.endDate ? formatDate(new Date(subscription.endDate)) : 'period end'}
            </Text>
            <Text style={styles.cancelingNote}>
              After this date, monitoring and alerts for {beneficiary.displayName} will stop.
            </Text>
          </View>
        );

      case 'none':
      default:
        return (
          <View style={[styles.statusCard, styles.statusCardNone]}>
            <View style={styles.statusIconNone}>
              <Ionicons name="shield-outline" size={32} color={AppColors.textMuted} />
            </View>
            <Text style={styles.statusTitleNone}>No Active Subscription</Text>
            <Text style={styles.statusSubtitleNone}>
              Subscribe to unlock monitoring for {beneficiary.displayName}
            </Text>
            <View style={styles.priceRow}>
              <Text style={styles.priceAmount}>${SUBSCRIPTION_PRICE}</Text>
              <Text style={styles.pricePeriod}>/month</Text>
            </View>
          </View>
        );
    }
  };

  // Render action button based on state
  const renderActionButton = () => {
    switch (subscriptionState) {
      case 'active':
        return (
          <TouchableOpacity
            style={styles.cancelButton}
            onPress={handleCancelSubscription}
            disabled={isCanceling}
          >
            {isCanceling ? (
              <ActivityIndicator size="small" color={AppColors.textMuted} />
            ) : (
              <Text style={styles.cancelButtonText}>Cancel Subscription</Text>
            )}
          </TouchableOpacity>
        );

      case 'canceling':
        return (
          <TouchableOpacity
            style={[styles.primaryButton, styles.reactivateButton, isProcessing && styles.buttonDisabled]}
            onPress={handleReactivateSubscription}
            disabled={isProcessing}
          >
            {isProcessing ? (
              <ActivityIndicator color={AppColors.white} />
            ) : (
              <>
                <Ionicons name="refresh" size={20} color={AppColors.white} />
                <Text style={styles.primaryButtonText}>Reactivate Subscription</Text>
              </>
            )}
          </TouchableOpacity>
        );

      case 'none':
      default:
        return (
          <TouchableOpacity
            style={[styles.primaryButton, isProcessing && styles.buttonDisabled]}
            onPress={handleSubscribe}
            disabled={isProcessing}
          >
            {isProcessing ? (
              <ActivityIndicator color={AppColors.white} />
            ) : (
              <>
                <Ionicons name="card" size={20} color={AppColors.white} />
                <Text style={styles.primaryButtonText}>Subscribe</Text>
              </>
            )}
          </TouchableOpacity>
        );
    }
  };

  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}>Subscription</Text>
        <BeneficiaryMenu
          beneficiaryId={id || ''}
          userRole={beneficiary?.role}
          currentPage="subscription"
        />
      </View>

      <ScrollView
        style={styles.scrollContent}
        contentContainerStyle={[
          styles.content,
          // Center content when no subscription and no transactions
          subscriptionState === 'none' && transactions.length === 0 && styles.contentCentered
        ]}
      >
        {/* Status Card */}
        {renderStatusCard()}

        {/* Action Button */}
        <View style={styles.actionSection}>
          {renderActionButton()}

          {/* Security note */}
          <View style={styles.securityRow}>
            <Ionicons name="shield-checkmark" size={14} color={AppColors.success} />
            <Text style={styles.securityText}>Secure payment by Stripe</Text>
          </View>
        </View>

        {/* Transaction History */}
        {transactions.length > 0 && (
          <View style={styles.transactionSection}>
            <Text style={styles.sectionTitle}>Payment History</Text>
            {transactions.map((tx) => (
              <TouchableOpacity
                key={tx.id}
                style={styles.transactionItem}
                onPress={() => openReceipt(tx.invoicePdf || tx.hostedUrl || tx.receiptUrl)}
                disabled={!tx.invoicePdf && !tx.hostedUrl && !tx.receiptUrl}
              >
                <View style={styles.transactionLeft}>
                  <Text style={styles.transactionDesc}>{tx.description}</Text>
                  <Text style={styles.transactionDate}>{formatDate(new Date(tx.date))}</Text>
                </View>
                <View style={styles.transactionRight}>
                  <Text style={styles.transactionAmount}>${tx.amount.toFixed(2)}</Text>
                  {(tx.invoicePdf || tx.hostedUrl || tx.receiptUrl) && (
                    <Ionicons name="chevron-forward" size={16} color={AppColors.textMuted} />
                  )}
                </View>
              </TouchableOpacity>
            ))}
          </View>
        )}
      </ScrollView>

      {/* Success Modal */}
      <Modal
        visible={showSuccessModal}
        transparent={true}
        animationType="fade"
        onRequestClose={handleSuccessModalClose}
      >
        <View style={styles.modalOverlay}>
          <View style={styles.modalContent}>
            <View style={styles.modalIcon}>
              <Ionicons name="checkmark-circle" size={56} color={AppColors.success} />
            </View>
            <Text style={styles.modalTitle}>Subscription Active!</Text>
            <Text style={styles.modalMessage}>
              Monitoring for {beneficiary?.name} is now enabled.
            </Text>
            <TouchableOpacity style={styles.modalButton} onPress={handleSuccessModalClose}>
              <Text style={styles.modalButtonText}>Continue</Text>
            </TouchableOpacity>
          </View>
        </View>
      </Modal>
    </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,
  },
  centerContainer: {
    flex: 1,
    justifyContent: 'center',
    alignItems: 'center',
  },
  errorText: {
    fontSize: FontSizes.base,
    color: AppColors.textMuted,
  },
  scrollContent: {
    flex: 1,
  },
  content: {
    padding: Spacing.lg,
    paddingBottom: Spacing.xxl,
  },
  contentCentered: {
    flexGrow: 1,
    justifyContent: 'center',
  },

  // Status Card Styles
  statusCard: {
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.xl,
    padding: Spacing.xl,
    alignItems: 'center',
    borderWidth: 2,
    borderColor: AppColors.success,
    ...Shadows.sm,
  },
  statusCardCanceling: {
    borderColor: '#F59E0B',
    backgroundColor: '#FFFBEB',
  },
  statusCardNone: {
    borderColor: AppColors.border,
    backgroundColor: AppColors.surface,
  },
  statusIconActive: {
    width: 56,
    height: 56,
    borderRadius: 28,
    backgroundColor: AppColors.success,
    alignItems: 'center',
    justifyContent: 'center',
    marginBottom: Spacing.md,
  },
  statusIconCanceling: {
    width: 56,
    height: 56,
    borderRadius: 28,
    backgroundColor: '#F59E0B',
    alignItems: 'center',
    justifyContent: 'center',
    marginBottom: Spacing.md,
  },
  statusIconNone: {
    width: 56,
    height: 56,
    borderRadius: 28,
    backgroundColor: AppColors.surfaceSecondary,
    alignItems: 'center',
    justifyContent: 'center',
    marginBottom: Spacing.md,
  },
  statusTitle: {
    fontSize: FontSizes.xl,
    fontWeight: FontWeights.bold,
    color: AppColors.textPrimary,
    marginBottom: Spacing.xs,
  },
  statusTitleNone: {
    fontSize: FontSizes.xl,
    fontWeight: FontWeights.bold,
    color: AppColors.textSecondary,
    marginBottom: Spacing.xs,
  },
  statusSubtitle: {
    fontSize: FontSizes.sm,
    color: AppColors.success,
    marginBottom: Spacing.md,
  },
  statusSubtitleCanceling: {
    fontSize: FontSizes.sm,
    color: '#B45309',
    fontWeight: FontWeights.medium,
    marginBottom: Spacing.sm,
  },
  statusSubtitleNone: {
    fontSize: FontSizes.sm,
    color: AppColors.textMuted,
    textAlign: 'center',
    marginBottom: Spacing.md,
  },
  cancelingNote: {
    fontSize: FontSizes.sm,
    color: '#92400E',
    textAlign: 'center',
    lineHeight: 20,
  },
  priceRow: {
    flexDirection: 'row',
    alignItems: 'baseline',
  },
  priceAmount: {
    fontSize: FontSizes['2xl'],
    fontWeight: FontWeights.bold,
    color: AppColors.primary,
  },
  pricePeriod: {
    fontSize: FontSizes.base,
    color: AppColors.textMuted,
    marginLeft: 2,
  },

  // Action Section
  actionSection: {
    marginTop: Spacing.xl,
    gap: Spacing.md,
  },
  primaryButton: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'center',
    gap: Spacing.sm,
    backgroundColor: AppColors.primary,
    paddingVertical: Spacing.md,
    borderRadius: BorderRadius.lg,
    ...Shadows.sm,
  },
  reactivateButton: {
    backgroundColor: AppColors.success,
  },
  buttonDisabled: {
    opacity: 0.7,
  },
  primaryButtonText: {
    fontSize: FontSizes.base,
    fontWeight: FontWeights.semibold,
    color: AppColors.white,
  },
  cancelButton: {
    paddingVertical: Spacing.sm,
    alignItems: 'center',
  },
  cancelButtonText: {
    fontSize: FontSizes.sm,
    color: AppColors.textMuted,
    textDecorationLine: 'underline',
  },
  securityRow: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'center',
    gap: Spacing.xs,
  },
  securityText: {
    fontSize: FontSizes.xs,
    color: AppColors.textMuted,
  },

  // Transaction Section
  transactionSection: {
    marginTop: Spacing.xl,
  },
  sectionTitle: {
    fontSize: FontSizes.base,
    fontWeight: FontWeights.semibold,
    color: AppColors.textPrimary,
    marginBottom: Spacing.md,
  },
  transactionItem: {
    flexDirection: 'row',
    justifyContent: 'space-between',
    alignItems: 'center',
    backgroundColor: AppColors.surface,
    padding: Spacing.md,
    borderRadius: BorderRadius.md,
    marginBottom: Spacing.sm,
  },
  transactionLeft: {
    flex: 1,
  },
  transactionDesc: {
    fontSize: FontSizes.sm,
    fontWeight: FontWeights.medium,
    color: AppColors.textPrimary,
  },
  transactionDate: {
    fontSize: FontSizes.xs,
    color: AppColors.textMuted,
    marginTop: 2,
  },
  transactionRight: {
    flexDirection: 'row',
    alignItems: 'center',
    gap: Spacing.xs,
  },
  transactionAmount: {
    fontSize: FontSizes.sm,
    fontWeight: FontWeights.semibold,
    color: AppColors.textPrimary,
  },

  // Modal
  modalOverlay: {
    flex: 1,
    backgroundColor: 'rgba(0, 0, 0, 0.5)',
    justifyContent: 'center',
    alignItems: 'center',
    padding: Spacing.lg,
  },
  modalContent: {
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.xl,
    padding: Spacing.xl,
    width: '100%',
    maxWidth: 320,
    alignItems: 'center',
    ...Shadows.lg,
  },
  modalIcon: {
    marginBottom: Spacing.md,
  },
  modalTitle: {
    fontSize: FontSizes.xl,
    fontWeight: FontWeights.bold,
    color: AppColors.textPrimary,
    marginBottom: Spacing.sm,
  },
  modalMessage: {
    fontSize: FontSizes.base,
    color: AppColors.textSecondary,
    textAlign: 'center',
    marginBottom: Spacing.lg,
  },
  modalButton: {
    backgroundColor: AppColors.primary,
    paddingVertical: Spacing.md,
    paddingHorizontal: Spacing.xl,
    borderRadius: BorderRadius.lg,
    width: '100%',
  },
  modalButtonText: {
    fontSize: FontSizes.base,
    fontWeight: FontWeights.semibold,
    color: AppColors.white,
    textAlign: 'center',
  },
});