import React, { useState, useEffect, useCallback } from 'react';
import {
    View,
    Text,
    StyleSheet,
    ScrollView,
    TouchableOpacity,
    ActivityIndicator,
    Platform,
} 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'; // Removed for web
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(); // Removed for web

    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 () => {
        // Web implementation: Placeholder or redirection to external Stripe checkout if needed.
        // For now, we just inform the user.
        alert('Purchases are currently only available in the mobile app.');
        return;
    };

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

    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>

                <View style={{ marginTop: 20, padding: 10, backgroundColor: '#f0f9ff', borderRadius: 8 }}>
                    <Text style={{ textAlign: 'center', color: '#0066cc', fontSize: 14 }}>
                        Web version: Payment flow is limited. Please use mobile app for purchases.
                    </Text>
                </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',
    },
});