import React, { useState } from 'react';
import {
  View,
  Text,
  StyleSheet,
  TouchableOpacity,
  TextInput,
  ScrollView,
  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 { AppColors, Spacing, BorderRadius, FontSizes, FontWeights } from '@/constants/theme';
import { useBeneficiary } from '@/contexts/BeneficiaryContext';
import { api } from '@/services/api';


export default function ActivateScreen() {
  // Get params - lovedOneName from purchase flow, beneficiaryId from existing beneficiary
  const params = useLocalSearchParams<{ lovedOneName?: string; beneficiaryId?: string }>();

  const [activationCode, setActivationCode] = useState('');
  const [isActivating, setIsActivating] = useState(false);
  const [step, setStep] = useState<'code' | 'beneficiary' | 'complete'>('code');
  // Pre-fill beneficiary name from params if available
  const [beneficiaryName, setBeneficiaryName] = useState(params.lovedOneName || '');

  const { addLocalBeneficiary, updateLocalBeneficiary, localBeneficiaries } = useBeneficiary();

  // Check if we're activating for an existing beneficiary
  const existingBeneficiaryId = params.beneficiaryId ? parseInt(params.beneficiaryId, 10) : null;
  const existingBeneficiary = existingBeneficiaryId
    ? localBeneficiaries.find(b => b.id === existingBeneficiaryId)
    : null;

  // Demo serial for testing without real hardware
  const DEMO_SERIAL = 'DEMO-00000';

  const handleActivate = async () => {
    const code = activationCode.trim().toUpperCase();

    if (!code) {
      Alert.alert('Error', 'Please enter serial number');
      return;
    }

    // Check for demo serial
    const isDemoMode = code === DEMO_SERIAL || code === 'DEMO-1234-5678';

    // Validate code format: minimum 8 characters (or demo serial)
    if (!isDemoMode && code.length < 8) {
      Alert.alert('Invalid Code', 'Please enter a valid serial number from your WellNuo Starter Kit.\n\nFor testing, use: DEMO-00000');
      return;
    }

    setIsActivating(true);

    try {
      // If we have an existing beneficiary, update them with device info
      if (existingBeneficiaryId && existingBeneficiary) {
        // Prepare update data
        const updateData: any = {
          hasDevices: true,
          device_id: code,
          equipmentStatus: 'active', // Clear awaiting state - sensors now active
        };

        // If beneficiary has pending subscription (from kit purchase), activate it
        if (existingBeneficiary.subscription?.status === 'pending') {
          updateData.subscription = {
            ...existingBeneficiary.subscription,
            status: 'active',
          };
        }

        await updateLocalBeneficiary(existingBeneficiaryId, updateData);
        setBeneficiaryName(existingBeneficiary.name);
        setStep('complete');
      } else {
        // Creating new beneficiary
        const beneficiaryData: any = {
          name: params.lovedOneName?.trim() || '',
          hasDevices: true,
          device_id: code,
        };

        if (isDemoMode) {
          beneficiaryData.isDemo = true;
        }

        // If name was already provided from add-loved-one screen, skip to saving
        if (params.lovedOneName && params.lovedOneName.trim()) {
          await addLocalBeneficiary(beneficiaryData);
          await api.setOnboardingCompleted(true);
          setStep('complete');
        } else {
          // No name provided, show beneficiary form
          setStep('beneficiary');
        }
      }
    } catch (error) {
      console.error('Failed to activate:', error);
      Alert.alert('Error', 'Failed to activate kit. Please try again.');
    } finally {
      setIsActivating(false);
    }
  };

  const handleAddBeneficiary = async () => {
    if (!beneficiaryName.trim()) {
      Alert.alert('Error', 'Please enter beneficiary name');
      return;
    }

    setIsActivating(true);

    try {
      const code = activationCode.trim().toUpperCase();
      const isDemoMode = code === DEMO_SERIAL || code === 'DEMO-1234-5678';

      // Add beneficiary with device info
      await addLocalBeneficiary({
        name: beneficiaryName.trim(),
        hasDevices: true,
        device_id: code,
        isDemo: isDemoMode,
      });
      // Mark onboarding as completed
      await api.setOnboardingCompleted(true);
      setStep('complete');
    } catch (error) {
      console.error('Failed to add beneficiary:', error);
      Alert.alert('Error', 'Failed to add beneficiary. Please try again.');
    } finally {
      setIsActivating(false);
    }
  };

  const handleComplete = () => {
    // If updating existing beneficiary, go back to their detail page
    if (existingBeneficiaryId) {
      router.replace(`/(tabs)/beneficiaries/${existingBeneficiaryId}`);
    } else {
      // Navigate to main app
      router.replace('/(tabs)');
    }
  };

  // Step 1: Enter activation code
  if (step === 'code') {
    return (
      <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
        <ScrollView contentContainerStyle={styles.content} keyboardShouldPersistTaps="handled">
          {/* Header */}
          <View style={styles.header}>
            {existingBeneficiary ? (
              <TouchableOpacity style={styles.backButton} onPress={() => router.back()}>
                <Ionicons name="arrow-back" size={24} color={AppColors.textPrimary} />
              </TouchableOpacity>
            ) : (
              <View style={styles.placeholder} />
            )}
            <Text style={styles.title}>
              {existingBeneficiary ? 'Connect Sensors' : 'Activate Kit'}
            </Text>
            <View style={styles.placeholder} />
          </View>

          {/* Icon */}
          <View style={styles.iconContainer}>
            <Ionicons name="qr-code" size={64} color={AppColors.primary} />
          </View>

          {/* Instructions */}
          <Text style={styles.instructions}>
            {existingBeneficiary
              ? `Connect sensors for ${existingBeneficiary.name}`
              : 'Enter the activation code from your WellNuo Starter Kit packaging'}
          </Text>

          {/* Input */}
          <View style={styles.inputContainer}>
            <TextInput
              style={styles.input}
              value={activationCode}
              onChangeText={setActivationCode}
              placeholder="WELLNUO-XXXX-XXXX"
              placeholderTextColor={AppColors.textMuted}
              autoCapitalize="characters"
              autoCorrect={false}
            />
          </View>

          {/* Demo Code Link */}
          <TouchableOpacity
            style={styles.demoCodeLink}
            onPress={() => setActivationCode('DEMO-1234-5678')}
          >
            <Ionicons name="flask-outline" size={14} color={AppColors.textMuted} />
            <Text style={styles.demoCodeLinkText}>Use demo code</Text>
          </TouchableOpacity>

          {/* Activate Button */}
          <TouchableOpacity
            style={[styles.primaryButton, isActivating && styles.buttonDisabled]}
            onPress={handleActivate}
            disabled={isActivating}
          >
            {isActivating ? (
              <ActivityIndicator color={AppColors.white} />
            ) : (
              <Text style={styles.primaryButtonText}>Activate</Text>
            )}
          </TouchableOpacity>

          {/* Skip for now - only show for new onboarding, not for existing beneficiary */}
          {!existingBeneficiary && (
            <TouchableOpacity style={styles.skipButton} onPress={handleComplete}>
              <Text style={styles.skipButtonText}>Skip for now</Text>
            </TouchableOpacity>
          )}
        </ScrollView>
      </SafeAreaView>
    );
  }

  // Step 2: Add beneficiary
  if (step === 'beneficiary') {
    return (
      <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
        <ScrollView contentContainerStyle={styles.content} keyboardShouldPersistTaps="handled">
          {/* Header */}
          <View style={styles.header}>
            <TouchableOpacity style={styles.backButton} onPress={() => setStep('code')}>
              <Ionicons name="arrow-back" size={24} color={AppColors.textPrimary} />
            </TouchableOpacity>
            <Text style={styles.title}>Add Beneficiary</Text>
            <View style={styles.placeholder} />
          </View>

          {/* Icon */}
          <View style={styles.iconContainer}>
            <Ionicons name="person-add" size={64} color={AppColors.primary} />
          </View>

          {/* Instructions */}
          <Text style={styles.instructions}>
            Who will you be monitoring with this kit?
          </Text>

          {/* Name Input */}
          <View style={styles.inputGroup}>
            <Text style={styles.inputLabel}>Full Name</Text>
            <TextInput
              style={styles.input}
              value={beneficiaryName}
              onChangeText={setBeneficiaryName}
              placeholder="e.g., Grandma Julia"
              placeholderTextColor={AppColors.textMuted}
              autoCapitalize="words"
              autoCorrect={false}
            />
          </View>

          {/* Continue Button */}
          <TouchableOpacity
            style={[styles.primaryButton, isActivating && styles.buttonDisabled]}
            onPress={handleAddBeneficiary}
            disabled={isActivating}
          >
            {isActivating ? (
              <ActivityIndicator color={AppColors.white} />
            ) : (
              <Text style={styles.primaryButtonText}>Continue</Text>
            )}
          </TouchableOpacity>
        </ScrollView>
      </SafeAreaView>
    );
  }

  // Step 3: Complete
  const displayName = beneficiaryName || existingBeneficiary?.name || params.lovedOneName;

  return (
    <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
      <View style={styles.content}>
        {/* Success Icon */}
        <View style={styles.successContainer}>
          <View style={styles.successIcon}>
            <Ionicons name="checkmark-circle" size={80} color={AppColors.success} />
          </View>

          <Text style={styles.successTitle}>
            {existingBeneficiary ? 'Sensors Connected!' : 'Kit Activated!'}
          </Text>
          <Text style={styles.successMessage}>
            {existingBeneficiary
              ? `Sensors have been connected for `
              : `Your WellNuo kit has been successfully activated for `}
            <Text style={styles.beneficiaryHighlight}>{displayName}</Text>
          </Text>

          {/* Next Steps */}
          <View style={styles.nextSteps}>
            <Text style={styles.nextStepsTitle}>Next Steps:</Text>
            {existingBeneficiary ? (
              <>
                <View style={styles.stepItem}>
                  <Text style={styles.stepNumber}>1</Text>
                  <Text style={styles.stepText}>Connect the hub to WiFi</Text>
                </View>
                <View style={styles.stepItem}>
                  <Text style={styles.stepNumber}>2</Text>
                  <Text style={styles.stepText}>Subscribe to start monitoring ($49/month)</Text>
                </View>
              </>
            ) : (
              <>
                <View style={styles.stepItem}>
                  <Text style={styles.stepNumber}>1</Text>
                  <Text style={styles.stepText}>Place sensors in your loved one's home</Text>
                </View>
                <View style={styles.stepItem}>
                  <Text style={styles.stepNumber}>2</Text>
                  <Text style={styles.stepText}>Connect the hub to WiFi</Text>
                </View>
                <View style={styles.stepItem}>
                  <Text style={styles.stepNumber}>3</Text>
                  <Text style={styles.stepText}>Subscribe to start monitoring ($49/month)</Text>
                </View>
              </>
            )}
          </View>
        </View>

        {/* Complete Button */}
        <TouchableOpacity style={styles.primaryButton} onPress={handleComplete}>
          <Text style={styles.primaryButtonText}>
            {existingBeneficiary ? 'Continue' : 'Go to Dashboard'}
          </Text>
        </TouchableOpacity>
      </View>
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: AppColors.background,
  },
  content: {
    flex: 1,
    padding: Spacing.lg,
  },
  header: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'space-between',
    marginBottom: Spacing.xl,
  },
  backButton: {
    padding: Spacing.sm,
    marginLeft: -Spacing.sm,
  },
  title: {
    fontSize: FontSizes.xl,
    fontWeight: FontWeights.bold,
    color: AppColors.textPrimary,
  },
  placeholder: {
    width: 40,
  },
  iconContainer: {
    alignItems: 'center',
    marginBottom: Spacing.xl,
  },
  instructions: {
    fontSize: FontSizes.base,
    color: AppColors.textSecondary,
    textAlign: 'center',
    marginBottom: Spacing.xl,
    lineHeight: 24,
  },
  inputContainer: {
    marginBottom: Spacing.lg,
  },
  inputGroup: {
    marginBottom: Spacing.lg,
  },
  inputLabel: {
    fontSize: FontSizes.sm,
    fontWeight: FontWeights.medium,
    color: AppColors.textPrimary,
    marginBottom: Spacing.sm,
  },
  input: {
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.lg,
    paddingHorizontal: Spacing.lg,
    paddingVertical: Spacing.md,
    fontSize: FontSizes.lg,
    color: AppColors.textPrimary,
    textAlign: 'center',
    borderWidth: 1,
    borderColor: AppColors.border,
  },
  devNotice: {
    alignItems: 'center',
    marginBottom: Spacing.xl,
    paddingVertical: Spacing.lg,
    paddingHorizontal: Spacing.lg,
    backgroundColor: `${AppColors.warning}10`,
    borderRadius: BorderRadius.lg,
    borderWidth: 1,
    borderColor: `${AppColors.warning}30`,
  },
  devNoticeTitle: {
    fontSize: FontSizes.base,
    fontWeight: FontWeights.semibold,
    color: AppColors.warning,
    marginTop: Spacing.sm,
    marginBottom: Spacing.sm,
  },
  devNoticeText: {
    fontSize: FontSizes.sm,
    color: AppColors.textSecondary,
    textAlign: 'center',
    lineHeight: 20,
    marginBottom: Spacing.md,
  },
  demoCodeButton: {
    paddingVertical: Spacing.sm,
    paddingHorizontal: Spacing.lg,
    backgroundColor: AppColors.warning,
    borderRadius: BorderRadius.md,
  },
  demoCodeButtonText: {
    fontSize: FontSizes.sm,
    fontWeight: FontWeights.medium,
    color: AppColors.white,
  },
  demoCodeLink: {
    flexDirection: 'row',
    alignItems: 'center',
    justifyContent: 'center',
    gap: 4,
    marginBottom: Spacing.md,
  },
  demoCodeLinkText: {
    fontSize: FontSizes.sm,
    color: AppColors.textMuted,
  },
  primaryButton: {
    backgroundColor: AppColors.primary,
    paddingVertical: Spacing.lg,
    borderRadius: BorderRadius.lg,
    alignItems: 'center',
    marginTop: Spacing.md,
  },
  buttonDisabled: {
    opacity: 0.7,
  },
  primaryButtonText: {
    fontSize: FontSizes.lg,
    fontWeight: FontWeights.semibold,
    color: AppColors.white,
  },
  skipButton: {
    alignItems: 'center',
    paddingVertical: Spacing.lg,
  },
  skipButtonText: {
    fontSize: FontSizes.base,
    color: AppColors.textSecondary,
    textDecorationLine: 'underline',
  },
  successContainer: {
    flex: 1,
    alignItems: 'center',
    justifyContent: 'center',
  },
  successIcon: {
    marginBottom: Spacing.xl,
  },
  successTitle: {
    fontSize: FontSizes['2xl'],
    fontWeight: FontWeights.bold,
    color: AppColors.textPrimary,
    marginBottom: Spacing.md,
  },
  successMessage: {
    fontSize: FontSizes.base,
    color: AppColors.textSecondary,
    textAlign: 'center',
    marginBottom: Spacing.md,
  },
  beneficiaryHighlight: {
    fontWeight: FontWeights.bold,
    color: AppColors.primary,
  },
  nextSteps: {
    width: '100%',
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.lg,
    padding: Spacing.lg,
  },
  nextStepsTitle: {
    fontSize: FontSizes.base,
    fontWeight: FontWeights.semibold,
    color: AppColors.textPrimary,
    marginBottom: Spacing.md,
  },
  stepItem: {
    flexDirection: 'row',
    alignItems: 'center',
    gap: Spacing.md,
    marginBottom: Spacing.sm,
  },
  stepNumber: {
    width: 24,
    height: 24,
    borderRadius: 12,
    backgroundColor: AppColors.primary,
    color: AppColors.white,
    textAlign: 'center',
    lineHeight: 24,
    fontSize: FontSizes.sm,
    fontWeight: FontWeights.bold,
    overflow: 'hidden',
  },
  stepText: {
    fontSize: FontSizes.sm,
    color: AppColors.textSecondary,
    flex: 1,
  },
});