import React, { useState, useEffect, useCallback, useMemo } from 'react';
import {
  View,
  Text,
  StyleSheet,
  TextInput,
  TouchableOpacity,
  Alert,
  ActivityIndicator,
  ScrollView,
  KeyboardAvoidingView,
  Platform,
  RefreshControl,
} from 'react-native';
import { Ionicons } from '@expo/vector-icons';
import { SafeAreaView } from 'react-native-safe-area-context';
import { router, useLocalSearchParams } from 'expo-router';
import { useBeneficiary } from '@/contexts/BeneficiaryContext';
import { useAuth } from '@/contexts/AuthContext';
import { useToast } from '@/components/ui/Toast';
import { api } from '@/services/api';
import {
  AppColors,
  BorderRadius,
  FontSizes,
  FontWeights,
  Spacing,
} from '@/constants/theme';
import { BeneficiaryMenu } from '@/components/ui/BeneficiaryMenu';

type Role = 'caretaker' | 'guardian';

// Local beneficiaries have timestamp-based IDs (>1000000000)
const isLocalBeneficiary = (id: string | number): boolean => {
  const numId = typeof id === 'string' ? parseInt(id, 10) : id;
  return numId > 1000000000;
};

interface Invitation {
  id: string;
  email: string;
  role: string;
  label?: string;
  status: string;
  created_at: string;
}

export default function ShareAccessScreen() {
  const { id } = useLocalSearchParams<{ id: string }>();
  const { currentBeneficiary, localBeneficiaries, updateLocalBeneficiary } = useBeneficiary();
  const { user } = useAuth();
  const toast = useToast();

  const [email, setEmail] = useState('');
  const [role, setRole] = useState<Role>('caretaker');
  const [isLoading, setIsLoading] = useState(false);
  const [invitations, setInvitations] = useState<Invitation[]>([]);
  const [isLoadingInvitations, setIsLoadingInvitations] = useState(true);
  const [refreshing, setRefreshing] = useState(false);

  const beneficiaryName = currentBeneficiary?.name || 'this person';
  const currentUserEmail = user?.email?.toLowerCase();

  // Check if this is a local beneficiary
  const isLocal = useMemo(() => id ? isLocalBeneficiary(id) : false, [id]);

  // Get local beneficiary data
  const localBeneficiary = useMemo(() => {
    if (!isLocal || !id) return null;
    return localBeneficiaries.find(b => b.id === parseInt(id, 10));
  }, [isLocal, id, localBeneficiaries]);

  // Load invitations on mount
  useEffect(() => {
    if (id) {
      loadInvitations();
    }
  }, [id, isLocal, localBeneficiary]);

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

    // For local beneficiaries, use stored invitations
    if (isLocal && localBeneficiary) {
      setInvitations(localBeneficiary.invitations || []);
      setIsLoadingInvitations(false);
      setRefreshing(false);
      return;
    }

    // For API beneficiaries
    try {
      const response = await api.getInvitations(id);
      if (response.ok && response.data) {
        setInvitations(response.data.invitations || []);
      }
    } catch (error) {
      // Failed to load invitations
    } finally {
      setIsLoadingInvitations(false);
      setRefreshing(false);
    }
  };

  const onRefresh = useCallback(() => {
    setRefreshing(true);
    loadInvitations();
  }, [id]);

  const validateEmail = (email: string): boolean => {
    const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
    return emailRegex.test(email);
  };

  const handleSendInvite = async () => {
    const trimmedEmail = email.trim().toLowerCase();

    if (!trimmedEmail) {
      Alert.alert('Error', 'Please enter an email address.');
      return;
    }

    if (!validateEmail(trimmedEmail)) {
      Alert.alert('Error', 'Please enter a valid email address.');
      return;
    }

    // Check if inviting self
    if (currentUserEmail && trimmedEmail === currentUserEmail) {
      Alert.alert('Error', 'You cannot invite yourself.');
      return;
    }

    // Check if already invited
    const alreadyInvited = invitations.some(inv => inv.email.toLowerCase() === trimmedEmail);
    if (alreadyInvited) {
      Alert.alert('Error', 'This person has already been invited.');
      return;
    }

    setIsLoading(true);

    // For local beneficiaries, store invitation locally
    if (isLocal && id) {
      try {
        const newInvitation: Invitation = {
          id: `local_${Date.now()}`,
          email: trimmedEmail,
          role: role,
          status: 'pending',
          created_at: new Date().toISOString(),
        };

        const currentInvitations = localBeneficiary?.invitations || [];
        await updateLocalBeneficiary(parseInt(id, 10), {
          invitations: [...currentInvitations, newInvitation],
        });

        setEmail('');
        setRole('caretaker');
        setInvitations([...currentInvitations, newInvitation]);
        toast.success('Invitation Sent', `Invitation sent to ${trimmedEmail}`);
      } catch (error) {
        toast.error('Error', 'Failed to send invitation');
      } finally {
        setIsLoading(false);
      }
      return;
    }

    // For API beneficiaries
    try {
      const response = await api.sendInvitation({
        beneficiaryId: id!,
        email: trimmedEmail,
        role: role,
      });

      if (response.ok) {
        setEmail('');
        setRole('caretaker');
        loadInvitations();
        toast.success('Success', `Invitation sent to ${trimmedEmail}`);
      } else {
        Alert.alert('Error', response.error?.message || 'Failed to send invitation');
      }
    } catch (error) {
      Alert.alert('Error', 'Failed to send invitation. Please try again.');
    } finally {
      setIsLoading(false);
    }
  };

  const handleRemoveInvitation = (invitation: Invitation) => {
    Alert.alert(
      'Remove Access',
      `Remove ${invitation.email} from accessing ${beneficiaryName}?`,
      [
        { text: 'Cancel', style: 'cancel' },
        {
          text: 'Remove',
          style: 'destructive',
          onPress: async () => {
            // For local beneficiaries
            if (isLocal && id) {
              try {
                const currentInvitations = localBeneficiary?.invitations || [];
                const updatedInvitations = currentInvitations.filter(inv => inv.id !== invitation.id);
                await updateLocalBeneficiary(parseInt(id, 10), {
                  invitations: updatedInvitations,
                });
                setInvitations(updatedInvitations);
                toast.success('Removed', 'Access removed successfully');
              } catch (error) {
                toast.error('Error', 'Failed to remove access');
              }
              return;
            }

            // For API beneficiaries
            try {
              const response = await api.deleteInvitation(invitation.id);
              if (response.ok) {
                loadInvitations();
                toast.success('Removed', 'Access removed successfully');
              } else {
                Alert.alert('Error', 'Failed to remove access');
              }
            } catch (error) {
              Alert.alert('Error', 'Failed to remove access');
            }
          },
        },
      ]
    );
  };

  const getRoleLabel = (role: string): string => {
    if (role === 'custodian') return 'Custodian';
    if (role === 'guardian') return 'Guardian';
    return 'Caretaker';
  };

  const handleChangeRole = (invitation: Invitation) => {
    const newRole = invitation.role === 'caretaker' ? 'guardian' : 'caretaker';
    const newRoleLabel = newRole === 'guardian' ? 'Guardian' : 'Caretaker';

    Alert.alert(
      'Change Role',
      `Change ${invitation.email}'s role to ${newRoleLabel}?`,
      [
        { text: 'Cancel', style: 'cancel' },
        {
          text: 'Change',
          onPress: async () => {
            // For local beneficiaries
            if (isLocal && id) {
              try {
                const currentInvitations = localBeneficiary?.invitations || [];
                const updatedInvitations = currentInvitations.map(inv =>
                  inv.id === invitation.id ? { ...inv, role: newRole } : inv
                );
                await updateLocalBeneficiary(parseInt(id, 10), {
                  invitations: updatedInvitations,
                });
                setInvitations(updatedInvitations);
                toast.success('Updated', `Role changed to ${newRoleLabel}`);
              } catch (error) {
                toast.error('Error', 'Failed to change role');
              }
              return;
            }

            // For API beneficiaries
            try {
              const response = await api.updateInvitation(invitation.id, newRole as 'caretaker' | 'guardian');
              if (response.ok) {
                loadInvitations();
                toast.success('Updated', `Role changed to ${newRoleLabel}`);
              } else {
                Alert.alert('Error', response.error?.message || 'Failed to change role');
              }
            } catch (error) {
              Alert.alert('Error', 'Failed to change role');
            }
          },
        },
      ]
    );
  };

  const getStatusColor = (status: string): string => {
    switch (status) {
      case 'accepted': return AppColors.success;
      case 'pending': return AppColors.warning;
      case 'rejected': return AppColors.error;
      default: return AppColors.textMuted;
    }
  };

  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}>Access</Text>
        <BeneficiaryMenu
          beneficiaryId={id || ''}
          userRole={currentBeneficiary?.role}
          currentPage="access"
        />
      </View>

      <KeyboardAvoidingView
        style={styles.content}
        behavior={Platform.OS === 'ios' ? 'padding' : undefined}
      >
        <ScrollView
          contentContainerStyle={styles.scrollContent}
          showsVerticalScrollIndicator={false}
          refreshControl={
            <RefreshControl refreshing={refreshing} onRefresh={onRefresh} />
          }
        >
          {/* Invite Section */}
          <View style={styles.section}>
            <Text style={styles.sectionTitle}>Invite Someone</Text>

            {/* Role Toggle - above email */}
            <View style={styles.roleToggle}>
              <TouchableOpacity
                style={[styles.roleButton, role === 'caretaker' && styles.roleButtonActive]}
                onPress={() => setRole('caretaker')}
              >
                <Text style={[styles.roleButtonText, role === 'caretaker' && styles.roleButtonTextActive]}>
                  Caretaker
                </Text>
              </TouchableOpacity>
              <TouchableOpacity
                style={[styles.roleButton, role === 'guardian' && styles.roleButtonActive]}
                onPress={() => setRole('guardian')}
              >
                <Text style={[styles.roleButtonText, role === 'guardian' && styles.roleButtonTextActive]}>
                  Guardian
                </Text>
              </TouchableOpacity>
            </View>

            <Text style={styles.roleHint}>
              {role === 'caretaker'
                ? 'Can view activity and chat with Julia'
                : 'Full access: edit info, manage subscription'}
            </Text>

            <View style={[styles.inputRow, { marginTop: Spacing.md }]}>
              <TextInput
                style={styles.input}
                placeholder="Email address"
                placeholderTextColor={AppColors.textMuted}
                value={email}
                onChangeText={setEmail}
                autoCapitalize="none"
                autoCorrect={false}
                keyboardType="email-address"
                editable={!isLoading}
              />
              <TouchableOpacity
                style={[styles.sendButton, isLoading && styles.sendButtonDisabled]}
                onPress={handleSendInvite}
                disabled={isLoading}
              >
                {isLoading ? (
                  <ActivityIndicator size="small" color={AppColors.white} />
                ) : (
                  <Ionicons name="send" size={18} color={AppColors.white} />
                )}
              </TouchableOpacity>
            </View>
          </View>

          {/* People with Access */}
          <View style={styles.section}>
            <Text style={styles.sectionTitle}>People with Access</Text>

            {isLoadingInvitations ? (
              <View style={styles.loadingContainer}>
                <ActivityIndicator size="small" color={AppColors.primary} />
              </View>
            ) : invitations.length === 0 ? (
              <View style={styles.emptyState}>
                <Ionicons name="people-outline" size={32} color={AppColors.textMuted} />
                <Text style={styles.emptyText}>No one else has access yet</Text>
              </View>
            ) : (
              <View style={styles.invitationsList}>
                {invitations.map((invitation) => (
                  <View key={invitation.id} style={styles.invitationItem}>
                    <View style={styles.invitationInfo}>
                      <View style={styles.invitationAvatar}>
                        <Text style={styles.avatarText}>
                          {invitation.email.charAt(0).toUpperCase()}
                        </Text>
                      </View>
                      <View style={styles.invitationDetails}>
                        <Text style={styles.invitationEmail} numberOfLines={1}>
                          {invitation.email}
                        </Text>
                        <View style={styles.invitationMeta}>
                          <TouchableOpacity
                            style={styles.roleChip}
                            onPress={() => handleChangeRole(invitation)}
                          >
                            <Text style={styles.invitationRole}>
                              {getRoleLabel(invitation.role)}
                            </Text>
                            <Ionicons name="chevron-down" size={12} color={AppColors.primary} />
                          </TouchableOpacity>
                          <View style={[styles.statusDot, { backgroundColor: getStatusColor(invitation.status) }]} />
                          <Text style={[styles.invitationStatus, { color: getStatusColor(invitation.status) }]}>
                            {invitation.status}
                          </Text>
                        </View>
                      </View>
                    </View>
                    <TouchableOpacity
                      style={styles.removeButton}
                      onPress={() => handleRemoveInvitation(invitation)}
                    >
                      <Ionicons name="close" size={18} color={AppColors.textMuted} />
                    </TouchableOpacity>
                  </View>
                ))}
              </View>
            )}
          </View>
        </ScrollView>
      </KeyboardAvoidingView>
    </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,
  },
  content: {
    flex: 1,
  },
  scrollContent: {
    padding: Spacing.lg,
    paddingBottom: Spacing.xxl,
  },
  section: {
    marginBottom: Spacing.xl,
  },
  sectionTitle: {
    fontSize: FontSizes.sm,
    fontWeight: FontWeights.semibold,
    color: AppColors.textSecondary,
    marginBottom: Spacing.md,
    textTransform: 'uppercase',
    letterSpacing: 0.5,
  },
  inputRow: {
    flexDirection: 'row',
    gap: Spacing.sm,
  },
  input: {
    flex: 1,
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.lg,
    paddingHorizontal: Spacing.md,
    paddingVertical: Spacing.md,
    fontSize: FontSizes.base,
    color: AppColors.textPrimary,
    borderWidth: 1,
    borderColor: AppColors.border,
  },
  sendButton: {
    width: 48,
    height: 48,
    borderRadius: BorderRadius.lg,
    backgroundColor: AppColors.primary,
    justifyContent: 'center',
    alignItems: 'center',
  },
  sendButtonDisabled: {
    opacity: 0.7,
  },
  roleToggle: {
    flexDirection: 'row',
    backgroundColor: AppColors.surfaceSecondary,
    borderRadius: BorderRadius.lg,
    padding: 4,
    marginTop: Spacing.md,
  },
  roleButton: {
    flex: 1,
    paddingVertical: Spacing.sm,
    alignItems: 'center',
    borderRadius: BorderRadius.md,
  },
  roleButtonActive: {
    backgroundColor: AppColors.surface,
  },
  roleButtonText: {
    fontSize: FontSizes.sm,
    fontWeight: FontWeights.medium,
    color: AppColors.textSecondary,
  },
  roleButtonTextActive: {
    color: AppColors.primary,
    fontWeight: FontWeights.semibold,
  },
  roleHint: {
    fontSize: FontSizes.xs,
    color: AppColors.textMuted,
    marginTop: Spacing.sm,
    textAlign: 'center',
  },
  loadingContainer: {
    padding: Spacing.xl,
    alignItems: 'center',
  },
  emptyState: {
    alignItems: 'center',
    padding: Spacing.xl,
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.lg,
  },
  emptyText: {
    fontSize: FontSizes.sm,
    color: AppColors.textMuted,
    marginTop: Spacing.sm,
  },
  invitationsList: {
    backgroundColor: AppColors.surface,
    borderRadius: BorderRadius.lg,
    overflow: 'hidden',
  },
  invitationItem: {
    flexDirection: 'row',
    alignItems: 'center',
    padding: Spacing.md,
    borderBottomWidth: 1,
    borderBottomColor: AppColors.border,
  },
  invitationInfo: {
    flex: 1,
    flexDirection: 'row',
    alignItems: 'center',
  },
  invitationAvatar: {
    width: 36,
    height: 36,
    borderRadius: 18,
    backgroundColor: AppColors.primaryLight,
    justifyContent: 'center',
    alignItems: 'center',
    marginRight: Spacing.md,
  },
  avatarText: {
    fontSize: FontSizes.sm,
    fontWeight: FontWeights.semibold,
    color: AppColors.white,
  },
  invitationDetails: {
    flex: 1,
  },
  invitationEmail: {
    fontSize: FontSizes.sm,
    fontWeight: FontWeights.medium,
    color: AppColors.textPrimary,
  },
  invitationMeta: {
    flexDirection: 'row',
    alignItems: 'center',
    marginTop: 2,
  },
  roleChip: {
    flexDirection: 'row',
    alignItems: 'center',
    backgroundColor: AppColors.primaryLighter,
    paddingHorizontal: Spacing.sm,
    paddingVertical: 2,
    borderRadius: BorderRadius.full,
    gap: 2,
  },
  invitationRole: {
    fontSize: FontSizes.xs,
    color: AppColors.primary,
    fontWeight: FontWeights.medium,
  },
  statusDot: {
    width: 6,
    height: 6,
    borderRadius: 3,
    marginHorizontal: Spacing.xs,
  },
  invitationStatus: {
    fontSize: FontSizes.xs,
    textTransform: 'capitalize',
  },
  removeButton: {
    padding: Spacing.xs,
  },
});