import React, { useState } from 'react';
import {
  View,
  Text,
  TextInput,
  TouchableOpacity,
  StyleSheet,
  ScrollView,
  KeyboardAvoidingView,
  Platform,
  ActivityIndicator,
  Alert,
} from 'react-native';
import { useRouter } from 'expo-router';
import { useAuthStore } from '../lib/auth-store';

export default function LoginScreen() {
  const router = useRouter();
  const { login, isLoading, error, clearError } = useAuthStore();

  const [email, setEmail] = useState('');
  const [password, setPassword] = useState('');
  const [showPassword, setShowPassword] = useState(false);
  const [validationErrors, setValidationErrors] = useState<{
    email?: string;
    password?: string;
  }>({});

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

  // Validate form
  const validateForm = (): boolean => {
    const errors: { email?: string; password?: string } = {};

    if (!email.trim()) {
      errors.email = 'Email is required';
    } else if (!validateEmail(email)) {
      errors.email = 'Please enter a valid email';
    }

    if (!password) {
      errors.password = 'Password is required';
    } else if (password.length < 6) {
      errors.password = 'Password must be at least 6 characters';
    }

    setValidationErrors(errors);
    return Object.keys(errors).length === 0;
  };

  // Handle login
  const handleLogin = async () => {
    clearError();

    if (!validateForm()) {
      return;
    }

    try {
      await login({ email: email.trim().toLowerCase(), password });
      router.replace('/(tabs)');
    } catch {
      // Error is handled by the store
    }
  };

  // Navigate to signup
  const handleSignup = () => {
    clearError();
    router.push('/(auth)/signup');
  };

  // Navigate to forgot password
  const handleForgotPassword = () => {
    clearError();
    router.push('/(auth)/forgot-password');
  };

  return (
    <KeyboardAvoidingView
      style={styles.container}
      behavior={Platform.OS === 'ios' ? 'padding' : 'height'}
    >
      <ScrollView
        contentContainerStyle={styles.scrollContent}
        keyboardShouldPersistTaps="handled"
        showsVerticalScrollIndicator={false}
      >
        {/* Header */}
        <View style={styles.header}>
          <Text style={styles.title}>Welcome Back</Text>
          <Text style={styles.subtitle}>Sign in to your account</Text>
        </View>

        {/* Form */}
        <View style={styles.form}>
          {/* Email Input */}
          <View style={styles.inputContainer}>
            <Text style={styles.label}>Email</Text>
            <TextInput
              style={[styles.input, validationErrors.email && styles.inputError]}
              placeholder="Enter your email"
              placeholderTextColor="#999"
              value={email}
              onChangeText={(text) => {
                setEmail(text);
                if (validationErrors.email) {
                  setValidationErrors((prev) => ({ ...prev, email: undefined }));
                }
              }}
              keyboardType="email-address"
              autoCapitalize="none"
              autoCorrect={false}
              autoComplete="email"
              editable={!isLoading}
            />
            {validationErrors.email && (
              <Text style={styles.errorText}>{validationErrors.email}</Text>
            )}
          </View>

          {/* Password Input */}
          <View style={styles.inputContainer}>
            <Text style={styles.label}>Password</Text>
            <View style={styles.passwordContainer}>
              <TextInput
                style={[
                  styles.input,
                  styles.passwordInput,
                  validationErrors.password && styles.inputError,
                ]}
                placeholder="Enter your password"
                placeholderTextColor="#999"
                value={password}
                onChangeText={(text) => {
                  setPassword(text);
                  if (validationErrors.password) {
                    setValidationErrors((prev) => ({ ...prev, password: undefined }));
                  }
                }}
                secureTextEntry={!showPassword}
                autoCapitalize="none"
                autoCorrect={false}
                autoComplete="password"
                editable={!isLoading}
              />
              <TouchableOpacity
                style={styles.showPasswordButton}
                onPress={() => setShowPassword(!showPassword)}
                disabled={isLoading}
              >
                <Text style={styles.showPasswordText}>
                  {showPassword ? 'Hide' : 'Show'}
                </Text>
              </TouchableOpacity>
            </View>
            {validationErrors.password && (
              <Text style={styles.errorText}>{validationErrors.password}</Text>
            )}
          </View>

          {/* Forgot Password Link */}
          <TouchableOpacity
            style={styles.forgotPassword}
            onPress={handleForgotPassword}
            disabled={isLoading}
          >
            <Text style={styles.forgotPasswordText}>Forgot Password?</Text>
          </TouchableOpacity>

          {/* API Error */}
          {error && (
            <View style={styles.apiError}>
              <Text style={styles.apiErrorText}>{error}</Text>
            </View>
          )}

          {/* Sign In Button */}
          <TouchableOpacity
            style={[styles.button, isLoading && styles.buttonDisabled]}
            onPress={handleLogin}
            disabled={isLoading}
          >
            {isLoading ? (
              <ActivityIndicator color="#FFFFFF" />
            ) : (
              <Text style={styles.buttonText}>Sign In</Text>
            )}
          </TouchableOpacity>

          {/* Sign Up Link */}
          <View style={styles.signupContainer}>
            <Text style={styles.signupText}>Don't have an account? </Text>
            <TouchableOpacity onPress={handleSignup} disabled={isLoading}>
              <Text style={styles.signupLink}>Sign Up</Text>
            </TouchableOpacity>
          </View>
        </View>

        {/* App Info */}
        <View style={styles.footer}>
          <Text style={styles.footerText}>MoreThanADiagnosis</Text>
          <Text style={styles.footerSubtext}>
            Supporting the kidney disease community
          </Text>
        </View>
      </ScrollView>
    </KeyboardAvoidingView>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#FFFFFF',
  },
  scrollContent: {
    flexGrow: 1,
    paddingHorizontal: 24,
    paddingTop: 60,
    paddingBottom: 40,
  },
  header: {
    marginBottom: 40,
  },
  title: {
    fontSize: 32,
    fontWeight: 'bold',
    color: '#333333',
    marginBottom: 8,
  },
  subtitle: {
    fontSize: 16,
    color: '#666666',
  },
  form: {
    flex: 1,
  },
  inputContainer: {
    marginBottom: 20,
  },
  label: {
    fontSize: 14,
    fontWeight: '600',
    color: '#333333',
    marginBottom: 8,
  },
  input: {
    height: 50,
    borderWidth: 1,
    borderColor: '#E0E0E0',
    borderRadius: 8,
    paddingHorizontal: 16,
    fontSize: 16,
    color: '#333333',
    backgroundColor: '#FAFAFA',
  },
  inputError: {
    borderColor: '#FF3B30',
  },
  passwordContainer: {
    position: 'relative',
  },
  passwordInput: {
    paddingRight: 60,
  },
  showPasswordButton: {
    position: 'absolute',
    right: 16,
    top: 0,
    bottom: 0,
    justifyContent: 'center',
  },
  showPasswordText: {
    fontSize: 14,
    color: '#007AFF',
    fontWeight: '600',
  },
  errorText: {
    fontSize: 12,
    color: '#FF3B30',
    marginTop: 4,
  },
  forgotPassword: {
    alignSelf: 'flex-end',
    marginBottom: 24,
  },
  forgotPasswordText: {
    fontSize: 14,
    color: '#007AFF',
    fontWeight: '600',
  },
  apiError: {
    backgroundColor: '#FFF0F0',
    borderRadius: 8,
    padding: 12,
    marginBottom: 16,
    borderWidth: 1,
    borderColor: '#FF3B30',
  },
  apiErrorText: {
    fontSize: 14,
    color: '#FF3B30',
    textAlign: 'center',
  },
  button: {
    height: 50,
    backgroundColor: '#007AFF',
    borderRadius: 8,
    justifyContent: 'center',
    alignItems: 'center',
    marginBottom: 24,
  },
  buttonDisabled: {
    backgroundColor: '#B0B0B0',
  },
  buttonText: {
    fontSize: 16,
    fontWeight: '600',
    color: '#FFFFFF',
  },
  signupContainer: {
    flexDirection: 'row',
    justifyContent: 'center',
    alignItems: 'center',
  },
  signupText: {
    fontSize: 14,
    color: '#666666',
  },
  signupLink: {
    fontSize: 14,
    color: '#007AFF',
    fontWeight: '600',
  },
  footer: {
    marginTop: 40,
    alignItems: 'center',
  },
  footerText: {
    fontSize: 16,
    fontWeight: '600',
    color: '#333333',
    marginBottom: 4,
  },
  footerSubtext: {
    fontSize: 12,
    color: '#999999',
  },
});