keystone-app/components/LoginScreen.tsx

import React, { useState } from 'react';
import { View, Text, TextInput, TouchableOpacity, StyleSheet, ActivityIndicator, KeyboardAvoidingView, Platform, Alert } from 'react-native';
import { MaterialIcons } from '@expo/vector-icons';
import AsyncStorage from '@react-native-async-storage/async-storage';
import { BACKEND_URL } from '../app/utils/syncManager';

interface Props {
  onLoginSuccess: (token: string) => void;
}

export default function LoginScreen({ onLoginSuccess }: Props) {
  const [username, setUsername] = useState('');
  const [password, setPassword] = useState('');
  const [isLoading, setIsLoading] = useState(false);

  const handleLogin = async () => {
    if (!username || !password) {
      Alert.alert('Error', 'Please enter both username and password.');
      return;
    }

    setIsLoading(true);
    try {
      const res = await fetch(`${BACKEND_URL}/auth/login`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ username, password }),
      });
      
      const data = await res.json();
      
      if (res.ok && data.token) {
        await AsyncStorage.setItem('jwt_token', data.token);
        onLoginSuccess(data.token);
      } else {
        Alert.alert('Login Failed', data.detail || 'Invalid credentials');
      }
    } catch (e) {
      Alert.alert('Network Error', 'Could not connect to server.');
    } finally {
      setIsLoading(false);
    }
  };

  return (
    <KeyboardAvoidingView 
      behavior={Platform.OS === 'ios' ? 'padding' : 'height'}
      style={styles.container}
    >
      <View style={styles.card}>
        <View style={styles.header}>
          <MaterialIcons name="cloud-sync" size={48} color="#1a73e8" />
          <Text style={styles.title}>KeyStone</Text>
          <Text style={styles.subtitle}>Sign in to your private cloud</Text>
        </View>

        <View style={styles.form}>
          <View style={styles.inputContainer}>
            <MaterialIcons name="person" size={20} color="#5f6368" style={styles.inputIcon} />
            <TextInput
              style={styles.input}
              placeholder="Username"
              placeholderTextColor="#9aa0a6"
              value={username}
              onChangeText={setUsername}
              autoCapitalize="none"
              autoCorrect={false}
            />
          </View>

          <View style={styles.inputContainer}>
            <MaterialIcons name="lock" size={20} color="#5f6368" style={styles.inputIcon} />
            <TextInput
              style={styles.input}
              placeholder="Password"
              placeholderTextColor="#9aa0a6"
              secureTextEntry
              value={password}
              onChangeText={setPassword}
            />
          </View>

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

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#F6EAE1',
    justifyContent: 'center',
    padding: 24,
  },
  card: {
    backgroundColor: '#F6EAE1',
    borderRadius: 24,
    padding: 32,
    shadowColor: '#000',
    shadowOffset: { width: 0, height: 8 },
    shadowOpacity: 0.05,
    shadowRadius: 24,
    elevation: 4,
  },
  header: {
    alignItems: 'center',
    marginBottom: 32,
  },
  title: {
    fontSize: 28,
    fontWeight: '800',
    color: '#202124',
    marginTop: 16,
    letterSpacing: -0.5,
  },
  subtitle: {
    fontSize: 15,
    color: '#5f6368',
    marginTop: 8,
  },
  form: {
    gap: 16,
  },
  inputContainer: {
    flexDirection: 'row',
    alignItems: 'center',
    backgroundColor: '#f1f3f4',
    borderRadius: 12,
    paddingHorizontal: 16,
    height: 56,
  },
  inputIcon: {
    marginRight: 12,
  },
  input: {
    flex: 1,
    fontSize: 16,
    color: '#202124',
    height: '100%',
  },
  button: {
    backgroundColor: '#1a73e8',
    height: 56,
    borderRadius: 12,
    justifyContent: 'center',
    alignItems: 'center',
    marginTop: 8,
  },
  buttonDisabled: {
    opacity: 0.7,
  },
  buttonText: {
    color: '#fff',
    fontSize: 16,
    fontWeight: '700',
  },
});