import { useState, useEffect } from 'react';
import { Text, View, TextInput, StyleSheet, Animated, Pressable, ActivityIndicator } from "react-native";
import { Ionicons } from '@expo/vector-icons';
import { useAuth } from '../context/AuthContext';

/**
 * LoginForm component handles user authentication with a Portainer instance.
 * It includes a multi-step form that first validates the domain URL,
 * then allows entering username/password credentials.
 */
export default function LoginForm() {
    // Form state and animation values
    const [formData, setFormData] = useState({ username: '', password: '', domain: '' });
    const [isDomainValid, setIsDomainValid] = useState(false);
    const [isLoading, setIsLoading] = useState(false);
    const buttonScale = useState(new Animated.Value(1))[0];
    const buttonRotation = useState(new Animated.Value(0))[0];
    const fadeAnim = useState(new Animated.Value(0))[0];
    const { setAuthState } = useAuth();

    /**
     * Validates domain input and animates the login form appearance
     * when a valid domain is entered
     */
    useEffect(() => {
        // Basic FQDN validation
        const fqdnRegex = /^(?:https?:\/\/)?(?:[a-zA-Z0-9-]+\.)+[a-zA-Z]{2,}(?::\d+)?(?:\/\S*)?$/;
        const isValid = fqdnRegex.test(formData.domain);
        setIsDomainValid(isValid);

        // Fade animation
        Animated.timing(fadeAnim, {
            toValue: isValid ? 1 : 0,
            duration: 500,
            useNativeDriver: true
        }).start();
    }, [formData.domain]);

    /**
     * Handles the login form submission and authentication process
     * Includes success/failure animations for visual feedback
     */
    const handleLogin = async () => {
        setIsLoading(true);
        try {
            const response = await fetch(`${formData.domain}/api/auth`, {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json',
                    'Access-Control-Allow-Origin': '*',
                    'Access-Control-Allow-Methods': 'POST, OPTIONS',
                    'Access-Control-Allow-Headers': 'Content-Type',
                },
                credentials: 'include', // Include cookies if needed
                body: JSON.stringify({
                    username: formData.username,
                    password: formData.password,
                }),
            });

            if (!response.ok) {
                throw new Error(`HTTP error! status: ${response.status}`);
            }

            const data = await response.json();
            // Store the domain and auth data
            await setAuthState(formData.domain, formData.username, data);

            // Success animation sequence: rotate -> scale up -> scale back
            Animated.sequence([
                Animated.timing(buttonRotation, {
                    toValue: 1,
                    duration: 400,
                    useNativeDriver: true
                }),
                Animated.spring(buttonScale, {
                    toValue: 1.1,
                    useNativeDriver: true
                }),
                Animated.spring(buttonScale, {
                    toValue: 1,
                    useNativeDriver: true
                })
            ]).start();

        } catch (error) {
            console.error('Login error:', error);
        } finally {
            setIsLoading(false);
        }
    };

    return (
        <View style={styles.container}>
            {/* Domain input section */}
            <Text style={styles.title}>Please enter your Portainer domain</Text>
            <Text style={styles.infoText}>Domain must be HTTPS</Text>
            <TextInput
                style={styles.domainInput}
                placeholder="https://your-portainer-domain.com"
                placeholderTextColor="#9EA0A4"
                onChangeText={text => setFormData({ ...formData, domain: text })}
            />

            {/* Login credentials section - appears after valid domain */}
            <Animated.View
                style={[
                    styles.loginSection,
                    {
                        opacity: fadeAnim,
                        transform: [{
                            translateY: fadeAnim.interpolate({
                                inputRange: [0, 1],
                                outputRange: [20, 0]
                            })
                        }]
                    }
                ]}
            >
                <Text style={styles.title}>Please enter your username and password</Text>
                <TextInput
                    style={styles.input}
                    placeholder="Username"
                    placeholderTextColor="#9EA0A4"
                    onChangeText={text => setFormData({ ...formData, username: text })}
                />
                <TextInput
                    style={styles.input}
                    secureTextEntry
                    placeholder="Password"
                    placeholderTextColor="#9EA0A4"
                    onChangeText={text => setFormData({ ...formData, password: text })}
                />

                {/* Animated login button */}
                <Animated.View style={{
                    transform: [
                        { scale: buttonScale },
                        {
                            rotate: buttonRotation.interpolate({
                                inputRange: [0, 1],
                                outputRange: ['0deg', '360deg']
                            })
                        }
                    ]
                }}>
                    <Pressable
                        onPress={() => {
                            if (!isLoading) {
                                // Button press animation
                                Animated.sequence([
                                    Animated.spring(buttonScale, {
                                        toValue: 0.95,
                                        useNativeDriver: true
                                    }),
                                    Animated.spring(buttonScale, {
                                        toValue: 1,
                                        useNativeDriver: true
                                    })
                                ]).start();
                                handleLogin();
                            }
                        }}
                        style={styles.loginButton}
                    >
                        <View style={styles.buttonContent}>
                            {isLoading ? (
                                <ActivityIndicator color="#fff" />
                            ) : (
                                <>
                                    <Ionicons name="log-in-outline" size={24} color="#fff" style={styles.buttonIcon} />
                                    <Text style={styles.buttonText}>Login</Text>
                                </>
                            )}
                        </View>
                    </Pressable>
                </Animated.View>
            </Animated.View>
        </View>
    );
}

/**
 * Component styles
 * Includes styling for container, form inputs, buttons, and animations
 */
const styles = StyleSheet.create({
    container: {
        width: '100%',
        padding: 10,
        backgroundColor: '#ffffff',
        borderRadius: 10,
        shadowColor: "#000",
        shadowOffset: {
            width: 0,
            height: 2,
        },
        shadowOpacity: 0.25,
        shadowRadius: 3.84,
        elevation: 5,
    },
    loginSection: {
        marginTop: 20,
        paddingTop: 20,
        borderTopWidth: 1,
        borderTopColor: '#E9ECEF'
    },
    domainInput: {
        backgroundColor: '#EDF2F7',
        borderRadius: 8,
        padding: 15,
        borderWidth: 1,
        borderColor: '#CBD5E0',
        fontSize: 16,
        color: '#4A5568',
        fontWeight: '500'
    },
    title: {
        fontSize: 18,
        fontWeight: '600',
        color: '#2C3E50',
        marginBottom: 20,
        textAlign: 'center'
    },
    input: {
        backgroundColor: '#F8F9FA',
        borderRadius: 8,
        padding: 15,
        marginBottom: 15,
        borderWidth: 1,
        borderColor: '#E9ECEF',
        fontSize: 16,
        color: '#2C3E50'
    },
    loginButton: {
        backgroundColor: '#4299E1',
        borderRadius: 8,
        padding: 15,
        marginTop: 10,
        shadowColor: "#4299E1",
        shadowOffset: {
            width: 0,
            height: 4,
        },
        shadowOpacity: 0.3,
        shadowRadius: 4.65,
        elevation: 8,
    },
    buttonContent: {
        flexDirection: 'row',
        alignItems: 'center',
        justifyContent: 'center',
    },
    buttonIcon: {
        marginRight: 8,
    },
    buttonText: {
        color: '#fff',
        fontSize: 16,
        marginLeft: 8,
        fontWeight: '600'
    },
    infoText: {
        fontSize: 14,
        color: '#718096',
        marginBottom: 15,
        textAlign: 'center',
        fontStyle: 'italic'
    },
});