/**
 * Authentication Module for Weight Tracker
 * Provides password protection for the application
 */
const Auth = (() => {
    // Session storage key
    const AUTH_KEY = 'weight_tracker_auth';
    
    // Default password hash (can be overridden via environment variables)
    // This is a bcrypt hash of "password" - should be replaced in production
    let passwordHash = '$2a$10$EgxHKjDDFcZKtQY9hl/N4.QvEQHCXVnQXw9dzFYlUDVKOcLMGp9eq';
    
    // Login state
    let isAuthenticated = false;
    
    /**
     * Initialize the authentication module
     */
    const init = () => {
        // Check for password hash in environment variables (passed via meta tag)
        const envPasswordHash = document.querySelector('meta[name="password-hash"]')?.getAttribute('content');
        if (envPasswordHash) {
            passwordHash = envPasswordHash;
        }
        
        // Check if already authenticated
        checkAuthStatus();
        
        // If not authenticated, show login screen
        if (!isAuthenticated) {
            showLoginScreen();
        }
    };
    
    /**
     * Check if the user is authenticated
     */
    const checkAuthStatus = () => {
        const authData = sessionStorage.getItem(AUTH_KEY);
        isAuthenticated = authData === 'true';
        return isAuthenticated;
    };
    
    /**
     * Show the login screen
     */
    const showLoginScreen = () => {
        // Create login overlay
        const overlay = document.createElement('div');
        overlay.className = 'login-overlay';
        overlay.style.position = 'fixed';
        overlay.style.top = '0';
        overlay.style.left = '0';
        overlay.style.width = '100%';
        overlay.style.height = '100%';
        overlay.style.backgroundColor = 'var(--background-color, #f8f9fa)';
        overlay.style.zIndex = '9999';
        overlay.style.display = 'flex';
        overlay.style.justifyContent = 'center';
        overlay.style.alignItems = 'center';
        
        // Create login form
        overlay.innerHTML = `
            <div class="login-container" style="background-color: var(--card-bg, #ffffff); border-radius: 8px; box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1); width: 100%; max-width: 400px; padding: 30px;">
                <div style="text-align: center; margin-bottom: 30px;">
                    <h1 style="color: var(--primary-color, #4a6fa5); font-size: 2rem; margin-bottom: 5px;">Keep My Weight</h1>
                </div>
                <p style="color: #666; font-size: 1rem; margin-bottom: 30px; text-align: center;">Simple, private weight & meal tracking</p>
                
                <form id="login-form">
                    <div style="margin-bottom: 20px;">
                        <label for="password" style="display: block; margin-bottom: 8px; font-weight: 500;">Password</label>
                        <input type="password" id="password" required style="width: 100%; padding: 12px; border-radius: 8px; border: 1px solid #e0e0e0; font-family: inherit; font-size: 1rem;">
                    </div>
                    
                    <button type="submit" style="width: 100%; padding: 12px; background-color: var(--primary-color, #4a6fa5); color: white; border: none; border-radius: 8px; cursor: pointer; font-weight: 600; font-size: 1rem;">Login</button>
                    
                    <div id="error-message" style="color: #d9534f; margin-top: 20px; text-align: center; font-size: 0.9rem;"></div>
                </form>
                
                <p style="margin-top: 30px; text-align: center; font-size: 0.8rem; color: #666;">Your data stays private, always. This password protects your personal health information.</p>
            </div>
        `;
        
        // Add to DOM
        document.body.appendChild(overlay);
        
        // Handle form submission
        const form = document.getElementById('login-form');
        form.addEventListener('submit', async (e) => {
            e.preventDefault();
            
            const password = document.getElementById('password').value;
            const errorMessage = document.getElementById('error-message');
            
            try {
                // Use bcrypt.js for password verification
                const bcrypt = window.dcodeIO?.bcrypt;
                if (!bcrypt) {
                    throw new Error('bcrypt.js not loaded');
                }
                
                // Verify password
                const isMatch = await new Promise((resolve) => {
                    bcrypt.compare(password, passwordHash, (err, result) => {
                        if (err) {
                            console.error('Error verifying password:', err);
                            resolve(false);
                        } else {
                            resolve(result);
                        }
                    });
                });
                
                if (isMatch) {
                    // Set as authenticated
                    sessionStorage.setItem(AUTH_KEY, 'true');
                    isAuthenticated = true;
                    
                    // Remove login overlay
                    document.body.removeChild(overlay);
                } else {
                    errorMessage.textContent = 'Invalid password. Please try again.';
                }
            } catch (error) {
                console.error('Authentication error:', error);
                errorMessage.textContent = 'An error occurred during authentication. Please try again.';
            }
        });
    };
    
    /**
     * Log out the user
     */
    const logout = () => {
        sessionStorage.removeItem(AUTH_KEY);
        isAuthenticated = false;
        showLoginScreen();
    };
    
    // Return public API
    return {
        init,
        checkAuthStatus,
        logout
    };
})();