/**
 * Audiobook Player - App JavaScript
 * Minimalist immersive reading experience
 */

// Theme Management
function initTheme() {
    const savedTheme = localStorage.getItem('theme') || 'light';
    if (savedTheme === 'dark') {
        document.body.classList.remove('light-mode');
        document.body.classList.add('dark-mode');
        updateThemeIcon(true);
    }
}

function toggleTheme() {
    const isDark = document.body.classList.contains('dark-mode');
    
    if (isDark) {
        document.body.classList.remove('dark-mode');
        document.body.classList.add('light-mode');
        localStorage.setItem('theme', 'light');
    } else {
        document.body.classList.remove('light-mode');
        document.body.classList.add('dark-mode');
        localStorage.setItem('theme', 'dark');
    }
    
    updateThemeIcon(!isDark);
}

function updateThemeIcon(isDark) {
    const toggle = document.querySelector('.theme-toggle');
    if (toggle) {
        toggle.textContent = isDark ? '☀️' : '🌙';
    }
}

// Navigation
function goBack() {
    window.history.back();
}

function closePlayer() {
    // Override in player page
    window.history.back();
}

// Save and Restore Reading Position
function saveReadingPosition(storyId, scrollPosition) {
    const positions = JSON.parse(localStorage.getItem('readingPositions') || '{}');
    positions[storyId] = {
        position: scrollPosition,
        timestamp: Date.now()
    };
    localStorage.setItem('readingPositions', JSON.stringify(positions));
}

function getReadingPosition(storyId) {
    const positions = JSON.parse(localStorage.getItem('readingPositions') || '{}');
    return positions[storyId]?.position || 0;
}

// Smooth Scroll
function scrollToPosition(position) {
    window.scrollTo({
        top: position,
        behavior: 'smooth'
    });
}

// Touch Gestures (for mobile)
let touchStartX = 0;
let touchEndX = 0;

function initTouchGestures() {
    document.addEventListener('touchstart', (e) => {
        touchStartX = e.changedTouches[0].screenX;
    }, { passive: true });
    
    document.addEventListener('touchend', (e) => {
        touchEndX = e.changedTouches[0].screenX;
        handleSwipe();
    }, { passive: true });
}

function handleSwipe() {
    const swipeThreshold = 100;
    const diff = touchStartX - touchEndX;
    
    // Swipe right (go back)
    if (diff < -swipeThreshold) {
        // Only if we're not on the home page
        if (window.location.pathname !== '/') {
            goBack();
        }
    }
}

// Keyboard Shortcuts
function initKeyboardShortcuts() {
    document.addEventListener('keydown', (e) => {
        // Space: Play/Pause (on player page)
        if (e.code === 'Space' && document.getElementById('playBtn')) {
            e.preventDefault();
            togglePlay();
        }
        
        // Escape: Go back
        if (e.code === 'Escape') {
            if (window.location.pathname !== '/') {
                goBack();
            }
        }
    });
}

// Audio Player Enhancements
function initAudioPlayer() {
    const audio = document.getElementById('audioPlayer');
    if (!audio) return;
    
    // Handle errors
    audio.addEventListener('error', (e) => {
        console.error('Audio error:', e);
        showNotification('播放出错，请重试');
    });
    
    // Handle ended
    audio.addEventListener('ended', () => {
        isPlaying = false;
        updatePlayButton();
    });
    
    // Handle loading
    audio.addEventListener('loadstart', () => {
        showNotification('加载中...', 1000);
    });
}

// Notification System
function showNotification(message, duration = 3000) {
    // Remove existing notification
    const existing = document.querySelector('.notification');
    if (existing) {
        existing.remove();
    }
    
    const notification = document.createElement('div');
    notification.className = 'notification';
    notification.textContent = message;
    notification.style.cssText = `
        position: fixed;
        bottom: 20px;
        left: 50%;
        transform: translateX(-50%);
        background: var(--bg-card);
        color: var(--text-primary);
        padding: 12px 24px;
        border-radius: 24px;
        box-shadow: 0 4px 16px var(--shadow);
        z-index: 9999;
        font-size: 0.9rem;
        animation: slideUp 0.3s ease;
    `;
    
    document.body.appendChild(notification);
    
    if (duration > 0) {
        setTimeout(() => {
            notification.style.animation = 'slideDown 0.3s ease';
            setTimeout(() => notification.remove(), 300);
        }, duration);
    }
    
    return notification;
}

// Add animation styles
const style = document.createElement('style');
style.textContent = `
    @keyframes slideUp {
        from {
            opacity: 0;
            transform: translateX(-50%) translateY(20px);
        }
        to {
            opacity: 1;
            transform: translateX(-50%) translateY(0);
        }
    }
    
    @keyframes slideDown {
        from {
            opacity: 1;
            transform: translateX(-50%) translateY(0);
        }
        to {
            opacity: 0;
            transform: translateX(-50%) translateY(20px);
        }
    }
`;
document.head.appendChild(style);

// Prefetch next chunk (optimization)
function prefetchNextChunk(currentIndex) {
    // Implementation for preloading next audio chunk
    // This would be implemented in player.html
}

// Performance: Debounce scroll events
function debounce(func, wait) {
    let timeout;
    return function executedFunction(...args) {
        const later = () => {
            clearTimeout(timeout);
            func(...args);
        };
        clearTimeout(timeout);
        timeout = setTimeout(later, wait);
    };
}

// Initialize on DOM ready
document.addEventListener('DOMContentLoaded', () => {
    initTheme();
    initTouchGestures();
    initKeyboardShortcuts();
    initAudioPlayer();
});

// Handle page visibility change (pause when switching tabs)
document.addEventListener('visibilitychange', () => {
    const audio = document.getElementById('audioPlayer');
    if (document.hidden && audio && !audio.paused) {
        // Optional: pause when switching tabs
        // audio.pause();
        // isPlaying = false;
        // updatePlayButton();
    }
});

// Prevent zoom on double tap (mobile)
let lastTouchEnd = 0;
document.addEventListener('touchend', (event) => {
    const now = Date.now();
    if (now - lastTouchEnd <= 300) {
        event.preventDefault();
    }
    lastTouchEnd = now;
}, { passive: false });