/**
 * VideoCharm - Main Application
 * Core application logic and initialization
 */

const App = (function() {
    // DOM Elements
    let loadingScreen;
    let toast;
    let navItems;
    let screens;
    let historyList;
    let favoritesList;
    let emptyHistory;
    let emptyFavorites;
    let clearHistoryBtn;
    let clearFavoritesBtn;
    let likesCount;
    let favoritesCount;
    let viewsCount;
    let swipeIndicator;
    let profileActions;
    
    /**
     * Initialize the application
     */
    function init() {
        // Get DOM elements
        loadingScreen = document.getElementById('loadingScreen');
        toast = document.getElementById('toast');
        navItems = document.querySelectorAll('.nav-item');
        screens = document.querySelectorAll('.screen');
        historyList = document.getElementById('historyList');
        favoritesList = document.getElementById('favoritesList');
        emptyHistory = document.getElementById('emptyHistory');
        emptyFavorites = document.getElementById('emptyFavorites');
        clearHistoryBtn = document.getElementById('clearHistoryBtn');
        clearFavoritesBtn = document.getElementById('clearFavoritesBtn');
        likesCount = document.getElementById('likesCount');
        favoritesCount = document.getElementById('favoritesCount');
        viewsCount = document.getElementById('viewsCount');
        swipeIndicator = document.getElementById('swipeIndicator');
        profileActions = document.querySelectorAll('.action-row');
        
        // Initialize storage
        StorageManager.init();
        
        // Initialize video player
        VideoPlayer.init();
        
        // Set up event listeners
        setupEventListeners();
        
        // Load initial video and start playing immediately
        VideoPlayer.loadVideos(1, true).then(() => {
            // Show swipe indicator after initial load
            setTimeout(() => {
                swipeIndicator.style.display = 'flex';
                setTimeout(() => {
                    swipeIndicator.style.opacity = '0';
                    setTimeout(() => {
                        swipeIndicator.style.display = 'none';
                    }, 500);
                }, 3000);
            }, 500);
            
            // Load more videos in background for smooth experience
            setTimeout(() => {
                VideoPlayer.loadVideos(3, false);
            }, 1000);
        });
        
        // Update statistics
        updateStats();
    }
    
    /**
     * Set up event listeners
     */
    function setupEventListeners() {
        // Navigation
        navItems.forEach(item => {
            item.addEventListener('click', function() {
                const targetScreen = this.getAttribute('data-screen');
                switchToScreen(targetScreen);
            });
        });
        
        // Clear history button
        clearHistoryBtn.addEventListener('click', function() {
            if (confirm('确定要清空所有观看历史吗？')) {
                StorageManager.clearHistory();
                loadHistoryList();
                updateStats();
                showToast('历史记录已清空');
            }
        });
        
        // Clear favorites button
        clearFavoritesBtn.addEventListener('click', function() {
            if (confirm('确定要清空所有收藏吗？')) {
                StorageManager.clearFavorites();
                loadFavoritesList();
                updateStats();
                showToast('收藏夹已清空');
            }
        });
        
        // Profile actions
        profileActions.forEach(action => {
            action.addEventListener('click', function() {
                const actionType = this.getAttribute('data-action');
                handleProfileAction(actionType);
            });
        });
        
        // Comment button
        document.getElementById('commentButton').addEventListener('click', function() {
            showToast('评论功能开发中，敬请期待！');
        });
        
        // Share button
        document.getElementById('shareButton').addEventListener('click', function() {
            showToast('分享功能开发中，敬请期待！');
        });
    }
    
    /**
     * Switch to a different screen
     * @param {String} screenId ID of screen to switch to
     */
    function switchToScreen(screenId) {
        // Update navigation
        navItems.forEach(item => {
            item.classList.remove('active');
            if (item.getAttribute('data-screen') === screenId) {
                item.classList.add('active');
            }
        });
        
        // Update screens
        screens.forEach(screen => {
            screen.classList.remove('active');
            if (screen.id === screenId) {
                screen.classList.add('active');
            }
        });
        
        // Handle specific screen actions
        if (screenId === 'historyScreen') {
            loadHistoryList();
        } else if (screenId === 'favoritesScreen') {
            loadFavoritesList();
        }
    }
    
    /**
     * Load history list from storage
     */
    function loadHistoryList() {
        const history = StorageManager.getHistory();
        
        // Clear list
        historyList.innerHTML = '';
        
        if (history.length === 0) {
            // Show empty state
            emptyHistory.style.display = 'flex';
            historyList.style.display = 'none';
        } else {
            // Hide empty state
            emptyHistory.style.display = 'none';
            historyList.style.display = 'grid';
            
            // Add history items
            history.forEach(item => {
                const videoItem = createVideoListItem(item, 'history');
                historyList.appendChild(videoItem);
            });
        }
    }
    
    /**
     * Load favorites list from storage
     */
    function loadFavoritesList() {
        const favorites = StorageManager.getFavorites();
        
        // Clear list
        favoritesList.innerHTML = '';
        
        if (favorites.length === 0) {
            // Show empty state
            emptyFavorites.style.display = 'flex';
            favoritesList.style.display = 'none';
        } else {
            // Hide empty state
            emptyFavorites.style.display = 'none';
            favoritesList.style.display = 'grid';
            
            // Add favorite items
            favorites.forEach(item => {
                const videoItem = createVideoListItem(item, 'favorite');
                favoritesList.appendChild(videoItem);
            });
        }
    }
    
    /**
     * Create a video list item for history or favorites
     * @param {Object} videoData Video data
     * @param {String} type Item type ('history' or 'favorite')
     * @returns {HTMLElement} Video list item element
     */
    function createVideoListItem(videoData, type) {
        const videoItem = document.createElement('div');
        videoItem.className = 'video-item';
        videoItem.setAttribute('data-id', videoData.id);
        
        // Use thumbnail if available, otherwise use placeholder
        let thumbnailUrl;
        if (videoData.thumbnail) {
            thumbnailUrl = videoData.thumbnail;
        } else {
            thumbnailUrl = generatePlaceholderImage(videoData.id);
        }
        
        videoItem.innerHTML = `
            <div class="video-thumbnail">
                <img src="${thumbnailUrl}" alt="${videoData.title}" onerror="this.src='${generatePlaceholderImage(videoData.id)}'">
                <div class="video-duration">${formatDuration(videoData.duration)}</div>
            </div>
            <div class="video-item-info">
                <div class="video-item-title">${videoData.title}</div>
                <div class="video-item-meta">
                    <div class="time-ago">
                        <svg viewBox="0 0 24 24" fill="currentColor" xmlns="http://www.w3.org/2000/svg">
                            <path d="M11.99 2C6.47 2 2 6.48 2 12C2 17.52 6.47 22 11.99 22C17.52 22 22 17.52 22 12C22 6.48 17.52 2 11.99 2ZM12 20C7.58 20 4 16.42 4 12C4 7.58 7.58 4 12 4C16.42 4 20 7.58 20 12C20 16.42 16.42 20 12 20ZM12.5 7H11V13L16.2 16.2L17 14.9L12.5 12.2V7Z"/>
                        </svg>
                        ${formatTimeAgo(videoData.timestamp)}
                    </div>
                </div>
            </div>
        `;
        
        // Add click event
        videoItem.addEventListener('click', function() {
            VideoPlayer.playVideoFromLibrary(videoData);
            showToast(`正在播放${type === 'favorite' ? '收藏' : '历史'}视频`);
        });
        
        return videoItem;
    }
    
    /**
     * Update profile statistics
     */
    function updateStats() {
        const likes = StorageManager.getLikes().length;
        const favorites = StorageManager.getFavorites().length;
        const views = StorageManager.getViews();
        
        likesCount.textContent = likes;
        favoritesCount.textContent = favorites;
        viewsCount.textContent = views;
    }
    
    /**
     * Handle profile action
     * @param {String} actionType Type of action
     */
    function handleProfileAction(actionType) {
        switch (actionType) {
            case 'settings':
            case 'preferences':
            case 'about':
                showToast(`${actionType} 功能开发中，敬请期待`);
                break;
            case 'logout':
                if (confirm('确定要退出登录吗？')) {
                    showToast('退出登录成功');
                }
                break;
        }
    }
    
    /**
     * Show loading screen
     */
    function showLoading() {
        loadingScreen.style.display = 'flex';
    }
    
    /**
     * Hide loading screen
     */
    function hideLoading() {
        loadingScreen.style.display = 'none';
    }
    
    /**
     * Show toast message
     * @param {String} message Message to show
     * @param {Number} duration Duration in ms
     */
    function showToast(message, duration = 2000) {
        toast.textContent = message;
        toast.classList.add('show');
        
        setTimeout(() => {
            toast.classList.remove('show');
        }, duration);
    }
    
    /**
     * Format duration in seconds to MM:SS
     * @param {Number} seconds Duration in seconds
     * @returns {String} Formatted duration
     */
    function formatDuration(seconds) {
        if (!seconds) return '00:00';
        
        const minutes = Math.floor(seconds / 60);
        const remainingSeconds = Math.floor(seconds % 60);
        return `${minutes < 10 ? '0' : ''}${minutes}:${remainingSeconds < 10 ? '0' : ''}${remainingSeconds}`;
    }
    
    /**
     * Format timestamp to relative time
     * @param {Number} timestamp Timestamp
     * @returns {String} Formatted time
     */
    function formatTimeAgo(timestamp) {
        const now = new Date().getTime();
        const diff = now - timestamp;
        
        // Less than 1 minute
        if (diff < 60 * 1000) {
            return "刚刚";
        }
        
        // Less than 1 hour
        if (diff < 60 * 60 * 1000) {
            return Math.floor(diff / (60 * 1000)) + "分钟前";
        }
        
        // Less than 24 hours
        if (diff < 24 * 60 * 60 * 1000) {
            return Math.floor(diff / (60 * 60 * 1000)) + "小时前";
        }
        
        // Less than 7 days
        if (diff < 7 * 24 * 60 * 60 * 1000) {
            return Math.floor(diff / (24 * 60 * 60 * 1000)) + "天前";
        }
        
        // Format as date
        const date = new Date(timestamp);
        return `${date.getMonth() + 1}月${date.getDate()}日`;
    }
    
    /**
     * Generate consistent placeholder image URL based on ID
     * @param {String} id Item ID for consistent image generation
     * @returns {String} Image URL
     */
    function generatePlaceholderImage(id) {
        // Generate a deterministic number from the string ID
        let hash = 0;
        if (id && id.length > 0) {
            for (let i = 0; i < id.length; i++) {
                hash = ((hash << 5) - hash) + id.charCodeAt(i);
                hash |= 0; // Convert to 32bit integer
            }
        }
        const randomId = Math.abs(hash % 1000); // Ensure positive
        return `https://picsum.photos/seed/${randomId}/300/500`;
    }
    
    // Public API
    return {
        init: init,
        showLoading: showLoading,
        hideLoading: hideLoading,
        showToast: showToast,
        switchToScreen: switchToScreen,
        updateStats: updateStats
    };
})();

// Initialize application when DOM is loaded
document.addEventListener('DOMContentLoaded', function() {
    App.init();
});