/**
 * VideoCharm - Video Player
 * Handles video playback and interaction
 */

const VideoPlayer = (function() {
    // DOM Elements
    let videoFeed;
    let progressFill;
    let playPauseOverlay;
    let playIcon;
    let pauseIcon;
    let volumeControl;
    let volumeOnIcon;
    let volumeOffIcon;
    let likeButton;
    let favoriteButton;
    let likeCount;
    let favoriteCount;
    
    // State
    let videos = [];
    let currentIndex = 0;
    let touchStartY = 0;
    let touchEndY = 0;
    let isLoading = false;
    let isMuted = false;
    let videoLoadTimeout;
    
    /**
     * Initialize the video player
     */
    function init() {
        // Get DOM elements
        videoFeed = document.getElementById('videoFeed');
        progressFill = document.getElementById('progressFill');
        playPauseOverlay = document.getElementById('playPauseOverlay');
        playIcon = document.getElementById('playIcon');
        pauseIcon = document.getElementById('pauseIcon');
        volumeControl = document.getElementById('volumeControl');
        volumeOnIcon = document.getElementById('volumeOnIcon');
        volumeOffIcon = document.getElementById('volumeOffIcon');
        likeButton = document.getElementById('likeButton');
        favoriteButton = document.getElementById('favoriteButton');
        likeCount = document.getElementById('likeCount');
        favoriteCount = document.getElementById('favoriteCount');
        
        // Set up event listeners
        setupEventListeners();
    }
    
    /**
     * Set up event listeners for player controls
     */
    function setupEventListeners() {
        // Touch swipe detection
        document.addEventListener('touchstart', handleTouchStart);
        document.addEventListener('touchend', handleTouchEnd);
        
        // Video feed click
        videoFeed.addEventListener('click', handleVideoClick);
        
        // Volume control
        volumeControl.addEventListener('click', toggleMute);
        
        // Action buttons
        likeButton.addEventListener('click', toggleLike);
        favoriteButton.addEventListener('click', toggleFavorite);
    }
    
    /**
     * Load videos from the API
     * @param {Number} count Number of videos to load
     * @param {Boolean} showLoading Whether to show loading screen
     * @returns {Promise} Promise that resolves when videos are loaded
     */
    function loadVideos(count = 1, showLoading = true) {
        if (isLoading) return Promise.resolve();
        
        isLoading = true;
        if (showLoading) {
            App.showLoading();
        }
        
        // Clear any existing timeout
        if (videoLoadTimeout) {
            clearTimeout(videoLoadTimeout);
        }
        
        // Set a timeout to ensure loading doesn't hang
        videoLoadTimeout = setTimeout(() => {
            if (isLoading) {
                isLoading = false;
                if (showLoading) {
                    App.hideLoading();
                }
                App.showToast('加载超时，请检查网络后重试');
            }
        }, 8000);
        
        return fetch(`/api/videos?count=${count}`)
            .then(response => {
                if (!response.ok) {
                    throw new Error('Network response was not ok');
                }
                return response.json();
            })
            .then(data => {
                if (data.success && data.videos && data.videos.length > 0) {
                    // Immediately create and start playing the first video
                    const firstVideo = data.videos[0];
                    createVideoElement(firstVideo.url);
                    
                    // If this is the first video, play it immediately
                    if (videos.length === 1) {
                        playCurrentVideo();
                        if (showLoading) {
                            App.hideLoading();
                        }
                    }
                    
                    // Asynchronously load remaining videos without blocking UI
                    if (data.videos.length > 1) {
                        setTimeout(() => {
                            for (let i = 1; i < data.videos.length; i++) {
                                createVideoElement(data.videos[i].url);
                            }
                        }, 300);
                    }
                } else {
                    throw new Error('No videos returned from API');
                }
            })
            .catch(error => {
                console.error('Error loading videos:', error);
                App.showToast('加载视频失败，请重试');
            })
            .finally(() => {
                clearTimeout(videoLoadTimeout);
                isLoading = false;
                if (showLoading) {
                    App.hideLoading();
                }
            });
    }
    
    /**
     * Create a new video element
     * @param {String} videoUrl URL of the video
     */
    function createVideoElement(videoUrl) {
        if (!videoUrl) return;
        
        // Create container
        const videoCard = document.createElement('div');
        videoCard.className = 'video-card';
        videoCard.style.transform = `translateY(${100 * videos.length}%)`;
        
        // Create video element
        const video = document.createElement('video');
        video.src = videoUrl;
        video.loop = true;
        video.preload = 'auto';
        video.muted = isMuted;
        video.playsInline = true;
        video.setAttribute('webkit-playsinline', '');
        
        // Generate random data for the video
        const videoId = generateVideoId();
        const videoTitle = `精彩视频 #${videos.length + 1}`;
        const videoDesc = getRandomDescription();
        const randomLikes = Math.floor(Math.random() * 1000) + 1;
        
        // Create video object
        const videoObj = {
            id: videoId,
            url: videoUrl,
            title: videoTitle,
            desc: videoDesc,
            element: videoCard,
            video: video,
            likes: randomLikes,
            timestamp: new Date().getTime(),
            duration: 0
        };
        
        // Create video overlay with info
        const overlay = document.createElement('div');
        overlay.className = 'video-overlay';
        
        const videoInfo = document.createElement('div');
        videoInfo.className = 'video-info';
        
        const titleEl = document.createElement('div');
        titleEl.className = 'video-title';
        titleEl.textContent = videoObj.title;
        
        const descEl = document.createElement('div');
        descEl.className = 'video-desc';
        descEl.textContent = videoObj.desc;
        
        const metaEl = document.createElement('div');
        metaEl.className = 'video-meta';
        
        const durationEl = document.createElement('div');
        durationEl.className = 'video-meta-item duration';
        durationEl.innerHTML = `
            <svg width="14" height="14" viewBox="0 0 24 24" fill="currentColor" xmlns="http://www.w3.org/2000/svg">
                <path d="M12 2C6.5 2 2 6.5 2 12C2 17.5 6.5 22 12 22C17.5 22 22 17.5 22 12C22 6.5 17.5 2 12 2ZM12 20C7.59 20 4 16.41 4 12C4 7.59 7.59 4 12 4C16.41 4 20 7.59 20 12C20 16.41 16.41 20 12 20ZM12.5 7H11V13L16.2 16.2L17 14.9L12.5 12.2V7Z"/>
            </svg>
            <span>00:00</span>
        `;
        
        metaEl.appendChild(durationEl);
        videoInfo.appendChild(titleEl);
        videoInfo.appendChild(descEl);
        videoInfo.appendChild(metaEl);
        overlay.appendChild(videoInfo);
        
        // Add elements to DOM
        videoCard.appendChild(video);
        videoCard.appendChild(overlay);
        videoFeed.appendChild(videoCard);
        
        // Add to videos array
        videos.push(videoObj);
        
        // Set up video event listeners
        setupVideoEvents(video, videoObj, durationEl);
    }
    
    /**
     * Set up event listeners for a video
     * @param {HTMLElement} video Video element
     * @param {Object} videoObj Video object
     * @param {HTMLElement} durationEl Duration display element
     */
    function setupVideoEvents(video, videoObj, durationEl) {
        // Use video's first frame as thumbnail when available
        video.addEventListener('loadeddata', function() {
            videoObj.hasLoadedData = true;
            // Capture first frame as thumbnail
            videoObj.thumbnail = captureVideoFrame(video);
        });
        
        // Update duration when metadata is loaded
        video.addEventListener('loadedmetadata', function() {
            videoObj.duration = Math.round(video.duration);
            const durationSpan = durationEl.querySelector('span');
            if (durationSpan) {
                durationSpan.textContent = formatDuration(videoObj.duration);
            }
        });
        
        // Update progress bar
        video.addEventListener('timeupdate', function() {
            if (videos.indexOf(videoObj) === currentIndex) {
                const progress = (video.currentTime / video.duration) * 100;
                progressFill.style.width = `${progress}%`;
            }
        });
        
        // Handle playback end (for non-looping videos)
        video.addEventListener('ended', function() {
            if (!video.loop) {
                // Automatically advance to next video
                switchToVideo(currentIndex + 1);
            }
        });
        
        // Handle video errors
        video.addEventListener('error', function() {
            console.error('Video load error:', videoObj.url);
            App.showToast('视频加载失败，正在尝试下一个');
            if (videos.indexOf(videoObj) === currentIndex) {
                switchToVideo(currentIndex + 1);
            }
        });
    }
    
    /**
     * Capture a frame from video to use as thumbnail
     * @param {HTMLVideoElement} video Video element
     * @returns {String} Data URL of thumbnail
     */
    function captureVideoFrame(video) {
        try {
            const canvas = document.createElement('canvas');
            canvas.width = video.videoWidth;
            canvas.height = video.videoHeight;
            
            const ctx = canvas.getContext('2d');
            ctx.drawImage(video, 0, 0, canvas.width, canvas.height);
            
            return canvas.toDataURL('image/jpeg', 0.7);
        } catch (e) {
            console.error('Error capturing video frame:', e);
            return null;
        }
    }
    
    /**
     * Switch to a different video
     * @param {Number} index Index of video to switch to
     */
    function switchToVideo(index) {
        if (index < 0 || isLoading) return;
        
        // Handle case where requested index exceeds available videos
        if (index >= videos.length) {
            // Show loading toast and load more videos
            App.showToast('正在加载新视频...');
            loadVideos(1, false).then(() => {
                // After loading, try again if video exists now
                if (index < videos.length) {
                    switchToVideo(index);
                }
            });
            return;
        }
        
        // Pause all videos
        videos.forEach(item => {
            item.video.pause();
        });
        
        // Update current index
        currentIndex = index;
        
        // Update video positions
        updateVideoPositions();
        
        // Play current video
        playCurrentVideo();
        
        // Reset progress bar
        progressFill.style.width = '0';
        
        // Update action buttons
        updateActionButtons();
        
        // Add to history
        if (videos[currentIndex]) {
            StorageManager.addToHistory(videos[currentIndex]);
        }
        
        // Preload more videos when close to end
        if (currentIndex >= videos.length - 1) {
            loadVideos(2, false);
        }
    }
    
    /**
     * Play the current video
     */
    function playCurrentVideo() {
        if (!videos[currentIndex]) return;
        
        const video = videos[currentIndex].video;
        
        // Try to play and handle autoplay restrictions
        const playPromise = video.play();
        
        if (playPromise !== undefined) {
            playPromise.catch(error => {
                console.log('Autoplay prevented, trying muted playback');
                // Auto-play was prevented, set muted and try again
                video.muted = true;
                isMuted = true;
                updateVolumeUI();
                video.play().catch(e => {
                    console.error('Failed to play video even with mute:', e);
                    // If even muted autoplay fails, show a play button overlay
                    App.showToast('点击视频开始播放');
                });
            });
        }
    }
    
    /**
     * Update positions of all videos
     */
    function updateVideoPositions() {
        videos.forEach((item, idx) => {
            item.element.style.transform = `translateY(${(idx - currentIndex) * 100}%)`;
        });
    }
    
    /**
     * Update action buttons state based on current video
     */
    function updateActionButtons() {
        if (!videos[currentIndex]) return;
        
        const videoId = videos[currentIndex].id;
        
        // Update like button
        if (StorageManager.isLiked(videoId)) {
            likeButton.classList.add('active');
        } else {
            likeButton.classList.remove('active');
        }
        
        // Update favorite button
        if (StorageManager.isFavorite(videoId)) {
            favoriteButton.classList.add('active');
        } else {
            favoriteButton.classList.remove('active');
        }
        
        // Update counts
        likeCount.textContent = Math.floor(videos[currentIndex].likes);
        favoriteCount.textContent = StorageManager.isFavorite(videoId) ? '1' : '0';
    }
    
    /**
     * Handle touch start event
     * @param {Event} e Touch event
     */
    function handleTouchStart(e) {
        touchStartY = e.touches[0].clientY;
    }
    
    /**
     * Handle touch end event
     * @param {Event} e Touch event
     */
    function handleTouchEnd(e) {
        // Only process touch events on home screen
        if (!document.getElementById('homeScreen').classList.contains('active')) {
            return;
        }
        
        touchEndY = e.changedTouches[0].clientY;
        const deltaY = touchStartY - touchEndY;
        
        // If swipe distance is significant
        if (Math.abs(deltaY) > 50) {
            if (deltaY > 0) {
                // Swipe up - next video
                switchToVideo(currentIndex + 1);
            } else {
                // Swipe down - previous video
                switchToVideo(currentIndex - 1);
            }
        }
    }
    
    /**
     * Handle click on video feed
     * @param {Event} e Click event
     */
    function handleVideoClick(e) {
        // Ignore clicks on controls
        if (e.target.closest('.action-button') || 
            e.target.closest('.volume-control')) {
            return;
        }
        
        // Toggle play/pause
        if (!videos[currentIndex]) return;
        
        const video = videos[currentIndex].video;
        
        if (video.paused) {
            video.play();
            playIcon.style.display = 'block';
            pauseIcon.style.display = 'none';
        } else {
            video.pause();
            playIcon.style.display = 'none';
            pauseIcon.style.display = 'block';
        }
        
        // Show play/pause overlay
        playPauseOverlay.classList.add('visible');
        setTimeout(() => {
            playPauseOverlay.classList.remove('visible');
        }, 800);
    }
    
    /**
     * Toggle mute state
     */
    function toggleMute() {
        isMuted = !isMuted;
        
        // Update all videos
        videos.forEach(item => {
            item.video.muted = isMuted;
        });
        
        // Update UI
        updateVolumeUI();
        
        // Show toast
        App.showToast(isMuted ? '已静音' : '已开启声音');
    }
    
    /**
     * Update volume control UI
     */
    function updateVolumeUI() {
        if (isMuted) {
            volumeOnIcon.style.display = 'none';
            volumeOffIcon.style.display = 'block';
        } else {
            volumeOnIcon.style.display = 'block';
            volumeOffIcon.style.display = 'none';
        }
    }
    
    /**
     * Toggle like for current video
     */
    function toggleLike() {
        if (!videos[currentIndex]) return;
        
        const videoId = videos[currentIndex].id;
        const newLikeState = StorageManager.toggleLike(videoId);
        
        // Update UI
        if (newLikeState) {
            likeButton.classList.add('active');
            videos[currentIndex].likes++;
            App.showToast('已添加到喜欢');
        } else {
            likeButton.classList.remove('active');
            videos[currentIndex].likes--;
            App.showToast('已取消喜欢');
        }
        
        // Update count
        likeCount.textContent = Math.floor(videos[currentIndex].likes);
        
        // Update profile stats
        App.updateStats();
    }
    
    /**
     * Toggle favorite for current video
     */
    function toggleFavorite() {
        if (!videos[currentIndex]) return;
        
        const newFavoriteState = StorageManager.toggleFavorite(videos[currentIndex]);
        
        // Update UI
        if (newFavoriteState) {
            favoriteButton.classList.add('active');
            favoriteCount.textContent = '1';
            App.showToast('已添加到收藏');
        } else {
            favoriteButton.classList.remove('active');
            favoriteCount.textContent = '0';
            App.showToast('已取消收藏');
        }
        
        // Update profile stats
        App.updateStats();
    }
    
    /**
     * Play a video from the history or favorites
     * @param {Object} videoData Video data from storage
     */
    function playVideoFromLibrary(videoData) {
        if (!videoData || !videoData.url) return;
        
        // Check if video is already loaded
        const existingIndex = videos.findIndex(v => v.id === videoData.id);
        
        if (existingIndex !== -1) {
            // Switch to existing video
            switchToVideo(existingIndex);
        } else {
            // Create new video element
            createVideoElement(videoData.url);
            
            // Switch to the new video
            switchToVideo(videos.length - 1);
        }
        
        // Switch to home screen
        App.switchToScreen('homeScreen');
    }
    
    /**
     * Generate a unique video ID
     * @returns {String} Unique ID
     */
    function generateVideoId() {
        return 'v_' + Math.random().toString(36).substr(2, 9) + '_' + Date.now();
    }
    
    /**
     * 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}`;
    }
    
    /**
     * Get random video description
     * @returns {String} Random description
     */
    function getRandomDescription() {
        const descriptions = [
            "精选高质量视频，带给你视觉享受",
            "每日精选，让你流连忘返",
            "热门推荐，不容错过的精彩瞬间",
            "探索更多精彩内容，尽在VideoCharm",
            "发现生活中的美好瞬间",
            "精彩纷呈，尽在眼前",
            "让心情放松的精选内容",
            "视觉盛宴，触手可及"
        ];
        
        return descriptions[Math.floor(Math.random() * descriptions.length)];
    }
    
    // Public API
    return {
        init: init,
        loadVideos: loadVideos,
        switchToVideo: switchToVideo,
        playVideoFromLibrary: playVideoFromLibrary,
        updateVideoPositions: updateVideoPositions
    };
})();