Search/static/js/dynamicscrollingimages.js

(function() {
    // Configuration
    const imageStatusInterval = 500; // Interval in milliseconds to check image status
    const scrollThreshold = 500;      // Distance from bottom of the page to trigger loading
    const loadingIndicator = document.getElementById('message-bottom-left');
    let loadingTimer;
    let isFetching = false;
    let page = parseInt(document.getElementById('template-data').getAttribute('data-page')) || 1;
    let query = document.getElementById('template-data').getAttribute('data-query');
    let hardCacheEnabled = document.getElementById('template-data').getAttribute('data-hard-cache-enabled') === 'true';
    let noMoreImages = false; // Flag to indicate if there are no more images to load

    let imageElements = [];
    let imageIds = [];

    /**
     * Function to handle image load errors with retry logic
     * @param {HTMLElement} imgElement - The image element that failed to load
     * @param {number} retryCount - Number of retries left
     * @param {number} retryDelay - Delay between retries in milliseconds
     */
    function handleImageError(imgElement, retryCount = 3, retryDelay = 1000) {
        if (retryCount > 0) {
            setTimeout(() => {
                imgElement.src = imgElement.getAttribute('data-full');
                imgElement.onerror = function() {
                    handleImageError(imgElement, retryCount - 1, retryDelay);
                };
            }, retryDelay);
        } else {
            // After retries, hide the image container or set a fallback image
            console.warn('Image failed to load after retries:', imgElement.getAttribute('data-full'));
            imgElement.parentElement.style.display = 'none'; // Hide the image container
            // Alternatively, set a fallback image:
            // imgElement.src = '/static/images/fallback.svg';
        }
    }

    /**
     * Function to ensure the page is scrollable by loading more images if necessary
     */
    function ensureScrollable() {
        if (noMoreImages) return; // Do not attempt if no more images are available
        // Check if the page is not scrollable
        if (document.body.scrollHeight <= window.innerHeight) {
            // If not scrollable, fetch the next page
            fetchNextPage();
        }
    }

    /**
     * Function to fetch the next page of images
     */
    function fetchNextPage() {
        if (isFetching || noMoreImages) return;
    
        // Start the timer for loading indicator
        loadingTimer = setTimeout(() => {
            loadingIndicator.style.display = 'flex';
        }, 150);
    
        isFetching = true;
        page += 1;
    
        fetch(`/search?q=${encodeURIComponent(query)}&t=image&p=${page}&ajax=true`)
            .then(response => response.text())
            .then(html => {
                clearTimeout(loadingTimer); // Clear the timer if fetch is successful
                loadingIndicator.style.display = 'none'; // Hide the loading indicator
    
                let parser = new DOMParser();
                let doc = parser.parseFromString(html, 'text/html');
                let newImages = doc.querySelectorAll('.image');
    
                if (newImages.length > 0) {
                    let resultsContainer = document.querySelector('.images');
                    newImages.forEach(imageDiv => {
                        // Append new images to the container
                        resultsContainer.appendChild(imageDiv);

                        // Get the img element
                        let img = imageDiv.querySelector('img');
                        if (img) {
                            let id = img.getAttribute('data-id');
                            if (id) {
                                imageElements.push(img);
                                imageIds.push(id);
                            }
                            if (hardCacheEnabled) {
                                // Replace image with placeholder
                                img.src = '/static/images/placeholder.svg';
                                img.onerror = function() {
                                    handleImageError(img);
                                };
                            } else {
                                // HardCacheEnabled is false; load images immediately
                                img.src = img.getAttribute('data-full');
                                img.onerror = function() {
                                    handleImageError(img);
                                };
                            }
                        }
                    });
                    if (hardCacheEnabled) {
                        checkImageStatus();
                    }
                    // After appending new images, ensure the page is scrollable
                    ensureScrollable();
                } else {
                    // No more images to load
                    noMoreImages = true;
                }
                isFetching = false;
            })
            .catch(error => {
                clearTimeout(loadingTimer); // Clear the timer if fetch fails
                loadingIndicator.style.display = 'none'; // Hide the loading indicator
                console.error('Error fetching next page:', error);
                isFetching = false;
            });
    }

    /**
     * Function to check image status via AJAX
     */
    function checkImageStatus() {
        if (!hardCacheEnabled) return;
        if (imageIds.length === 0) {
            // No images to check, do nothing
            return;
        }

        // Send AJAX request to check image status
        fetch(`/image_status?image_ids=${imageIds.join(',')}`)
            .then(response => response.json())
            .then(statusMap => {
                imageElements = imageElements.filter(img => {
                    let id = img.getAttribute('data-id');
                    if (statusMap[id]) {
                        // Image is ready, update src
                        img.src = statusMap[id];
                        img.onerror = function() {
                            handleImageError(img);
                        };
                        // Remove the image id from the list
                        imageIds = imageIds.filter(imageId => imageId !== id);
                        return false; // Remove img from imageElements
                    }
                    return true; // Keep img in imageElements
                });
                // After updating images, ensure the page is scrollable
                ensureScrollable();
            })
            .catch(error => {
                console.error('Error checking image status:', error);
            });
    }

    // Initialize imageElements and imageIds
    imageElements = Array.from(document.querySelectorAll('img[data-id]'));
    imageIds = imageElements
        .map(img => img.getAttribute('data-id'))
        .filter(id => id); // Exclude empty IDs

    if (hardCacheEnabled) {
        // Replace images with placeholders
        imageElements.forEach(img => {
            img.src = '/static/images/placeholder.svg';
        });

        // Start checking image status
        let imageStatusTimer = setInterval(checkImageStatus, imageStatusInterval);
        checkImageStatus(); // Initial check
    } else {
        // HardCacheEnabled is false; load images immediately
        imageElements.forEach(img => {
            img.src = img.getAttribute('data-full');
            img.onerror = function() {
                handleImageError(img);
            };
        });
    }

    // After initial images are loaded, ensure the page is scrollable
    window.addEventListener('load', ensureScrollable);

    // Infinite scrolling
    window.addEventListener('scroll', function() {
        if (isFetching || noMoreImages) return;

        if (window.innerHeight + window.scrollY >= document.body.offsetHeight - scrollThreshold) {
            // User scrolled near the bottom
            fetchNextPage();
        }
    });

})();