bethaus-app/static/gallery.js

// Assume that currentGalleryImages is already declared in app.js.
// Only declare currentGalleryIndex if it isn't defined already.
if (typeof currentGalleryIndex === "undefined") {
  var currentGalleryIndex = -1;
}

function openGalleryModal(relUrl) {
  document.body.style.overflow = 'hidden'; // Disable background scrolling.
  currentGalleryIndex = currentGalleryImages.indexOf(relUrl);
  showGalleryImage(relUrl);
  document.getElementById('gallery-modal').style.display = 'flex';
}

function showGalleryImage(relUrl) {
  const fullUrl = '/media/' + relUrl;
  const modal = document.getElementById('gallery-modal');
  const currentImage = document.getElementById('gallery-modal-content');
  const loader = document.getElementById('gallery-loader');
  const closeBtn = document.getElementById('gallery-close');
  
  // Set a timeout for showing the loader after 500ms.
  let loaderTimeout = setTimeout(() => {
    loader.style.display = 'block';
  }, 500);

  // Preload the new image.
  const tempImg = new Image();
  tempImg.src = fullUrl;

  tempImg.onload = function () {
      clearTimeout(loaderTimeout);
      loader.style.display = 'none';
  
      // Select all current images in the gallery modal
      const existingImages = document.querySelectorAll('#gallery-modal img');
  
      // Create a new image element for the transition
      const newImage = document.createElement('img');
      newImage.src = fullUrl;
      newImage.style.position = 'absolute';
      newImage.style.top = '50%';   // Center vertically
      newImage.style.left = '50%';  // Center horizontally
      newImage.style.transform = 'translate(-50%, -50%)'; // Ensure centering
      newImage.style.maxWidth = '95vw'; // Prevent overflow on large screens
      newImage.style.maxHeight = '95vh'; // Prevent overflow on tall screens
      newImage.style.transition = 'opacity 0.5s ease-in-out';
      newImage.style.opacity = 0;  // Start fully transparent
      newImage.id = 'gallery-modal-content';
  
      // Append new image on top of existing ones
      modal.appendChild(newImage);
  
      // Fade out all old images and fade in the new one
      setTimeout(() => {
          existingImages.forEach(img => {
              img.style.opacity = 0; // Apply fade-out
          });
          newImage.style.opacity = 1; // Fade in the new image
      }, 10);
  
      // Wait for fade-out to finish, then remove all old images
      setTimeout(() => {
          existingImages.forEach(img => {
              if (img.parentNode) {
                  img.parentNode.removeChild(img); // Remove old images
              }
          });
      }, 510); // 500ms for fade-out + small buffer
  
      // Preload the next image
      preloadNextImage();
  };
  

  tempImg.onerror = function() {
    clearTimeout(loaderTimeout);
    loader.style.display = 'none';
    console.error('Error loading image:', fullUrl);
  };
}

function preloadNextImage() {
  if (currentGalleryIndex < currentGalleryImages.length - 1) {
    const nextImage = new Image();
    nextImage.src = '/media/' + currentGalleryImages[currentGalleryIndex + 1];
  }
}

function closeGalleryModal() {
  document.getElementById('gallery-modal').style.display = 'none';
  document.body.style.overflow = ''; // Restore scrolling.
}

function handleGalleryImageClick(e) {
  if (e.target.classList.contains('gallery-next') || e.target.classList.contains('gallery-prev')) {
      return; // Prevent conflict
  }

  const imgRect = this.getBoundingClientRect();
  if (e.clientX < imgRect.left + imgRect.width / 2) {
      if (currentGalleryIndex > 0) {
          currentGalleryIndex--;
          showGalleryImage(currentGalleryImages[currentGalleryIndex]);
      }
  } else {
      if (currentGalleryIndex < currentGalleryImages.length - 1) {
          currentGalleryIndex++;
          showGalleryImage(currentGalleryImages[currentGalleryIndex]);
      }
  }
}




function initGallerySwipe() {
  let touchStartX = 0;
  let touchEndX = 0;
  const galleryModal = document.getElementById('gallery-modal');

  galleryModal.addEventListener('touchstart', function(e) {
    touchStartX = e.changedTouches[0].screenX;
  }, false);

  galleryModal.addEventListener('touchend', function(e) {
    touchEndX = e.changedTouches[0].screenX;
    handleSwipe();
  }, false);

  function handleSwipe() {
    const deltaX = touchEndX - touchStartX;
    if (Math.abs(deltaX) > 50) { // Swipe threshold.
      if (deltaX > 0) { // Swipe right: previous image.
        if (currentGalleryIndex > 0) {
          currentGalleryIndex--;
          showGalleryImage(currentGalleryImages[currentGalleryIndex]);
        }
      } else { // Swipe left: next image.
        if (currentGalleryIndex < currentGalleryImages.length - 1) {
          currentGalleryIndex++;
          showGalleryImage(currentGalleryImages[currentGalleryIndex]);
        }
      }
    }
  }
}




function initGalleryControls() {
  const nextButton = document.querySelector('.gallery-next');
  const prevButton = document.querySelector('.gallery-prev');
  const closeButton = document.getElementById('gallery-close');

  if (nextButton) {
      nextButton.addEventListener('click', function () {
          if (currentGalleryIndex < currentGalleryImages.length - 1) {
              currentGalleryIndex++;
              showGalleryImage(currentGalleryImages[currentGalleryIndex]);
          }
      });
  }

  if (prevButton) {
      prevButton.addEventListener('click', function () {
          if (currentGalleryIndex > 0) {
              currentGalleryIndex--;
              showGalleryImage(currentGalleryImages[currentGalleryIndex]);
          }
      });
  }

  if (closeButton) {
      closeButton.addEventListener('click', closeGalleryModal);
  }
}


function initGallery() {
  const galleryImage = document.getElementById('gallery-modal-content');
  if (galleryImage) {
    galleryImage.addEventListener('click', handleGalleryImageClick);
  }
  initGallerySwipe();
  initGalleryControls();

  // Close modal when clicking outside the image.
  const galleryModal = document.getElementById('gallery-modal');
  galleryModal.addEventListener('click', function(e) {
    if (e.target === galleryModal) {
      closeGalleryModal();
    }
  });

}

// Initialize the gallery once the DOM content is loaded.
if (document.readyState === "loading") {
  document.addEventListener('DOMContentLoaded', initGallery);
} else {
  initGallery();
}