add lightbox for post image previews

js/ui.js

@@ -21,6 +21,86 @@ function activateSelfDeactivateSibs(button) {
   });
 }
 
+function openLightbox(post, idx) {
+  lightboxCurrentPost = post;
+  lightboxCurrentIdx = idx;
+  lightboxObj.img.src = lightboxImages.get(post)[idx].src;
+  lightboxObj.openOriginalAnchor.href = lightboxImages.get(post)[idx].src
+  lightboxObj.prevButton.disabled = lightboxImages.get(post).length === 1
+  lightboxObj.nextButton.disabled = lightboxImages.get(post).length === 1
+  lightboxObj.imageCount.textContent = `Image ${idx + 1} of ${lightboxImages.get(post).length}`
+  
+  if (!lightboxObj.dialog.open) {
+    lightboxObj.dialog.showModal();
+  }
+}
+
+const modulo = (n, m) => ((n % m) + m) % m
+
+function lightboxNext() {
+  const l = lightboxImages.get(lightboxCurrentPost).length;
+  const target = modulo(lightboxCurrentIdx + 1, l);
+  openLightbox(lightboxCurrentPost, target);
+}
+
+function lightboxPrev() {
+  const l = lightboxImages.get(lightboxCurrentPost).length;
+  const target = modulo(lightboxCurrentIdx - 1, l);
+  openLightbox(lightboxCurrentPost, target);
+}
+
+function constructLightbox() {
+  const dialog = document.createElement("dialog");
+  dialog.classList.add("lightbox-dialog");
+  dialog.addEventListener("click", (e) => {
+    if (e.target === dialog) {
+      dialog.close();
+    }
+  })
+  const dialogInner = document.createElement("div");
+  dialogInner.classList.add("lightbox-inner");
+  dialog.appendChild(dialogInner);
+  const img = document.createElement("img");
+  img.classList.add("lightbox-image")
+  dialogInner.appendChild(img);
+  const openOriginalAnchor = document.createElement("a")
+  openOriginalAnchor.text = "Open original in new window"
+  openOriginalAnchor.target = "_blank"
+  openOriginalAnchor.rel = "noopener noreferrer nofollow"
+  dialogInner.appendChild(openOriginalAnchor);
+  
+  const navSpan = document.createElement("span");
+  navSpan.classList.add("lightbox-nav");
+  const prevButton = document.createElement("button");
+  prevButton.type = "button";
+  prevButton.textContent = "Previous";
+  prevButton.addEventListener("click", lightboxPrev);
+  const nextButton = document.createElement("button");
+  nextButton.type = "button";
+  nextButton.textContent = "Next";
+  nextButton.addEventListener("click", lightboxNext);
+  const imageCount = document.createElement("span");
+  imageCount.textContent = "Image of ";
+  navSpan.appendChild(prevButton);
+  navSpan.appendChild(imageCount);
+  navSpan.appendChild(nextButton);
+  
+  dialogInner.appendChild(navSpan);
+  return {
+    img: img,
+    dialog: dialog,
+    openOriginalAnchor: openOriginalAnchor,
+    prevButton: prevButton,
+    nextButton: nextButton,
+    imageCount: imageCount,
+  }
+}
+
+let lightboxImages = new Map(); //.post-inner : Array<Object>
+let lightboxObj = null;
+let lightboxCurrentPost = null;
+let lightboxCurrentIdx = -1;
+
 document.addEventListener("DOMContentLoaded", () => {
   // tabs
   document.querySelectorAll(".tab-button").forEach(button => {
@@ -45,4 +125,23 @@ document.addEventListener("DOMContentLoaded", () => {
     
     toggleButton.addEventListener("click", toggle);
   });
+  
+  //lightboxes
+  lightboxObj = constructLightbox();
+  document.body.appendChild(lightboxObj.dialog);
+  const postImages = document.querySelectorAll(".post-inner img.block-img");
+  postImages.forEach(postImage => {
+    const belongingTo = postImage.closest(".post-inner");
+    const images = lightboxImages.get(belongingTo) ?? [];
+    images.push({
+      src: postImage.src,
+      alt: postImage.alt,
+    });
+    const idx = images.length - 1;
+    lightboxImages.set(belongingTo, images);
+    postImage.style.cursor = "pointer";
+    postImage.addEventListener("click", () => {
+      openLightbox(belongingTo, idx);
+    });
+  });
 });