feat: add fullscreen download action

src/client/app.ts

@@ -75,6 +75,7 @@ const overlayLoadingText = mustGet("overlay-loading-text");
 const overlayMedia = mustGet("overlay-media");
 const overlayPrev = mustGet("overlay-prev");
 const overlayNext = mustGet("overlay-next");
+const overlayDownload = mustGet("overlay-download");
 const closeOverlay = mustGet("close-overlay");
 const routeToggle = mustGet("route-toggle");
 const routeToggleIcon = mustGet("route-toggle-icon");
@@ -274,6 +275,20 @@ function syncPhotoNameInLocation(photoName) {
   }
 }
 
+function syncOverlayDownload(photo) {
+  if (!photo) {
+    overlayDownload.setAttribute("href", "#");
+    overlayDownload.setAttribute("aria-disabled", "true");
+    overlayDownload.removeAttribute("download");
+    return;
+  }
+
+  overlayDownload.href = photo.fullUrl;
+  overlayDownload.download = photo.name;
+  overlayDownload.setAttribute("aria-label", "Download photo");
+  overlayDownload.setAttribute("aria-disabled", "false");
+}
+
 function getOverlayPhotos() {
   if (!state.visiblePhotos.length) {
     return state.photos;
@@ -566,6 +581,7 @@ function openOverlay(photo) {
   overlay.setAttribute("aria-hidden", "false");
   overlayTitle.textContent = photo.name;
   overlayImage.alt = photo.name;
+  syncOverlayDownload(photo);
   overlay.classList.add("loading");
   overlayLoading.classList.add("active");
   overlayLoading.classList.remove("error");
@@ -600,6 +616,7 @@ function closeOverlayView() {
   overlayLoading.classList.remove("error");
   overlayLoadingText.textContent = "Loading full-size image...";
   overlayImage.removeAttribute("src");
+  syncOverlayDownload(null);
   syncPhotoNameInLocation("");
   overlaySwipeState = null;
 }