Show error when trying to open a shared PDF without download permissions

In order to show a PDF file it needs to be downloaded. Therefore, if a
shared PDF file does not have download permissions it is not possible to
show it, so now an error is shown instead.

The error is a custom one rather than a standard error from the viewer
(although with the same appearance) to better explain the reason.

Note that the error is shown only when the PDF file is loaded through
the viewer, which should be always the case. There is a fallback to
inject the UI in public shares in case the viewer is not available, but
handling the error also in that case was not trivial and that fallback
should never be used anyway, so it was not taken into account.

Signed-off-by: Daniel Calviño Sánchez <[email protected]>

src/views/PDFView.vue

@@ -3,9 +3,14 @@
   - SPDX-License-Identifier: AGPL-3.0-or-later
   -->
 <template>
-	<iframe ref="iframe"
+	<iframe v-if="isDownloadable"
+		ref="iframe"
 		:src="iframeSrc"
 		@load="onIFrameLoaded" />
+	<div v-else id="emptycontent">
+		<div class="icon-error" />
+		<h3>{{ t('files_pdfviewer', 'To view a shared PDF file, the download needs to be allowed for this file share') }}</h3>
+	</div>
 </template>
 
 <script>
@@ -41,12 +46,32 @@ export default {
 			return this.fileList.find((file) => file.fileid === this.fileid)
 		},
 
+		isDownloadable() {
+			if (!this.file.shareAttributes) {
+				return true
+			}
+
+			const shareAttributes = JSON.parse(this.file.shareAttributes)
+			const downloadPermissions = shareAttributes.find(({ scope, key }) => scope === 'permissions' && key === 'download')
+			if (downloadPermissions) {
+				return downloadPermissions.value
+			}
+
+			return true
+		},
+
 		isEditable() {
 			return this.file?.permissions?.indexOf('W') >= 0
 		},
 	},
 
 	async mounted() {
+		if (!this.isDownloadable) {
+			this.doneLoading()
+
+			return
+		}
+
 		document.addEventListener('webviewerloaded', this.handleWebviewerloaded)
 
 		if (isPublicPage() && isPdf()) {
@@ -186,6 +211,12 @@ export default {
 </script>
 
 <style lang="scss" scoped>
+#emptycontent {
+	margin: 0;
+	padding: 10% 5%;
+	background-color: var(--color-main-background);
+}
+
 iframe {
 	width: 100%;
 	height: calc(100vh - var(--header-height));