viewer/command: add item download button

This adds a download button which allows the user to save the current
item as a file.

This is necessary because some item viewers do not expose a download
option on their own.

The download icon appears together with the other command buttons at the
top-left corner of the screen, replacing the listing sorting menu which
is only relevant for item lists (directory and search views).

GitHub: closes #308

4 files changed, 48 insertions, 5 deletions

diff --git a/viewer/ldgallery-viewer.7.md b/viewer/ldgallery-viewer.7.md
index 736f61f..46509fb 100644
--- a/viewer/ldgallery-viewer.7.md
+++ b/viewer/ldgallery-viewer.7.md
@@ -41,6 +41,7 @@ Items of the following formats can be opened and visualised within the web appli
 * PDFs
 
 Formats which are not listed above or which are not supported by the user's web browser are offered for download instead of being directly displayed in the same window.
+The item being visualised can be downloaded using the download button at the top-left corner.
 
 
 # KEYBOARD SHORTCUTS
diff --git a/viewer/src/locales/en.yml b/viewer/src/locales/en.yml
index acbe24b..86ecd49 100644
--- a/viewer/src/locales/en.yml
+++ b/viewer/src/locales/en.yml
@@ -1,6 +1,7 @@
 command:
   back: Go back
   parent: Go to parent directory
+  download: Download
   search:
     clear: Clear
     search: Search
diff --git a/viewer/src/views/layout/top/LayoutCommand.vue b/viewer/src/views/layout/top/LayoutCommand.vue
index 8919da3..d930fd2 100644
--- a/viewer/src/views/layout/top/LayoutCommand.vue
+++ b/viewer/src/views/layout/top/LayoutCommand.vue
@@ -2,7 +2,7 @@
 --             pictures into a searchable web gallery.
 --
 -- Copyright (C) 2019-2022  Guillaume FOUET
---               2020       Pacien TRAN-GIRARD
+--               2020-2022  Pacien TRAN-GIRARD
 --
 -- This program is free software: you can redistribute it and/or modify
 -- it under the terms of the GNU Affero General Public License as
@@ -33,7 +33,24 @@
         size="lg"
       />
     </LdLink>
-    <LayoutCommandSort :tabindex="20" />
+
+    <LayoutCommandSort
+      v-if="isListing"
+      :tabindex="20"
+    />
+    <a
+      v-else
+      :title="t('command.download')"
+      :download="itemFileName"
+      :href="itemResourceUrl"
+      :tabindex="20"
+    >
+      <fa-icon
+        :icon="faFileDownload"
+        size="lg"
+      />
+    </a>
+
     <LdLink
       :class="{ disabled: isEntryPoint(), [$style.commandSecondary]: true }"
       :title="t('command.back')"
@@ -67,21 +84,42 @@
 import { Item } from '@/@types/gallery';
 import LdLink from '@/components/LdLink.vue';
 import { useUiStore } from '@/store/uiStore';
-import { faAngleDoubleLeft, faArrowLeft, faFolder, faLevelUpAlt, faSearch } from '@fortawesome/free-solid-svg-icons';
+import { useGalleryStore } from '@/store/galleryStore';
+import { useNavigation } from '@/services/navigation';
+import { isDirectory, isDownloadableItem } from '@/services/itemGuards';
+import {
+  faAngleDoubleLeft,
+  faArrowLeft,
+  faFolder,
+  faLevelUpAlt,
+  faSearch,
+  faFileDownload,
+} from '@fortawesome/free-solid-svg-icons';
 import { computedEager } from '@vueuse/shared';
-import { computed } from 'vue';
+import { computed, PropType } from 'vue';
 import { useI18n } from 'vue-i18n';
 import { useRoute, useRouter } from 'vue-router';
 import LayoutCommandSort from './LayoutCommandSort.vue';
 
 const props = defineProps({
   currentItemPath: { type: Array<Item>, required: true },
+  item: { type: Object as PropType<Item>, required: true },
 });
 
 const { t } = useI18n();
 const route = useRoute();
 const router = useRouter();
 const uiStore = useUiStore();
+const galleryStore = useGalleryStore();
+const navigation = useNavigation();
+
+const isListing = computedEager(() => !props.item || isDirectory(props.item));
+const itemFileName = computed(() => navigation.getFileName(props.item));
+const itemResourceUrl = computed(() =>
+  isDownloadableItem(props.item)
+    ? galleryStore.resourceRoot + props.item.properties.resource
+    : '',
+);
 
 const commandToggleSearchPanelIcon = computed(() => uiStore.fullWidth ? faSearch : faAngleDoubleLeft);
 const isRoot = computedEager(() => props.currentItemPath.length <= 1 && !uiStore.searchMode);
diff --git a/viewer/src/views/layout/top/LayoutTop.vue b/viewer/src/views/layout/top/LayoutTop.vue
index b755c42..0362840 100644
--- a/viewer/src/views/layout/top/LayoutTop.vue
+++ b/viewer/src/views/layout/top/LayoutTop.vue
@@ -19,7 +19,10 @@
 
 <template>
   <div class="flex">
-    <LayoutCommand :current-item-path="galleryStore.currentItemPath" />
+    <LayoutCommand
+      :current-item-path="galleryStore.currentItemPath"
+      :item="galleryStore.currentItem"
+    />
     <LayoutBreadcrumb
       :current-item-path="galleryStore.currentItemPath"
       :search-mode="uiStore.searchMode"