apply suggested changes from code review

src/utils/jellyfin-apiclient/backdropImage.ts

@@ -0,0 +1,52 @@
+import type { BaseItemDto } from '@jellyfin/sdk/lib/generated-client/models/base-item-dto';
+import type { ApiClient } from 'jellyfin-apiclient';
+import { ImageType } from '@jellyfin/sdk/lib/generated-client/models/image-type';
+import { randomInt } from '../number';
+
+export interface ScaleImageOptions {
+    maxWidth?: number;
+    width?: number;
+    maxHeight?: number;
+    height?: number;
+    fillWidth?: number;
+    fillHeight?: number;
+    quality?: number;
+}
+
+/**
+ * Returns the url of the first or a random backdrop image of an item.
+ * If the item has no backdrop image, the url of the first or a random backdrop image of the parent item is returned.
+ * Falls back to the primary image (cover) of the item, if neither the item nor it's parent have at least one backdrop image.
+ * Returns undefined if no usable image was found.
+ * @param apiClient The ApiClient to generate the url.
+ * @param item The item for which the backdrop image is requested.
+ * @param options Optional; allows to scale the backdrop image.
+ * @param random If set to true and the item has more than one backdrop, a random image is returned.
+ * @returns The url of the first or a random backdrop image of the provided item.
+ */
+export const getItemBackdropImageUrl = (apiClient: ApiClient, item: BaseItemDto, options: ScaleImageOptions = {}, random = false): string | undefined => {
+    if (item.Id && item.BackdropImageTags?.length) {
+        const backdropImgIndex = random ? randomInt(0, item.BackdropImageTags.length - 1) : 0;
+        return apiClient.getScaledImageUrl(item.Id, {
+            type: ImageType.Backdrop,
+            index: backdropImgIndex,
+            tag: item.BackdropImageTags[backdropImgIndex],
+            ...options
+        });
+    } else if (item.ParentBackdropItemId && item.ParentBackdropImageTags?.length) {
+        const backdropImgIndex = random ? randomInt(0, item.ParentBackdropImageTags.length - 1) : 0;
+        return apiClient.getScaledImageUrl(item.ParentBackdropItemId, {
+            type: ImageType.Backdrop,
+            index: backdropImgIndex,
+            tag: item.ParentBackdropImageTags[backdropImgIndex],
+            ...options
+        });
+    } else if (item.Id && item.ImageTags?.Primary) {
+        return apiClient.getScaledImageUrl(item.Id, {
+            type: ImageType.Primary,
+            tag: item.ImageTags.Primary,
+            ...options
+        });
+    }
+    return undefined;
+};