Step 12.12: Create pictures store

imports/collections/pictures.ts

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+import { MongoObservable } from 'meteor-rxjs';
+import { UploadFS } from 'meteor/jalik:ufs';
+import { Meteor } from 'meteor/meteor';
+import { Picture, DEFAULT_PICTURE_URL } from '../models';
+
+export interface PicturesCollection<T> extends MongoObservable.Collection<T> {
+  getPictureUrl(selector?: Object | string): string;
+}
+
+export const Pictures =
+  new MongoObservable.Collection<Picture>('pictures') as PicturesCollection<Picture>;
+
+export const PicturesStore = new UploadFS.store.GridFS({
+  collection: Pictures.collection,
+  name: 'pictures',
+  filter: new UploadFS.Filter({
+    contentTypes: ['image/*']
+  }),
+  permissions: new UploadFS.StorePermissions({
+    insert: picturesPermissions,
+    update: picturesPermissions,
+    remove: picturesPermissions
+  }),
+  transformWrite(from, to) {
+    // The transformation function will only be invoked on the server. Accordingly,
+    // the 'sharp' library is a server-only library which will cause an error to be
+    // thrown when loaded on the global scope
+    const Sharp = Npm.require('sharp');
+    // Compress picture to 75% from its original quality
+    const transform = Sharp().png({ quality: 75 });
+    from.pipe(transform).pipe(to);
+  }
+});
+
+// Gets picture's url by a given selector
+Pictures.getPictureUrl = function (selector) {
+  const picture = this.findOne(selector) || {};
+  return picture.url || DEFAULT_PICTURE_URL;
+};
+
+function picturesPermissions(userId: string): boolean {
+  return Meteor.isServer || !!userId;
+}