1 files changed, 49 insertions, 0 deletions
diff --git a/app/assets/javascripts/lib/utils/tappable_promise.js b/app/assets/javascripts/lib/utils/tappable_promise.js
new file mode 100644
index 00000000000..8d327dabe1b
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+++ b/app/assets/javascripts/lib/utils/tappable_promise.js
@@ -0,0 +1,49 @@
+/**
+ * A promise that is also tappable, i.e. something you can subscribe
+ * to to get progress of a promise until it resolves.
+ *
+ * @example Usage
+ *   const tp = new TappablePromise((resolve, reject, tap) => {
+ *     for (let i = 0; i < 10; i++) {
+ *       tap(i/10);
+ *     }
+ *     resolve();
+ *   });
+ *
+ *  tp.tap((progress) => {
+ *    console.log(progress);
+ *  }).then(() => {
+ *    console.log('done');
+ *  });
+ *
+ *  // Output:
+ *  // 0
+ *  // 0.1
+ *  // 0.2
+ *  // ...
+ *  // 0.9
+ *  // done
+ *
+ *
+ * @param {(resolve: Function, reject: Function, tap: Function) => void} callback
+ * @returns {Promise & { tap: Function }}}
+ */
+export default function TappablePromise(callback) {
+  let progressCallback;
+
+  const promise = new Promise((resolve, reject) => {
+    try {
+      const tap = (progress) => progressCallback?.(progress);
+      resolve(callback(tap, resolve, reject));
+    } catch (e) {
+      reject(e);
+    }
+  });
+
+  promise.tap = function tap(_progressCallback) {
+    progressCallback = _progressCallback;
+    return this;
+  };
+
+  return promise;
+}