[PM-14161] Add getById and getByIds rjxs helpers (#11742)

libs/common/src/platform/misc/index.ts

@@ -0,0 +1 @@
+export * from "./rxjs-operators";

libs/common/src/platform/misc/rxjs-operators.spec.ts

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+import { firstValueFrom, of } from "rxjs";
+
+import { getById, getByIds } from "./rxjs-operators";
+
+describe("custom rxjs operators", () => {
+  describe("getById", () => {
+    it("returns an object with a matching id", async () => {
+      const obs = of([
+        {
+          id: 1,
+          data: "one",
+        },
+        {
+          id: 2,
+          data: "two",
+        },
+        {
+          id: 3,
+          data: "three",
+        },
+      ]).pipe(getById(2));
+
+      const result = await firstValueFrom(obs);
+
+      expect(result).toEqual({ id: 2, data: "two" });
+    });
+  });
+
+  describe("getByIds", () => {
+    it("returns an array of objects with matching ids", async () => {
+      const obs = of([
+        {
+          id: 1,
+          data: "one",
+        },
+        {
+          id: 2,
+          data: "two",
+        },
+        {
+          id: 3,
+          data: "three",
+        },
+        {
+          id: 4,
+          data: "four",
+        },
+      ]).pipe(getByIds([2, 3]));
+
+      const result = await firstValueFrom(obs);
+
+      expect(result).toEqual([
+        { id: 2, data: "two" },
+        { id: 3, data: "three" },
+      ]);
+    });
+  });
+});

libs/common/src/platform/misc/rxjs-operators.ts

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+import { map } from "rxjs";
+
+/**
+ * An rxjs operator that extracts an object by ID from an array of objects.
+ * @param id The ID of the object to return.
+ * @returns The first object with a matching ID, or undefined if no matching object is present.
+ */
+export const getById = <TId, T extends { id: TId }>(id: TId) =>
+  map<T[], T | undefined>((objects) => objects.find((o) => o.id === id));
+
+/**
+ * An rxjs operator that extracts a subset of objects by their IDs from an array of objects.
+ * @param id The IDs of the objects to return.
+ * @returns An array containing objects with matching IDs, or an empty array if there are no matching objects.
+ */
+export const getByIds = <TId, T extends { id: TId }>(ids: TId[]) => {
+  const idSet = new Set(ids);
+  return map<T[], T[]>((objects) => {
+    return objects.filter((o) => idSet.has(o.id));
+  });
+};