Introduce function to remove duplication from things that are startable and stoppable

Co-authored-by: Janne Savolainen <janne.savolainen@live.fi>

Signed-off-by: Iku-turso <mikko.aspiala@gmail.com>

src/common/utils/get-startable-stoppable.test.ts

@@ -0,0 +1,68 @@
+/**
+ * Copyright (c) OpenLens Authors. All rights reserved.
+ * Licensed under MIT License. See LICENSE in root directory for more information.
+ */
+import { getStartableStoppable } from "./get-startable-stoppable";
+
+describe("getStartableStoppable", () => {
+  let stopMock: jest.Mock<() => void>;
+  let startMock: jest.Mock<() => () => void>;
+  let actual: { stop: () => void; start: () => void };
+
+  beforeEach(() => {
+    stopMock = jest.fn();
+    startMock = jest.fn(() => stopMock);
+
+    actual = getStartableStoppable(startMock);
+  });
+
+  it("does not start yet", () => {
+    expect(startMock).not.toHaveBeenCalled();
+  });
+
+  it("does not stop yet", () => {
+    expect(stopMock).not.toHaveBeenCalled();
+  });
+
+  it("when stopping before ever starting, throws", () => {
+    expect(() => {
+      actual.stop();
+    }).toThrow("Tried to stop something that has not started yet.");
+  });
+
+  describe("when started", () => {
+    beforeEach(() => {
+      actual.start();
+    });
+
+    it("starts", () => {
+      expect(startMock).toHaveBeenCalled();
+    });
+
+    it("does not stop yet", () => {
+      expect(stopMock).not.toHaveBeenCalled();
+    });
+
+    describe("when stopped", () => {
+      beforeEach(() => {
+        actual.stop();
+      });
+
+      it("stops", () => {
+        expect(stopMock).toHaveBeenCalled();
+      });
+
+      it("when stopped again, throws", () => {
+        expect(() => {
+          actual.stop();
+        }).toThrow("Tried to stop something that has already stopped.");
+      });
+
+      it("when started again, throws for restart being YAGNI with logical blind spots", () => {
+        expect(() => {
+          actual.start();
+        }).toThrow("Tried to restart something that has stopped.");
+      });
+    });
+  });
+});

src/common/utils/get-startable-stoppable.ts

@@ -0,0 +1,37 @@
+/**
+ * Copyright (c) OpenLens Authors. All rights reserved.
+ * Licensed under MIT License. See LICENSE in root directory for more information.
+ */
+export const getStartableStoppable = (
+  startAndGetStopCallback: () => () => void,
+) => {
+  let dispose: () => void;
+  let stopped = false;
+  let started = false;
+
+  return {
+    start: () => {
+      if (started) {
+        throw new Error("Tried to restart something that has stopped.");
+      }
+
+      dispose = startAndGetStopCallback();
+
+      started = true;
+    },
+
+    stop: () => {
+      if (!started) {
+        throw new Error("Tried to stop something that has not started yet.");
+      }
+
+      if (stopped) {
+        throw new Error("Tried to stop something that has already stopped.");
+      }
+
+      dispose();
+
+      stopped = true;
+    },
+  };
+};