Refactor the speaker detection logic into observeSpeaker and add tests (#2814)

* Refactor the speaker detection logic into observeSpeaker and add tests

@robintown the tests pass, but some of the values were off by 1ms from what I was expecting. Please can you sanity check them?

* Extra test cases and clean up

* Make distinctUntilChanged part of the observable itself

* More suggestions from code review

src/state/observeSpeaker.test.ts

@@ -0,0 +1,119 @@
+/*
+Copyright 2024 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only
+Please see LICENSE in the repository root for full details.
+*/
+
+import { describe, test } from "vitest";
+
+import { withTestScheduler } from "../utils/test";
+import { observeSpeaker } from "./observeSpeaker";
+
+const yesNo = {
+  y: true,
+  n: false,
+};
+
+describe("observeSpeaker", () => {
+  describe("does not activate", () => {
+    const expectedOutputMarbles = "n";
+    test("starts correctly", () => {
+      // should default to false when no input is given
+      const speakingInputMarbles = "";
+      withTestScheduler(({ hot, expectObservable }) => {
+        expectObservable(observeSpeaker(hot(speakingInputMarbles, yesNo))).toBe(
+          expectedOutputMarbles,
+          yesNo,
+        );
+      });
+    });
+
+    test("after no speaking", () => {
+      const speakingInputMarbles = "n";
+      withTestScheduler(({ hot, expectObservable }) => {
+        expectObservable(observeSpeaker(hot(speakingInputMarbles, yesNo))).toBe(
+          expectedOutputMarbles,
+          yesNo,
+        );
+      });
+    });
+
+    test("with speaking for 1ms", () => {
+      const speakingInputMarbles = "y n";
+      withTestScheduler(({ hot, expectObservable }) => {
+        expectObservable(observeSpeaker(hot(speakingInputMarbles, yesNo))).toBe(
+          expectedOutputMarbles,
+          yesNo,
+        );
+      });
+    });
+
+    test("with speaking for 999ms", () => {
+      const speakingInputMarbles = "y 999ms n";
+      withTestScheduler(({ hot, expectObservable }) => {
+        expectObservable(observeSpeaker(hot(speakingInputMarbles, yesNo))).toBe(
+          expectedOutputMarbles,
+          yesNo,
+        );
+      });
+    });
+
+    test("with speaking intermittently", () => {
+      const speakingInputMarbles =
+        "y 199ms n 199ms y 199ms n 199ms y 199ms n 199ms y 199ms n 199ms y 199ms n 199ms y 199ms n 199ms y 199ms n 199ms y 199ms n";
+      withTestScheduler(({ hot, expectObservable }) => {
+        expectObservable(observeSpeaker(hot(speakingInputMarbles, yesNo))).toBe(
+          expectedOutputMarbles,
+          yesNo,
+        );
+      });
+    });
+
+    test("with consecutive speaking then stops speaking", () => {
+      const speakingInputMarbles = "y y y y y y y y y y n";
+      withTestScheduler(({ hot, expectObservable }) => {
+        expectObservable(observeSpeaker(hot(speakingInputMarbles, yesNo))).toBe(
+          expectedOutputMarbles,
+          yesNo,
+        );
+      });
+    });
+  });
+
+  describe("activates", () => {
+    test("after 1s", () => {
+      // this will active after 1s as no `n` follows it:
+      const speakingInputMarbles = " y";
+      const expectedOutputMarbles = "n 999ms y";
+      withTestScheduler(({ hot, expectObservable }) => {
+        expectObservable(observeSpeaker(hot(speakingInputMarbles, yesNo))).toBe(
+          expectedOutputMarbles,
+          yesNo,
+        );
+      });
+    });
+
+    test("speaking for 1001ms activates for 60s", () => {
+      const speakingInputMarbles = " y 1s    n      ";
+      const expectedOutputMarbles = "n 999ms y 60s n";
+      withTestScheduler(({ hot, expectObservable }) => {
+        expectObservable(observeSpeaker(hot(speakingInputMarbles, yesNo))).toBe(
+          expectedOutputMarbles,
+          yesNo,
+        );
+      });
+    });
+
+    test("speaking for 5s activates for 64s", () => {
+      const speakingInputMarbles = " y 5s    n      ";
+      const expectedOutputMarbles = "n 999ms y 64s n";
+      withTestScheduler(({ hot, expectObservable }) => {
+        expectObservable(observeSpeaker(hot(speakingInputMarbles, yesNo))).toBe(
+          expectedOutputMarbles,
+          yesNo,
+        );
+      });
+    });
+  });
+});