feat: Adds support for draft in conversation reply box (#4205)

* Add draft support

* Fixes issue with draft loading

* Adds draft for private notes

* Use localstorage helper

* .remove instead of .clear

* Remove timestamp

* clearLocalStorageOnLogout

* Fix draft save on refresh

* Remove usage of delete operator

* Adds autosave for draft messages

* Remove setinterval and add debounce

* Removes draft redundancy check

* Adds test cases for debouncer

* Update app/javascript/shared/helpers/specs/TimeHelpers.spec.js

Co-authored-by: Nithin David Thomas <1277421+nithindavid@users.noreply.github.com>

* Update app/javascript/shared/helpers/specs/TimeHelpers.spec.js

Co-authored-by: Nithin David Thomas <1277421+nithindavid@users.noreply.github.com>

* Review fixes

* Fixes issue with debouncer

* FIxes debouncer issue

* Fixes issue with draft empty message

* Removes empty keys from local storage drafts

* Fixes error with empty draft

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>
Co-authored-by: Fayaz Ahmed <15716057+fayazara@users.noreply.github.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>

app/javascript/shared/helpers/TimeHelpers.js

@@ -0,0 +1,21 @@
+// Returns a function, that, as long as it continues to be invoked, will not
+// be triggered. The function will be called after it stops being called for
+// N milliseconds. If `immediate` is passed, trigger the function on the
+// leading edge, instead of the trailing.
+
+export const debounce = (func, delay, immediate) => {
+  let timerId;
+  return (...args) => {
+    const boundFunc = func.bind(this, ...args);
+    clearTimeout(timerId);
+    if (immediate && !timerId) {
+      boundFunc();
+    }
+    const calleeFunc = immediate
+      ? () => {
+          timerId = null;
+        }
+      : boundFunc;
+    timerId = setTimeout(calleeFunc, delay);
+  };
+};

app/javascript/shared/helpers/specs/TimeHelpers.spec.js

@@ -0,0 +1,32 @@
+import { debounce } from '../TimeHelpers';
+// Tell Jest to mock all timeout functions
+jest.useFakeTimers('modern');
+
+describe('debounce', () => {
+  test('execute just once with immediate false', () => {
+    let func = jest.fn();
+    let debouncedFunc = debounce(func, 1000);
+
+    for (let i = 0; i < 100; i += 1) {
+      debouncedFunc();
+    }
+
+    // Fast-forward time
+    jest.runAllTimers();
+
+    expect(func).toBeCalledTimes(1);
+  });
+
+  test('execute just once with immediate true', () => {
+    let func = jest.fn();
+    let debouncedFunc = debounce(func, 1000, true);
+
+    for (let i = 0; i < 100; i += 1) {
+      debouncedFunc();
+    }
+
+    jest.runAllTimers();
+
+    expect(func).toBeCalledTimes(1);
+  });
+});