From 803bbfa0fe9dc9a560bae1b282aa688c32ed93fc Mon Sep 17 00:00:00 2001
From: Jerko Steiner <jerko.steiner@gmail.com>
Date: Mon, 26 Aug 2019 20:00:48 +0700
Subject: [PATCH] Add debounce to tasq

---
 packages/tasq/src/debounce.test.ts | 17 +++++++++++++++++
 packages/tasq/src/debounce.ts      | 13 +++++++++++++
 packages/tasq/src/index.ts         |  2 +-
 3 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 packages/tasq/src/debounce.test.ts
 create mode 100644 packages/tasq/src/debounce.ts

diff --git a/packages/tasq/src/debounce.test.ts b/packages/tasq/src/debounce.test.ts
new file mode 100644
index 0000000..b95c0d0
--- /dev/null
+++ b/packages/tasq/src/debounce.test.ts
@@ -0,0 +1,17 @@
+import {debounce} from './debounce'
+
+describe('debounce', () => {
+
+  it('executes only once', async () => {
+    const add = jest.fn()
+    const d = debounce(add, 0)
+    d(1, 2)
+    d(3, 4)
+    d(5, 6)
+    d(7, 8)
+
+    await new Promise(resolve => setTimeout(resolve, 0))
+    expect(add.mock.calls).toEqual([[ 7, 8 ]])
+  })
+
+})
diff --git a/packages/tasq/src/debounce.ts b/packages/tasq/src/debounce.ts
new file mode 100644
index 0000000..e7418dc
--- /dev/null
+++ b/packages/tasq/src/debounce.ts
@@ -0,0 +1,13 @@
+export function debounce<A, R>(fn: (...args: A[]) => R, delay: number) {
+  let timeout: NodeJS.Timeout | null = null
+
+  return async function debounceImpl(...args: A[]) {
+    if (timeout) {
+      clearTimeout(timeout)
+    }
+
+    timeout = setTimeout(() => {
+      fn(...args)
+    }, delay)
+  }
+}
diff --git a/packages/tasq/src/index.ts b/packages/tasq/src/index.ts
index 8b13789..3c52094 100644
--- a/packages/tasq/src/index.ts
+++ b/packages/tasq/src/index.ts
@@ -1 +1 @@
-
+export * from './debounce'