From db3592c53eaaa1ddfaab17b3aca0304ce05fcb34 Mon Sep 17 00:00:00 2001
From: Eugene <yarastqt@gmail.com>
Date: Sun, 23 Aug 2020 22:34:29 +0300
Subject: [PATCH] perf: replace throttle to debounce for watcher cb

---
 src/cli/build.ts  |  4 ++--
 src/core/utils.ts | 27 +++++++++++----------------
 2 files changed, 13 insertions(+), 18 deletions(-)

diff --git a/src/cli/build.ts b/src/cli/build.ts
index 6217011..4289ad7 100644
--- a/src/cli/build.ts
+++ b/src/cli/build.ts
@@ -6,7 +6,7 @@ import chalk from 'chalk'
 import { loadConfig } from '../core/config'
 import { build } from '../core/build'
 import { loadTheme } from '../core/load-theme'
-import { throttle, flatten } from '../core/utils'
+import { debounce, flatten } from '../core/utils'
 
 type Flags = {
   config: string
@@ -61,7 +61,7 @@ export default class Build extends Command {
       }
 
       const watcher = watch(themes, { ignoreInitial: true })
-      const onChange = throttle(async () => {
+      const onChange = debounce(async () => {
         if (!isShutdown) {
           this.clear()
           await this.build(config)
diff --git a/src/core/utils.ts b/src/core/utils.ts
index 45bf63c..d91db35 100644
--- a/src/core/utils.ts
+++ b/src/core/utils.ts
@@ -19,24 +19,19 @@ export function isAlias(value: string | number): boolean {
   return /^{.+}$/.test(String(value))
 }
 
-export function throttle<T extends []>(
-  callback: (..._: T) => void,
-  delay: number,
-): (..._: T) => void {
-  let timeout: NodeJS.Timeout | undefined
-  let lastArgs: T
-  const next = () => {
-    timeout = clearTimeout(timeout as any) as undefined
-    callback(...lastArgs)
-  }
-
-  return (...args: T) => {
-    lastArgs = args
-
-    if (timeout === undefined) {
-      timeout = setTimeout(next, delay)
+// eslint-disable-next-line space-before-function-paren
+export function debounce<F extends (...args: any[]) => any>(func: F, waitFor: number) {
+  let timeout: ReturnType<typeof setTimeout> | null = null
+
+  const debounced = (...args: Parameters<F>) => {
+    if (timeout !== null) {
+      clearTimeout(timeout)
+      timeout = null
     }
+    timeout = setTimeout(() => func(...args), waitFor)
   }
+
+  return debounced as (...args: Parameters<F>) => ReturnType<F>
 }
 
 type ArrayType<T> = T extends (infer U)[] ? U : never