From 5304dcdc56fbe225d8a7c46b95845d2dfb9b2031 Mon Sep 17 00:00:00 2001
From: Liam Tait <Liam-Tait@users.noreply.github.com>
Date: Fri, 23 Jul 2021 17:50:33 +1200
Subject: [PATCH] Add clamp function (#2498)

Added a new `clamp` function that allows to bound a date to an interval.
---
 src/clamp/index.ts | 37 +++++++++++++++++++++++++++++++++++++
 src/clamp/test.ts  | 43 +++++++++++++++++++++++++++++++++++++++++++
 src/index.js       |  1 +
 3 files changed, 81 insertions(+)
 create mode 100644 src/clamp/index.ts
 create mode 100644 src/clamp/test.ts

diff --git a/src/clamp/index.ts b/src/clamp/index.ts
new file mode 100644
index 0000000000..dec410b8fc
--- /dev/null
+++ b/src/clamp/index.ts
@@ -0,0 +1,37 @@
+import max from '../max'
+import min from '../min'
+import requiredArgs from '../_lib/requiredArgs/index'
+
+/**
+ * @name clamp
+ * @category Interval Helpers
+ * @summary Return a date bounded by the start and the end of the given interval
+ *
+ * @description
+ * Clamps a date to the lower bound with the start of the interval and the upper
+ * bound with the end of the interval.
+ *
+ * - When the date is less than the start of the interval, the start is returned.
+ * - When the date is greater than the end of the interval, the end is returned.
+ * - Otherwise the date is returned.
+ *
+ * @example
+ * // What is Mar, 21, 2021 bounded to an interval starting at Mar, 22, 2021 and ending at Apr, 01, 2021
+ * const result = clamp(new Date(2021, 2, 21), {
+ *   start: new Date(2021, 2, 22),
+ *   end: new Date(2021, 3, 1),
+ * })
+ * //=> Mon Mar 22 2021 00:00:00
+ *
+ * @param {Date | Number} date - the date to be bounded
+ * @param {Interval} interval - the interval to bound to
+ * @returns {Date} the date bounded by the start and the end of the interval
+ * @throws {TypeError} 2 arguments required
+ */
+export default function clamp(
+  date: Date | number,
+  { start, end }: Interval
+): Date {
+  requiredArgs(2, arguments)
+  return min([max([date, start]), end])
+}
diff --git a/src/clamp/test.ts b/src/clamp/test.ts
new file mode 100644
index 0000000000..66376c1bb4
--- /dev/null
+++ b/src/clamp/test.ts
@@ -0,0 +1,43 @@
+import assert from 'assert'
+import clamp from '.'
+
+describe('clamp', () => {
+  it('accepts timestamps', () => {
+    const start = new Date(2000, 1, 1).getTime()
+    const date = new Date(2000, 1, 2).getTime()
+    const end = new Date(2000, 1, 3).getTime()
+    const result = clamp(date, { start, end })
+    assert.deepStrictEqual(result, new Date(2000, 1, 2))
+  })
+
+  it('returns the start date when the date is less than start', () => {
+    const start = new Date(2001, 1, 1)
+    const date = new Date(2000, 1, 1)
+    const end = new Date(2020, 1, 1)
+    const result = clamp(date, { start, end })
+    assert.deepStrictEqual(result, new Date(2001, 1, 1))
+  })
+
+  it('returns the end date when the date is greater than the end date', () => {
+    const start = new Date(2000, 1, 1)
+    const date = new Date(2003, 1, 1)
+    const end = new Date(2001, 1, 1)
+    const result = clamp(date, { start, end })
+    assert.deepStrictEqual(result, new Date(2001, 1, 1))
+  })
+
+  it('returns the date when the date is within the bound of start and end', () => {
+    const start = new Date(2000, 1, 1)
+    const date = new Date(2001, 1, 1)
+    const end = new Date(2003, 1, 1)
+    const result = clamp(date, { start, end })
+    assert.deepStrictEqual(result, new Date(2001, 1, 1))
+  })
+
+  it('throws TypeError exception if passed less than 2 arguments', () => {
+    // @ts-expect-error
+    assert.throws(clamp.bind(null), TypeError)
+    // @ts-expect-error
+    assert.throws(clamp.bind(null, 1), TypeError)
+  })
+})
diff --git a/src/index.js b/src/index.js
index 45095f8961..bbf7fb1c4f 100644
--- a/src/index.js
+++ b/src/index.js
@@ -13,6 +13,7 @@ export { default as addSeconds } from './addSeconds/index'
 export { default as addWeeks } from './addWeeks/index'
 export { default as addYears } from './addYears/index'
 export { default as areIntervalsOverlapping } from './areIntervalsOverlapping/index'
+export { default as clamp } from './clamp/index'
 export { default as closestIndexTo } from './closestIndexTo/index'
 export { default as closestTo } from './closestTo/index'
 export { default as compareAsc } from './compareAsc/index'