4 files changed, 244 insertions, 0 deletions
diff --git a/date-fns/src/formatDuration/index.d.ts b/date-fns/src/formatDuration/index.d.ts
new file mode 100644
index 0000000..be96776
--- /dev/null
+++ b/date-fns/src/formatDuration/index.d.ts
@@ -0,0 +1,4 @@
+// This file is generated automatically by `scripts/build/typings.js`. Please, don't change it.
+
+import { formatDuration } from 'date-fns'
+export default formatDuration
diff --git a/date-fns/src/formatDuration/index.js b/date-fns/src/formatDuration/index.js
new file mode 100644
index 0000000..c4130a6
--- /dev/null
+++ b/date-fns/src/formatDuration/index.js
@@ -0,0 +1,100 @@
+import defaultLocale from '../locale/en-US/index'
+
+const defaultFormat = [
+  'years',
+  'months',
+  'weeks',
+  'days',
+  'hours',
+  'minutes',
+  'seconds',
+]
+
+/**
+ * @name formatDuration
+ * @category Common Helpers
+ * @summary Formats a duration in human-readable format
+ *
+ * @description
+ * Return human-readable duration string i.e. "9 months 2 days"
+ *
+ * @param {Duration} duration - the duration to format
+ * @param {Object} [options] - an object with options.
+
+ * @param {string[]} [options.format=['years', 'months', 'weeks', 'days', 'hours', 'minutes', 'seconds']] - the array of units to format
+ * @param {boolean} [options.zero=false] - should be zeros be included in the output?
+ * @param {string} [options.delimiter=' '] - delimiter string
+ * @param {Locale} [options.locale=defaultLocale] - the locale object. See [Locale]{@link https://date-fns.org/docs/Locale}
+ * @returns {string} the formatted date string
+ * @throws {TypeError} 1 argument required
+ *
+ * @example
+ * // Format full duration
+ * formatDuration({
+ *   years: 2,
+ *   months: 9,
+ *   weeks: 1,
+ *   days: 7,
+ *   hours: 5,
+ *   minutes: 9,
+ *   seconds: 30
+ * })
+ * //=> '2 years 9 months 1 week 7 days 5 hours 9 minutes 30 seconds
+ *
+ * @example
+ * // Format partial duration
+ * formatDuration({ months: 9, days: 2 })
+ * //=> '9 months 2 days'
+ *
+ * @example
+ * // Customize the format
+ * formatDuration(
+ *   {
+ *     years: 2,
+ *     months: 9,
+ *     weeks: 1,
+ *     days: 7,
+ *     hours: 5,
+ *     minutes: 9,
+ *     seconds: 30
+ *   },
+ *   { format: ['months', 'weeks'] }
+ * ) === '9 months 1 week'
+ *
+ * @example
+ * // Customize the zeros presence
+ * formatDuration({ years: 0, months: 9 })
+ * //=> '9 months'
+ * formatDuration({ years: 0, months: 9 }, { zero: true })
+ * //=> '0 years 9 months'
+ *
+ * @example
+ * // Customize the delimiter
+ * formatDuration({ years: 2, months: 9, weeks: 3 }, { delimiter: ', ' })
+ * //=> '2 years, 9 months, 3 weeks'
+ */
+export default function formatDuration(duration, options) {
+  if (arguments.length < 1) {
+    throw new TypeError(
+      `1 argument required, but only ${arguments.length} present`
+    )
+  }
+
+  const format = options?.format || defaultFormat
+  const locale = options?.locale || defaultLocale
+  const zero = options?.zero || false
+  const delimiter = options?.delimiter || ' '
+
+  const result = format
+    .reduce((acc, unit) => {
+      const token = `x${unit.replace(/(^.)/, (m) => m.toUpperCase())}`
+      const addChunk =
+        typeof duration[unit] === 'number' && (zero || duration[unit])
+      return addChunk
+        ? acc.concat(locale.formatDistance(token, duration[unit]))
+        : acc
+    }, [])
+    .join(delimiter)
+
+  return result
+}
diff --git a/date-fns/src/formatDuration/index.js.flow b/date-fns/src/formatDuration/index.js.flow
new file mode 100644
index 0000000..022ea8e
--- /dev/null
+++ b/date-fns/src/formatDuration/index.js.flow
@@ -0,0 +1,60 @@
+// @flow
+// This file is generated automatically by `scripts/build/typings.js`. Please, don't change it.
+
+export type Interval = {
+  start: Date | number,
+  end: Date | number,
+}
+
+export type Locale = {
+  code?: string,
+  formatDistance?: (...args: Array<any>) => any,
+  formatRelative?: (...args: Array<any>) => any,
+  localize?: {
+    ordinalNumber: (...args: Array<any>) => any,
+    era: (...args: Array<any>) => any,
+    quarter: (...args: Array<any>) => any,
+    month: (...args: Array<any>) => any,
+    day: (...args: Array<any>) => any,
+    dayPeriod: (...args: Array<any>) => any,
+  },
+  formatLong?: {
+    date: (...args: Array<any>) => any,
+    time: (...args: Array<any>) => any,
+    dateTime: (...args: Array<any>) => any,
+  },
+  match?: {
+    ordinalNumber: (...args: Array<any>) => any,
+    era: (...args: Array<any>) => any,
+    quarter: (...args: Array<any>) => any,
+    month: (...args: Array<any>) => any,
+    day: (...args: Array<any>) => any,
+    dayPeriod: (...args: Array<any>) => any,
+  },
+  options?: {
+    weekStartsOn?: 0 | 1 | 2 | 3 | 4 | 5 | 6,
+    firstWeekContainsDate?: 1 | 2 | 3 | 4 | 5 | 6 | 7,
+  },
+}
+
+export type Duration = {
+  years?: number,
+  months?: number,
+  weeks?: number,
+  days?: number,
+  hours?: number,
+  minutes?: number,
+  seconds?: number,
+}
+
+export type Day = 0 | 1 | 2 | 3 | 4 | 5 | 6
+
+declare module.exports: (
+  duration: Duration,
+  options?: {
+    format?: string[],
+    zero?: boolean,
+    delimiter?: string,
+    locale?: Locale,
+  }
+) => string
diff --git a/date-fns/src/formatDuration/test.js b/date-fns/src/formatDuration/test.js
new file mode 100644
index 0000000..f9bb7af
--- /dev/null
+++ b/date-fns/src/formatDuration/test.js
@@ -0,0 +1,80 @@
+// @flow
+/* eslint-env mocha */
+
+import assert from 'power-assert'
+import formatDuration from '.'
+
+describe('formatDuration', () => {
+  it('formats full duration', () => {
+    assert(
+      formatDuration({
+        years: 2,
+        months: 9,
+        weeks: 1,
+        days: 7,
+        hours: 5,
+        minutes: 9,
+        seconds: 30
+      }) === '2 years 9 months 1 week 7 days 5 hours 9 minutes 30 seconds'
+    )
+  })
+
+  it('formats partial duration', () => {
+    assert(formatDuration({ months: 9, days: 2 }) === '9 months 2 days')
+  })
+
+  it('allows to customize the format', () => {
+    assert(
+      formatDuration(
+        {
+          years: 2,
+          months: 9,
+          weeks: 1,
+          days: 7,
+          hours: 5,
+          minutes: 9,
+          seconds: 30
+        },
+        { format: ['months', 'weeks'] }
+      ) === '9 months 1 week'
+    )
+  })
+
+  it('does not include zeros by default', () => {
+    assert(
+      formatDuration({
+        years: 0,
+        months: 0,
+        weeks: 1,
+        days: 0,
+        hours: 0,
+        minutes: 0,
+        seconds: 0
+      }) === '1 week'
+    )
+  })
+
+  it('allows to include zeros', () => {
+    assert(
+      formatDuration(
+        {
+          years: 0,
+          months: 0,
+          weeks: 1,
+          days: 0,
+          hours: 0,
+          minutes: 0,
+          seconds: 0
+        },
+        { zero: true }
+      ) === '0 years 0 months 1 week 0 days 0 hours 0 minutes 0 seconds'
+    )
+  })
+
+  it('allows to customize the delimiter', () => {
+    assert(
+      formatDuration({ months: 9, days: 2 }, { delimiter: ', ' }) ===
+        '9 months, 2 days'
+    )
+  })
+})