periodOverlap.ts

periodOverlap.spec.ts

import { describe, expect, it } from 'vitest'
import { periodOverlap, type Period } from './date'

describe('periodOverlap', () => {
	it('should return true if periods overlap', () => {
		const period1: Period = { start: "2023-04-01", end: "2023-04-10" }
		const period2: Period = { start: "2023-04-05", end: "2023-04-15" }
		expect(periodOverlap(period1, period2)).toBe(true)
		expect(periodOverlap(period2, period1)).toBe(true)
	})

	it('should return true if one period starts and ends within another', () => {
		const period1: Period = { start: "2023-04-01", end: "2023-04-10" }
		const period2: Period = { start: "2023-04-05", end: "2023-04-07" }
		expect(periodOverlap(period1, period2)).toBe(true)
		expect(periodOverlap(period2, period1)).toBe(true)
	})

	it('should return false if periods do not overlap', () => {
		const period1: Period = { start: "2023-04-01", end: "2023-04-10" }
		const period2: Period = { start: "2023-04-11", end: "2023-04-15" }
		expect(periodOverlap(period1, period2)).toBe(false)
		expect(periodOverlap(period2, period1)).toBe(false)
	})

	it('should handle edge cases where periods touch (inclusive)', () => {
		const period1: Period = { start: "2023-04-01", end: "2023-04-10" }
		const period2: Period = { start: "2023-04-10", end: "2023-04-15" }
		expect(periodOverlap(period1, period2)).toBe(true)
		expect(periodOverlap(period2, period1)).toBe(true)
	})

	it('should handle edge cases where periods touch (exclusive)', () => {
		const period1: Period = { start: "2023-04-01", end: "2023-04-10" }
		const period2: Period = { start: "2023-04-10", end: "2023-04-15" }
		expect(periodOverlap(period1, period2, true)).toBe(false)
		expect(periodOverlap(period2, period1, true)).toBe(false)
	})
})

periodOverlap.ts

export interface PeriodString {
  start: string
  end: string
}
export interface PeriodDate {
  start: Date
  end: Date
}

export type Period = PeriodString | PeriodDate

type PeriodOverlap = {
  (period1: PeriodString, period2: PeriodString, exclusive?: boolean): boolean
  (period1: PeriodDate, period2: PeriodDate, exclusive?: boolean): boolean
}
/** 
 * check if two periods overlap
 * @param period1 - first period
 * @param period2 - second period
 * @param exclusive - if true, check for strict overlap (exclusive), otherwise inclusive (default)
 * @returns true if periods overlap, false otherwise.
 */
export const periodOverlap: PeriodOverlap = (period1: Period, period2: Period, exclusive: boolean = false) => {
  if (exclusive) {
    return period1.start < period2.end && period2.start < period1.end
  }
  return period1.start <= period2.end && period2.start <= period1.end
}