feat(shared/helpers): add getNextOccurrence of ISO R/interval

package.json

@@ -30,10 +30,12 @@
     "class-variance-authority": "^0.7.0",
     "constants-browserify": "^1.0.0",
     "crypto-browserify": "^3.12.0",
+    "date-fns": "^3.6.0",
     "events": "^3.3.0",
     "framer-motion": "^11.2.10",
     "http-message-signatures": "^1.0.4",
     "httpbis-digest-headers": "^1.0.0",
+    "iso8601-duration": "^2.1.2",
     "loglevel": "^1.9.1",
     "path-browserify": "^1.0.1",
     "process": "^0.11.10",

src/shared/helpers.test.ts

@@ -1,4 +1,10 @@
-import { isOkState, objectEquals, removeQueryParams } from './helpers'
+import { addDays, addMonths, addSeconds } from 'date-fns'
+import {
+  isOkState,
+  objectEquals,
+  removeQueryParams,
+  getNextOccurrence
+} from './helpers'
 
 describe('objectEquals', () => {
   it('should return true if objects are equal', () => {
@@ -45,3 +51,74 @@ describe('isOkState', () => {
     ).toBe(false)
   })
 })
+
+describe('getNextOccurrence', () => {
+  const now = new Date()
+  const nowISO = now.toISOString()
+  const dateJan = new Date('2024-01-03T00:00:00.000Z')
+  const dateJanEnd = new Date('2024-01-30T00:00:00.000Z')
+  const dateFeb = new Date('2023-02-03T00:00:00.000Z')
+  const dateFebLeap = new Date('2024-02-29T00:00:00.000Z')
+  const dateApr = new Date('2024-04-03T00:00:00.000Z')
+
+  it('should return the next occurrence with /P1M', () => {
+    expect(
+      getNextOccurrence(`R/${dateJan.toISOString()}/P1M`, dateJan)
+    ).toEqual(addMonths(dateJan, 1))
+    expect(
+      getNextOccurrence(`R/${dateJan.toISOString()}/P1M`, addDays(dateJan, 2))
+    ).toEqual(addMonths(dateJan, 1))
+    expect(
+      getNextOccurrence(`R/${dateJanEnd.toISOString()}/P1M`, dateJanEnd)
+    ).toEqual(new Date('2024-03-01T00:00:00.000Z'))
+    expect(
+      getNextOccurrence(`R/${dateFeb.toISOString()}/P1M`, dateFeb)
+    ).toEqual(addMonths(dateFeb, 1))
+    expect(
+      getNextOccurrence(`R/${dateFebLeap.toISOString()}/P1M`, dateFebLeap)
+    ).toEqual(addMonths(dateFebLeap, 1))
+    expect(
+      getNextOccurrence(`R/${dateApr.toISOString()}/P1M`, dateApr)
+    ).toEqual(addMonths(dateApr, 1))
+  })
+
+  it('should return next occurrence with /P1W', () => {
+    expect(
+      getNextOccurrence(`R/${dateJan.toISOString()}/P1W`, dateJan)
+    ).toEqual(addDays(dateJan, 7))
+    expect(
+      getNextOccurrence(`R/${dateFeb.toISOString()}/P1W`, dateFeb)
+    ).toEqual(addDays(dateFeb, 7))
+    expect(
+      getNextOccurrence(`R/${dateFebLeap.toISOString()}/P1W`, dateFebLeap)
+    ).toEqual(addDays(dateFebLeap, 7))
+    expect(
+      getNextOccurrence(`R/${dateApr.toISOString()}/P1W`, dateApr)
+    ).toEqual(addDays(dateApr, 7))
+  })
+
+  it('should throw if no more occurrences are possible', () => {
+    const interval = `R1/${dateJan.toISOString()}/P1M`
+    const errorMsg = /No next occurrence is possible/
+
+    expect(() =>
+      getNextOccurrence(interval, addMonths(dateJan, 0))
+    ).not.toThrow(errorMsg)
+    expect(() => getNextOccurrence(interval, addDays(dateJan, 10))).not.toThrow(
+      errorMsg
+    )
+
+    expect(() => getNextOccurrence(interval, addMonths(dateJan, 1))).toThrow(
+      errorMsg
+    )
+    expect(() => getNextOccurrence(interval, addMonths(dateJan, 2))).toThrow(
+      errorMsg
+    )
+  })
+
+  it('should return the next occurrence with /PT', () => {
+    expect(getNextOccurrence(`R/${nowISO}/PT30S`, now)).toEqual(
+      addSeconds(now, 30)
+    )
+  })
+})

src/shared/helpers.ts

@@ -1,9 +1,13 @@
-import { SuccessResponse } from '@/shared/messages'
-import { WalletAddress } from '@interledger/open-payments/dist/types'
+import type { SuccessResponse } from '@/shared/messages'
+import type { WalletAddress } from '@interledger/open-payments/dist/types'
 import { cx, CxOptions } from 'class-variance-authority'
 import { twMerge } from 'tailwind-merge'
+import { addSeconds } from 'date-fns/addSeconds'
+import { isAfter } from 'date-fns/isAfter'
+import { isBefore } from 'date-fns/isBefore'
+import { parse, toSeconds } from 'iso8601-duration'
 import type { Browser } from 'webextension-polyfill'
-import type { Storage } from './types'
+import type { Storage, RepeatingInterval } from './types'
 
 export const cn = (...inputs: CxOptions) => {
   return twMerge(cx(inputs))
@@ -226,3 +230,29 @@ export const removeQueryParams = (urlString: string) => {
 export const isOkState = (state: Storage['state']) => {
   return Object.values(state).every((value) => value === false)
 }
+
+export const getNextOccurrence = (
+  interval: RepeatingInterval,
+  base = new Date()
+): Date => {
+  const re = /^R(\d*)\/(\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z)\/(P.+)$/
+  const match = interval.match(re)
+  if (!match) {
+    throw new Error(`Invalid interval: ${interval}`)
+  }
+  const count = match[1] ? parseInt(match[1], 10) : null
+  const startDate = new Date(match[2])
+  const pattern = parse(match[3])
+  const seconds = toSeconds(pattern, base)
+
+  if (count && isAfter(base, addSeconds(startDate, count * seconds))) {
+    throw new Error('No next occurrence is possible beyond given time')
+  }
+
+  let date = new Date(startDate)
+  while (!isBefore(base, date)) {
+    date = addSeconds(date, seconds)
+  }
+
+  return date
+}

src/shared/types.ts

@@ -3,11 +3,13 @@ import { WalletAddress } from '@interledger/open-payments/dist/types'
 /** Bigint amount, before transformation with assetScale */
 export type AmountValue = string
 
+/** https://en.wikipedia.org/wiki/ISO_8601#Repeating_intervals */
+export type RepeatingInterval = string
+
 /** Wallet amount */
 export interface WalletAmount {
   value: string
-  /** https://en.wikipedia.org/wiki/ISO_8601#Repeating_intervals */
-  interval?: string
+  interval?: RepeatingInterval
 }
 
 /** Amount interface - used in the `exceptionList` */