payment-docs

import { addMonths, daysBetween, parseDate, formatDate } from './dates.js'

// Billing cycle. anchorDay (1..28) is the day each monthly cycle starts.
// Returns the [start, end) of the cycle containing `at`. `end` is the next cycle's start date.
export function cycleBounds(anchorDay, at) {
  if (!Number.isInteger(anchorDay) || anchorDay < 1 || anchorDay > 28) {
    throw new RangeError(`anchorDay must be 1..28: ${anchorDay}`)
  }
  const d = parseDate(at)
  let start = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth(), anchorDay))
  if (start > d) start = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth() - 1, anchorDay))
  const startStr = formatDate(start)
  return { start: startStr, end: addMonths(startStr, 1) }
}

// Prorates `amount` by the days remaining from `at` to the end of the cycle. The day of `at` counts.
export function prorate(amount, cycle, at) {
  const total = daysBetween(cycle.start, cycle.end)
  const remaining = daysBetween(at, cycle.end)
  if (remaining < 0 || remaining > total) throw new RangeError(`${at} is outside the cycle`)
  return Math.floor((amount * remaining) / total)
}
---
coupons.js
dates.js
format.js
invoice.js
payment.js
plans.js
proration.js
---
CLAUDE.md
package.json
README.md
src
test

=== dates.js ===
// Dates are handled only as 'YYYY-MM-DD' strings. Time of day and time zones are outside this module.

export function parseDate(s) {
  const m = /^(\d{4})-(\d{2})-(\d{2})$/.exec(s)
  if (!m) throw new TypeError(`invalid date: ${s}`)
  return new Date(Date.UTC(+m[1], +m[2] - 1, +m[3]))
}

export function formatDate(d) {
  return d.toISOString().slice(0, 10)
}

export function addDays(s, n) {
  const d = parseDate(s)
  d.setUTCDate(d.getUTCDate() + n)
  return formatDate(d)
}

export function addMonths(s, n) {
  const d = parseDate(s)
  const day = d.getUTCDate()
  d.setUTCDate(1)
  d.setUTCMonth(d.getUTCMonth() + n)
  const last = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth() + 1, 0)).getUTCDate()
  d.setUTCDate(Math.min(day, last))
  return formatDate(d)
}

export function daysBetween(a, b) {
  return Math.round((parseDate(b) - parseDate(a)) / 86400000)
}
=== plans.js ===
export const PLANS = [
  { id: 'starter', name: 'Starter', monthlyPrice: 29000, seatLimit: 5, legacy: false },
  { id: 'team', name: 'Team', monthlyPrice: 99000, seatLimit: 20, legacy: false },
  { id: 'business', name: 'Business', monthlyPrice: 290000, seatLimit: 100, legacy: false },
  { id: 'L-startup-2019', name: 'Startup (2019)', monthlyPrice: 49000, seatLimit: 10, legacy: true },
  { id: 'L-growth-2019', name: 'Growth (2019)', monthlyPrice: 149000, seatLimit: 30, legacy: true },
]

export function findPlan(id) {
  const plan = PLANS.find((p) => p.id === id)
  if (!plan) throw new Error(`unknown plan: ${id}`)
  return plan
}
=== invoice.js ===
export const VAT_RATE = 0.1

let seq = 0

// Invoice number: INV-YYYYMM-NNNNN
export function nextInvoiceNumber(issuedOn) {
  seq += 1
  return `INV-${issuedOn.slice(0, 7).replace('-', '')}-${String(seq).padStart(5, '0')}`
}

export function resetInvoiceSequence() {
  seq = 0
}

export function createInvoice({ accountId, issuedOn, lines }) {
  if (!lines.length) throw new Error('invoice needs at least one line')
  const subtotal = lines.reduce((sum, l) => sum + l.amount, 0)
  const vat = Math.floor(subtotal * VAT_RATE)
  return {
    number: nextInvoiceNumber(issuedOn),
    accountId,
    issuedOn,
    lines,
    subtotal,
    vat,
    total: subtotal + vat,
  }
}
=== test dir ===
coupons.test.js
format.test.js
invoice.test.js
payment.test.js
plans.test.js
proration.test.js
=== existing proration test ===
import { test } from 'node:test'
import assert from 'node:assert/strict'
import { cycleBounds, prorate } from '../src/proration.js'

test('cycleBounds: anchor before the date', () => {
  assert.deepEqual(cycleBounds(10, '2026-03-15'), { start: '2026-03-10', end: '2026-04-10' })
})

test('cycleBounds: anchor after the date goes to previous month', () => {
  assert.deepEqual(cycleBounds(20, '2026-03-05'), { start: '2026-02-20', end: '2026-03-20' })
})

test('cycleBounds rejects anchor outside 1..28', () => {
  assert.throws(() => cycleBounds(31, '2026-03-05'), RangeError)
})

test('prorate: remaining days over cycle days, truncated', () => {
  const cycle = { start: '2026-03-10', end: '2026-04-10' } // 31 days
  assert.equal(prorate(99000, cycle, '2026-03-25'), Math.floor((99000 * 16) / 31))
})

=== coupons.js ===
// coupon: { code, type: 'percent' | 'fixed', value }
export function applyCoupon(subtotal, coupon) {
  if (coupon.type === 'percent') {
    return subtotal - Math.floor((subtotal * coupon.value) / 100)
  }
  if (coupon.type === 'fixed') {
    return Math.max(0, subtotal - coupon.value)
  }
  throw new Error(`unknown coupon type: ${coupon.type}`)
}
=== payment.js ===
export class GatewayError extends Error {
  constructor(code, message) {
    super(message ?? code)
    this.name = 'GatewayError'
    this.code = code
  }
}

// PayKo payment request.
// gateway.request({ path, headers, body }) returns { status, paymentKey } or throws GatewayError.
export async function charge(gateway, { orderId, amount, method = 'card' }) {
  if (!Number.isInteger(amount) || amount <= 0) {
    throw new RangeError('amount must be a positive integer (KRW)')
  }
  const res = await gateway.request({
    path: '/v1/payments',
    headers: {},
    body: { orderId, amount, currency: 'KRW', method },
  })
  return { status: res.status, paymentKey: res.paymentKey }
}
=== package.json ===
{
  "name": "workhub-billing",
  "version": "0.4.2",
  "private": true,
  "type": "module",
  "scripts": {
    "test": "node --test"
  }
}

The file /src/proration.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /src/proration.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/proration.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/proration.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (0.623125ms)
✔ fixed coupon never goes below zero (0.226458ms)
✔ formatKRW adds thousands separators (12.708875ms)
✔ createInvoice sums lines and adds VAT (0.696958ms)
✔ createInvoice truncates VAT below 1 KRW (0.078834ms)
✔ charge sends KRW amount and returns status (1.928625ms)
✔ charge rejects non-integer amount (0.28775ms)
✔ charge propagates gateway errors (0.1005ms)
✔ findPlan returns the plan by id (0.579084ms)
✔ findPlan throws on unknown id (0.326166ms)
✔ plan ids are unique (0.090417ms)
✔ cycleBounds: anchor before the date (1.965583ms)
✔ cycleBounds: anchor after the date goes to previous month (0.077ms)
✔ cycleBounds rejects anchor outside 1..28 (0.1675ms)
✔ prorate: remaining days over cycle days, truncated (0.075542ms)
✔ changePlan: upgrade charges the price difference prorated over remaining days (0.107292ms)
✔ changePlan: downgrade returns a negative amount (credit owed) (0.05175ms)
✔ changePlan: switching to the same plan nets to zero (0.04675ms)
✔ changePlan: on the first day of the cycle charges/credits the full month difference (0.043875ms)
✔ changePlan: works with legacy plan ids (0.060959ms)
✔ changePlan: rejects an unknown plan id (0.260667ms)
ℹ tests 21
ℹ suites 0
ℹ pass 21
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 123.767625

     1	import { addMonths, daysBetween, parseDate, formatDate } from './dates.js'
     2	
     3	// Billing cycle. anchorDay (1..28) is the day each monthly cycle starts.
     4	// Returns the [start, end) of the cycle containing `at`. `end` is the next cycle's start date.
     5	export function cycleBounds(anchorDay, at) {
     6	  if (!Number.isInteger(anchorDay) || anchorDay < 1 || anchorDay > 28) {
     7	    throw new RangeError(`anchorDay must be 1..28: ${anchorDay}`)
     8	  }
     9	  const d = parseDate(at)
    10	  let start = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth(), anchorDay))
    11	  if (start > d) start = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth() - 1, anchorDay))
    12	  const startStr = formatDate(start)
    13	  return { start: startStr, end: addMonths(startStr, 1) }
    14	}
    15	
    16	// Prorates `amount` by the days remaining from `at` to the end of the cycle. The day of `at` counts.
    17	export function prorate(amount, cycle, at) {
    18	  const total = daysBetween(cycle.start, cycle.end)
    19	  const remaining = daysBetween(at, cycle.end)
    20	  if (remaining < 0 || remaining > total) throw new RangeError(`${at} is outside the cycle`)
    21	  return Math.floor((amount * remaining) / total)
    22	}
---
src/:
coupons.js
dates.js
format.js
invoice.js
payment.js
plans.js
proration.js

test/:
coupons.test.js
format.test.js
invoice.test.js
payment.test.js
plans.test.js
proration.test.js
---
./test/proration.test.js
./docs/billing-cycle-and-proration.md
./src/proration.js

1	import { test } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { cycleBounds, prorate } from '../src/proration.js'
4	
5	test('cycleBounds: anchor before the date', () => {
6	  assert.deepEqual(cycleBounds(10, '2026-03-15'), { start: '2026-03-10', end: '2026-04-10' })
7	})
8	
9	test('cycleBounds: anchor after the date goes to previous month', () => {
10	  assert.deepEqual(cycleBounds(20, '2026-03-05'), { start: '2026-02-20', end: '2026-03-20' })
11	})
12	
13	test('cycleBounds rejects anchor outside 1..28', () => {
14	  assert.throws(() => cycleBounds(31, '2026-03-05'), RangeError)
15	})
16	
17	test('prorate: remaining days over cycle days, truncated', () => {
18	  const cycle = { start: '2026-03-10', end: '2026-04-10' } // 31 days
19	  assert.equal(prorate(99000, cycle, '2026-03-25'), Math.floor((99000 * 16) / 31))
20	})
21	

1	export const PLANS = [
2	  { id: 'starter', name: 'Starter', monthlyPrice: 29000, seatLimit: 5, legacy: false },
3	  { id: 'team', name: 'Team', monthlyPrice: 99000, seatLimit: 20, legacy: false },
4	  { id: 'business', name: 'Business', monthlyPrice: 290000, seatLimit: 100, legacy: false },
5	  { id: 'L-startup-2019', name: 'Startup (2019)', monthlyPrice: 49000, seatLimit: 10, legacy: true },
6	  { id: 'L-growth-2019', name: 'Growth (2019)', monthlyPrice: 149000, seatLimit: 30, legacy: true },
7	]
8	
9	export function findPlan(id) {
10	  const plan = PLANS.find((p) => p.id === id)
11	  if (!plan) throw new Error(`unknown plan: ${id}`)
12	  return plan
13	}
14	

1	// Dates are handled only as 'YYYY-MM-DD' strings. Time of day and time zones are outside this module.
2	
3	export function parseDate(s) {
4	  const m = /^(\d{4})-(\d{2})-(\d{2})$/.exec(s)
5	  if (!m) throw new TypeError(`invalid date: ${s}`)
6	  return new Date(Date.UTC(+m[1], +m[2] - 1, +m[3]))
7	}
8	
9	export function formatDate(d) {
10	  return d.toISOString().slice(0, 10)
11	}
12	
13	export function addDays(s, n) {
14	  const d = parseDate(s)
15	  d.setUTCDate(d.getUTCDate() + n)
16	  return formatDate(d)
17	}
18	
19	export function addMonths(s, n) {
20	  const d = parseDate(s)
21	  const day = d.getUTCDate()
22	  d.setUTCDate(1)
23	  d.setUTCMonth(d.getUTCMonth() + n)
24	  const last = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth() + 1, 0)).getUTCDate()
25	  d.setUTCDate(Math.min(day, last))
26	  return formatDate(d)
27	}
28	
29	export function daysBetween(a, b) {
30	  return Math.round((parseDate(b) - parseDate(a)) / 86400000)
31	}
32	

1	# Billing cycle and proration policy
2	
3	This document covers the Workhub subscription billing cycle, how money is handled on plan changes, and the proration rules.
4	The code (`src/proration.js`) only provides calculation tools; which calculation applies in which situation is decided by the
5	policy here. The finance team owns this policy, and changes go through finance review (see "Change procedure" in `glossary-and-incident-log.md`).
6	
7	## 1. Billing cycle
8	
9	- Every account has an `anchorDay` (1..28). A new cycle starts on that day each month, and one month's fee is charged up front on the cycle start date.
10	- A cycle is `[start date, next start date)`. With an anchor of March 10, one cycle runs from March 10 through April 9.
11	- `anchorDay` is set from the date of the first paid conversion. The paid conversion date is the day the 14-day trial ends.
12	- Days 29, 30, and 31 are never used as anchors. In August 2023 we moved all 412 accounts with those anchors to day 28,
13	  because cycle lengths diverged per account in February and CS tickets piled up. The finance team keeps the list of moved accounts.
14	- The billing batch runs at 09:00 KST on the cycle start date. Plan changes made before that time are reflected in the cycle starting that day.
15	
16	## 2. Date basis: Korea Standard Time (KST) calendar dates
17	
18	- Every billing-related date is a **KST calendar date**. Servers and the database run in UTC, but any date entering billing logic must already be a
19	  `YYYY-MM-DD` string converted to KST.
20	- Reason: the "issue date" on the tax invoice must equal the cycle start date, and tax invoices are issued on Korean time.
21	  Using UTC dates would push charges between 00:00 and 09:00 KST to the previous day. This actually happened in June 2023 (INC-2023-06).
22	- So billing logic never uses the time component of a `Date` or the user's browser time zone. Overseas customers are on KST as well.
23	
24	## 3. Money handling on plan changes
25	
26	Plan changes fall into three kinds. The criterion is **the monthly fee**. Seat count and features are not considered.
27	
28	| Change | Takes effect | Billing |
29	|---|---|---|
30	| Upgrade (monthly fee goes up) | Immediately | Prorate the difference over the remaining days and charge immediately |
31	| Downgrade (monthly fee goes down) | Next cycle start date | No charge and no refund this cycle. New fee from the next cycle |
32	| Lateral move (same monthly fee) | Immediately | 0 |
33	
34	### 3.1 Upgrade
35	
36	- The change date itself counts as a remaining day. Changing on March 25 with a cycle ending April 10 leaves 16 remaining days.
37	- Charge = (new plan monthly fee − old plan monthly fee) × remaining days ÷ cycle days. Truncate below 1 KRW.
38	- Cycle days are actual calendar days (28..31). Legacy plans follow section 4 instead.
39	- The upgrade invoice is issued and charged immediately. If the payment fails, the plan change is rolled back too.
40	
41	### 3.2 Downgrade: no money moves this cycle
42	
43	- A downgrade takes effect **from the next cycle start date**. The change request is stored only as a "scheduled" change.
44	- The difference for the rest of the current cycle is not refunded or returned as credit. The system must never produce a negative amount.
45	- Background: until November 2022, downgrades were also prorated immediately and the difference became a negative invoice. Every negative invoice
46	  then required a corrected tax invoice at month-end close, and the finance team closed November 8 days late (INC-2022-11).
47	  The December 2022 policy meeting fixed "downgrades are deferred, no refunds", and it is in section 7.3 of the terms of service.
48	- If CS requests an exception, the finance team handles it as a manual credit. The system has no exception path.
49	- Upgrading again while a downgrade is scheduled cancels the scheduled downgrade.
50	
51	### 3.3 Lateral move
52	
53	- Moving to a plan with the same monthly fee (none in the current catalog, but past regional plans had them). Immediate, charge 0.
54	
55	## 4. Proration for legacy plans (`L-` prefix)
56	
57	- 2019 contract, article 4: "For proration, one month is 30 days." So any proration involving a legacy plan uses **30 as the denominator**,
58	  regardless of the cycle's actual length. The numerator (remaining days) is the actual remaining days, capped at 30.
59	- This rule applies when the existing plan is legacy. Upgrading from a legacy plan to a current plan is still the last cycle under the old contract,
60	  so the 30-day basis applies.
61	- In a 31-day cycle a legacy customer who upgrades pays slightly more than a current customer. That is what the contract says, and customers know it.
62	  "Fixing" it to actual days would breach the contract.
63	
64	## 5. Worked examples
65	
66	| Situation | Calculation | Amount |
67	|---|---|---|
68	| Team (99,000) → Business (290,000), anchor 10, changed March 25 | (290,000 − 99,000) × 16 ÷ 31 | 98,580 KRW |
69	| Business → Team, changed March 25 | Team fee from the next cycle (April 10). This cycle charge 0 | 0 KRW |
70	| L-growth-2019 (149,000) → Business (290,000), anchor 10, changed March 25 | (290,000 − 149,000) × 16 ÷ 30 | 75,200 KRW |
71	| Starter → Team, changed on the cycle start date | Remaining days = cycle days, full difference | 70,000 KRW |
72	
73	## 6. Out of scope
74	
75	- Annual billing is not handled by this module. The 37 annual customers are invoiced manually by the finance team.
76	- Enterprise is invoiced per contract (net-30) and has no plan-change concept.
77	
78	## 7. Cancellation
79	
80	- Cancellation takes effect at the end of the cycle. The remaining period stays usable and there is no refund. Same principle as downgrades.
81	- Immediate cancellation with refund is finance-only (legal disputes, duplicate signups, and so on). The system has no immediate-cancel path.
82	- An account with a scheduled cancellation does not accept plan changes. The scheduled cancellation must be removed first.
83	
84	## 8. Trial and anchor selection
85	
86	- The trial is 14 days and needs no card. There are no invoices during the trial.
87	- If a card is on file when the trial ends, the account converts that day, and that day's date becomes `anchorDay`.
88	  If that day is the 29th, 30th, or 31st, `anchorDay` is set to 28 and only the first cycle runs a day or two longer. The first cycle is charged a full month.
89	- If no card is on file at trial end, the account becomes read-only, and the day a card is later added becomes the anchor.
90	
91	## 9. Common implementation mistakes
92	
93	- Excluding the change date from remaining days. It is included. A change on the cycle start date has the whole cycle remaining.
94	- Giving a "fair" credit on downgrade. Forbidden by policy, and the cause of INC-2022-11.
95	- Using a 30-day denominator for current plans, or actual days for legacy plans. Legacy status is decided by the **existing** plan.
96	- Truncating only once at the end. Truncate once in proration, once after coupons, once in VAT.
97	- Leaving the plan changed after an upgrade payment fails. On payment failure, roll back the plan change.
98	- Stacking a second scheduled downgrade on an account that already has one. Overwrite instead of stacking.
99	

1	export const VAT_RATE = 0.1
2	
3	let seq = 0
4	
5	// Invoice number: INV-YYYYMM-NNNNN
6	export function nextInvoiceNumber(issuedOn) {
7	  seq += 1
8	  return `INV-${issuedOn.slice(0, 7).replace('-', '')}-${String(seq).padStart(5, '0')}`
9	}
10	
11	export function resetInvoiceSequence() {
12	  seq = 0
13	}
14	
15	export function createInvoice({ accountId, issuedOn, lines }) {
16	  if (!lines.length) throw new Error('invoice needs at least one line')
17	  const subtotal = lines.reduce((sum, l) => sum + l.amount, 0)
18	  const vat = Math.floor(subtotal * VAT_RATE)
19	  return {
20	    number: nextInvoiceNumber(issuedOn),
21	    accountId,
22	    issuedOn,
23	    lines,
24	    subtotal,
25	    vat,
26	    total: subtotal + vat,
27	  }
28	}
29	

1	export class GatewayError extends Error {
2	  constructor(code, message) {
3	    super(message ?? code)
4	    this.name = 'GatewayError'
5	    this.code = code
6	  }
7	}
8	
9	// PayKo payment request.
10	// gateway.request({ path, headers, body }) returns { status, paymentKey } or throws GatewayError.
11	export async function charge(gateway, { orderId, amount, method = 'card' }) {
12	  if (!Number.isInteger(amount) || amount <= 0) {
13	    throw new RangeError('amount must be a positive integer (KRW)')
14	  }
15	  const res = await gateway.request({
16	    path: '/v1/payments',
17	    headers: {},
18	    body: { orderId, amount, currency: 'KRW', method },
19	  })
20	  return { status: res.status, paymentKey: res.paymentKey }
21	}
22	

1	// coupon: { code, type: 'percent' | 'fixed', value }
2	export function applyCoupon(subtotal, coupon) {
3	  if (coupon.type === 'percent') {
4	    return subtotal - Math.floor((subtotal * coupon.value) / 100)
5	  }
6	  if (coupon.type === 'fixed') {
7	    return Math.max(0, subtotal - coupon.value)
8	  }
9	  throw new Error(`unknown coupon type: ${coupon.type}`)
10	}
11	

The file /src/proration.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /src/proration.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/proration.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/proration.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (1.623667ms)
✔ fixed coupon never goes below zero (0.094959ms)
✔ formatKRW adds thousands separators (13.574709ms)
✔ createInvoice sums lines and adds VAT (1.031041ms)
✔ createInvoice truncates VAT below 1 KRW (0.089833ms)
✔ charge sends KRW amount and returns status (1.578625ms)
✔ charge rejects non-integer amount (0.554959ms)
✔ charge propagates gateway errors (0.26025ms)
✔ findPlan returns the plan by id (1.64925ms)
✔ findPlan throws on unknown id (0.496709ms)
✔ plan ids are unique (0.223ms)
✔ cycleBounds: anchor before the date (3.234083ms)
✔ cycleBounds: anchor after the date goes to previous month (0.084833ms)
✔ cycleBounds rejects anchor outside 1..28 (0.261584ms)
✔ prorate: remaining days over cycle days, truncated (0.134208ms)
✔ changePlan: upgrade charges the prorated difference immediately (0.494292ms)
✔ changePlan: downgrade charges nothing now and takes effect next cycle (0.280333ms)
✔ changePlan: lateral move is immediate and free (0.276459ms)
✔ changePlan: upgrade from a legacy plan prorates over a fixed 30-day month (0.076958ms)
✔ changePlan: upgrade on the cycle start date charges the full difference (0.084875ms)
✔ changePlan: legacy upgrade proration is capped at 30 days even in a longer cycle (0.100833ms)
ℹ tests 21
ℹ suites 0
ℹ pass 21
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 132.174

/test/plans.test.js
/test/payment.test.js
/test/proration.test.js
/test/coupons.test.js
/test/invoice.test.js
/test/format.test.js
/src/proration.js
/src/format.js
/src/dates.js
/src/invoice.js
/src/payment.js
/src/coupons.js
/src/plans.js

1	import { addMonths, daysBetween, parseDate, formatDate } from './dates.js'
2	
3	// Billing cycle. anchorDay (1..28) is the day each monthly cycle starts.
4	// Returns the [start, end) of the cycle containing `at`. `end` is the next cycle's start date.
5	export function cycleBounds(anchorDay, at) {
6	  if (!Number.isInteger(anchorDay) || anchorDay < 1 || anchorDay > 28) {
7	    throw new RangeError(`anchorDay must be 1..28: ${anchorDay}`)
8	  }
9	  const d = parseDate(at)
10	  let start = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth(), anchorDay))
11	  if (start > d) start = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth() - 1, anchorDay))
12	  const startStr = formatDate(start)
13	  return { start: startStr, end: addMonths(startStr, 1) }
14	}
15	
16	// Prorates `amount` by the days remaining from `at` to the end of the cycle. The day of `at` counts.
17	export function prorate(amount, cycle, at) {
18	  const total = daysBetween(cycle.start, cycle.end)
19	  const remaining = daysBetween(at, cycle.end)
20	  if (remaining < 0 || remaining > total) throw new RangeError(`${at} is outside the cycle`)
21	  return Math.floor((amount * remaining) / total)
22	}
23	

1	import { test } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { cycleBounds, prorate } from '../src/proration.js'
4	
5	test('cycleBounds: anchor before the date', () => {
6	  assert.deepEqual(cycleBounds(10, '2026-03-15'), { start: '2026-03-10', end: '2026-04-10' })
7	})
8	
9	test('cycleBounds: anchor after the date goes to previous month', () => {
10	  assert.deepEqual(cycleBounds(20, '2026-03-05'), { start: '2026-02-20', end: '2026-03-20' })
11	})
12	
13	test('cycleBounds rejects anchor outside 1..28', () => {
14	  assert.throws(() => cycleBounds(31, '2026-03-05'), RangeError)
15	})
16	
17	test('prorate: remaining days over cycle days, truncated', () => {
18	  const cycle = { start: '2026-03-10', end: '2026-04-10' } // 31 days
19	  assert.equal(prorate(99000, cycle, '2026-03-25'), Math.floor((99000 * 16) / 31))
20	})
21	

1	// Dates are handled only as 'YYYY-MM-DD' strings. Time of day and time zones are outside this module.
2	
3	export function parseDate(s) {
4	  const m = /^(\d{4})-(\d{2})-(\d{2})$/.exec(s)
5	  if (!m) throw new TypeError(`invalid date: ${s}`)
6	  return new Date(Date.UTC(+m[1], +m[2] - 1, +m[3]))
7	}
8	
9	export function formatDate(d) {
10	  return d.toISOString().slice(0, 10)
11	}
12	
13	export function addDays(s, n) {
14	  const d = parseDate(s)
15	  d.setUTCDate(d.getUTCDate() + n)
16	  return formatDate(d)
17	}
18	
19	export function addMonths(s, n) {
20	  const d = parseDate(s)
21	  const day = d.getUTCDate()
22	  d.setUTCDate(1)
23	  d.setUTCMonth(d.getUTCMonth() + n)
24	  const last = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth() + 1, 0)).getUTCDate()
25	  d.setUTCDate(Math.min(day, last))
26	  return formatDate(d)
27	}
28	
29	export function daysBetween(a, b) {
30	  return Math.round((parseDate(b) - parseDate(a)) / 86400000)
31	}
32	

1	export const PLANS = [
2	  { id: 'starter', name: 'Starter', monthlyPrice: 29000, seatLimit: 5, legacy: false },
3	  { id: 'team', name: 'Team', monthlyPrice: 99000, seatLimit: 20, legacy: false },
4	  { id: 'business', name: 'Business', monthlyPrice: 290000, seatLimit: 100, legacy: false },
5	  { id: 'L-startup-2019', name: 'Startup (2019)', monthlyPrice: 49000, seatLimit: 10, legacy: true },
6	  { id: 'L-growth-2019', name: 'Growth (2019)', monthlyPrice: 149000, seatLimit: 30, legacy: true },
7	]
8	
9	export function findPlan(id) {
10	  const plan = PLANS.find((p) => p.id === id)
11	  if (!plan) throw new Error(`unknown plan: ${id}`)
12	  return plan
13	}
14	

1	export const VAT_RATE = 0.1
2	
3	let seq = 0
4	
5	// Invoice number: INV-YYYYMM-NNNNN
6	export function nextInvoiceNumber(issuedOn) {
7	  seq += 1
8	  return `INV-${issuedOn.slice(0, 7).replace('-', '')}-${String(seq).padStart(5, '0')}`
9	}
10	
11	export function resetInvoiceSequence() {
12	  seq = 0
13	}
14	
15	export function createInvoice({ accountId, issuedOn, lines }) {
16	  if (!lines.length) throw new Error('invoice needs at least one line')
17	  const subtotal = lines.reduce((sum, l) => sum + l.amount, 0)
18	  const vat = Math.floor(subtotal * VAT_RATE)
19	  return {
20	    number: nextInvoiceNumber(issuedOn),
21	    accountId,
22	    issuedOn,
23	    lines,
24	    subtotal,
25	    vat,
26	    total: subtotal + vat,
27	  }
28	}
29	

1	// coupon: { code, type: 'percent' | 'fixed', value }
2	export function applyCoupon(subtotal, coupon) {
3	  if (coupon.type === 'percent') {
4	    return subtotal - Math.floor((subtotal * coupon.value) / 100)
5	  }
6	  if (coupon.type === 'fixed') {
7	    return Math.max(0, subtotal - coupon.value)
8	  }
9	  throw new Error(`unknown coupon type: ${coupon.type}`)
10	}
11	

credit starter 14967
charge team 51096
diff 36129
credit team 51096
charge starter 14967
diff downgrade -36129

The file /src/proration.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /src/proration.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/proration.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/proration.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (0.644084ms)
✔ fixed coupon never goes below zero (0.057125ms)
✔ formatKRW adds thousands separators (16.889125ms)
✔ createInvoice sums lines and adds VAT (1.62275ms)
✔ createInvoice truncates VAT below 1 KRW (0.214375ms)
✔ charge sends KRW amount and returns status (1.528042ms)
✔ charge rejects non-integer amount (0.294875ms)
✔ charge propagates gateway errors (0.103125ms)
✔ findPlan returns the plan by id (1.289792ms)
✔ findPlan throws on unknown id (0.220958ms)
✔ plan ids are unique (0.063791ms)
✔ cycleBounds: anchor before the date (3.835583ms)
✔ cycleBounds: anchor after the date goes to previous month (0.092459ms)
✔ cycleBounds rejects anchor outside 1..28 (0.159209ms)
✔ prorate: remaining days over cycle days, truncated (0.078125ms)
✔ changePlan: upgrade charges the prorated price difference (0.097875ms)
✔ changePlan: downgrade credits the prorated price difference (0.046791ms)
✔ changePlan: same plan nets to zero (0.0435ms)
✔ changePlan: change on the first day of the cycle charges the full difference (0.043875ms)
✔ changePlan: unknown plan throws (0.073875ms)
ℹ tests 20
ℹ suites 0
ℹ pass 20
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 137.829167

/test/plans.test.js
/test/payment.test.js
/test/proration.test.js
/test/coupons.test.js
/test/invoice.test.js
/test/format.test.js
/src/proration.js
/src/format.js
/src/dates.js
/src/invoice.js
/src/payment.js
/src/coupons.js
/src/plans.js

1	import { addMonths, daysBetween, parseDate, formatDate } from './dates.js'
2	
3	// Billing cycle. anchorDay (1..28) is the day each monthly cycle starts.
4	// Returns the [start, end) of the cycle containing `at`. `end` is the next cycle's start date.
5	export function cycleBounds(anchorDay, at) {
6	  if (!Number.isInteger(anchorDay) || anchorDay < 1 || anchorDay > 28) {
7	    throw new RangeError(`anchorDay must be 1..28: ${anchorDay}`)
8	  }
9	  const d = parseDate(at)
10	  let start = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth(), anchorDay))
11	  if (start > d) start = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth() - 1, anchorDay))
12	  const startStr = formatDate(start)
13	  return { start: startStr, end: addMonths(startStr, 1) }
14	}
15	
16	// Prorates `amount` by the days remaining from `at` to the end of the cycle. The day of `at` counts.
17	export function prorate(amount, cycle, at) {
18	  const total = daysBetween(cycle.start, cycle.end)
19	  const remaining = daysBetween(at, cycle.end)
20	  if (remaining < 0 || remaining > total) throw new RangeError(`${at} is outside the cycle`)
21	  return Math.floor((amount * remaining) / total)
22	}
23	

1	export const PLANS = [
2	  { id: 'starter', name: 'Starter', monthlyPrice: 29000, seatLimit: 5, legacy: false },
3	  { id: 'team', name: 'Team', monthlyPrice: 99000, seatLimit: 20, legacy: false },
4	  { id: 'business', name: 'Business', monthlyPrice: 290000, seatLimit: 100, legacy: false },
5	  { id: 'L-startup-2019', name: 'Startup (2019)', monthlyPrice: 49000, seatLimit: 10, legacy: true },
6	  { id: 'L-growth-2019', name: 'Growth (2019)', monthlyPrice: 149000, seatLimit: 30, legacy: true },
7	]
8	
9	export function findPlan(id) {
10	  const plan = PLANS.find((p) => p.id === id)
11	  if (!plan) throw new Error(`unknown plan: ${id}`)
12	  return plan
13	}
14	

1	// Dates are handled only as 'YYYY-MM-DD' strings. Time of day and time zones are outside this module.
2	
3	export function parseDate(s) {
4	  const m = /^(\d{4})-(\d{2})-(\d{2})$/.exec(s)
5	  if (!m) throw new TypeError(`invalid date: ${s}`)
6	  return new Date(Date.UTC(+m[1], +m[2] - 1, +m[3]))
7	}
8	
9	export function formatDate(d) {
10	  return d.toISOString().slice(0, 10)
11	}
12	
13	export function addDays(s, n) {
14	  const d = parseDate(s)
15	  d.setUTCDate(d.getUTCDate() + n)
16	  return formatDate(d)
17	}
18	
19	export function addMonths(s, n) {
20	  const d = parseDate(s)
21	  const day = d.getUTCDate()
22	  d.setUTCDate(1)
23	  d.setUTCMonth(d.getUTCMonth() + n)
24	  const last = new Date(Date.UTC(d.getUTCFullYear(), d.getUTCMonth() + 1, 0)).getUTCDate()
25	  d.setUTCDate(Math.min(day, last))
26	  return formatDate(d)
27	}
28	
29	export function daysBetween(a, b) {
30	  return Math.round((parseDate(b) - parseDate(a)) / 86400000)
31	}
32	

1	import { test } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { cycleBounds, prorate } from '../src/proration.js'
4	
5	test('cycleBounds: anchor before the date', () => {
6	  assert.deepEqual(cycleBounds(10, '2026-03-15'), { start: '2026-03-10', end: '2026-04-10' })
7	})
8	
9	test('cycleBounds: anchor after the date goes to previous month', () => {
10	  assert.deepEqual(cycleBounds(20, '2026-03-05'), { start: '2026-02-20', end: '2026-03-20' })
11	})
12	
13	test('cycleBounds rejects anchor outside 1..28', () => {
14	  assert.throws(() => cycleBounds(31, '2026-03-05'), RangeError)
15	})
16	
17	test('prorate: remaining days over cycle days, truncated', () => {
18	  const cycle = { start: '2026-03-10', end: '2026-04-10' } // 31 days
19	  assert.equal(prorate(99000, cycle, '2026-03-25'), Math.floor((99000 * 16) / 31))
20	})
21	

1	export const VAT_RATE = 0.1
2	
3	let seq = 0
4	
5	// Invoice number: INV-YYYYMM-NNNNN
6	export function nextInvoiceNumber(issuedOn) {
7	  seq += 1
8	  return `INV-${issuedOn.slice(0, 7).replace('-', '')}-${String(seq).padStart(5, '0')}`
9	}
10	
11	export function resetInvoiceSequence() {
12	  seq = 0
13	}
14	
15	export function createInvoice({ accountId, issuedOn, lines }) {
16	  if (!lines.length) throw new Error('invoice needs at least one line')
17	  const subtotal = lines.reduce((sum, l) => sum + l.amount, 0)
18	  const vat = Math.floor(subtotal * VAT_RATE)
19	  return {
20	    number: nextInvoiceNumber(issuedOn),
21	    accountId,
22	    issuedOn,
23	    lines,
24	    subtotal,
25	    vat,
26	    total: subtotal + vat,
27	  }
28	}
29	

1	export class GatewayError extends Error {
2	  constructor(code, message) {
3	    super(message ?? code)
4	    this.name = 'GatewayError'
5	    this.code = code
6	  }
7	}
8	
9	// PayKo payment request.
10	// gateway.request({ path, headers, body }) returns { status, paymentKey } or throws GatewayError.
11	export async function charge(gateway, { orderId, amount, method = 'card' }) {
12	  if (!Number.isInteger(amount) || amount <= 0) {
13	    throw new RangeError('amount must be a positive integer (KRW)')
14	  }
15	  const res = await gateway.request({
16	    path: '/v1/payments',
17	    headers: {},
18	    body: { orderId, amount, currency: 'KRW', method },
19	  })
20	  return { status: res.status, paymentKey: res.paymentKey }
21	}
22	

1	import { test, beforeEach } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { createInvoice, resetInvoiceSequence } from '../src/invoice.js'
4	
5	beforeEach(() => resetInvoiceSequence())
6	
7	test('createInvoice sums lines and adds VAT', () => {
8	  const inv = createInvoice({
9	    accountId: 'acc_1',
10	    issuedOn: '2026-03-10',
11	    lines: [{ description: 'Team plan', amount: 99000 }],
12	  })
13	  assert.equal(inv.number, 'INV-202603-00001')
14	  assert.equal(inv.subtotal, 99000)
15	  assert.equal(inv.vat, 9900)
16	  assert.equal(inv.total, 108900)
17	})
18	
19	test('createInvoice truncates VAT below 1 KRW', () => {
20	  const inv = createInvoice({ accountId: 'acc_1', issuedOn: '2026-03-10', lines: [{ description: 'x', amount: 12345 }] })
21	  assert.equal(inv.vat, 1234)
22	})
23	

1	import { test } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { PLANS, findPlan } from '../src/plans.js'
4	
5	test('findPlan returns the plan by id', () => {
6	  assert.equal(findPlan('team').monthlyPrice, 99000)
7	})
8	
9	test('findPlan throws on unknown id', () => {
10	  assert.throws(() => findPlan('nope'), /unknown plan/)
11	})
12	
13	test('plan ids are unique', () => {
14	  assert.equal(new Set(PLANS.map((p) => p.id)).size, PLANS.length)
15	})
16	

The file /src/proration.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /src/proration.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/proration.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/proration.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (1.24575ms)
✔ fixed coupon never goes below zero (0.175833ms)
✔ formatKRW adds thousands separators (15.625542ms)
✔ createInvoice sums lines and adds VAT (1.424417ms)
✔ createInvoice truncates VAT below 1 KRW (0.229042ms)
✔ charge sends KRW amount and returns status (1.670417ms)
✔ charge rejects non-integer amount (0.294834ms)
✔ charge propagates gateway errors (0.091917ms)
✔ findPlan returns the plan by id (1.796875ms)
✔ findPlan throws on unknown id (0.286542ms)
✔ plan ids are unique (0.174417ms)
✔ cycleBounds: anchor before the date (2.770791ms)
✔ cycleBounds: anchor after the date goes to previous month (0.10075ms)
✔ cycleBounds rejects anchor outside 1..28 (0.346833ms)
✔ prorate: remaining days over cycle days, truncated (0.252ms)
✔ changePlan: upgrade charges the difference between new and old proration (0.130083ms)
✔ changePlan: downgrade charges nothing this cycle (0.081333ms)
✔ changePlan: switching to the same plan charges nothing (0.07425ms)
✔ changePlan: on the anchor day, the full month difference is due (0.07225ms)
✔ changePlan: unknown plan id throws (0.110375ms)
ℹ tests 20
ℹ suites 0
ℹ pass 20
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 141.463

1	export class GatewayError extends Error {
2	  constructor(code, message) {
3	    super(message ?? code)
4	    this.name = 'GatewayError'
5	    this.code = code
6	  }
7	}
8	
9	// PayKo payment request.
10	// gateway.request({ path, headers, body }) returns { status, paymentKey } or throws GatewayError.
11	export async function charge(gateway, { orderId, amount, method = 'card' }) {
12	  if (!Number.isInteger(amount) || amount <= 0) {
13	    throw new RangeError('amount must be a positive integer (KRW)')
14	  }
15	  const res = await gateway.request({
16	    path: '/v1/payments',
17	    headers: {},
18	    body: { orderId, amount, currency: 'KRW', method },
19	  })
20	  return { status: res.status, paymentKey: res.paymentKey }
21	}
22	

./test/plans.test.js
./test/payment.test.js
./test/proration.test.js
./test/coupons.test.js
./test/invoice.test.js
./test/format.test.js

1	import { test } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { charge, GatewayError } from '../src/payment.js'
4	
5	function fakeGateway(handler) {
6	  const calls = []
7	  return {
8	    calls,
9	    async request(req) {
10	      calls.push(req)
11	      return handler(req, calls.length)
12	    },
13	  }
14	}
15	
16	test('charge sends KRW amount and returns status', async () => {
17	  const gw = fakeGateway(() => ({ status: 'DONE', paymentKey: 'pk_1' }))
18	  const res = await charge(gw, { orderId: 'ord_1', amount: 108900 })
19	  assert.equal(res.status, 'DONE')
20	  assert.equal(gw.calls[0].body.currency, 'KRW')
21	})
22	
23	test('charge rejects non-integer amount', async () => {
24	  const gw = fakeGateway(() => ({ status: 'DONE' }))
25	  await assert.rejects(charge(gw, { orderId: 'ord_1', amount: 100.5 }), RangeError)
26	})
27	
28	test('charge propagates gateway errors', async () => {
29	  const gw = fakeGateway(() => {
30	    throw new GatewayError('DECLINED', 'card declined')
31	  })
32	  await assert.rejects(charge(gw, { orderId: 'ord_1', amount: 1000 }), (e) => e.code === 'DECLINED')
33	})
34	

src/payment.js:1:export class GatewayError extends Error {
src/payment.js:4:    this.name = 'GatewayError'
src/payment.js:10:// gateway.request({ path, headers, body }) returns { status, paymentKey } or throws GatewayError.

The file /src/payment.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/payment.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (1.5ms)
✔ fixed coupon never goes below zero (0.223542ms)
✔ formatKRW adds thousands separators (14.825291ms)
✔ createInvoice sums lines and adds VAT (1.187542ms)
✔ createInvoice truncates VAT below 1 KRW (0.449292ms)
✔ charge sends KRW amount and returns status (1.624583ms)
✔ charge rejects non-integer amount (0.531834ms)
✔ charge propagates gateway errors (0.213875ms)
✔ charge retries on transient gateway errors and succeeds (4.664042ms)
✔ charge does not retry non-transient gateway errors (0.219375ms)
✔ charge gives up after exhausting retries (3.96175ms)
✔ charge retries on non-gateway (network) errors (1.014084ms)
✔ charge sends the same idempotency key on every retry (1.847041ms)
✔ findPlan returns the plan by id (2.495333ms)
✔ findPlan throws on unknown id (0.406ms)
✔ plan ids are unique (0.109417ms)
✔ cycleBounds: anchor before the date (3.47075ms)
✔ cycleBounds: anchor after the date goes to previous month (0.097875ms)
✔ cycleBounds rejects anchor outside 1..28 (0.250583ms)
✔ prorate: remaining days over cycle days, truncated (0.0955ms)
ℹ tests 20
ℹ suites 0
ℹ pass 20
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 186.5405

1	export class GatewayError extends Error {
2	  constructor(code, message) {
3	    super(message ?? code)
4	    this.name = 'GatewayError'
5	    this.code = code
6	  }
7	}
8	
9	// PayKo payment request.
10	// gateway.request({ path, headers, body }) returns { status, paymentKey } or throws GatewayError.
11	export async function charge(gateway, { orderId, amount, method = 'card' }) {
12	  if (!Number.isInteger(amount) || amount <= 0) {
13	    throw new RangeError('amount must be a positive integer (KRW)')
14	  }
15	  const res = await gateway.request({
16	    path: '/v1/payments',
17	    headers: {},
18	    body: { orderId, amount, currency: 'KRW', method },
19	  })
20	  return { status: res.status, paymentKey: res.paymentKey }
21	}
22	

./test
./test/plans.test.js
./test/payment.test.js
./test/proration.test.js
./test/coupons.test.js
./test/invoice.test.js
./test/format.test.js
---
CLAUDE.md
docs
package.json
README.md
src
test

1	import { test } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { charge, GatewayError } from '../src/payment.js'
4	
5	function fakeGateway(handler) {
6	  const calls = []
7	  return {
8	    calls,
9	    async request(req) {
10	      calls.push(req)
11	      return handler(req, calls.length)
12	    },
13	  }
14	}
15	
16	test('charge sends KRW amount and returns status', async () => {
17	  const gw = fakeGateway(() => ({ status: 'DONE', paymentKey: 'pk_1' }))
18	  const res = await charge(gw, { orderId: 'ord_1', amount: 108900 })
19	  assert.equal(res.status, 'DONE')
20	  assert.equal(gw.calls[0].body.currency, 'KRW')
21	})
22	
23	test('charge rejects non-integer amount', async () => {
24	  const gw = fakeGateway(() => ({ status: 'DONE' }))
25	  await assert.rejects(charge(gw, { orderId: 'ord_1', amount: 100.5 }), RangeError)
26	})
27	
28	test('charge propagates gateway errors', async () => {
29	  const gw = fakeGateway(() => {
30	    throw new GatewayError('DECLINED', 'card declined')
31	  })
32	  await assert.rejects(charge(gw, { orderId: 'ord_1', amount: 1000 }), (e) => e.code === 'DECLINED')
33	})
34	

The file /src/payment.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/payment.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (1.188875ms)
✔ fixed coupon never goes below zero (0.156667ms)
✔ formatKRW adds thousands separators (12.785125ms)
✔ createInvoice sums lines and adds VAT (1.093542ms)
✔ createInvoice truncates VAT below 1 KRW (0.090042ms)
✔ charge sends KRW amount and returns status (1.693292ms)
✔ charge rejects non-integer amount (0.542625ms)
✔ charge propagates gateway errors (0.207292ms)
✔ charge retries transient gateway failures and succeeds (0.180709ms)
✔ charge gives up after exhausting retries (0.216958ms)
✔ charge does not retry non-retryable gateway errors (0.262208ms)
✔ charge retries on unexpected network errors (0.272375ms)
✔ findPlan returns the plan by id (0.711542ms)
✔ findPlan throws on unknown id (0.1915ms)
✔ plan ids are unique (0.0605ms)
✔ cycleBounds: anchor before the date (3.6135ms)
✔ cycleBounds: anchor after the date goes to previous month (0.221167ms)
✔ cycleBounds rejects anchor outside 1..28 (0.425458ms)
✔ prorate: remaining days over cycle days, truncated (0.156125ms)
ℹ tests 19
ℹ suites 0
ℹ pass 19
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 161.0165

1	export class GatewayError extends Error {
2	  constructor(code, message) {
3	    super(message ?? code)
4	    this.name = 'GatewayError'
5	    this.code = code
6	  }
7	}
8	
9	// PayKo payment request.
10	// gateway.request({ path, headers, body }) returns { status, paymentKey } or throws GatewayError.
11	export async function charge(gateway, { orderId, amount, method = 'card' }) {
12	  if (!Number.isInteger(amount) || amount <= 0) {
13	    throw new RangeError('amount must be a positive integer (KRW)')
14	  }
15	  const res = await gateway.request({
16	    path: '/v1/payments',
17	    headers: {},
18	    body: { orderId, amount, currency: 'KRW', method },
19	  })
20	  return { status: res.status, paymentKey: res.paymentKey }
21	}
22	

/.git
/CLAUDE.md
/package.json
/README.md
/src/coupons.js
/src/dates.js
/src/format.js
/src/invoice.js
/src/payment.js
/src/plans.js
/src/proration.js
/test/coupons.test.js
/test/format.test.js
/test/invoice.test.js
/test/payment.test.js
/test/plans.test.js
/test/proration.test.js

1	import { test } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { charge, GatewayError } from '../src/payment.js'
4	
5	function fakeGateway(handler) {
6	  const calls = []
7	  return {
8	    calls,
9	    async request(req) {
10	      calls.push(req)
11	      return handler(req, calls.length)
12	    },
13	  }
14	}
15	
16	test('charge sends KRW amount and returns status', async () => {
17	  const gw = fakeGateway(() => ({ status: 'DONE', paymentKey: 'pk_1' }))
18	  const res = await charge(gw, { orderId: 'ord_1', amount: 108900 })
19	  assert.equal(res.status, 'DONE')
20	  assert.equal(gw.calls[0].body.currency, 'KRW')
21	})
22	
23	test('charge rejects non-integer amount', async () => {
24	  const gw = fakeGateway(() => ({ status: 'DONE' }))
25	  await assert.rejects(charge(gw, { orderId: 'ord_1', amount: 100.5 }), RangeError)
26	})
27	
28	test('charge propagates gateway errors', async () => {
29	  const gw = fakeGateway(() => {
30	    throw new GatewayError('DECLINED', 'card declined')
31	  })
32	  await assert.rejects(charge(gw, { orderId: 'ord_1', amount: 1000 }), (e) => e.code === 'DECLINED')
33	})
34	

/src/payment.js:1:export class GatewayError extends Error {
/src/payment.js:4:    this.name = 'GatewayError'
/src/payment.js:10:// gateway.request({ path, headers, body }) returns { status, paymentKey } or throws GatewayError.
/src/payment.js:15:  const res = await gateway.request({
/test/payment.test.js:3:import { charge, GatewayError } from '../src/payment.js'
/test/payment.test.js:30:    throw new GatewayError('DECLINED', 'card declined')

The file /src/payment.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/payment.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (0.638041ms)
✔ fixed coupon never goes below zero (0.157583ms)
✔ formatKRW adds thousands separators (15.666458ms)
✔ createInvoice sums lines and adds VAT (1.709833ms)
✔ createInvoice truncates VAT below 1 KRW (0.207542ms)
✔ charge sends KRW amount and returns status (0.865083ms)
✔ charge rejects non-integer amount (0.277417ms)
✔ charge propagates gateway errors (0.09975ms)
✔ charge retries on transient gateway errors and succeeds (0.09875ms)
✔ charge gives up after exhausting retries (0.11975ms)
✔ charge does not retry non-retryable gateway errors (0.071417ms)
✔ charge retries on unexpected non-gateway errors (0.088042ms)
✔ findPlan returns the plan by id (0.686792ms)
✔ findPlan throws on unknown id (0.236708ms)
✔ plan ids are unique (0.259042ms)
✔ cycleBounds: anchor before the date (3.017333ms)
✔ cycleBounds: anchor after the date goes to previous month (0.093208ms)
✔ cycleBounds rejects anchor outside 1..28 (0.186ms)
✔ prorate: remaining days over cycle days, truncated (0.087458ms)
ℹ tests 19
ℹ suites 0
ℹ pass 19
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 152.136166

export class GatewayError extends Error {
  constructor(code, message) {
    super(message ?? code)
    this.name = 'GatewayError'
    this.code = code
  }
}

// PayKo payment request.
// gateway.request({ path, headers, body }) returns { status, paymentKey } or throws GatewayError.
export async function charge(gateway, { orderId, amount, method = 'card' }) {
  if (!Number.isInteger(amount) || amount <= 0) {
    throw new RangeError('amount must be a positive integer (KRW)')
  }
  const res = await gateway.request({
    path: '/v1/payments',
    headers: {},
    body: { orderId, amount, currency: 'KRW', method },
  })
  return { status: res.status, paymentKey: res.paymentKey }
}

total 32
drwxr-xr-x@ 9 user  staff  288  8월 25 23:08 .
drwx------@ 3 user  staff   96  8월 25 23:08 ..
-rw-r--r--@ 1 user  staff  112  8월 25 23:08 .git
-rw-r--r--@ 1 user  staff  109  8월 25 23:08 CLAUDE.md
drwxr-xr-x@ 4 user  staff  128  8월 25 23:08 docs
-rw-r--r--@ 1 user  staff  139  8월 25 23:08 package.json
-rw-r--r--@ 1 user  staff  574  8월 25 23:08 README.md
drwxr-xr-x@ 9 user  staff  288  8월 25 23:08 src
drwxr-xr-x@ 8 user  staff  256  8월 25 23:08 test
./test/plans.test.js
./test/payment.test.js
./test/proration.test.js
./test/coupons.test.js
./test/invoice.test.js
./test/format.test.js
{
  "name": "workhub-billing",
  "version": "0.4.2",
  "private": true,
  "type": "module",
  "scripts": {
    "test": "node --test"
  }
}

import { test } from 'node:test'
import assert from 'node:assert/strict'
import { charge, GatewayError } from '../src/payment.js'

function fakeGateway(handler) {
  const calls = []
  return {
    calls,
    async request(req) {
      calls.push(req)
      return handler(req, calls.length)
    },
  }
}

test('charge sends KRW amount and returns status', async () => {
  const gw = fakeGateway(() => ({ status: 'DONE', paymentKey: 'pk_1' }))
  const res = await charge(gw, { orderId: 'ord_1', amount: 108900 })
  assert.equal(res.status, 'DONE')
  assert.equal(gw.calls[0].body.currency, 'KRW')
})

test('charge rejects non-integer amount', async () => {
  const gw = fakeGateway(() => ({ status: 'DONE' }))
  await assert.rejects(charge(gw, { orderId: 'ord_1', amount: 100.5 }), RangeError)
})

test('charge propagates gateway errors', async () => {
  const gw = fakeGateway(() => {
    throw new GatewayError('DECLINED', 'card declined')
  })
  await assert.rejects(charge(gw, { orderId: 'ord_1', amount: 1000 }), (e) => e.code === 'DECLINED')
})

coupons.js
dates.js
format.js
invoice.js
payment.js
plans.js
proration.js
/docs/payment-gateway-payko.md:21:- Generate a new key per request, but **when retrying the same payment, always send the same key again.** A new key on every retry is the same as no key.
/docs/payment-gateway-payko.md:22:- This was the cause of the March 2024 double-charge incident (INC-2024-03). A retry after a timeout had no key, and 27 customers were charged
/docs/payment-gateway-payko.md:25:### 2.2 Error codes and whether to retry
/docs/payment-gateway-payko.md:39:- Retrying a declined code trips the card network's fraud detection. PayKo tracks the "retry after decline" ratio per merchant, sends a warning when
/docs/payment-gateway-payko.md:43:  retrying with a different key creates a double charge.
/docs/payment-gateway-payko.md:48:- If all 3 attempts fail, record the payment as failed; the billing batch tries once more the next day at 09:00 (batch retry is a separate system).
/docs/payment-gateway-payko.md:100:- Generating a new idempotency key on each retry. One set of attempts for one payment shares one key.

1	# PG (PayKo) integration contract and operational notes
2	
3	We use a single PG, PayKo. `charge` in `src/payment.js` is a thin function that calls PayKo `/v1/payments`.
4	How the PayKo API behaves, what the contract restricts, and what went wrong in the past are not in the code. This document records them.
5	
6	## 1. Contract overview
7	
8	- Contract signed March 2022. Three payment methods: card, virtual account, bank transfer.
9	- Fees: card 2.3%, virtual account 300 KRW per transaction, bank transfer 1.5%.
10	- Settlement: D+2 business days. Settlement files arrive daily at 06:00 over SFTP; the finance team reconciles them against invoices.
11	- The PayKo contact channel and incident phone numbers are on the internal wiki under "Payments/PayKo". They are not recorded here.
12	
13	## 2. API behavior
14	
15	### 2.1 Idempotency key (`Idempotency-Key` header)
16	
17	- If a request carries an `Idempotency-Key` header, PayKo **returns the first response unchanged for any request with the same key for 24 hours.**
18	  It does not create a second payment.
19	- Without the header, every request creates a new payment. The same `orderId` does not prevent this (`DUPLICATE_ORDER` is raised only after a payment is
20	  `DONE`; while one is in progress, both can go through).
21	- Generate a new key per request, but **when retrying the same payment, always send the same key again.** A new key on every retry is the same as no key.
22	- This was the cause of the March 2024 double-charge incident (INC-2024-03). A retry after a timeout had no key, and 27 customers were charged
23	  twice. Refunds and the apology notice took two weeks.
24	
25	### 2.2 Error codes and whether to retry
26	
27	| Class | Code | Meaning | Retry |
28	|---|---|---|---|
29	| Transient | `NETWORK_ERROR` | Connection failed | Yes |
30	| Transient | `GATEWAY_TIMEOUT` | PayKo got no response from the card network. **The payment may have succeeded** | Only with the same idempotency key |
31	| Transient | `PROVIDER_UNAVAILABLE` | Card network maintenance | Yes |
32	| Limit | `RATE_LIMITED` | Requests per second exceeded | After 2 seconds |
33	| Declined | `DECLINED` | Declined by the card issuer | **Never** |
34	| Declined | `INSUFFICIENT_FUNDS` | Over limit or insufficient balance | **Never** |
35	| Declined | `INVALID_CARD` | Bad or expired card details | **Never** |
36	| Declined | `FRAUD_SUSPECTED` | Flagged by fraud detection | **Never**. Escalate to CS immediately |
37	| Duplicate | `DUPLICATE_ORDER` | Same `orderId` already `DONE` | Never. Look up the existing payment |
38	
39	- Retrying a declined code trips the card network's fraud detection. PayKo tracks the "retry after decline" ratio per merchant, sends a warning when
40	  it passes a threshold, and suspends payments on the third warning. We received the first warning in May 2024 (INC-2024-05).
41	  That time the cause was a person clicking "charge again" repeatedly in the CS tool, but automatic retries count the same way.
42	- `GATEWAY_TIMEOUT` may mean the payment actually succeeded. Retrying with the same idempotency key returns the successful payment's response;
43	  retrying with a different key creates a double charge.
44	
45	### 2.3 Retry count and interval
46	
47	- PayKo integration guide: for transient errors, **at most 3 attempts, at least 2 seconds apart**. Beyond that you get `RATE_LIMITED`.
48	- If all 3 attempts fail, record the payment as failed; the billing batch tries once more the next day at 09:00 (batch retry is a separate system).
49	
50	### 2.4 Payment status
51	
52	| Status | Meaning |
53	|---|---|
54	| `DONE` | Payment complete |
55	| `WAITING_FOR_DEPOSIT` | Virtual account issued, waiting for deposit. **Not a failure** |
56	| `CANCELED` | Canceled |
57	| `EXPIRED` | Virtual account deposit window (3 days) passed |
58	
59	- For virtual accounts the request response is `WAITING_FOR_DEPOSIT`, and `DONE` arrives later by webhook when the deposit lands. Do not treat the
60	  request response alone as a failure.
61	
62	## 3. Request rules
63	
64	- `orderId`: at most 64 characters, alphanumeric plus `_` and `-`. Must be unique within the merchant. Use the invoice number as is.
65	- `amount`: integer KRW. Card payments under 100 KRW return `INVALID_AMOUNT`. Zero-amount invoices do not call PayKo.
66	- `currency`: always `KRW`. No other currency is in the contract.
67	- Card payments over 5,000,000 KRW may require extra authentication from PayKo. Enterprise does not pay by card, so this is rare in practice.
68	
69	## 4. Test environment
70	
71	- Sandbox keys start with `pk_test_`. In the sandbox, `amount` `1004` returns `DECLINED` and `5000` returns `GATEWAY_TIMEOUT`.
72	- Unit tests do not call PayKo; they inject a fake `gateway` object. Integration tests run against the sandbox once a week.
73	
74	## 5. Settlement reconciliation
75	
76	- Match the `paymentKey` in each daily settlement file against the invoice's payment record. Unmatched rows go to the finance team.
77	- Store `paymentKey` **exactly** as received in the payment response. Refunds, cancellations, and reconciliation all key on it.
78	
79	## 6. Webhooks
80	
81	- PayKo POSTs to `/webhooks/payko` when a payment status changes: virtual account deposit (`DONE`), expiry (`EXPIRED`), cancellation (`CANCELED`).
82	- Verify the request signature header (`PayKo-Signature`). On verification failure respond 400 and do not process.
83	- If PayKo does not receive a 2xx it resends the same webhook **up to 5 times**. Webhook handling must therefore produce the same result when the same
84	  `paymentKey` and status arrive twice.
85	- There have been cases where the webhook arrived before the payment request's response (rarely, on card payments). If no payment record exists for the
86	  `paymentKey`, reprocess after 30 seconds.
87	
88	## 7. Cancellation and refunds
89	
90	- The cancel API is `/v1/payments/{paymentKey}/cancel`. Partial cancellation uses `cancelAmount`. Cancellation also uses an idempotency key.
91	- Cancel only after finance approval. The billing system calls cancel automatically in exactly **one** case: an upgrade payment succeeded but saving the
92	  plan change failed.
93	- Refunding a virtual account payment is a transfer to the customer's bank account and requires `refundReceiveAccount`. CS collects it from the customer.
94	- Card cancellations are authorization reversals; after settlement (D+2 or later) they become capture cancellations and show up as refunds on the
95	  customer's card statement.
96	
97	## 8. Common implementation mistakes
98	
99	- Retrying every exception. Declined codes are never retried.
100	- Generating a new idempotency key on each retry. One set of attempts for one payment shares one key.
101	- Treating `GATEWAY_TIMEOUT` as a definite failure. Retry with the same key or confirm through the lookup API.
102	- Treating `WAITING_FOR_DEPOSIT` as a failure.
103	- Retrying with no delay. At least 2 seconds, at most 3 attempts.
104	- Transforming `paymentKey` before storing it. Store it as received.
105	- Calling PayKo for a zero-amount invoice. Record zero-amount invoices as `DONE` with no payment.
106	

v25.6.1
function

The file /src/payment.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/payment.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (1.331459ms)
✔ fixed coupon never goes below zero (0.198ms)
✔ formatKRW adds thousands separators (16.552083ms)
✔ createInvoice sums lines and adds VAT (1.512667ms)
✔ createInvoice truncates VAT below 1 KRW (0.21125ms)
✔ charge sends KRW amount and returns status (1.41625ms)
✔ charge rejects non-integer amount (0.335833ms)
✔ charge propagates gateway errors (0.207208ms)
✔ charge retries transient errors and succeeds (2.432291ms)
✔ charge reuses the same idempotency key across retries (0.351291ms)
✔ charge gives up after 3 attempts and throws the last transient error (0.368042ms)
✔ charge does not retry declined or duplicate errors (0.464584ms)
✔ findPlan returns the plan by id (0.878833ms)
✔ findPlan throws on unknown id (0.223458ms)
✔ plan ids are unique (0.060333ms)
✔ cycleBounds: anchor before the date (2.541542ms)
✔ cycleBounds: anchor after the date goes to previous month (0.076583ms)
✔ cycleBounds rejects anchor outside 1..28 (0.176625ms)
✔ prorate: remaining days over cycle days, truncated (0.083ms)
ℹ tests 19
ℹ suites 0
ℹ pass 19
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 160.156375

1	export const PLANS = [
2	  { id: 'starter', name: 'Starter', monthlyPrice: 29000, seatLimit: 5, legacy: false },
3	  { id: 'team', name: 'Team', monthlyPrice: 99000, seatLimit: 20, legacy: false },
4	  { id: 'business', name: 'Business', monthlyPrice: 290000, seatLimit: 100, legacy: false },
5	  { id: 'L-startup-2019', name: 'Startup (2019)', monthlyPrice: 49000, seatLimit: 10, legacy: true },
6	  { id: 'L-growth-2019', name: 'Growth (2019)', monthlyPrice: 149000, seatLimit: 30, legacy: true },
7	]
8	
9	export function findPlan(id) {
10	  const plan = PLANS.find((p) => p.id === id)
11	  if (!plan) throw new Error(`unknown plan: ${id}`)
12	  return plan
13	}
14	

./test/plans.test.js
./test/payment.test.js
./test/proration.test.js
./test/coupons.test.js
./test/invoice.test.js
./test/format.test.js
./src/plans.js

1	import { test } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { PLANS, findPlan } from '../src/plans.js'
4	
5	test('findPlan returns the plan by id', () => {
6	  assert.equal(findPlan('team').monthlyPrice, 99000)
7	})
8	
9	test('findPlan throws on unknown id', () => {
10	  assert.throws(() => findPlan('nope'), /unknown plan/)
11	})
12	
13	test('plan ids are unique', () => {
14	  assert.equal(new Set(PLANS.map((p) => p.id)).size, PLANS.length)
15	})
16	

The file /src/plans.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/plans.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/plans.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (0.952417ms)
✔ fixed coupon never goes below zero (0.267208ms)
✔ formatKRW adds thousands separators (16.788167ms)
✔ createInvoice sums lines and adds VAT (0.846834ms)
✔ createInvoice truncates VAT below 1 KRW (0.089708ms)
✔ charge sends KRW amount and returns status (0.861166ms)
✔ charge rejects non-integer amount (0.258166ms)
✔ charge propagates gateway errors (0.099417ms)
✔ findPlan returns the plan by id (1.415334ms)
✔ findPlan throws on unknown id (0.40575ms)
✔ plan ids are unique (0.146042ms)
✔ listPlansByPrice sorts plans by monthly price ascending (1.572625ms)
✔ listPlansByPrice does not mutate the original PLANS array (0.219875ms)
✔ cycleBounds: anchor before the date (3.585042ms)
✔ cycleBounds: anchor after the date goes to previous month (0.091334ms)
✔ cycleBounds rejects anchor outside 1..28 (0.477375ms)
✔ prorate: remaining days over cycle days, truncated (0.108834ms)
ℹ tests 17
ℹ suites 0
ℹ pass 17
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 153.223708

1	export const PLANS = [
2	  { id: 'starter', name: 'Starter', monthlyPrice: 29000, seatLimit: 5, legacy: false },
3	  { id: 'team', name: 'Team', monthlyPrice: 99000, seatLimit: 20, legacy: false },
4	  { id: 'business', name: 'Business', monthlyPrice: 290000, seatLimit: 100, legacy: false },
5	  { id: 'L-startup-2019', name: 'Startup (2019)', monthlyPrice: 49000, seatLimit: 10, legacy: true },
6	  { id: 'L-growth-2019', name: 'Growth (2019)', monthlyPrice: 149000, seatLimit: 30, legacy: true },
7	]
8	
9	export function findPlan(id) {
10	  const plan = PLANS.find((p) => p.id === id)
11	  if (!plan) throw new Error(`unknown plan: ${id}`)
12	  return plan
13	}
14	

./test/plans.test.js
./test/payment.test.js
./test/proration.test.js
./test/coupons.test.js
./test/invoice.test.js
./test/format.test.js

1	import { test } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { PLANS, findPlan } from '../src/plans.js'
4	
5	test('findPlan returns the plan by id', () => {
6	  assert.equal(findPlan('team').monthlyPrice, 99000)
7	})
8	
9	test('findPlan throws on unknown id', () => {
10	  assert.throws(() => findPlan('nope'), /unknown plan/)
11	})
12	
13	test('plan ids are unique', () => {
14	  assert.equal(new Set(PLANS.map((p) => p.id)).size, PLANS.length)
15	})
16	

The file /src/plans.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/plans.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/plans.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (1.182416ms)
✔ fixed coupon never goes below zero (0.192833ms)
✔ formatKRW adds thousands separators (15.448ms)
✔ createInvoice sums lines and adds VAT (0.805875ms)
✔ createInvoice truncates VAT below 1 KRW (0.222625ms)
✔ charge sends KRW amount and returns status (1.760875ms)
✔ charge rejects non-integer amount (0.633125ms)
✔ charge propagates gateway errors (0.127667ms)
✔ findPlan returns the plan by id (0.95475ms)
✔ findPlan throws on unknown id (0.349417ms)
✔ plan ids are unique (0.208166ms)
✔ listPlansByPrice sorts plans by monthly price ascending (1.73125ms)
✔ cycleBounds: anchor before the date (2.35475ms)
✔ cycleBounds: anchor after the date goes to previous month (0.08ms)
✔ cycleBounds rejects anchor outside 1..28 (0.169917ms)
✔ prorate: remaining days over cycle days, truncated (0.087208ms)
ℹ tests 16
ℹ suites 0
ℹ pass 16
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 145.834959

1	export const PLANS = [
2	  { id: 'starter', name: 'Starter', monthlyPrice: 29000, seatLimit: 5, legacy: false },
3	  { id: 'team', name: 'Team', monthlyPrice: 99000, seatLimit: 20, legacy: false },
4	  { id: 'business', name: 'Business', monthlyPrice: 290000, seatLimit: 100, legacy: false },
5	  { id: 'L-startup-2019', name: 'Startup (2019)', monthlyPrice: 49000, seatLimit: 10, legacy: true },
6	  { id: 'L-growth-2019', name: 'Growth (2019)', monthlyPrice: 149000, seatLimit: 30, legacy: true },
7	]
8	
9	export function findPlan(id) {
10	  const plan = PLANS.find((p) => p.id === id)
11	  if (!plan) throw new Error(`unknown plan: ${id}`)
12	  return plan
13	}
14	

/test/plans.test.js

1	import { test } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { PLANS, findPlan } from '../src/plans.js'
4	
5	test('findPlan returns the plan by id', () => {
6	  assert.equal(findPlan('team').monthlyPrice, 99000)
7	})
8	
9	test('findPlan throws on unknown id', () => {
10	  assert.throws(() => findPlan('nope'), /unknown plan/)
11	})
12	
13	test('plan ids are unique', () => {
14	  assert.equal(new Set(PLANS.map((p) => p.id)).size, PLANS.length)
15	})
16	

The file /src/plans.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/plans.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/plans.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (1.320625ms)
✔ fixed coupon never goes below zero (0.1695ms)
✔ formatKRW adds thousands separators (13.72125ms)
✔ createInvoice sums lines and adds VAT (1.714083ms)
✔ createInvoice truncates VAT below 1 KRW (0.209084ms)
✔ charge sends KRW amount and returns status (0.756958ms)
✔ charge rejects non-integer amount (0.286542ms)
✔ charge propagates gateway errors (0.096459ms)
✔ findPlan returns the plan by id (1.786916ms)
✔ findPlan throws on unknown id (0.38975ms)
✔ plan ids are unique (0.124667ms)
✔ listPlansByPrice sorts plans by monthly price ascending (1.609375ms)
✔ listPlansByPrice does not mutate PLANS (0.084209ms)
✔ cycleBounds: anchor before the date (3.140375ms)
✔ cycleBounds: anchor after the date goes to previous month (0.17225ms)
✔ cycleBounds rejects anchor outside 1..28 (0.202792ms)
✔ prorate: remaining days over cycle days, truncated (0.100958ms)
ℹ tests 17
ℹ suites 0
ℹ pass 17
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 161.953916

1	export const PLANS = [
2	  { id: 'starter', name: 'Starter', monthlyPrice: 29000, seatLimit: 5, legacy: false },
3	  { id: 'team', name: 'Team', monthlyPrice: 99000, seatLimit: 20, legacy: false },
4	  { id: 'business', name: 'Business', monthlyPrice: 290000, seatLimit: 100, legacy: false },
5	  { id: 'L-startup-2019', name: 'Startup (2019)', monthlyPrice: 49000, seatLimit: 10, legacy: true },
6	  { id: 'L-growth-2019', name: 'Growth (2019)', monthlyPrice: 149000, seatLimit: 30, legacy: true },
7	]
8	
9	export function findPlan(id) {
10	  const plan = PLANS.find((p) => p.id === id)
11	  if (!plan) throw new Error(`unknown plan: ${id}`)
12	  return plan
13	}
14	

(eval):1: no matches found: tests*
./test/plans.test.js
./src/plans.js

1	import { test } from 'node:test'
2	import assert from 'node:assert/strict'
3	import { PLANS, findPlan } from '../src/plans.js'
4	
5	test('findPlan returns the plan by id', () => {
6	  assert.equal(findPlan('team').monthlyPrice, 99000)
7	})
8	
9	test('findPlan throws on unknown id', () => {
10	  assert.throws(() => findPlan('nope'), /unknown plan/)
11	})
12	
13	test('plan ids are unique', () => {
14	  assert.equal(new Set(PLANS.map((p) => p.id)).size, PLANS.length)
15	})
16	

The file /src/plans.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/plans.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

The file /test/plans.test.js has been updated successfully. (file state is current in your context — no need to Read it back)

> workhub-billing@0.4.2 test
> node --test

✔ percent coupon (0.983208ms)
✔ fixed coupon never goes below zero (0.226041ms)
✔ formatKRW adds thousands separators (17.310833ms)
✔ createInvoice sums lines and adds VAT (1.6405ms)
✔ createInvoice truncates VAT below 1 KRW (0.330834ms)
✔ charge sends KRW amount and returns status (0.860375ms)
✔ charge rejects non-integer amount (0.922334ms)
✔ charge propagates gateway errors (0.3755ms)
✔ findPlan returns the plan by id (0.953625ms)
✔ findPlan throws on unknown id (0.226708ms)
✔ plan ids are unique (0.066208ms)
✔ listPlansByPrice sorts plans by monthly price ascending (1.049708ms)
✔ cycleBounds: anchor before the date (5.848416ms)
✔ cycleBounds: anchor after the date goes to previous month (0.0955ms)
✔ cycleBounds rejects anchor outside 1..28 (0.204291ms)
✔ prorate: remaining days over cycle days, truncated (0.094958ms)
ℹ tests 16
ℹ suites 0
ℹ pass 16
ℹ fail 0
ℹ cancelled 0
ℹ skipped 0
ℹ todo 0
ℹ duration_ms 195.485042