Round subscription price and payment amount

src/api/subscriptions.ts

@@ -4,6 +4,7 @@ import { DateTime } from "luxon"
 
 import { BACKEND_URL } from "@/constants"
 import { ethereumAddressMatch, EthereumSignature } from "@/utils/ethereum"
+import { roundBigNumber } from "@/utils/numbers"
 import { http } from "./common"
 import { Contracts, getContract } from "./contracts"
 
@@ -70,7 +71,7 @@ export class Subscription {
   }
 
   get pricePerMonthInt(): BigNumber {
-    return this.price.mul(SECONDS_IN_MONTH)
+    return roundBigNumber(this.price.mul(SECONDS_IN_MONTH), 4)
   }
 
   get pricePerMonth(): FixedNumber {

src/utils/numbers.ts

@@ -0,0 +1,13 @@
+import { BigNumber } from "@ethersproject/bignumber"
+
+export function roundBigNumber(value: BigNumber, precision: number): BigNumber {
+  const decimals = value.toString().length
+  const divisor = BigNumber.from(10).pow(decimals - precision)
+  const remainder = value.mod(divisor)
+  const midpoint = BigNumber.from(10).pow(Math.max(decimals - precision - 1, 0)).mul(5)
+  if (remainder.gte(midpoint)) {
+    return value.div(divisor).add(1).mul(divisor)
+  } else {
+    return value.div(divisor).mul(divisor)
+  }
+}

tests/unit/numbers.spec.ts

@@ -0,0 +1,14 @@
+import { expect } from "chai"
+import { BigNumber } from "@ethersproject/bignumber"
+import { roundBigNumber } from "@/utils/numbers"
+
+describe("Numbers utils", () => {
+  it("Should round big number", () => {
+    const value = BigNumber.from(534985)
+    expect(roundBigNumber(value, 2).toNumber()).to.equal(530000)
+    expect(roundBigNumber(value, 3).toNumber()).to.equal(535000)
+    expect(roundBigNumber(value, 4).toNumber()).to.equal(535000)
+    expect(roundBigNumber(value, 5).toNumber()).to.equal(534990)
+    expect(roundBigNumber(value, 6).toNumber()).to.equal(534985)
+  })
+})