feat: calculate rate of pay slider values for different assets (#219)

* Fetch exchange rates and convert rate of pay

* Fix conversion

* Rename to `rateOfPay`

src/background/config.ts

@@ -1,3 +1,6 @@
-export const DEFAULT_AMOUNT = '0.6'
 export const DEFAULT_SCALE = 2
 export const DEFAULT_INTERVAL_MS = 3_600_000
+
+export const DEFAULT_RATE_OF_PAY = '60'
+export const MIN_RATE_OF_PAY = '1'
+export const MAX_RATE_OF_PAY = '100'

src/background/services/openPayments.ts

@@ -13,12 +13,17 @@ import { type Request } from 'http-message-signatures'
 import { signMessage } from 'http-message-signatures/lib/httpbis'
 import { createContentDigestHeader } from 'httpbis-digest-headers'
 import { Browser } from 'webextension-polyfill'
-import { getCurrentActiveTabId, toAmount } from '../utils'
+import { getCurrentActiveTabId, getRateOfPay, toAmount } from '../utils'
 import { StorageService } from '@/background/services/storage'
 import { exportJWK, generateEd25519KeyPair } from '@/shared/crypto'
 import { bytesToHex } from '@noble/hashes/utils'
-import { getWalletInformation } from '@/shared/helpers'
+import { getExchangeRates, getWalletInformation } from '@/shared/helpers'
 import { ConnectWalletPayload } from '@/shared/messages'
+import {
+  DEFAULT_RATE_OF_PAY,
+  MAX_RATE_OF_PAY,
+  MIN_RATE_OF_PAY
+} from '../config'
 
 interface KeyInformation {
   privateKey: string
@@ -217,6 +222,35 @@ export class OpenPaymentsService {
     recurring
   }: ConnectWalletPayload) {
     const walletAddress = await getWalletInformation(walletAddressUrl)
+    const exchangeRates = await getExchangeRates()
+
+    let rateOfPay = DEFAULT_RATE_OF_PAY
+    let minRateOfPay = MIN_RATE_OF_PAY
+    let maxRateOfPay = MAX_RATE_OF_PAY
+
+    if (!exchangeRates.rates[walletAddress.assetCode]) {
+      throw new Error(`Exchange rate for ${walletAddress.assetCode} not found.`)
+    }
+
+    const exchangeRate = exchangeRates.rates[walletAddress.assetCode]
+    if (exchangeRate < 0.8 || exchangeRate > 1.5) {
+      rateOfPay = getRateOfPay({
+        rate: DEFAULT_RATE_OF_PAY,
+        exchangeRate,
+        assetScale: walletAddress.assetScale
+      })
+      minRateOfPay = getRateOfPay({
+        rate: MIN_RATE_OF_PAY,
+        exchangeRate,
+        assetScale: walletAddress.assetScale
+      })
+      maxRateOfPay = getRateOfPay({
+        rate: MAX_RATE_OF_PAY,
+        exchangeRate,
+        assetScale: walletAddress.assetScale
+      })
+    }
+
     const transformedAmount = toAmount({
       value: amount,
       recurring,
@@ -262,6 +296,9 @@ export class OpenPaymentsService {
 
     this.storage.set({
       walletAddress,
+      rateOfPay,
+      minRateOfPay,
+      maxRateOfPay,
       amount: transformedAmount,
       token: {
         value: continuation.access_token.value,

src/background/services/storage.ts

@@ -1,4 +1,4 @@
-import { DEFAULT_AMOUNT, DEFAULT_INTERVAL_MS } from '@/background/config'
+import { DEFAULT_RATE_OF_PAY, DEFAULT_INTERVAL_MS } from '@/background/config'
 import { Logger } from '@/shared/logger'
 import type {
   PopupStore,
@@ -16,6 +16,9 @@ const defaultStorage = {
   amount: null,
   token: null,
   grant: null,
+  rateOfPay: null,
+  minRateOfPay: null,
+  maxRateOfPay: null
 } satisfies Omit<Storage, 'publicKey' | 'privateKey' | 'keyId'>
 
 export class StorageService {
@@ -87,7 +90,7 @@ export class StorageService {
         website.amount = data.exceptionList[url]
       } else {
         website.amount = {
-          value: DEFAULT_AMOUNT,
+          value: DEFAULT_RATE_OF_PAY,
           interval: DEFAULT_INTERVAL_MS
         }
       }

src/background/utils.ts

@@ -1,5 +1,6 @@
 import { WalletAmount } from '@/shared/types'
 import { type Browser, action, runtime } from 'webextension-polyfill'
+import { DEFAULT_SCALE } from './config'
 
 const iconActive34 = runtime.getURL('assets/icons/icon-active-34.png')
 const iconActive128 = runtime.getURL('assets/icons/icon-active-128.png')
@@ -49,3 +50,20 @@ export const OPEN_PAYMENTS_ERRORS: Record<string, string> = {
   'invalid client':
     'Please make sure that you uploaded the public key for your desired wallet address.'
 }
+
+export interface GetRateOfPayParams {
+  rate: string
+  exchangeRate: number
+  assetScale: number
+}
+
+export const getRateOfPay = ({
+  rate,
+  exchangeRate,
+  assetScale
+}: GetRateOfPayParams) => {
+  const scaleDiff = assetScale - DEFAULT_SCALE
+  const scaledExchangeRate = (1 / exchangeRate) * 10 ** scaleDiff
+
+  return BigInt(Math.round(Number(rate) * scaledExchangeRate)).toString()
+}

src/shared/helpers.ts

@@ -58,3 +58,25 @@ export const failure = (message: string) => ({
   success: false,
   message
 })
+
+interface ExchangeRates {
+  base: string
+  rates: Record<string, number>
+}
+
+export const getExchangeRates = async (): Promise<ExchangeRates> => {
+  const response = await fetch(
+    'https://telemetry-exchange-rates.s3.amazonaws.com/exchange-rates-usd.json'
+  )
+  if (!response.ok) {
+    throw new Error(
+      `Could not fetch exchange rates. [Status code: ${response.status}]`
+    )
+  }
+  const rates = await response.json()
+  if (!rates.base || !rates.rates) {
+    throw new Error('Invalid rates format')
+  }
+
+  return rates
+}

src/shared/types.ts

@@ -33,6 +33,11 @@ export interface Storage {
   enabled: boolean
   /** If a wallet is connected or not */
   connected: boolean
+
+  rateOfPay?: string | undefined | null
+  minRateOfPay?: string | undefined | null
+  maxRateOfPay?: string | undefined | null
+
   /** User wallet address information */
   walletAddress?: WalletAddress | undefined | null
   /** Overall amount */
@@ -60,6 +65,5 @@ export type PopupStore = Omit<
 }
 
 export type DeepNonNullable<T> = {
-        [P in keyof T]?: NonNullable<T[P]>;
+  [P in keyof T]?: NonNullable<T[P]>
 }
-