feat(api): add exchange rate api (#146)

.vscode/settings.json

@@ -14,6 +14,7 @@
   },
   "editor.formatOnSave": true,
   "cSpell.words": [
+    "EXCHANGERATES",
     "hono",
     "openai"
   ]

apps/api/package.json

@@ -24,6 +24,7 @@
     "@prisma/client": "^5.16.0",
     "@vercel/blob": "^0.23.4",
     "dayjs": "^1.11.11",
+    "got": "^14.4.1",
     "hono": "^4.4.8",
     "next": "^14.2.4",
     "openai": "^4.52.7",

apps/api/prisma/migrations/20240718080526_add_currency_exchange_rate/migration.sql

@@ -0,0 +1,15 @@
+-- CreateTable
+CREATE TABLE "CurrencyExchangeRate" (
+    "id" TEXT NOT NULL,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL,
+    "fromCurrency" TEXT NOT NULL,
+    "toCurrency" TEXT NOT NULL,
+    "rate" DECIMAL(65,30) NOT NULL,
+    "date" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "CurrencyExchangeRate_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "CurrencyExchangeRate_fromCurrency_toCurrency_date_key" ON "CurrencyExchangeRate"("fromCurrency", "toCurrency", "date");

apps/api/prisma/migrations/20240718080935_set_exchange_rate_date_to_string/migration.sql

@@ -0,0 +1,2 @@
+-- AlterTable
+ALTER TABLE "CurrencyExchangeRate" ALTER COLUMN "date" SET DATA TYPE TEXT;

apps/api/prisma/schema.prisma

@@ -199,3 +199,16 @@ model CachedGptResponse {
   query    String
   response String
 }
+
+model CurrencyExchangeRate {
+  id        String   @id @default(cuid())
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+
+  fromCurrency String
+  toCurrency   String
+  rate         Decimal
+  date         String // YYYY-MM-DD
+
+  @@unique([fromCurrency, toCurrency, date])
+}

apps/api/types/got-fix.d.ts

@@ -0,0 +1,4 @@
+declare module 'got' {
+  import * as got from 'got/dist/source'
+  export = got
+}

apps/api/v1/index.ts

@@ -3,11 +3,13 @@ import { authMiddleware } from './middlewares/auth'
 import authApp from './routes/auth'
 import budgetsApp from './routes/budgets'
 import categoriesApp from './routes/categories'
+import exchangeRatesApp from './routes/exchange-rates'
 import transactionsApp from './routes/transactions'
 import usersApp from './routes/users'
 import walletsApp from './routes/wallets'
 
 export const hono = new Hono()
+  .route('/exchange-rates', exchangeRatesApp)
 
   .use('*', authMiddleware)
 

apps/api/v1/routes/exchange-rates.ts

@@ -0,0 +1,70 @@
+import { zValidator } from '@hono/zod-validator'
+import { Hono } from 'hono'
+import { z } from 'zod'
+import {
+  getExchangeRate,
+  getExchangeRates,
+} from '../services/exchange-rates.service'
+
+const router = new Hono()
+  .use(async (c, next) => {
+    const apiKey = c.req.header('x-api-key')
+
+    if (!apiKey || apiKey !== process.env.API_SECRET_KEY) {
+      return c.json({ message: 'Unauthorized' }, 401)
+    }
+
+    await next()
+  })
+
+  .get(
+    '/',
+    zValidator(
+      'query',
+      z.object({
+        date: z.string().default('latest'),
+      }),
+    ),
+    async (c) => {
+      const { date } = c.req.valid('query')
+
+      const exchangeRates = await getExchangeRates({ date })
+
+      return c.json(exchangeRates)
+    },
+  )
+
+  .get(
+    '/:fromCurrency/:toCurrency',
+    zValidator(
+      'query',
+      z.object({
+        date: z.string().default('latest'),
+      }),
+    ),
+    zValidator(
+      'param',
+      z.object({
+        fromCurrency: z.string(),
+        toCurrency: z.string(),
+      }),
+    ),
+    async (c) => {
+      const { fromCurrency, toCurrency } = c.req.valid('param')
+      const { date } = c.req.valid('query')
+
+      const exchangeRate = await getExchangeRate({
+        date,
+        fromCurrency: fromCurrency,
+        toCurrency: toCurrency,
+      })
+
+      if (!exchangeRate) {
+        return c.json({ message: 'Exchange rate not found' }, 404)
+      }
+
+      return c.json(exchangeRate)
+    },
+  )
+
+export default router

apps/api/v1/services/exchange-rates.service.ts

@@ -0,0 +1,138 @@
+import got from 'got'
+import { getLogger } from '../../lib/log'
+import prisma from '../../lib/prisma'
+
+const API_KEY = process.env.EXCHANGERATES_API_KEY
+const BASE_URL = 'http://api.exchangeratesapi.io/v1/'
+const BASE_CURRENCY = 'EUR'
+const DEFAULT_SYMBOLS = ['USD', 'JPY', 'AUD', 'VND', 'SGD', 'CNY']
+const client = got.extend({
+  prefixUrl: BASE_URL,
+})
+
+export async function getExchangeRates({
+  date = 'latest',
+  base = BASE_CURRENCY,
+  symbols = DEFAULT_SYMBOLS,
+}: {
+  date?: string | 'latest'
+  base?: string
+  symbols?: string[]
+}) {
+  const logger = getLogger(`services.exchange-rates:${getExchangeRates.name}`)
+  logger.debug(
+    'Getting exchange rates. Date: %s, Base: %s, Symbols: %o',
+    date,
+    base,
+    symbols,
+  )
+
+  // YYYY-MM-DD
+  const dateStr = (date === 'latest' ? new Date() : new Date(date))
+    .toISOString()
+    .split('T')[0]
+
+  // Find records in database
+  const rates = await prisma.currencyExchangeRate.findMany({
+    where: {
+      date: dateStr,
+      fromCurrency: base,
+      toCurrency: {
+        in: symbols,
+      },
+    },
+  })
+
+  // If some rates are missing, call the API
+  const missingSymbols = symbols.filter(
+    (symbol) =>
+      !rates.find(
+        (rate) => rate.toCurrency === symbol && rate.fromCurrency === base,
+      ),
+  )
+
+  if (missingSymbols.length === 0) {
+    logger.debug('All rates are found in the database')
+    return rates
+  }
+
+  const missingSymbolsStr = missingSymbols.join(',')
+
+  logger.debug('Some rates are missing. Calling the API: %s', missingSymbolsStr)
+
+  const missingRates = await client
+    .get(`${date === 'latest' ? date : dateStr}`, {
+      searchParams: {
+        access_key: API_KEY,
+        base,
+        symbols: missingSymbolsStr,
+      },
+    })
+    .json<{
+      success: boolean
+      timestamp: number
+      base: string
+      date: string
+      rates: Record<string, number>
+    }>()
+  // Save the result to database
+  logger.debug('Saving the missing rates to the database')
+  await prisma.currencyExchangeRate.createMany({
+    data: Object.entries(missingRates.rates).map(([toCurrency, rate]) => ({
+      date: missingRates.date,
+      fromCurrency: base,
+      toCurrency,
+      rate,
+    })),
+  })
+  // Return all the rates
+  const allRates = await prisma.currencyExchangeRate.findMany({
+    where: {
+      date: dateStr,
+      fromCurrency: base,
+      toCurrency: {
+        in: symbols,
+      },
+    },
+  })
+
+  logger.debug('All rates are found')
+
+  return allRates
+}
+
+export async function getExchangeRate({
+  date = 'latest',
+  fromCurrency = BASE_CURRENCY,
+  toCurrency,
+}: {
+  date?: string | 'latest'
+  fromCurrency?: string
+  toCurrency: string
+}) {
+  const baseRates = await getExchangeRates({
+    date,
+    base: BASE_CURRENCY,
+    symbols: [fromCurrency, toCurrency],
+  })
+  const fromRate = baseRates.find((rate) => rate.toCurrency === fromCurrency)
+  const toRate = baseRates.find((rate) => rate.toCurrency === toCurrency)
+
+  if (!(fromRate && toRate)) {
+    return null
+  }
+
+  const rateDecimal = toRate.rate.div(fromRate.rate)
+  const rate = rateDecimal.toNumber()
+
+  return {
+    rate,
+    rateDecimal,
+    fromCurrency,
+    toCurrency,
+    // YYYY-MM-DD
+    date: date === 'latest' ? new Date().toISOString().split('T')[0] : date,
+    [fromCurrency]: 1,
+    [toCurrency]: rate,
+  }
+}