[BlockchainApi] Add ability to get exchange rates from/to cGLD or cUSD

packages/blockchain-api/.env

@@ -1,6 +1,7 @@
 DEPLOY_ENV=local
 EXCHANGE_RATES_API=https://apilayer.net/api
 BLOCKSCOUT_API=https://integration-blockscout.celo-testnet.org/api
+FIREBASE_DB=https://celo-org-mobile-int.firebaseio.com
 FAUCET_ADDRESS=0x47e172F6CfB6c7D01C1574fa3E2Be7CC73269D95
 VERIFICATION_REWARDS_ADDRESS=0xb4fdaf5f3cd313654aa357299ada901b1d2dd3b5
 WEB3_PROVIDER_URL=https://integration-forno.celo-testnet.org

packages/blockchain-api/.gcloudignore

@@ -6,3 +6,6 @@ dist/
 # Exclude dependencies
 node_modules/
 .env
+
+# Exclude tests
+*.test.ts

packages/blockchain-api/.gitignore

@@ -6,5 +6,6 @@ dist/
 # Exclude dependencies
 node_modules/
 
-# keys
+# Exclude secrets
+serviceAccountKey.json
 src/secrets.json

packages/blockchain-api/__mocks__/@celo/contractkit.ts

@@ -0,0 +1,2 @@
+// Empty implementation because it currently adds ~8 secs for each test
+// TODO: investigate why

packages/blockchain-api/__mocks__/firebase-admin.ts

@@ -0,0 +1,2 @@
+export const initializeApp = jest.fn()
+export const database = jest.fn()

packages/blockchain-api/app.alfajores.yaml

@@ -5,6 +5,7 @@ env_variables:
   DEPLOY_ENV: "alfajores"
   EXCHANGE_RATES_API: "https://apilayer.net/api"
   BLOCKSCOUT_API: "https://alfajores-blockscout.celo-testnet.org/api"
+  FIREBASE_DB: "https://celo-org-mobile-alfajores.firebaseio.com"
   # TODO Pull addresses from the build artifacts of the network in protocol/build
   FAUCET_ADDRESS: "0xCEa3eF8e187490A9d85A1849D98412E5D27D1Bb3"
   VERIFICATION_REWARDS_ADDRESS: "0xb4fdaf5f3cd313654aa357299ada901b1d2dd3b5"

packages/blockchain-api/app.alfajoresstaging.yaml

@@ -5,6 +5,7 @@ env_variables:
   DEPLOY_ENV: "alfajoresstaging"
   EXCHANGE_RATES_API: "https://apilayer.net/api"
   BLOCKSCOUT_API: "https://alfajoresstaging-blockscout.celo-testnet.org/api"
+  FIREBASE_DB: "https://celo-org-mobile-alfajoresstaging.firebaseio.com"
   # TODO Pull addresses from the build artifacts of the network in protocol/build
   FAUCET_ADDRESS: "0xF4314cb9046bECe6AA54bb9533155434d0c76909"
   VERIFICATION_REWARDS_ADDRESS: "0xb4fdaf5f3cd313654aa357299ada901b1d2dd3b5"

packages/blockchain-api/app.integration.yaml

@@ -5,6 +5,7 @@ env_variables:
   DEPLOY_ENV: "integration"
   EXCHANGE_RATES_API: "https://apilayer.net/api"
   BLOCKSCOUT_API: "https://integration-blockscout.celo-testnet.org/api"
+  FIREBASE_DB: "https://celo-org-mobile-int.firebaseio.com"
   # TODO Pull addresses from the build artifacts of the network in protocol/build
   FAUCET_ADDRESS: "0x47e172F6CfB6c7D01C1574fa3E2Be7CC73269D95"
   VERIFICATION_REWARDS_ADDRESS: "0xb4fdaf5f3cd313654aa357299ada901b1d2dd3b5"

packages/blockchain-api/app.pilot.yaml

@@ -5,6 +5,7 @@ env_variables:
   DEPLOY_ENV: "pilot"
   EXCHANGE_RATES_API: "https://apilayer.net/api"
   BLOCKSCOUT_API: "https://pilot-blockscout.celo-testnet.org/api"
+  FIREBASE_DB: "https://celo-org-mobile-pilot.firebaseio.com"
   # TODO Pull addresses from the build artifacts of the network in protocol/build
   FAUCET_ADDRESS: "0x387bCb16Bfcd37AccEcF5c9eB2938E30d3aB8BF2"
   VERIFICATION_REWARDS_ADDRESS: "0xb4fdaf5f3cd313654aa357299ada901b1d2dd3b5"

packages/blockchain-api/app.pilotstaging.yaml

@@ -5,6 +5,7 @@ env_variables:
   DEPLOY_ENV: "pilotstaging"
   EXCHANGE_RATES_API: "https://apilayer.net/api"
   BLOCKSCOUT_API: "https://pilotstaging-blockscout.celo-testnet.org/api"
+  FIREBASE_DB: "https://celo-org-mobile-pilotstaging.firebaseio.com"
   # TODO Pull addresses from the build artifacts of the network in protocol/build
   FAUCET_ADDRESS: "0x545DEBe3030B570731EDab192640804AC8Cf65CA"
   VERIFICATION_REWARDS_ADDRESS: "0xb4fdaf5f3cd313654aa357299ada901b1d2dd3b5"

packages/blockchain-api/package.json

@@ -23,6 +23,7 @@
     "bignumber.js": "^7.2.0",
     "dotenv": "^6.1.0",
     "express": "^4.16.4",
+    "firebase-admin": "^8.6.1",
     "graphql": "^14.1.1",
     "utf8": "^3.0.0",
     "web3-eth-abi": "1.0.0-beta.37"

packages/blockchain-api/src/apolloServer.ts

@@ -1,6 +1,6 @@
 import { ApolloServer } from 'apollo-server-express'
 import { BlockscoutAPI } from './blockscout'
-import { CurrencyConversionAPI } from './currencyConversion'
+import CurrencyConversionAPI from './currencyConversion/CurrencyConversionAPI'
 import { resolvers, typeDefs } from './schema'
 
 export interface DataSources {

packages/blockchain-api/src/config.ts

@@ -14,10 +14,34 @@ function getSecrets(deployEnv: string) {
   return envSecrets
 }
 
+export function getFirebaseAdminCreds(admin: any) {
+  // TODO: move project to celo-org-mobile
+  // until then, using serviceAccountKey for all envs
+  // tslint:disable-next-line: no-constant-condition
+  if (true /* DEPLOY_ENV === 'local' */) {
+    try {
+      const serviceAccount = require('../serviceAccountKey.json')
+      return admin.credential.cert(serviceAccount)
+    } catch (error) {
+      console.error(
+        'Error: Could not initialize admin credentials. Is serviceAccountKey.json missing?',
+        error
+      )
+    }
+  } else {
+    try {
+      return admin.credential.applicationDefault()
+    } catch (error) {
+      console.error('Error: Could not retrieve default app creds', error)
+    }
+  }
+}
+
 export const DEPLOY_ENV = (process.env.DEPLOY_ENV as string).toLowerCase()
 export const EXCHANGE_RATES_API = (process.env.EXCHANGE_RATES_API as string).toLowerCase()
 export const { EXCHANGE_RATES_API_ACCESS_KEY } = getSecrets(DEPLOY_ENV)
 export const BLOCKSCOUT_API = (process.env.BLOCKSCOUT_API as string).toLowerCase()
+export const FIREBASE_DB = process.env.FIREBASE_DB
 export const FAUCET_ADDRESS = (process.env.FAUCET_ADDRESS as string).toLowerCase()
 export const VERIFICATION_REWARDS_ADDRESS = (process.env
   .VERIFICATION_REWARDS_ADDRESS as string).toLowerCase()

packages/blockchain-api/src/currencyConversion/CurrencyConversionAPI.test.ts

@@ -0,0 +1,134 @@
+import { InMemoryLRUCache } from 'apollo-server-caching'
+import BigNumber from 'bignumber.js'
+import CurrencyConversionAPI from './CurrencyConversionAPI'
+import ExchangeRateAPI from './ExchangeRateAPI'
+import GoldExchangeRateAPI from './GoldExchangeRateAPI'
+
+jest.mock('./ExchangeRateAPI')
+jest.mock('./GoldExchangeRateAPI')
+
+const mockDefaultGetExchangeRate = ExchangeRateAPI.prototype.getExchangeRate as jest.Mock
+mockDefaultGetExchangeRate.mockResolvedValue(new BigNumber(20))
+
+const mockGoldGetExchangeRate = GoldExchangeRateAPI.prototype.getExchangeRate as jest.Mock
+mockGoldGetExchangeRate.mockResolvedValue(new BigNumber(10))
+
+describe('CurrencyConversionAPI', () => {
+  let currencyConversionAPI: CurrencyConversionAPI
+
+  beforeEach(() => {
+    jest.clearAllMocks()
+    currencyConversionAPI = new CurrencyConversionAPI()
+    currencyConversionAPI.initialize({ context: {}, cache: new InMemoryLRUCache() })
+  })
+
+  it('should retrieve rate for cGLD/cUSD', async () => {
+    const result = await currencyConversionAPI.getExchangeRate({
+      sourceCurrencyCode: 'cGLD',
+      currencyCode: 'cUSD',
+    })
+    expect(result).toEqual(new BigNumber(10))
+    expect(mockDefaultGetExchangeRate).toHaveBeenCalledTimes(0)
+    expect(mockGoldGetExchangeRate).toHaveBeenCalledTimes(1)
+  })
+
+  it('should retrieve rate for cUSD/cGLD', async () => {
+    const result = await currencyConversionAPI.getExchangeRate({
+      sourceCurrencyCode: 'cUSD',
+      currencyCode: 'cGLD',
+    })
+    expect(result).toEqual(new BigNumber(10))
+    expect(mockDefaultGetExchangeRate).toHaveBeenCalledTimes(0)
+    expect(mockGoldGetExchangeRate).toHaveBeenCalledTimes(1)
+  })
+
+  it('should retrieve rate for cGLD/USD', async () => {
+    const result = await currencyConversionAPI.getExchangeRate({
+      sourceCurrencyCode: 'cGLD',
+      currencyCode: 'USD',
+    })
+    expect(result).toEqual(new BigNumber(10))
+    expect(mockDefaultGetExchangeRate).toHaveBeenCalledTimes(0)
+    expect(mockGoldGetExchangeRate).toHaveBeenCalledTimes(1)
+  })
+
+  it('should retrieve rate for USD/cGLD', async () => {
+    const result = await currencyConversionAPI.getExchangeRate({
+      sourceCurrencyCode: 'USD',
+      currencyCode: 'cGLD',
+    })
+    expect(result).toEqual(new BigNumber(10))
+    expect(mockDefaultGetExchangeRate).toHaveBeenCalledTimes(0)
+    expect(mockGoldGetExchangeRate).toHaveBeenCalledTimes(1)
+  })
+
+  it('should retrieve rate for cGLD/MXN', async () => {
+    const result = await currencyConversionAPI.getExchangeRate({
+      sourceCurrencyCode: 'cGLD',
+      currencyCode: 'MXN',
+    })
+    expect(result).toEqual(new BigNumber(200))
+    expect(mockDefaultGetExchangeRate).toHaveBeenCalledTimes(1)
+    expect(mockGoldGetExchangeRate).toHaveBeenCalledTimes(1)
+  })
+
+  it('should retrieve rate for MXN/cGLD', async () => {
+    const result = await currencyConversionAPI.getExchangeRate({
+      sourceCurrencyCode: 'MXN',
+      currencyCode: 'cGLD',
+    })
+    expect(result).toEqual(new BigNumber(200))
+    expect(mockDefaultGetExchangeRate).toHaveBeenCalledTimes(1)
+    expect(mockGoldGetExchangeRate).toHaveBeenCalledTimes(1)
+  })
+
+  it('should retrieve rate for USD/MXN', async () => {
+    const result = await currencyConversionAPI.getExchangeRate({
+      sourceCurrencyCode: 'USD',
+      currencyCode: 'MXN',
+    })
+    expect(result).toEqual(new BigNumber(20))
+    expect(mockDefaultGetExchangeRate).toHaveBeenCalledTimes(1)
+    expect(mockGoldGetExchangeRate).toHaveBeenCalledTimes(0)
+  })
+
+  it('should retrieve rate for MXN/USD', async () => {
+    const result = await currencyConversionAPI.getExchangeRate({
+      sourceCurrencyCode: 'MXN',
+      currencyCode: 'USD',
+    })
+    expect(result).toEqual(new BigNumber(20))
+    expect(mockDefaultGetExchangeRate).toHaveBeenCalledTimes(1)
+    expect(mockGoldGetExchangeRate).toHaveBeenCalledTimes(0)
+  })
+
+  it('should retrieve rate for cUSD/MXN', async () => {
+    const result = await currencyConversionAPI.getExchangeRate({
+      sourceCurrencyCode: 'cUSD',
+      currencyCode: 'MXN',
+    })
+    expect(result).toEqual(new BigNumber(20))
+    expect(mockDefaultGetExchangeRate).toHaveBeenCalledTimes(1)
+    expect(mockGoldGetExchangeRate).toHaveBeenCalledTimes(0)
+  })
+
+  it('should retrieve rate for MXN/cUSD', async () => {
+    const result = await currencyConversionAPI.getExchangeRate({
+      sourceCurrencyCode: 'MXN',
+      currencyCode: 'cUSD',
+    })
+    expect(result).toEqual(new BigNumber(20))
+    expect(mockDefaultGetExchangeRate).toHaveBeenCalledTimes(1)
+    expect(mockGoldGetExchangeRate).toHaveBeenCalledTimes(0)
+  })
+
+  it('should return 1 when using the same currency code', async () => {
+    const result = await currencyConversionAPI.getExchangeRate({
+      sourceCurrencyCode: 'ABC',
+      currencyCode: 'ABC',
+    })
+    expect(result).toEqual(new BigNumber(1))
+    expect(mockDefaultGetExchangeRate).toHaveBeenCalledTimes(0)
+    expect(mockGoldGetExchangeRate).toHaveBeenCalledTimes(0)
+  })
+})

packages/blockchain-api/src/currencyConversion/CurrencyConversionAPI.ts

@@ -0,0 +1,98 @@
+import { DataSource, DataSourceConfig } from 'apollo-datasource'
+import BigNumber from 'bignumber.js'
+import { CurrencyConversionArgs } from '../schema'
+import { CGLD, CUSD, USD } from './consts'
+import ExchangeRateAPI from './ExchangeRateAPI'
+import GoldExchangeRateAPI from './GoldExchangeRateAPI'
+
+function insertIf<T>(condition: boolean, element: T) {
+  return condition ? [element] : []
+}
+
+export default class CurrencyConversionAPI<TContext = any> extends DataSource {
+  exchangeRateAPI = new ExchangeRateAPI()
+  goldExchangeRateAPI = new GoldExchangeRateAPI()
+
+  initialize(config: DataSourceConfig<TContext>): void {
+    this.exchangeRateAPI.initialize(config)
+    this.goldExchangeRateAPI.initialize(config)
+  }
+
+  async getExchangeRate({
+    sourceCurrencyCode,
+    currencyCode,
+    timestamp,
+  }: CurrencyConversionArgs): Promise<BigNumber> {
+    const fromCode = sourceCurrencyCode || USD
+    const toCode = currencyCode
+
+    const steps = this.getConversionSteps(fromCode, toCode)
+
+    const ratesPromises = []
+    for (let i = 1; i < steps.length; i++) {
+      const prevCode = steps[i - 1]
+      const code = steps[i]
+      ratesPromises.push(this.getSupportedExchangeRate(prevCode, code, timestamp))
+    }
+
+    const rates = await Promise.all(ratesPromises)
+
+    // Multiply all rates
+    return rates.reduce((acc, rate) => acc.multipliedBy(rate), new BigNumber(1))
+  }
+
+  // Get conversion steps given the data we have today
+  // Going from cGLD to local currency (or vice versa) is currently assumed to be the same as cGLD -> cUSD -> USD -> local currency.
+  // And similar to cUSD to local currency, but with one less step.
+  private getConversionSteps(fromCode: string, toCode: string) {
+    if (fromCode === toCode) {
+      // Same code, nothing to do
+      return []
+    } else if (fromCode === CGLD || toCode === CGLD) {
+      // cGLD -> X (where X !== cUSD)
+      if (fromCode === CGLD && toCode !== CUSD) {
+        return [CGLD, CUSD, ...insertIf(toCode !== USD, USD), toCode]
+      }
+      // X -> cGLD (where X !== cUSD)
+      else if (fromCode !== CUSD && toCode === CGLD) {
+        return [fromCode, ...insertIf(fromCode !== USD, USD), CUSD, CGLD]
+      }
+    } else {
+      // cUSD -> X (where X !== USD)
+      if (fromCode === CUSD && toCode !== USD) {
+        return [CUSD, USD, toCode]
+      }
+      // X -> cUSD (where X !== USD)
+      else if (fromCode !== USD && toCode === CUSD) {
+        return [fromCode, USD, CUSD]
+      }
+    }
+
+    return [fromCode, toCode]
+  }
+
+  private getSupportedExchangeRate(
+    fromCode: string,
+    toCode: string,
+    timestamp?: number
+  ): Promise<BigNumber> {
+    const pair = `${fromCode}/${toCode}`
+
+    if (pair === 'cUSD/USD' || pair === 'USD/cUSD') {
+      // TODO: use real rates once we have the data
+      return Promise.resolve(new BigNumber(1))
+    } else if (pair === 'cGLD/cUSD' || pair === 'cUSD/cGLD') {
+      return this.goldExchangeRateAPI.getExchangeRate({
+        sourceCurrencyCode: fromCode,
+        currencyCode: toCode,
+        timestamp,
+      })
+    } else {
+      return this.exchangeRateAPI.getExchangeRate({
+        sourceCurrencyCode: fromCode,
+        currencyCode: toCode,
+        timestamp,
+      })
+    }
+  }
+}