From 25b2a8b0e5e53a6dbaff164947ad6124771c12f3 Mon Sep 17 00:00:00 2001
From: Sebastian Kippe <sebastian@kip.pe>
Date: Wed, 30 Sep 2020 15:03:55 +0200
Subject: [PATCH] Create exchange rate service , use CORS proxy for requests

---
 app/components/add-reimbursement/component.js |  6 ++++
 app/components/add-reimbursement/template.hbs |  3 ++
 app/services/exchange-rates.js                | 29 +++++++++++++++++
 app/utils/fetch-exchange-rate.js              | 20 ------------
 config/environment.js                         |  6 +++-
 tests/unit/services/exchange-rates-test.js    | 29 +++++++++++++++++
 tests/unit/utils/fetch-exchange-rate-test.js  | 31 -------------------
 7 files changed, 72 insertions(+), 52 deletions(-)
 create mode 100644 app/services/exchange-rates.js
 delete mode 100644 app/utils/fetch-exchange-rate.js
 create mode 100644 tests/unit/services/exchange-rates-test.js
 delete mode 100644 tests/unit/utils/fetch-exchange-rate-test.js

diff --git a/app/components/add-reimbursement/component.js b/app/components/add-reimbursement/component.js
index 1284821..78a6446 100644
--- a/app/components/add-reimbursement/component.js
+++ b/app/components/add-reimbursement/component.js
@@ -10,6 +10,7 @@ import isValidAmount from 'kredits-web/utils/is-valid-amount';
 
 export default class AddReimbursementComponent extends Component {
   @service kredits;
+  @service exchangeRates;
 
   @alias('kredits.contributorsSorted') contributors;
 
@@ -19,6 +20,11 @@ export default class AddReimbursementComponent extends Component {
   @tracked expenses = A([]);
   @tracked expenseFormVisible = true;
 
+  constructor() {
+    super(...arguments);
+    this.exchangeRates.fetchRates();
+  }
+
   get isValidTotal () {
     return isValidAmount(this.total);
   }
diff --git a/app/components/add-reimbursement/template.hbs b/app/components/add-reimbursement/template.hbs
index 513929f..4964fc3 100644
--- a/app/components/add-reimbursement/template.hbs
+++ b/app/components/add-reimbursement/template.hbs
@@ -1,3 +1,6 @@
+<p>
+  {{this.exchangeRates.btceur}}, {{this.exchangeRates.btcusd}}
+</p>
 <form onsubmit={{action "submit"}} novalidate>
   <label>
     <p class="label">Contributor:</p>
diff --git a/app/services/exchange-rates.js b/app/services/exchange-rates.js
new file mode 100644
index 0000000..82dbd46
--- /dev/null
+++ b/app/services/exchange-rates.js
@@ -0,0 +1,29 @@
+import Service from '@ember/service';
+import { tracked } from '@glimmer/tracking';
+import config from 'kredits-web/config/environment';
+
+// Need to go through proxy for CORS headers
+const bitstampBaseUrl = `${config.corsProxy}https://www.bitstamp.net/api/v2`;
+
+async function fetchFromBitstamp(currencyPair) {
+  try {
+    const res = await fetch(`${bitstampBaseUrl}/ticker/${currencyPair}/`).then(r => r.json());
+    return res.vwap; // Last 24 hours volume weighted average price
+  } catch(e) {
+    console.error('Could not fetch exchange rate from Bitstamp:', e);
+    return 0;
+  }
+}
+
+export default class ExchangeRatesService extends Service {
+  @tracked btceur = 0;
+  @tracked btcusd = 0;
+
+  async fetchRates (source='bitstamp') {
+    switch(source) {
+      case 'bitstamp':
+        this.btceur = await fetchFromBitstamp('btceur');
+        this.btcusd = await fetchFromBitstamp('btcusd');
+    }
+  }
+}
diff --git a/app/utils/fetch-exchange-rate.js b/app/utils/fetch-exchange-rate.js
deleted file mode 100644
index 4eaf97d..0000000
--- a/app/utils/fetch-exchange-rate.js
+++ /dev/null
@@ -1,20 +0,0 @@
-const bitstampBaseUrl = 'https://www.bitstamp.net/api/v2';
-
-async function fetchFromBitstamp(currencyPair) {
-  try {
-    const res = await fetch(`${bitstampBaseUrl}/ticker/${currencyPair}/`).then(r => r.json());
-    return res.vwap; // Last 24 hours volume weighted average price
-  } catch(e) {
-    console.error('Could not fetch exchange rate from Bitstamp:', e);
-    return 0;
-  }
-}
-
-export default function fetchExchangeRate(currencyPair, source='bitstamp') {
-  if (!currencyPair) throw 'Currency pair required';
-
-  switch(source) {
-    case 'bitstamp':
-      return fetchFromBitstamp(currencyPair);
-  }
-}
diff --git a/config/environment.js b/config/environment.js
index 9d18af7..eb48ae2 100644
--- a/config/environment.js
+++ b/config/environment.js
@@ -55,7 +55,9 @@ module.exports = function(environment) {
     gnosisSafe: {
       txServiceHost: 'https://safe-transaction.mainnet.gnosis.io',
       address: '0x9CC29b8373FF92B01C1f09F31B5DD862350c167E'
-    }
+    },
+
+    corsProxy: 'https://cors.5apps.com/?uri='
   };
 
   if (environment === 'development') {
@@ -75,6 +77,8 @@ module.exports = function(environment) {
       protocol: 'http',
       gatewayUrl: 'http://localhost:8080/ipfs'
     };
+
+    ENV.corsProxy = 'https://cors-anywhere.herokuapp.com/';
   }
 
   if (environment === 'test') {
diff --git a/tests/unit/services/exchange-rates-test.js b/tests/unit/services/exchange-rates-test.js
new file mode 100644
index 0000000..e01a790
--- /dev/null
+++ b/tests/unit/services/exchange-rates-test.js
@@ -0,0 +1,29 @@
+import { module, test } from 'qunit';
+import { setupTest } from 'ember-qunit';
+import config from 'kredits-web/config/environment';
+import fetchMock from 'fetch-mock';
+
+const corsProxy = config.corsProxy;
+
+fetchMock.get(`${corsProxy}https://www.bitstamp.net/api/v2/ticker/btceur/`, {
+  "high": "9258.43", "last": "9165.14", "timestamp": "1601455909", "bid":
+  "9159.93", "vwap": "9167.57", "volume": "1542.54764854", "low": "9080.20",
+  "ask": "9165.14", "open": "9240.84"
+});
+
+fetchMock.get(`${corsProxy}https://www.bitstamp.net/api/v2/ticker/btcusd/`, {
+  "high": "10865.00", "last": "10714.62", "timestamp": "1601455914", "bid":
+  "10711.31", "vwap": "10749.70", "volume": "4460.32091975", "low": "10636.66",
+  "ask": "10715.99", "open": "10840.00"
+});
+
+module('Unit | Service | exchange-rates', function(hooks) {
+  setupTest(hooks);
+
+  test('#fetchRates', async function(assert) {
+    let service = this.owner.lookup('service:exchange-rates');
+    await service.fetchRates();
+    assert.equal(service.btceur, 9167.57, 'fetches BTCEUR from Bitstamp');
+    assert.equal(service.btcusd, 10749.70, 'fetches BTCUSD from Bitstamp');
+  });
+});
diff --git a/tests/unit/utils/fetch-exchange-rate-test.js b/tests/unit/utils/fetch-exchange-rate-test.js
deleted file mode 100644
index b2007ce..0000000
--- a/tests/unit/utils/fetch-exchange-rate-test.js
+++ /dev/null
@@ -1,31 +0,0 @@
-import fetchExchangeRate from 'kredits-web/utils/fetch-exchange-rate';
-import { module, test } from 'qunit';
-import fetchMock from 'fetch-mock';
-
-fetchMock.get('https://www.bitstamp.net/api/v2/ticker/btceur/', {
-  "high": "9258.43", "last": "9165.14", "timestamp": "1601455909", "bid":
-  "9159.93", "vwap": "9167.57", "volume": "1542.54764854", "low": "9080.20",
-  "ask": "9165.14", "open": "9240.84"
-});
-
-fetchMock.get('https://www.bitstamp.net/api/v2/ticker/btcusd/', {
-  "high": "10865.00", "last": "10714.62", "timestamp": "1601455914", "bid":
-  "10711.31", "vwap": "10749.70", "volume": "4460.32091975", "low": "10636.66",
-  "ask": "10715.99", "open": "10840.00"
-});
-
-module('Unit | Utility | fetch-exchange-rate', function() {
-  test('it requires a currency pair', function(assert) {
-    assert.throws(fetchExchangeRate);
-  });
-
-  test('it fetches BTCEUR from Bitstamp', async function(assert) {
-    let result = await fetchExchangeRate('btceur');
-    assert.equal(result, 9167.57, 'returns 24-hour volume-weighted average price');
-  });
-
-  test('it fetches BTCUSD from Bitstamp', async function(assert) {
-    let result = await fetchExchangeRate('btcusd');
-    assert.equal(result, 10749.70, 'returns 24-hour volume-weighted average price');
-  });
-});