Create exchange rate service , use CORS proxy for requests

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);
   }

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>

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');
+    }
+  }
+}

app/utils/fetch-exchange-rate.js

@@ -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);
-  }
-}