Initial commit

src/currencyservice/.dockerignore

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+node_modules/

src/currencyservice/.gitignore

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+node_modules/

src/currencyservice/Dockerfile

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+FROM node:8
+WORKDIR /usr/src/app
+COPY package*.json ./
+RUN npm install --only=production
+COPY . .
+EXPOSE 31337
+CMD [ "node", "server.js" ]

src/currencyservice/client.js

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+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+const path = require('path');
+const grpc = require('grpc');
+
+const PROTO_PATH = path.join(__dirname, './proto/currency_service.proto');
+const PORT = 31337;
+
+const shopProto = grpc.load(PROTO_PATH).hipstershop;
+const client = new shopProto.CurrencyService(`localhost:${PORT}`,
+  grpc.credentials.createInsecure());
+
+const request = {
+  from: {
+    currency_code: 'USD',
+    amount: {
+      decimal: 300,
+      fractional: 0
+    }
+  },
+  to_code: 'CHF'
+};
+
+client.convert(request, function (err, response) {
+  if (err) {
+    console.error(err);
+  } else {
+    const amount = response.amount;
+    console.log(`OUTPUT: ${amount.decimal}.${amount.fractional}`);
+  }
+});

src/currencyservice/currency_service.proto

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+syntax = "proto3";
+package hipstershop;
+
+message Empty {}
+
+service CurrencyService {
+    rpc GetSupportedCurrencies(Empty) returns (GetSupportedCurrenciesResponse) {}
+    rpc Convert(CurrencyConversionRequest) returns (Money) {}
+}
+// Describes a money amount without currency. For example, decimal=2 and
+// fractional=500 (or fractional=5) makes up 2.5 units.
+message MoneyAmount {
+    uint32 decimal = 1;
+    uint32 fractional = 2;
+}
+message Money {
+    // The 3-letter currency code defined in ISO 4217.
+    string currency_code = 1;
+    MoneyAmount amount = 2;
+}
+message GetSupportedCurrenciesResponse {
+    // The 3-letter currency code defined in ISO 4217.
+    repeated string currency_codes = 1;
+}
+message CurrencyConversionRequest {
+    Money from = 1;
+    // The 3-letter currency code defined in ISO 4217.
+    string to_code = 2;
+}

src/currencyservice/package.json

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+{
+  "name": "grpc-currency-service",
+  "version": "0.1.0",
+  "description": "A gRPC currency conversion microservice",
+  "repository": "TODO",
+  "license": "Apache-2.0",
+  "dependencies": {
+    "async": "^1.5.2",
+    "google-protobuf": "^3.0.0",
+    "grpc": "^1.0.0",
+    "request": "^2.87.0",
+    "xml2js": "^0.4.19"
+  }
+}

src/currencyservice/proto/currency_service.proto

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+syntax = "proto3";
+package hipstershop;
+
+message Empty {}
+
+service CurrencyService {
+    rpc GetSupportedCurrencies(Empty) returns (GetSupportedCurrenciesResponse) {}
+    rpc Convert(CurrencyConversionRequest) returns (Money) {}
+}
+// Describes a money amount without currency. For example, decimal=2 and
+// fractional=500 (or fractional=5) makes up 2.5 units.
+message MoneyAmount {
+    uint32 decimal = 1;
+    uint32 fractional = 2;
+}
+message Money {
+    // The 3-letter currency code defined in ISO 4217.
+    string currency_code = 1;
+    MoneyAmount amount = 2;
+}
+message GetSupportedCurrenciesResponse {
+    // The 3-letter currency code defined in ISO 4217.
+    repeated string currency_codes = 1;
+}
+message CurrencyConversionRequest {
+    Money from = 1;
+    // The 3-letter currency code defined in ISO 4217.
+    string to_code = 2;
+}

src/currencyservice/server.js

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+/*
+ * Copyright 2018 Google LLC.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const path = require('path');
+const grpc = require('grpc');
+const request = require('request');
+const xml2js = require('xml2js');
+
+const PROTO_PATH = path.join(__dirname, './proto/currency_service.proto');
+const PORT = 31337;
+const DATA_URL = 'http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml';
+const shopProto = grpc.load(PROTO_PATH).hipstershop;
+
+/**
+ * Helper function that gets currency data from an XML webpage
+ * Uses public data from European Central Bank
+ */
+function _getCurrencyData (callback) {
+  request(DATA_URL, (err, res) => {
+    if (err) {
+      throw new Error(`Error getting data: ${err}`);
+    }
+
+    const body = res.body.split('\n').slice(7, -2).join('\n');
+    xml2js.parseString(body, (err, resJs) => {
+      if (err) {
+        throw new Error(`Error parsing HTML: ${err}`);
+      }
+
+      const array = resJs['Cube']['Cube'].map(x => x['$']);
+      const results = array.reduce((acc, x) => {
+        acc[x['currency']] = x['rate'];
+        return acc;
+      }, { 'EUR': '1.0' });
+      callback(results);
+    });
+  });
+}
+
+/**
+ * Helper function that handles decimal/fractional carrying
+ */
+function _carry (amount) {
+  amount.fractional += (amount.decimal % 1) * 100;
+  amount.decimal = Math.floor(amount.decimal + amount.fractional / 100);
+  amount.fractional = amount.fractional % 100;
+  return amount;
+}
+
+/**
+ * Lists the supported currencies
+ */
+function getSupportedCurrencies (call, callback) {
+  _getCurrencyData((data) => {
+    callback(null, {currency_codes: data.keys()});
+  });
+}
+
+/**
+ * Converts between currencies
+ */
+function convert (call, callback) {
+  try {
+    _getCurrencyData((data) => {
+      const request = call.request;
+
+      // Convert: from_currency --> EUR
+      const from = request.from;
+      const euros = _carry({
+        decimal: from.amount.decimal / data[from.currency_code],
+        fractional: from.amount.fractional / data[from.currency_code]
+      });
+
+      // Convert: EUR --> to_currency
+      const target = _carry({
+        decimal: euros.decimal * data[request.to_code],
+        fractional: euros.fractional * data[request.to_code]
+      });
+      target.fractional = Math.round(target.fractional);
+
+      callback(null, {amount: target});
+    });
+  } catch (err) {
+    callback(err.message);
+  }
+}
+
+/**
+ * Starts an RPC server that receives requests for the
+ * CurrencyConverter service at the sample server port
+ */
+function main () {
+  var server = new grpc.Server();
+  server.addService(shopProto.CurrencyService.service, {getSupportedCurrencies, convert});
+  server.bind(`0.0.0.0:${PORT}`, grpc.ServerCredentials.createInsecure());
+  server.start();
+}
+
+main();