131 lines
3.7 KiB
JavaScript
131 lines
3.7 KiB
JavaScript
/*
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* Copyright 2018 Google LLC.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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const path = require('path');
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const grpc = require('grpc');
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const request = require('request');
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const xml2js = require('xml2js');
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const PROTO_PATH = path.join(__dirname, './proto/demo.proto');
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const PORT = 31337;
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const DATA_URL = 'http://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml';
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const shopProto = grpc.load(PROTO_PATH).hipstershop;
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/**
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* Helper function that gets currency data from an XML webpage
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* Uses public data from European Central Bank
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*/
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let _data;
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function _getCurrencyData (callback) {
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if (!_data) {
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console.log('Fetching currency data...');
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request(DATA_URL, (err, res) => {
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if (err) {
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throw new Error(`Error getting data: ${err}`);
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}
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const body = res.body.split('\n').slice(7, -2).join('\n');
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xml2js.parseString(body, (err, resJs) => {
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if (err) {
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throw new Error(`Error parsing HTML: ${err}`);
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}
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const array = resJs['Cube']['Cube'].map(x => x['$']);
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const results = array.reduce((acc, x) => {
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acc[x['currency']] = x['rate'];
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return acc;
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}, { 'EUR': '1.0' });
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_data = results;
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callback(_data);
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});
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});
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} else {
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callback(_data);
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}
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}
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/**
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* Helper function that handles decimal/fractional carrying
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*/
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function _carry (amount) {
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const fractionSize = Math.pow(10, 9);
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amount.nanos += (amount.units % 1) * fractionSize;
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amount.units = Math.floor(amount.units) + Math.floor(amount.nanos / fractionSize);
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amount.nanos = amount.nanos % fractionSize;
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return amount;
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}
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/**
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* Lists the supported currencies
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*/
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function getSupportedCurrencies (call, callback) {
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console.log('Getting supported currencies...');
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_getCurrencyData((data) => {
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callback(null, {currency_codes: Object.keys(data)});
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});
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}
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/**
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* Converts between currencies
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*/
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function convert (call, callback) {
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console.log('received conversion request');
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try {
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_getCurrencyData((data) => {
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const request = call.request;
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// Convert: from_currency --> EUR
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const from = request.from;
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const euros = _carry({
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units: from.units / data[from.currency_code],
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nanos: from.nanos / data[from.currency_code]
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});
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euros.nanos = Math.round(euros.nanos);
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// Convert: EUR --> to_currency
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const result = _carry({
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units: euros.units * data[request.to_code],
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nanos: euros.nanos * data[request.to_code]
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});
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result.units = Math.floor(result.units)
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result.nanos = Math.floor(result.nanos)
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result.currency_code = request.to_code;
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console.log(`conversion request successful`);
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callback(null, result);
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});
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} catch (err) {
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console.error('conversion request failed.');
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console.error(err);
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callback(err.message);
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}
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}
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/**
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* Starts an RPC server that receives requests for the
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* CurrencyConverter service at the sample server port
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*/
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function main () {
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console.log(`Starting gRPC server on port ${PORT}...`);
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const server = new grpc.Server();
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server.addService(shopProto.CurrencyService.service, {getSupportedCurrencies, convert});
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server.bind(`0.0.0.0:${PORT}`, grpc.ServerCredentials.createInsecure());
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server.start();
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}
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main();
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