'use strict';

const joi = require('joi');

const api = require('./api');
const Exchange = require('./exchange');
const xmlParser = require('./parse-xml');

const schema = joi
  .object({
    source: joi.string().required().min(3).max(3).example('EUR'),
    target: joi.string().required().min(3).max(3).example('GBP')
  })
  .unknown()
  .required();

const defaults = {
  timeout: 1000 // 1 sec
};

const exchange = async (pair, options = {}) => {
  options = Object.assign({}, defaults, options);
  const {source, target} = joi.attempt(pair, schema);

  const {requestApi = api, parser = xmlParser} = options;

  const exchange = new Exchange(requestApi, parser, options);
  const rate = await exchange.convert({source, target});
  return {source, target, rate};
};

module.exports = exchange;

'use strict';

const URL = 'https://www.ecb.europa.eu/stats/eurofxref/eurofxref-daily.xml';

class Exchange {
  constructor(api, parser, options = {}) {
    this.api = api;
    this.options = options;
    this.parser = parser;
  }

  async convert({source, target}) {
    if (!this.xml) {
      await this.fetch();
      this.euroToAll = this.parser(this.xml);
    }
    const euroToSource = this.euroToAll[source];
    const euroToTarget = this.euroToAll[target];
    return exchange(euroToSource, euroToTarget);
  }

  async fetch() {
    const response = await this.api.fetch(URL, this.options);
    this.xml = response.body || '';
  }
}

function exchange(from, to) {
  return round(parseFloat(to) / parseFloat(from));
}

function round(result, digits = 4) {
  return Math.round(result * (10 ** digits)) / (10 ** digits);
}

module.exports = Exchange;

'use strict';

const xmldoc = require('xmldoc');
const debug = require('debug')('exchange-rate:parse');

const currencies = require('./currencies');

const parse = xml => {
  const doc = new xmldoc.XmlDocument(xml);
  const cube = doc.childNamed('Cube').childNamed('Cube');

  const rates = currencies.reduce(
    (accumulator, currency) => {
      const exchange = cube.childWithAttribute('currency', currency);
      if (exchange) {
        const {rate} = exchange.attr;
        accumulator[currency] = rate;
      } else {
        debug(`Node not found for currency: ${currency}`);
      }
      return accumulator;
    },
    {}
  );
  // Add EUR rate to make it consistent
  rates.EUR = '1.0';
  return rates;
};

module.exports = parse;

'use strict';

const got = require('got');

module.exports = {
  async fetch(url, options = {}) {
    return got(url, options);
  }
};