createStatementData.js

export default function createStatementData(invoice, plays) {
  const statementData = {};
  statementData.customer = invoice.customer;
  statementData.performances = invoice.performances.map(enrichPerformance);
  statementData.totalAmount = totalAmount(statementData);
  statementData.totalVolumeCredits = totalVolumeCredits(statementData);

  function totalAmount(data) {
    return data.performances.reduce((total, p) => total + p.amount, 0);
  }
  function totalVolumeCredits(data) {
    return data.performances.reduce((total, p) => total + p.volumeCredits, 0);
  }
  function enrichPerformance(aPerformance) {
    const result = Object.assign({}, aPerformance);
    result.play = playFor(result);
    result.amount = amountFor(result);
    result.volumeCredits = volumeCreditsFor(result);
    return result;
  }
  function volumeCreditsFor(aPerformance) {
    let result = 0;
    result += Math.max(aPerformance.audience - 30, 0);
    // soma um crédito extra para cada dez espectadores de comédia
    if ("comedy" == playFor(aPerformance).type)
      result += Math.floor(aPerformance.audience / 5);

    return result;
  }
  function amountFor(aPerformance) {
    let result = 0;
    switch (aPerformance.play.type) {
      case "tragedy":
        result = 40000;
        if (aPerformance.audience > 30) {
          result += 1000 * (aPerformance.audience - 30);
        }
        break;
      case "comedy":
        result = 30000;
        if (aPerformance.audience > 20) {
          result += 10000 + 500 * (aPerformance.audience - 20);
        }
        result += 300 * aPerformance.audience;
        break;
      default:
        throw new Error(`Unknown type: ${aPerformance.play.type}`);
    }
    return result;
  }
  function playFor(aPerformance) {
    return plays[aPerformance.playID];
  }

  return statementData;
}