chapter_1.js

function statement(invoice, plays) {
  let totalAmount = 0
  let volumeCredits = 0
  let result = `Statement for ${invoice.customer}\n`
  const format = new Intl.NumberFormat('en-US', {
    style: 'currency',
    currency: 'USD',
    minimumFractionDigits: 2,
  }).format

  for (const perf of invoice.performances) {
    const play = plays[perf.playID]
    let thisAmount = 0

    switch (play.type) {
    case 'tragedy':
      thisAmount = 40000
      if (perf.audience > 30) {
        thisAmount += 1000 * (perf.audience - 30)
      }
      break
    case 'comedy':
      thisAmount = 30000
      if (perf.audience > 20) {
        thisAmount += 10000 + (500 * (perf.audience - 20))
      }
      thisAmount += 300 * perf.audience
      break
    default:
      throw new Error(`unknown type: ${play.type}`)
    }

    // 加入 volume credit
    volumeCredits += Math.max(perf.audience - 30, 0)
    // 每十名喜劇觀眾可獲得額外分數
    if (play.type === 'comedy') volumeCredits += Math.floor(perf.audience / 5)

    // 印出這筆訂單
    result += `${play.name}: ${format(thisAmount / 100)} (${perf.audience} seats)\n`
    totalAmount += thisAmount
  }

  result += `Amount owed is ${format(totalAmount / 100)}\n`
  result += `You earned ${volumeCredits} credits\n`

  return result
}

module.exports = { statement }