const constant = n => () => [() => n]

const pool = (die) => {
  return die().map((d) => d())
}

const roll = (die) => {
  return pool(die).reduce((a, b) => (a + b), 0)
}

const d = (number, sides) => {
  return () => {
    let pool = []

    const currentNumber = roll(number)
    const currentSides = roll(sides)

    for (let i = 0; i < currentNumber; i++) {
      pool.push(() => (1 + Math.floor(Math.random() * currentSides)))
    }

    return pool
  }
}

const add = (die1, die2) => {
  return () => {
    return die1().concat(die2())
  }
}

const negative = (die) => {
  return () => {
    return die().map(die => () => (-die()))
  }
}

const subtract = (die1, die2) => {
  return () => {
    return die1().concat(negative(die2)())
  }
}

const explode = (die1, die2) => {
  return () => {
    return die1()
  }
}

exports.pool = pool
exports.roll = roll
exports.constant = constant
exports.d = d
exports.add = add
exports.subtract = subtract
exports.negative = negative
exports.explode = explode