logbot/dice.js

const diceRegex = () => /\b(\d*)[dD](\d+)\b(?:\s?([+-])\s?(\d+))?/g

class Roll {
  constructor(roll) {
    if (roll) Object.assign(this, roll)
  }
  value() {
    return this.values.reduce((a, b) => a + b, this.bonus || 0)
  }
  toString() {
    let str = this.values.map(val => `[${val}]`).join(' + ')
    if (this.bonus < 0) {
      str += ` - ${Math.abs(this.bonus)}`
    } else if (this.bonus > 0) {
      str += ` + ${this.bonus}`
    }
    if (this.values.length > 1 || this.bonus) {
      str += ` = ${this.value()}`
    }
    return str
  }
}

class BadRoll extends Roll {
  constructor(text) {
    super({text})
  }
  toString() {
    return this.text
  }
}

class Dice {
  constructor(dice) {
    if (dice) Object.assign(this, dice)
  }
  roll() {
    if (this.count > 100) return new BadRoll(`I lost count rolling ${this}`)
    if (this.sides > 256) return new BadRoll(`The faces are too small to read on ${this}`)
    if (this.count === 0) return new BadRoll(`I finished before I started rolling ${this}`)
    if (this.sides === 0) return new BadRoll(`I lost my grip on ${this}`)
    if (this.sides === 1) return new BadRoll(`The mobius ${this} never stopped rolling`)
    if (this.bonusSign === '-' && this.bonus > this.sides) return new BadRoll(`It doesn't seem fair to roll ${this}`)

    let values = []
    for (let i = 0; i < this.count; i++) {
      values.push(Math.floor(Math.random() * this.sides) + 1)
    }
    let bonus = 0
    switch (this.bonusSign) {
      case '-': bonus = -this.bonus; break
      case '+': bonus = this.bonus; break
    }
    return new Roll({
      values,
      bonus
    })
  }
  toString() {
    let str = `${this.count}d${this.sides}`
    if (this.bonusSign) {
      str += this.bonusSign + this.bonus
    }
    return str
  }
}

Dice.parse = str => {
  const regex = diceRegex()
  const ret = []
  let dice
  while (dice = regex.exec(str)) {
    ret.push(new Dice({
      match: dice,
      count: dice[1] === '' ? 1 : parseFloat(dice[1]),
      sides: parseFloat(dice[2]),
      bonusSign: dice[3] || null,
      bonus: dice[4] === undefined ? null : parseFloat(dice[4])
    }))
  }
  return ret
}

Dice.chat = chat => {
  const dice = Dice.parse(chat)
  if (dice.length) {
    const diceStrings = dice.map(x => x.toString())
    if (diceStrings.length > 1) {
      diceStrings[diceStrings.length - 1] = `and ${diceStrings[diceStrings.length - 1]}`
    }
    const rollingString = `Rolling ${diceStrings.join(', ')}...`
    const rollsStrings = dice.map(die => die.roll().toString())
    return `${rollingString} ${rollsStrings.join(', ')}.`
  }
}

module.exports = {Dice, Roll}