dice-roller/dice.ts

const util = require('util');

/**
 * Counts the occurrences of a number in an array of numbers
 *
 * @param inputArray - array of numbers
 * @param checkNumber - number to count occurrences of
 * @returns number of occurrences
 *
 */
function countOccurrencesOfNumber(inputArray: Array<number>, checkNumber: number): number {
        return inputArray.filter(c => c === checkNumber).length;
}

/**
 * Generate a random integer between *1* and `max` (inclusive)
 *
 * @param max - upper bound of random integer to generate
 * @returns random integer
 */
function randIntMinOne(max: number): number {
	return (1 + Math.floor(Math.random() * Math.floor(max)));
}

interface Dice {
	readonly sides: number;
	readonly type: string;
}

enum Outcomes {
	Success = "Success",
	Fail = "Failure",
	CritSuccess = "Critical Success",
	CritFail = "Critical Failure",
	Other = "Something Else"
}

interface DiceResult {
	total: number;
	dice: Array<number>;
	olddice?: Array<number>;
	reroll?: boolean;
	outcome?: Outcomes;
	balance?: number;

}
/**
 * Simple d10, implements `roll()`
 */
class D10 implements Dice {
	sides: number = 10;
	type: string = "d10"

	constructor() {
	}

	[util.inspect.custom](): string {
		return this.type;
	}

	/**
	 * Roll a specified number of dice
	 *
	 * @param numberToRoll - integer number of dice to roll
	 * @returns DiceResult: .total and .dice (individual dice)
	 *
	 * @example Roll 4d10
	 *
	 * ```
	 * D10.roll(4)
	 * { total: 16, dice [ 3, 5, 6, 2] }
	 *
	 */
	roll(numberToRoll: number): DiceResult {
		let results: DiceResult = { total: 0, dice: [] };
		for (let i = 0; i < numberToRoll; i++) {
			results.dice.push(randIntMinOne(this.sides));
		}

		results.total = results.dice.reduce((acc: number, curr: number) => acc + curr);

		return results;
	}
}

class Asphodice extends D10 {
	readonly type: string = "asphodice";
	readonly passCrit: number = 10;
	readonly failCrit: number = 1;
	readonly successCutOff: number = 6; // this or larger

	/**
	 * Re-roll the high dice (ie >= 6) for a chance of failure
	 * happens on eg 1
	 *
	 * @remarks
	 * Basically we want to remove a die from the original result,
	 * as long as that die isn't a 10, and is above the
	 * cutoff. So we filter to get rerollCandidates, find the
	 * highest value and get the index of that value in the
	 * original results. We use that to splice() out (remove) that
	 * value and push the rerolled dice onto the modified array
	 *
	 * @param rerollDice
	 * @returns rerollOutcome
	 *
	 * @example Re-roll High Dice on 1
	 * ```
	 * rerollHighDice([8, 1, 1, 4, 7, 10]);
	 * [ 1, 1, 4, 7, 10, 6]
	 * ```
	 *
	 * ## Explanation
	 *
	 * - first filter dice to be not 10 and >= 6 (see {@link Asphodice.successCutOff})
	 * - rerollCandidates are [8, 7]
	 * - max([8, 7] = 8
	 * - indexOf(8) = 0
	 * - rerollResult = 6 (see {@link randIntMinOne()})
	 * - `splice()` replaced dice out of array = [ 1, 1, 4, 7, 10 ]
	 * - `push()` new dice = [ 1, 1, 4, 7, 10, 6]
	 */
	rerollHighDice (rerollDice: Array<number>): Array<number> {
		let rerollCandidates: Array<number> = rerollDice.filter(die => (die < 10 && die >= this.successCutOff));
		let maxValue: number = Math.max(...rerollCandidates);
		let maxIndex = rerollDice.indexOf(maxValue);
		let rerollResult: number = randIntMinOne(this.sides);

		rerollDice.splice(maxIndex, 1);
		rerollDice.push(rerollResult);
		return rerollDice
	}

	/**
	 * Re-roll low dice (ie < 6) for chance of success (ie getting >= 6)
	 *
	 * @remarks
	 *
	 * Generally happens on a 10.
	 *
	 * @see {@link Asphodice.rerollHighDice} for a fuller explanation
	 * for what process in opposite direction
	 */
	rerollLowDice (rerollDice: Array<number>): Array<number> {
		let rerollCandidates: Array<number> = rerollDice.filter(die => (die > 1 && die < this.successCutOff));
		let minValue: number = Math.min(...rerollCandidates);
		let minIndex = rerollDice.indexOf(minValue);
		let rerollResult: number = randIntMinOne(this.sides);

		rerollDice.splice(minIndex, 1);
		rerollDice.push(rerollResult);
		return rerollDice
	}

	/**
	 * Used to determine if all dice are above Asphodice.successCutOff
	 *
	 * @param checkDice - Array of Dice to test
	 *
	 * @see {@link Asphodice.roll} where it is used to determine if
	 * a re-roll can be skipped
	 *
	 * @see {@link allBelowCutOff} also.
	 */
	allAboveCutOff (checkDice: Array<number>): boolean {
		// if filtering those *below* cutoff results in empty set
		// then all must be above cutoff
		return ((checkDice.filter(die => die < this.successCutOff).length == 0));
	}

	/**
	 * Used to determine if all dice are below Asphodice.successCutOff
	 *
	 * @param checkDice - Array of Dice to test
	 *
	 * @see {@link Asphodice.roll} where it is used to determine if
	 * a re-roll can be skipped
	 *
	 * @see {@link allAboveCutOff} also.
	 */
	allBelowCutOff (checkDice: Array<number>): boolean {
		// if filtering those *above or equal to* cutoff results in empty set
		// then all must be below cutoff
		return ((checkDice.filter(die => die >= this.successCutOff).length == 0));
	}

	/**
	 * Determine balance of outcomes - ie successes minus failures
	 *
	 * @remarks
	 *
	 * Success = 1, failure = -1
	 *
	 * Particularly for Asphodice, we aren't terribly concerned with the
	 * numeric sum total of the dice values, we are more concerned with
	 * the overall outcome (see {@link Outcomes}) and for narrative purposes
	 * perhaps the balance of outcomes; for example, 1 success may be
	 * narrated differently than 4 successes.
	 *
	 * **Special note**: This ignores crits! **End special note**
	 *
	 * TODO: Special consideration of a single die roll (?)
	 *
	 * @param resultDice - the final dice after any re-rolls
	 * @returns Single positive/negative number with balance of roll outcomes
	 *
	 * @example Count Outcomes of 5 Dice
	 * ```
	 * countOutcomeBalance([ 7, 4, 4, 9, 1 ])
	 * -1
	 * ```
	 *
	 * - 7 and 9 are above successCutOff → +2
	 * - 4, 4, 1 are below successCutOff → -3
	 */
	countOutcomeBalance (resultDice: Array<number>): number{
		// fun with ternary operators
		return resultDice.reduce(
			(acc: number, curr: number) =>
			{ return (curr < this.successCutOff) ? acc - 1 : acc + 1 },
			0);
			// PS also good practice to supply initialValue (0)
	}

	/**
	 * Roll an Asphodie or Asphodice
	 *
	 * @param numToRoll
	 * @returns a {@link DiceResult} with additional properties:
	 * - reroll: boolean - whether we rerolled
	 * - olddice: Array - original roll
	 * - dice: Array - final outcome
	 * - balance: number - +/- of outcomes (successes/failures)
	 */
	roll (numToRoll: number): DiceResult {
		let results: DiceResult = { total: 0, dice: [] };

		// Initial roll
		for (let i = 0; i < numToRoll; i++) {
			results.dice.push(randIntMinOne(this.sides));
		}

		// Check for re-rolls
		// 1. if no re-rolls we can finish here
		if (!(results.dice.includes(this.passCrit) || results.dice.includes(this.failCrit))) {
			// results.total = results.dice.reduce((acc: number, curr: number) => acc + curr);
			results.reroll = false;
		} else {
			// count successes and fails
			let rerollGood = countOccurrencesOfNumber(results.dice, this.passCrit); 
			let rerollBad = countOccurrencesOfNumber(results.dice, this.failCrit); 
			
			// 2. only reroll if they don't cancel each other out
			if (rerollGood == rerollBad) {
				// console.log("Good = Bad, no need to reroll");
				results.reroll = false;
				// results.total = results.dice.reduce((acc: number, curr: number) => acc + curr);
			} 
			// If all dice are above/below cutoff we don't need to reroll
			// 3a. Above
			else if (this.allAboveCutOff(results.dice)) {
				console.log("All above cutoff, auto-success", results.dice);
				results.reroll = false;
		       	} 
			// 3b. Below
			else if (this.allBelowCutOff(results.dice)) {
				console.log("All below cutoff, auto-fail", results.dice);
				results.reroll = false;
		       	} 
			// Reroll
			else {
				// Reminder: arr1 = arr2 is a copy by reference!
				let olddice = results.dice.slice();
				if (rerollGood > rerollBad) {
					// Re-roll low (<6) dice for chance of success
					results.dice = this.rerollLowDice(results.dice);
				} else {
					// Re-roll high (>=6) dice for chance of failure
					results.dice = this.rerollHighDice(results.dice);
				}
				results.olddice = olddice;
				results.reroll = true;
			}
		}

		results.balance = this.countOutcomeBalance(results.dice);
		results.total = results.dice.reduce((acc: number, curr: number) => acc + curr);
		return results;
	}
}

let asphodice: Asphodice  = new Asphodice();
let number: number = 4;
for (let i = 0; i < 10; i++) {
	console.log("Rolling", number, asphodice);
	console.log(asphodice.roll(4));
}