dice-roller/dice.ts

const util = require('util');

function countOccurrencesOfNumber(inputArray: Array<number>, checkNumber: number): number {
	/*
	return inputArray.reduce(function(n: number, val: number) {
		return n + (val === checkNumber);
	}, 0);
       */
        return inputArray.filter(c => c === checkNumber).length;
}

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;

}

class D10 implements Dice {
	sides: number = 10;
	type: string = "d10"

	constructor() {
		// this.sides = 10;
	}

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

	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

	rerollHighDice (rerollDice: Array<number>): Array<number> {
		// Re-roll the high dice (ie >= 6) for a chance of failure
		// happens on eg 1
		//
		// 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
		//
		// Example:
		// rerollDice: [ 8, 1, 1, 4, 7, 10] --> filter (not 10, >= 6)
		// rerollCandidates : [8, 7] --> maxValue: 8
		// maxIndex: 0 (in original array)
		// rerollResult: 6
		// rerollOutcome: [ 1, 1, 4, 7, 10, 6] --> return

		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
	}

	rerollLowDice (rerollDice: Array<number>): Array<number> {
		// Re-roll the low dice (ie < 6) for a chance of success
		// happens on eg 10
		//
		// see this.rerollHighDice() for a full explanation

		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
	}

	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));
	}

	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));
	}

	countOutcomeBalance (resultDice: Array<number>): number{
		// Return a positive / negative number representing
		// the overall outcomes: each failure (eg < 6) is -1
		// while each success (eg >= 6) is +1

		// fun with ternary operators
		return resultDice.reduce(
			(acc: number, curr: number) =>
			{ return (curr < this.successCutOff) ? acc - 1 : acc + 1 },
			0);
	}

	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));
}