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index.js
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index.js
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'use strict';
import factorial from 'factorial';
const X = 22;
/**
* @typedef {object} SocketColorChanceOptions
* @property {number} sockets
* @property {number} [red]
* @property {number} [green]
* @property {number} [blue]
* @property {number} [strength]
* @property {number} [dexterity]
* @property {number} [intelligence]
*/
/**
* @param {SocketColorChanceOptions} opts
* @returns {number}
*/
function chance(opts) {
if (!opts.sockets || opts.sockets < 1 || opts.sockets > 6) {
throw new Error('expected: 0 < opts.sockets < 7');
}
const red = opts.red || 0;
const green = opts.green || 0;
const blue = opts.blue || 0;
if (red < 0 || green < 0 || blue < 0
|| red + blue + green === 0
|| red + blue + green > opts.sockets) {
throw new Error('invalid number of desired sockets');
}
let strength = opts.strength || 0;
let dexterity = opts.dexterity || 0;
let intelligence = opts.intelligence || 0;
if (strength > 0 && dexterity === 0 && intelligence === 0) {
strength += 32;
}
else if (strength === 0 && dexterity > 0 && intelligence === 0) {
dexterity += 32;
}
else if (strength === 0 && dexterity === 0 && intelligence > 0) {
intelligence += 32;
}
if (strength < 0 || dexterity < 0 || intelligence < 0) {
throw new Error('expected: non-negative strength, dexterity, intelligence');
}
const div = strength + dexterity + intelligence + 3 * X;
const rc = (X + strength) / div;
const gc = (X + dexterity) / div;
const bc = (X + intelligence) / div;
/**
* @param {number} red
* @param {number} green
* @param {number} blue
* @param {number} free
* @param {number} [pos]
* @returns {number}
*/
function multinomial(red, green, blue, free, pos = 1) {
if (free > 0) {
return (pos <= 1 ? multinomial(red + 1, green, blue, free - 1, 1) : 0)
+ (pos <= 2 ? multinomial(red, green + 1, blue, free - 1, 2) : 0)
+ multinomial(red, green, blue + 1, free - 1, 3);
}
return factorial(red + green + blue) / (factorial(red) * factorial(green)
* factorial(blue)) * Math.pow(rc, red) * Math.pow(gc, green)
* Math.pow(bc, blue);
}
return multinomial(red, green, blue, opts.sockets - red - green - blue);
}
export default chance;