WaterContainer

/**
 * A simulation written to help experiment with the well known water puzzle:
 * 
 * If you have two unmarked jugs: a 5 gallon one and a 3 gallon. Provide a series of steps
 * to fill one of the jugs with 4 gallons of water.
 * This doesn't acutally solve the puzzle, but provides constraints to let the user experiment
 * with the puzzle.
 *
 * The constraints are:
 * # You can drain a jug completely see: drain
 * # You can fill a jug completely from tap. See: fill
 * # You can fill a jug from a another jug, where you will fill the current jug
 *   to capacity, and the rest of the water, if any, remain in the jug that is
 *   the source.
 **/

function WaterContainer(capacity) {
	if (typeof capacity !== 'number' && number <= 0) {
		throw new TypeError('capacity has to be > 0');
	}

	this.capacity = capacity;
	this.currentVolume = 0;
}

WaterContainer.prototype.fill = function() {
	this.currentVolume = this.capacity;
	return this;
};

WaterContainer.prototype.drain = function() {
	this.currentVolume = 0;
	return this;
};

WaterContainer.prototype.drainBy = function(amount) {
	if (typeof amount !== 'number' && number <= 0) {
		throw new TypeError('amount has to be > 0');
	}

	this.currentVolume = Math.max(this.currentVolume - amount, 0);
	return this;
};

WaterContainer.prototype.fillFrom = function(otherWaterContainer) {
	var amountPouredIntoThisContainer = Math.min(this.remainingCapacity(), otherWaterContainer.currentVolume);
	otherWaterContainer.drainBy(amountPouredIntoThisContainer);
	this.currentVolume = this.currentVolume + amountPouredIntoThisContainer;

	return this;
};

WaterContainer.prototype.toString = function() {
	return 'Capacity: ' + this.capacity + ', CurrentVolume: ' + this.currentVolume;
};

WaterContainer.prototype.remainingCapacity = function() {
	return this.capacity - this.currentVolume;
};

module.exports = WaterContainer;


// > var WaterContainer = require('./watercontainer.js')
// undefined
// > var jug5 = new WaterContainer(5);
// undefined
// > var jug3 = new WaterContainer(3);
// undefined
//
// Fill the 5 gallon jug
//
// > jug5.fill()
// { capacity: 5, currentVolume: 5 }
// > jug3.fillFrom(jug5)
// { capacity: 3, currentVolume: 3 }
// > jug5
// { capacity: 5, currentVolume: 2 }
// > jug3.drain()
// { capacity: 3, currentVolume: 0 }
// > jug3.fillFrom(jug5)
// { capacity: 3, currentVolume: 2 }
// > jug3
// { capacity: 3, currentVolume: 2 }
// > jug5
// { capacity: 5, currentVolume: 0 }
// > jug5.fill()
// { capacity: 5, currentVolume: 5 }
// > jug3.fillFrom(jug5)
// { capacity: 3, currentVolume: 3 }
// > jug5
// { capacity: 5, currentVolume: 4 }