Tone.js/Tone/control/CtrlInterpolate.js

import Tone from "../core/Tone";
import "../type/Type";

/**
 *  @class Tone.CtrlInterpolate will interpolate between given values based
 *         on the "index" property. Passing in an array or object literal
 *         will interpolate each of the parameters. Note (i.e. "C3")
 *         and Time (i.e. "4n + 2") can be interpolated. All other values are
 *         assumed to be numbers. 
 *  @example
 * var interp = new Tone.CtrlInterpolate([0, 2, 9, 4]);
 * interp.index = 0.75;
 * interp.value; //returns 1.5
 *
 *  @example
 * var interp = new Tone.CtrlInterpolate([
 * 	[2, 4, 5],
 * 	[9, 3, 2],
 * ]);
 * @param {Array} values The array of values to interpolate over
 * @param {Positive} index The initial interpolation index.
 * @extends {Tone}
 */
Tone.CtrlInterpolate = function(){

	var options = Tone.defaults(arguments, ["values", "index"], Tone.CtrlInterpolate);
	Tone.call(this);

	/**
	 *  The values to interpolate between
	 *  @type  {Array}
	 */
	this.values = options.values;

	/**
	 *  The interpolated index between values. For example: a value of 1.5
	 *  would interpolate equally between the value at index 1
	 *  and the value at index 2. 
	 *  @example
	 * interp.index = 0; 
	 * interp.value; //returns the value at 0
	 * interp.index = 0.5;
	 * interp.value; //returns the value between indices 0 and 1. 
	 *  @type  {Positive}
	 */
	this.index = options.index;
};

Tone.extend(Tone.CtrlInterpolate);

/**
 *  The defaults
 *  @const
 *  @type  {Object}
 */
Tone.CtrlInterpolate.defaults = {
	"index" : 0,
	"values" : []
};

/**
 *  The current interpolated value based on the index
 *  @readOnly
 *  @memberOf Tone.CtrlInterpolate#
 *  @type {*}
 *  @name value
 */
Object.defineProperty(Tone.CtrlInterpolate.prototype, "value", {
	get : function(){
		var index = this.index;
		index = Math.min(index, this.values.length - 1);
		var lowerPosition = Math.floor(index);
		var lower = this.values[lowerPosition];
		var upper = this.values[Math.ceil(index)];
		return this._interpolate(index - lowerPosition, lower, upper);
	}
});

/**
 *  Internal interpolation routine
 *  @param  {NormalRange}  index  The index between the lower and upper
 *  @param  {*}  lower 
 *  @param  {*}  upper 
 *  @return  {*}  The interpolated value
 *  @private
 */
Tone.CtrlInterpolate.prototype._interpolate = function(index, lower, upper){
	if (Tone.isArray(lower)){
		var retArray = [];
		for (var i = 0; i < lower.length; i++){
			retArray[i] = this._interpolate(index, lower[i], upper[i]);
		}
		return retArray;
	} else if (Tone.isObject(lower)){
		var retObj = {};
		for (var attr in lower){
			retObj[attr] = this._interpolate(index, lower[attr], upper[attr]);
		}
		return retObj;
	} else {
		lower = this._toNumber(lower);
		upper = this._toNumber(upper);
		return (1 - index) * lower + index * upper;
	}
};

/**
 *  Convert from the given type into a number
 *  @param  {Number|String}  value
 *  @return  {Number}
 *  @private
 */
Tone.CtrlInterpolate.prototype._toNumber = function(val){
	if (Tone.isNumber(val)){
		return val;
	} else {
		//otherwise assume that it's Time...
		return this.toSeconds(val);
	}
};

/**
 *  Clean up
 *  @return  {Tone.CtrlInterpolate}  this
 */
Tone.CtrlInterpolate.prototype.dispose = function(){
	this.values = null;
};

export default Tone.CtrlInterpolate;