/*
RainbowVis-JS 
Released under MIT License
*/

function Rainbow()
{
    var gradients = null;
    var minNum = 0;
    var maxNum = 100;
    var colours = ['ff0000', 'ffff00', '00ff00', '0000ff']; 
    setColours(colours);
    
    function setColours (spectrum) 
    {
	if (spectrum.length < 2) {
	    throw new Error('Rainbow must have two or more colours.');
	} else {
	    var increment = (maxNum - minNum)/(spectrum.length - 1);
	    var firstGradient = new ColourGradient();
	    firstGradient.setGradient(spectrum[0], spectrum[1]);
	    firstGradient.setNumberRange(minNum, minNum + increment);
	    gradients = [ firstGradient ];
	    
	    for (var i = 1; i < spectrum.length - 1; i++) {
		var colourGradient = new ColourGradient();
		colourGradient.setGradient(spectrum[i], spectrum[i + 1]);
		colourGradient.setNumberRange(minNum + increment * i, minNum + increment * (i + 1)); 
		gradients[i] = colourGradient; 
	    }

	    colours = spectrum;
	    return this;
	}
    }

    this.setColors = this.setColours;

    this.setSpectrum = function () 
    {
	setColours(arguments);
	return this;
    }

    this.setSpectrumByArray = function (array)
    {
	setColours(array);
        return this;
    }

    this.colourAt = function (number)
    {
	if (isNaN(number)) {
	    throw new TypeError(number + ' is not a number');
	} else if (gradients.length === 1) {
	    return gradients[0].colourAt(number);
	} else {
	    var segment = (maxNum - minNum)/(gradients.length);
	    var index = Math.min(Math.floor((Math.max(number, minNum) - minNum)/segment), gradients.length - 1);
	    return gradients[index].colourAt(number);
	}
    }

    this.colorAt = this.colourAt;

    this.setNumberRange = function (minNumber, maxNumber)
    {
	if (maxNumber > minNumber) {
	    minNum = minNumber;
	    maxNum = maxNumber;
	    setColours(colours);
	} else {
	    throw new RangeError('maxNumber (' + maxNumber + ') is not greater than minNumber (' + minNumber + ')');
	}
	return this;
    }
}

function ColourGradient() 
{
    var startColour = 'ff0000';
    var endColour = '0000ff';
    var minNum = 0;
    var maxNum = 100;

    this.setGradient = function (colourStart, colourEnd)
    {
	startColour = getHexColour(colourStart);
	endColour = getHexColour(colourEnd);
    }

    this.setNumberRange = function (minNumber, maxNumber)
    {
	if (maxNumber > minNumber) {
	    minNum = minNumber;
	    maxNum = maxNumber;
	} else {
	    throw new RangeError('maxNumber (' + maxNumber + ') is not greater than minNumber (' + minNumber + ')');
	}
    }

    this.colourAt = function (number)
    {
	return calcHex(number, startColour.substring(0,2), endColour.substring(0,2)) 
	+ calcHex(number, startColour.substring(2,4), endColour.substring(2,4)) 
	+ calcHex(number, startColour.substring(4,6), endColour.substring(4,6));
    }
    
    function calcHex(number, channelStart_Base16, channelEnd_Base16)
    {
	var num = number;
	if (num < minNum) {
	    num = minNum;
	}
	if (num > maxNum) {
	    num = maxNum;
	} 
	var numRange = maxNum - minNum;
	var cStart_Base10 = parseInt(channelStart_Base16, 16);
	var cEnd_Base10 = parseInt(channelEnd_Base16, 16); 
	var cPerUnit = (cEnd_Base10 - cStart_Base10)/numRange;
	var c_Base10 = Math.round(cPerUnit * (num - minNum) + cStart_Base10);
	return formatHex(c_Base10.toString(16));
    }

    formatHex = function (hex) 
    {
	if (hex.length === 1) {
	    return '0' + hex;
	} else {
	    return hex;
	}
    } 
    
    function isHexColour(string)
    {
	var regex = /^#?[0-9a-fA-F]{6}$/i;
	return regex.test(string);
    }

    function getHexColour(string)
    {
	if (isHexColour(string)) {
	    return string.substring(string.length - 6, string.length);
	} else {
	    var colourNames =
		[
		 ['red', 'ff0000'],
		 ['lime', '00ff00'],
		 ['blue', '0000ff'],
		 ['yellow', 'ffff00'],
		 ['orange', 'ff8000'],
		 ['aqua', '00ffff'],
		 ['fuchsia', 'ff00ff'],
		 ['white', 'ffffff'],
		 ['black', '000000'],
		 ['gray', '808080'],
		 ['grey', '808080'],
		 ['silver', 'c0c0c0'],
		 ['maroon', '800000'],
		 ['olive', '808000'],
		 ['green', '008000'],
		 ['teal', '008080'],
		 ['navy', '000080'],
		 ['purple', '800080']
		 ];
	    for (var i = 0; i < colourNames.length; i++) {
		if (string.toLowerCase() === colourNames[i][0]) {
		    return colourNames[i][1];
		}
	    }
	    throw new Error(string + ' is not a valid colour.');
	}
    }
}