/**
 *  Calculate Bus Line Color
 *  @author Trewbot
 *  @param lineName - The name of the bus line as a string.
 *  @return A 6 digit hexadecimal string describing line color.
 */
function lineColor(lineName){
    if(typeof lineName !== "string") throw new Error("Parameter 'abbr' must be a string");
    function letterValue(letter){
        if(letter.length !== 1) throw new Error("Parameter 'letter' must be a single character");
        const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        var value = alphabet.indexOf(letter.toUpperCase());
        if(value < 0) throw new Error("Parameter 'letter' must be alphanumeric");
        return value;
    }
    function HSVtoRGB(h,s,v){
        if(typeof h !== "number" || typeof s !== "number" || typeof v !== "number")
            throw new Error("Parameters 'h', 's', and 'v' must be numbers");
        if(h < 0 || h > 1 || s < 0 || s > 1 || v < 0 || v > 1)
            throw new Error("Parameters must be numbers between 0 and 1");
        var r,g,b,
            i=Math.floor(h*6),
            f=h*6-i,
            p=v*(1-s),
            q=v*(1-f*s),
            t=v*(1-(1-f)*s);
        switch(i%6){
            case 0:r=v,g=t,b=p;break;
            case 1:r=q,g=v,b=p;break;
            case 2:r=p,g=v,b=t;break;
            case 3:r=p,g=q,b=v;break;
            case 4:r=t,g=p,b=v;break;
            case 5:r=v,g=p,b=q;break;
        }
        return[r*255,g*255,b*255];
    }
    function toHexadecimal(n){
        if(typeof n !== "number") throw new Error("Paramter 'n' must be a number");
        n = parseInt(n,10); // Force n to be an integer anyway
        if(isNaN(n)) return "00"; // If that didn't work just return zeroes
        if(n < 0 || n > 255) throw new Error("Parameter 'n' must be in range 0 <= n < 256");
		n = Math.max(0,Math.min(n,255)); // Force n into range anyway
        const hex = "0123456789ABCDEF";
        return hex.charAt((n-n%16)/16)+hex.charAt(n%16);
    }
    //  Calculate a hue using first to letters of lineName
    var h       = letterValue(lineName.charAt(0))/26
                + letterValue(lineName.charAt(1))/(26**2),
        rgb     = HSVtoRGB(h,1,1);
    return toHexadecimal(rgb[0])+toHexadecimal(rgb[1])+toHexadecimal(rgb[2]);
}