var regex = /((([a-zA-Z]+(-[a-zA-Z0-9]+){0,2})|\*)(;q=[0-1](\.[0-9]+)?)?)*/g;

module.exports.parse = function(al){
    var strings = (al || "").match(regex);
    return strings.map(function(m){
        if(!m){
            return;
        }

        var bits = m.split(';');
        var ietf = bits[0].split('-');
        var hasScript = ietf.length === 3;

        return {
            code: ietf[0],
            script: hasScript ? ietf[1] : null,
            region: hasScript ? ietf[2] : ietf[1],
            quality: bits[1] ? parseFloat(bits[1].split('=')[1]) : 1.0
        };
    }).filter(function(r){
            return r;
        }).sort(function(a, b){
            return b.quality - a.quality;
        });
};

module.exports.pick = function(supportedLanguages, acceptLanguage){
    if (!supportedLanguages || !supportedLanguages.length || !acceptLanguage) {
        return null;
    }

    var accept = this.parse(acceptLanguage);

    var supported = supportedLanguages.map(function(support){
        var bits = support.split('-');
        var hasScript = bits.length === 3;

        return {
            code: bits[0],
            script: hasScript ? bits[1] : null,
            region: hasScript ? bits[2] : bits[1]
        };
    });

    for (var i = 0; i < accept.length; i++) {
        var lang = accept[i];
        var langCode = lang.code.toLowerCase();
        var langRegion = lang.region ? lang.region.toLowerCase() : lang.region;
        var langScript = lang.script ? lang.script.toLowerCase() : lang.script;
        for (var j = 0; j < supported.length; j++) {
            var supportedCode = supported[j].code.toLowerCase();
            var supportedScript = supported[j].script ? supported[j].script.toLowerCase() : supported[j].script;
            var supportedRegion = supported[j].region ? supported[j].region.toLowerCase() : supported[j].region;
            if (langCode === supportedCode &&
              (!langScript || langScript === supportedScript) &&
              (!langRegion || langRegion === supportedRegion)) {
                return supportedLanguages[j];
            }
        }
    }

    return null;
};