// ==UserScript==
// @name         Steam - Default language
// @version      0.1
// @description  Make sure you always see the steam page in your preferred language. You can configure the language in the language variable.
// @author       Royalgamer06
// @include      *://steamcommunity.com/*
// @include      *://*.steampowered.com/*
// @run-at       document-start
// @grant        none
// @namespace https://greasyfork.org/users/13642
// @downloadURL none
// ==/UserScript==

//SET YOUR LANGUAGE HERE
var language = "en";
/*
bulgarian: bg,
czech: cs,
danish: da,
dutch: nl,
finnish: fi,
french: fr,
greek: el,
german: de,
hungarian: hu,
italian: it,
japanese: ja,
koreana: ko,
norwegian: no,
polish: pl,
portuguese: pt-PT,
brazilian: pt-BR,
russian: ru,
romanian: ro,
schinese: zh-CN,
spanish: es-ES,
swedish: sv-SE,
tchinese: zh-TW,
thai: th,
turkish: tr,
ukrainian: uk
*/

if (location.href.indexOf("l=" + language) == -1) {
    location.href = addParameter(location.href, "l", language, false);
}

function addParameter(url, parameterName, parameterValue, atStart) {
    replaceDuplicates = true;
    var cl = "";
    if(url.indexOf('#') > 0){
        cl = url.indexOf('#');
        urlhash = url.substring(url.indexOf('#'),url.length);
    } else {
        urlhash = '';
        cl = url.length;
    }
    sourceUrl = url.substring(0,cl);

    var urlParts = sourceUrl.split("?");
    var newQueryString = "";

    if (urlParts.length > 1)
    {
        var parameters = urlParts[1].split("&");
        for (var i=0; (i < parameters.length); i++)
        {
            var parameterParts = parameters[i].split("=");
            if (!(replaceDuplicates && parameterParts[0] == parameterName))
            {
                if (newQueryString === "")
                    newQueryString = "?";
                else
                    newQueryString += "&";
                newQueryString += parameterParts[0] + "=" + (parameterParts[1]?parameterParts[1]:'');
            }
        }
    }
    if (newQueryString === "")
        newQueryString = "?";

    if(atStart){
        newQueryString = '?'+ parameterName + "=" + parameterValue + (newQueryString.length>1?'&'+newQueryString.substring(1):'');
    } else {
        if (newQueryString !== "" && newQueryString != '?')
            newQueryString += "&";
        newQueryString += parameterName + "=" + (parameterValue?parameterValue:'');
    }
    return urlParts[0] + newQueryString + urlhash;
}