Language API

if shell then
    local tArgs = {...}
    local apiName = fs.getName(shell.getRunningProgram())
    assert(#tArgs > 0, "Usage:\n"..apiName.."<function> [arguments]")
    getfenv()[apiName][tArgs[1]](select(2, unpack(tArgs)))
else
    local translations = {}
    local curLang = "en_US"
    local path = "lang:rom/lang" -- just in case there's a resource pack with lang files

    local function checkString(s)
        if type(s) ~= "string" then
            error("Expected string", 3) -- level three to return to user source; only called from within this API
        end
    end
    function setString(langType, key, value)
        checkString(langType)
        checkString(key)
        checkString(value)
        if not translations[langType] then
            translations[langType] = {}
        end

        translations[langType][key] = value
    end

    function removeString(langType, key)
        checkString(langType)
        checkString(key)
        if translations[langType] then
            translations[langType][key] = nil
        end
    end

    function removeStringForAll(key)
        checkString(key)
        for k,v in pairs(translations) do
            removeString(k, key)
        end
    end

    function getString(key)
        if not translations[curLang] or not translations[curLang][key] then
            return key
        end
        return translations[curLang][key]
    end

    function setPath(sPath)
        checkString(sPath)
        path = sPath
    end

    function appendPath(sPath)
        checkString(sPath)
    end

    function getPath()
        return path
    end

    function getCurrentLanguage()
        return curLang
    end

    function setCurrentLanguage(sCurLang)
        checkString(sCurLang)
        curLang = sCurLang
    end

    function reloadLanguageFiles()
        for sPath in string.gmatch(path, "[^:]+") do
            if fs.isDir(sPath) then
                for i,v in ipairs(fs.list(sPath)) do
                    local filePath = fs.combine(sPath, v)
                    local langName = (v:sub(-5) == ".lang") and v:sub(1, -6) or v
                    if fs.exists(filePath) and not fs.isDir(filePath) then
                        local fileHandle = assert(fs.open(filePath, "r"), "Error reading language file: " .. filePath)
                        local fileContents = fileHandle.readAll()
                        fileHandle.close()
                        for key,val in fileContents:gmatch("([^%s=]+)%s*=%s*([^\n]+)\n?") do
                            setString(langName, key, val)
                        end
                    end
                end
            end
        end
    end

    reloadLanguageFiles()
end