classdef MyNewpUsbComm < MySingleton
    
    properties (GetAccess = public, SetAccess = private)
        
        % Driver in use
        isbusy = false
    end
    
    properties (Access = public)
        
        % An instance of Newport.USBComm.USB class 
        Usb
    end
    
    methods(Access = private)
        
        % The constructor of a singleton class should only be invoked from
        % the instance method.
        function this = MyNewpUsbComm()
            disp(['Creating a new instance of ' class(this)])
            loadLib(this);
        end
    end
    
    methods(Access = public)
        
        % Load dll
        function loadLib(this)
            dll_path = which('UsbDllWrap.dll');
            if isempty(dll_path)
                error(['UsbDllWrap.dll is not found. This library ',...
                    'is a part of Newport USB driver and needs ',...
                    'to be present on Matlab path.'])
            end
            NetAsm = NET.addAssembly(dll_path);
            
            % Create an instance of Newport.USBComm.USB class
            Type = GetType(NetAsm.AssemblyHandle, 'Newport.USBComm.USB');
            this.Usb = System.Activator.CreateInstance(Type);
        end
        
        function str = query(this, addr, cmd)
            
            % Check if the driver is already being used by another process.
            % A race condition with various strange consequences is 
            % potentially possible if it is.
            assert(~this.isbusy, 'Newport Usb Comm is already in use.')
            
            this.isbusy = true;
            
            % Send query using QueryData buffer. A new buffer needs to be
            % created every time to ensure the absence of interference 
            % between different queries.
            QueryData = System.Text.StringBuilder(64);
            
            stat = Query(this.Usb, addr, cmd, QueryData);
            
            if stat ~= 0
                warning(['Query to Newport usb driver was unsuccessful. '...
                    MyNewpUsbComm.commStatToMessage(stat)]);
            end
            
            str = char(ToString(QueryData));
            
            this.isbusy = false;
        end
    end
    
    methods (Static)
        
        % Convert the code returned by read/write/query functions to
        % a message
        function str = commStatToMessage(stat)
            switch stat
                case 0
                    
                    % No error
                    str = 'Success'; 
                case 1
                    str = ['Error: More than one device on the bus has '...
                        'the same device ID'];
                case -1
                    str = 'General Error';
                case -2
                    str = ['Error: The device ID cannot be found ' ...
                        'among the open devices on the bus'];
                case -3
                    str = ['Error: The device ID is outside the valid ' ...
                        'range of 0 - 31'];
                otherwise
                    str = sprintf('Error Code = %i', stat);
            end
        end
        
        % Concrete implementation of the singleton constructor.
        function this = instance()
            persistent UniqueInstance

            if isempty(UniqueInstance) || ~isvalid(UniqueInstance)
                this = MyNewpUsbComm();
                UniqueInstance = this;
            else
                this = UniqueInstance;
            end
        end
    end
end