module Tk
  # Manipulate Tk clipboard
  #
  # This command provides an interface to the Tk clipboard, which stores data
  # for later retrieval.
  # In order to copy data into the clipboard, [Clipboard.clear] must be called,
  # followed by a sequence of one or more calls to [Clipboard.append].
  # To ensure that the clipboard is updated atomically, all appends should be
  # completed before returning to the event loop.
  module Clipboard
    def clipboard_clear
      Clipboard.clear(self)
    end

    def clipboard_append(options = {})
      Clipboard.append({displayof: self}.merge(options))
    end

    def clipboard_get(type = None)
      Clipboard.get(self, type)
    end

    def clipboard_set(string, options = {})
      clipboard_clear
      clipboard_append(options.merge(data: string))
    end

    module_function

    # Claims ownership of the clipboard on window's display and removes any
    # previous contents.
    # Window defaults to ".".
    def clear(window = None)
      if None == window
        Tk.execute_only(:clipboard, :clear)
      else
        Tk.execute_only(:clipboard, :clear, '-displayof', window)
      end
    end

    # Appends data to the clipboard on window's display in the form given by
    # +type+ with the representation given by +format+ and claims ownership of
    # the clipboard on window's display.
    #
    # +type+ specifies the form in which the selection is to be returned (the
    # desired "target" for conversion, in ICCCM terminology), and should be an
    # atom name such as STRING or FILE_NAME; see the Inter-Client Communication
    # Conventions Manual for complete details.
    # +type+ defaults to STRING.
    #
    # The +format+ argument specifies the representation that should be used to
    # transmit the selection to the requester (the second column of Table 2 of
    # the ICCCM), and defaults to STRING.
    #
    # If +format+ is STRING, the selection is transmitted as 8-bit ASCII
    # characters. If +format+ is ATOM, then the data is divided into fields
    # separated by white space; each field is converted to its atom value, and
    # the 32-bit atom value is transmitted instead of the atom name.
    # For any other +format+, data is divided into fields separated by white
    # space and each field is converted to a 32-bit integer; an array of
    # integers is transmitted to the selection requester.
    # Note that strings passed to clipboard append are concatenated before
    # conversion, so the caller must take care to ensure appropriate spacing
    # across string boundaries.
    # All items appended to the clipboard with the same +type+ must have the
    # same +format+.
    # The +format+ is needed only for compatibility with clipboard requesters
    # that do not use Tk.
    # If the Tk toolkit is being used to retrieve the CLIPBOARD selection then
    # the value is converted back to a string at the requesting end, so +format+
    # is irrelevant.
    def append(options = {})
      args = []

      displayof, format, type, data =
        options.values_at(:displayof, :format, :type, :data)

      format = format.to_s.upcase if format

      args << "-displayof" << displayof if displayof
      args << "-format" << format.to_s.upcase if format
      args << "-type" << type.to_s.upcase if type
      args << "--" << data.to_s

      Tk.execute_only(:clipboard, :append, *args)
    end

    # Retrieve data from the clipboard on +window+'s display.
    # +window+ defaults to ".".
    # +type+ specifies the form in which the data is to be returned and should be
    # an atom name such as STRING or FILE_NAME.
    # +type+ defaults to STRING.
    # This is equivalent to `Selection.get(selection: :clipboard)`.
    def get(window = None, type = None)
      options = {}
      options[:displayof] = window unless None == window
      options[:type] = type.to_s.upcase unless None == type

      Tk.execute(:clipboard, :get, options.to_tcl_options).to_s
    end
  end
end