(****
 *
 * Module StudentEdit defines the objects and operations related to generic editing
 * in the Student Application system
 *
 *)
module StudentEdit;

	from StudentApp import Quarters;
	from StudentFile import UserID;
	export Clipboard, Selection, SelectionContext, UserWorkSpace;

	object Clipboard is
		components: string;
		description: (*
			The clipboard holds a selection of cut or copied text.
		*);
	end Clipboard;

	object Selection is
		components: start_position:integer and end_position:integer and
			context:string;
		description: (*
			The workspace text selection is the defined as the starting and ending
			character positions in current workspace text context.
		*);
	end Selection;

	object SelectionContext is
		components: string;
		description: (*
			SelectionContext is the text context in which the user makes a
			selection.
	*);
	end SelectionContext;

	operation EditUndo is
		inputs: uws:UserWorkSpace;
		outputs: uws':UserWorkSpace;
		description: (*
			Undo the most recent student plan operation.  Only one level of undo/redo
			is specified here.  Successive invocations of undo toggle between the
			current and previous states of the Student Application.  
		*);
	end EditUndo;

	operation EditRedo is
		inputs: uws:UserWorkSpace;
		outputs: uws':UserWorkSpace;
		description: (*
			Redo the most recent student plan operation.  Only one level of undo/redo
			is specified here.  Successive invocations of undo toggle between the
			current and next states of the Student Application.
		*);
	end EditRedo;

	operation EditCut is
		inputs: uws:UserWorkSpace;
		outputs: uws':UserWorkSpace;
		description: (*
			The currently selected text segment is copied into the clipboard and
			removed from its context.  The workspace selection in set to empty.
		*);
	end EditCut;

	operation EditCopy is
		inputs: uws:UserWorkSpace;
		outputs: uws':UserWorkSpace;
		description: (*
			The currently selected text segment is copied into the clipboard;
    	*);
  	end EditCopy;

	operation EditPaste is
		inputs: uws:UserWorkSpace;
		outputs: uws':UserWorkSpace;
		description: (*
			Paste the contents of the clipboard into the currently selected
		start position, replacing any selected text from start to end position.
		*);
	end EditPaste;

	object UserWorkSpace is
		components: uid:UserID and qtr:Quarters* and previous_state:PreviousState 
			and clipboard:Clipboard and selection:Selection and  next_state:NextState
			context:SelectionContext;
    	description: (*
			The UserWorkSpace contains the active plan upon which the user is
			working.  The first component is the UserId of the current user, which
			is used as necessary by operations that input the workspace to
			determine who the user is.  The Quarters* component is the list of
			planned quarters.  The previous_state component is used to support one 
			level of command undo. The next_state component is used to support one 
			level of command redo. The Clipboard is used with the Edit cut, copy, 
			and paste operations.
		*);
	end UserWorkSpace;

	object PreviousState is
		components: Quarters*;
		description: (*
			PreviousState is the snapshot of planned items before the most
			recently performed planning operation used by EditUndo.
		*);
	end PreviousState;

	object NextState is
		components: Quarters*;
		description: (*
			NextState is the snapshot of planned items aftere the most
			recently performed planning operation used by EditRedo.
		*);
	end PreviousState;
	
end StudentEdit;