module File;

   from EclassDB import all;
   export all;

   object FileSpace is File*
	components: ;
	description: (*
		A File Space is a representation of where File(s) are present in the E-Class operating environment.
	*);
   end;

   object File is 
	components: name:FileName and file_type:FileType and approval:FileApproval and data:FileData;
	description: (*
		The File object is a representation of a file stored in a file space. It has a file name and a file type.
	*);
   end File;


   object FileName is string
	components: ;
	description: (*
		This is a string reprepresentation of the name of the file.
	*);
   end;

   object FileType is html_type:HtmlType or other_type:OtherType or eclass_type:EclassType
	components: ;
	description: (*
		The type of data is either Html or another type of data.

	*);
   end;

   object HtmlType
	components: ;
	description: (*
		File data typing tag indicating that the file contains html data.
	*);
   end HtmlType;
   
   object EclassType
	components: ;
	description: (*
		File data typing tag indicating that the file contains Eclass data.
	*);
   end EclassType;

   object OtherType
	components: ;
	description: (*
		File data typing tag indicating that the file conatins data different from html data.
	*);
   end OtherType;

   object FileApproval is writable:FileWritable and readable:FileReadable
	description: (*
		Indicates whether a file is readable and/or writable.
	*);
   end;

   object FileReadable is boolean
	components: ;
	description: (*
		Flag indicating whether the file can be read by the FileOpen operation.  Flag has to be true by the FileOpen operation.
		
	*);
   end;

   object FileWritable is boolean
	components: ;
	description: (*
		Flag indicating whether the file can be saved by the FileSave operation.  Flag has to be true by the FileSave operation.
		
	*);
   end;
   
   object Server is users:Users and db:Database
	description: (*
		The server has a list of users that can access and a database.
	*);
   end;

   
   object Users is UserRecord*
	description: (*
		Users is a part of the user record that has a user id and password.
	*);
   end;

   
   object UserRecord is id:UserID and pwd:Password
	description: (*
		A user record consists of a user id and password.
	*);
   end;

   
   object UserID is string
	description: (*
		The ID of a user is in the form of a string.
	*);
   end;

   
   object Password is string
	description: (*
		The password of a user is in the form of a string.
	*);
   end;

   
   object Database is string
	description: (*
		The database of servers on the network.
	*);
   end;

   object FileData is UserLecture
	description: (*
		Data type of file is UserLecture.
	*);
   end;   

   object ServerUp is boolean
   	description: (*
		Indicates whether the server is connected.
	*);
   end;

   operation LogOn is
	inputs: server:Server, id:UserID, pwd:Password, url:URL, cn:CourseNumber,
		sec:Section;
	outputs: db:Database, connect:ServerUp;
	precondition: 
		exists (u in server.users) (u.id = id) and (u.pwd = pwd) and
		(url != nil) and	
		(cn != nil) and
		(sec != nil);
	postcondition: db = server.db and connect = true;
	description: (*
		Operation that takes in the inputs and make sure that they are not empty
		and also makes sure that user exists in server.  Has post conditions
		for makeing sure that the server is connected.		
	*);	
   end;

   operation LogOut is
	inputs: server:Server, db:Database, connect:ServerUp;
	outputs: db':Database, connect':ServerUp;
	precondition: db = server.db and connect = true;
	postcondition: db' != server.db and connect = false;
	description: (*
		Terminates the server.
	*);	
   end;
 
   operation FileOpen is
	inputs: fs:FileSpace, fn:FileName, ews:EclassWorkSpace;
	outputs: ews':EclassWorkSpace;
	precondition:
		exists (file in fs)
		(file.name= fn) and
		file.approval.readable and
		(file.file_type?html_type or file.file_type?eclass_type);
	postcondition:
		(exists (ul:UserLecture)
		(ul = ews'.lectures[1]) and
		(ul.id = ews.id) and
		(exists (file in fs)
		   (file.name = fn) and
		   (ul = file.data)) and
		(not ul.nts) and
		(#ews'.lectures)  = #(ews.lectures) +1) and
		(forall (i:integer | (i >= 2) and (i <= #(ews.lectures)))
		   ews'.lectures[i+1] = ews.lectures[i+1]
		);
	description: (*
		Opening an existing html or other file.
	*);	
   end;

   operation FileSave is
	inputs: fs:FileSpace, ews:EclassWorkSpace;
	outputs: fs':FileSpace, ews':EclassWorkSpace;
	precondition:
		(ews.lectures[1].nts)
		and
		(exists (file in fs)
		   (file.name = ews.lectures[1].file.name) and
		   (file.approval.writable));
	postcondition:
		(exists (file in fs')
		   (file.name = ews'.lectures[1].file.name) and
		   (file.data = ews'.lectures[1]) and
		   (file.approval.writable) and
		   (file.file_type?html_type or file.file_type?eclass_type) and
		   (not ews'.lectures[1].nts)
		);
	description: (*
		Saves work done in the lecture in a html or eclass format.
	*);	
   end;

   operation FileSaveAs is
	inputs: fs:FileSpace, ews:EclassWorkSpace;
	outputs: fs':FileSpace, ews':EclassWorkSpace;
	precondition:
		(ews.lectures[1].nts)
		and
		(exists (file in fs)
		   (file.name = ews.lectures[1].file.name) and
		   (file.approval.writable));
	postcondition:
		(exists (file in fs')
		   (file.name = ews'.lectures[1].file.name) and
		   (file.data = ews'.lectures[1]) and
		   (file.approval.writable) and
		   (file.file_type?html_type or file.file_type?eclass_type) and
		   (not ews'.lectures[1].nts));
		
	description: (*
		Saves work from a previously saved to a html or eclass format.
	*);	
   end;

   operation FileSaveAll is
	inputs: fs:FileSpace, ews:EclassWorkSpace;
	outputs: fs':FileSpace, ews':EclassWorkSpace;
	precondition: 
		(forall (i:integer | (i >= 1) and (i <= #(ews.lectures)))
		   (ews.lectures[i].nts))
		and
		(forall (i:integer | (i >= 1) and (i <= #(ews.lectures)))		
		   (exists (file in fs)
		   (file.name = ews.lectures[i].file.name) and
		   (file.approval.writable)));
	postcondition:
		(forall (i:integer | (i >= 1) and (i <= #(ews.lectures)))		
		   (exists (file in fs')
		   (file.name = ews'.lectures[i].file.name) and
		   (file.data = ews'.lectures[i]) and
		   (file.approval.writable) and
		   (file.file_type?html_type or file.file_type?eclass_type) and
		   (not ews'.lectures[i].nts)
		));
	description: (*
		Saves all the lecture opened to a html or eclass format.
	*);
   end;

   operation FileExit is
	inputs: fs:FileSpace, ews:EclassWorkSpace;
	outputs: ews':EclassWorkSpace;
	precondition:
		(forall (i:integer | (i>=1) and (i < #(ews.lectures)))
		not(ews.lectures[1].nts));
	postcondition: ;

	description: (*
		Exits from the program and makes sure that the files don't need to be saved.
	*);	
   end;

   object UserName is string
   	description: (*
		The UserName is in the form of a string.
	*);
   end;
   object IsAnonymous is boolean
   	description: (*
		Indicates whether the user is anonymous or not.
	*);
   end;
   object URL is string
   	description: (*
		The URL of the server is in the form of a string.
	*);
   end;
   object CourseNumber is integer
   	description: (*
		The course number of class logging onto is in the form of an integer.	
	*);
   end;
   object Section is integer
   	description: (*
		The section of the class logging onto is in the form of an integer.
	*);
   end;
   
   object IsConnected is boolean
   	description: (*
		Indicates whether the user is connected to the server.
	*);
   end;

   operation ConnectToLecture
	inputs: un:UserName, anon:IsAnonymous, url:URL, cn:CourseNumber,
		sec:Section;
	outputs: connect:IsConnected;
	precondition: (*
		The UserName, URL, CourseNumber, and Section must not be null. 
	*)
	un != nil and
	url != nil and	
	cn != nil and
	sec != nil;
			
	postcondition: (*
		The user successfully connected to the lecture.
	*)
	connect = true;
	description: (*
		Connects user to an active lecture
	*);
   end ConnectToLecture;


end File;