(**** 5.3. QuestionBank (editdb.rsl) 
 *
 * Module QuestionBank defines the objects and operations related to using the
 * database to add, insert, view, mask, and modify questions in the database.
 *
 *)
module QuestionBank;

from Question import all;
export all;
		object Question inherits from RawQuestion
    		components: qid:QID, cd:CreationDate, md:ModifiedDate;
    		description:(* adds the following fields SelectCell, QID, CreationDate and ModifiedDate *);
    end Question;

		object QuestionBank is
        components: q:Question* ;
        operations: AddQuestion, DeleteQuestion, SellectAll, MaskQuestions, SortQuestions, InsertSelectedQuestions, ZoomIn, ZoomOut;
            description: (* allows the user to quickly add, insert, modify, sort and delete questions in the database *);
    end QuestionBank;

    
    object QID is integer
        description:(* each question has a unique number in the question bank *);
    end QID;

    object CreationDate is integer
        description:(* indicates the date when the question was added to the question bank *);
    end CreationDate; 

    object ModifiedDate is integer
        description:(* indicates the date and time the question was modified in the question bank *);
    end ModifiedDate; 

    operation AddQuestion is
    		inputs: qb:QuestionBank, q:Question;
    		outputs: qb':QuestionBank;
    		description:(*Add question to QuestionBank*);
    		precondition:(*none*);
    		postcondition:(* The question exists in QuestionBank *)
    									(q in qb')
    										and
    									(* new question bank is old question bank plus qestion*)
    									qb'=qb+q;
    end AddQuestion;
    
    operation MaskQuestions is
        inputs: qb:QuestionBank, qclass:Question.QuestionClassName, qtype:Question.QuestionType, qtime:Question.TimeToComplete;
        outputs: qb':QuestionBank;
        precondition:(* Question parameters like class name, type and time to complete are selected otherwise qb'=qb*)  ;
        postcondition:(* Question matching input parameters are not in the database*)
        							not((qclass in qb') and (qtype in qb') and (qtime in qb')) ;
        description: (*Mask fields in the question bank *);
    end MaskQuestion;

    operation SortQuestions is
        inputs: qb:QuestionBank;
        outputs: qb':QuestionBank;
        precondition: ;
        postcondition: ;
        description: (* takes the database with one header flagged and returns same database with question sorted according with the header field *);
    end SortQuestions;

    operation SelectQuestions is
        inputs: qb:QuestionBank, q:Question;
        outputs: qb':QuestionBank;
        precondition: ;
        postcondition: ;
        description: (*selects one or more questions in the question bank  *);
    end Select;

    operation SelectAll is
        inputs: qb:QuestionBank;
        outputs: qb':QuestionBank, q:Question*;
        precondition: (* question bank is not empty*)
        							not(qb=nil);
        postcondition: (* question bank has not changed and questions are selected*)
        							qb'=qb 
        							and
        							not(q=nil);
        description: (* selects all questions in the question bank *);
    end SelectAll;

    operation DeleteQuestions is
        inputs: qb:QuestionBank, q:Question;
        outputs: qb':QuestionBank;
        precondition:(*a question is selected and the question bank is not empty*)
        						not((q=nil) and (qb=nil));
        postcondition:(*selected question does not exist in the database*) 
        							qb'=qb-q;
        description: (* Deletes selected questions from the question bank *);
    end DeleteQuestions;

    operation InsertSelectedQuestions is
        inputs: qb:QuestionBank, q:Question*;
        outputs: qb':QuestionBank;
        precondition: (* this operation only works if the question bank is not empty and a at least a question is selected *)
        						not((q=nil) and (qb=nil));
        postcondition:qb=qb' ;
        description: (* Copy selected questions into current test *);
    end InsertSelectedQuestions;

    operation ZoomIn is
        inputs: qb:QuestionBank;
        outputs: qb':QuestionBank;
        precondition: ;
        postcondition: qb'=qb;
        description: (* the width and height of cells is incremented *);
    end ZoomIn;

    operation ZoomOut is
        inputs: qb:QuestionBank;
        outputs: qb':QuestionBank;
        precondition: ;
        postcondition: qb'=qb;
        description: (* the width and height of cells is decremented *);
    end ZoomOut;

end QuestionBank;