module TestGeneration;

from Test_Preferences import all;
from QuestionManagement import all;
from TestPackage import all;
export all;

object TestFilter is
   components: tn:TestName and class:Class and ft:FilterTime and fl:FilterLength and td:TestDifficulty
      and useOld:IsReuse and numDays:DaysOld and author:Author* and rand:IsRandom and tkw:TestKeyword* and
      ntf:NumTF and nmc:NumMC and ness:NumEssay and ncde:NumCode and nfill:NumFill;
   description: (*Specefies the parameters for which questions in
       QuestionDatabase must adhere to.
   *);
end TestFilter;

object FilterTime is 
   components: integer;
   description: (*
      The user-inputted duration of a test.
   *);
end FilterTime;

object FilterLength is
   components: integer;
   description: (*
      The user-inputted number of questions of a test.
   *);
end FilterLength;

object IsReuse is 
   components: boolean;
   description: (*
      Determines whether the user wants to enable the filter by days option
   for question filtering from a question database.
   *);
end IsReuse;

object DaysOld is 
   components: integer;
   description: (*
      The user-inputted value that uses questions whose LastUsed component
   is more than DaysOld away. IsReuse must be true for this option to be
   enabled.
   *);
end DaysOld;

object IsRandom is
   components: boolean;
   description: (*
      Determines whether the user wants to specify the number of each question
   format or not.
   *);
end IsRandom;

object NumTF is 
   components: integer;
   description: (*
      Allows the user to specify how many true/false questions should be on
   a test. IsRandom must be false for this object to be valid.
   *);
end NumTF;

object NumMC is 
   components: integer;
   description: (*
      Allows the user to specify how many multiple choice questions should be
   on a test. IsRandom must be false for this object to be valid.
   *);
end NumMC;

object NumEssay is
   components: integer;
   description: (*
      Allows the user to specify how many essay questions should be on a test.
   IsRandom must be false for this object to be valid.
   *);
end NumEssay;

object NumCode is 
   components: integer;
   description: (*
      Allows the user to specify how many coding questions should be on a test.
   IsRandom must be false for this object to be valid.
   *);
end NumCode;

object NumFill is
   components: integer;
   description: (*
      Allows the user to specify how many fill in the blank questions should
   be on a test.  IsRandom must be false for this object to be valid.
   *);
end NumFill;

object SystemTime is
	components: t:integer;
	description: (*
		The current system time.
	*);
end SystemTime;

function Today(st:SystemTime) =
   (*
      Today's date in an integer form.
   *)
   st.t;

operation CreateTest
   inputs: tst:Test, tf:TestFilter, qdb:QuestionDatabase, tp:TestPreferences,
      st:SystemTime;
   outputs: tst':Test;

   precondition: 
      (*
       * The test is blank.
       *)
      #tst.qs = 0
      
         and
      
      (*
       * The TestName field has a value.
       *)
      tf.tn != nil
       
         and
       
      (*
       * The Class field has a value.
       *)

      exists (q in qdb.qs) q.class = tf.class

         and

      (*
       * The FilterTime field has a valid value defined
       * as more than 0 and less than 24 hours.
       *)

      (tf.ft != nil) and (tf.ft > 0) and (tf.ft <= 1440)

         and

      (*
       * The Difficulty field has a valud value between
       * 1 and 10.
       *)

      (tf.td >= 1) and (tf.td <= 10)

         and

      (*
       * IsReuse is true iff DaysOld has a valid value
       *)

      tf.useOld iff (tf.numDays > 0)

         and

      (*
       * Question format is defined by the user iff
       * all question format counts have valid values, and
       * all values add to total number of questions, if
       * number of questions is defined by the user.
       *)

      tf.rand iff (tf.ntf >= 0) and (tf.nmc >= 0) and
      (tf.ness >= 0) and (tf.ncde >= 0) and (tf.nfill >= 0)
         and
      (if (tf.fl != nil) then (tf.ntf + tf.nmc + tf.ness +
      tf.ncde + tf.nfill = tf.fl));


   postcondition: 
      (*
       * All questions in tst' were pulled from qdb.
       *)
      forall (q:TestQuestion)
         (q in tst'.qs) iff (q in qdb.qs)

      and

      (*
       * All questions in tst' satisfy the TestFilter
       * conditions.
       *)
      forall (q:TestQuestion)
         (if (q in tst'.qs) then ((q.class = tf.class) and 
         ((q.diff + tp.df.v >= tf.td) or
         (q.diff - tp.df.v <= tf.td)) and
         (if (tf.useOld) then (q.lu + tf.numDays < Today(st))) and
         forall (j:integer | j >= 1 and j <= #q.keywords)
            (q.keywords[j] in tf.tkw))

      and

      (*
       * The outputted test satisfies the TestFilter
       * conditions.
       *)
      (tst'.tn = tf.tn) and (tst'.cl = tf.class) and
         ((tst'.tl + tp.tv.v >= tf.ft) or
         (tst'.tl - tp.tv.v <= tf.ft)) and
         ((#tst'.qs + tp.tlv.v >= tf.fl) or
         (#tst'.qs - tp.tlv.v <= tf.fl)) and
         ((tst'.td + tp.df.v >= tf.td) or
         (tst'.td - tp.df.v <= tf.td)) and
         (tst'.tkw = tf.tkw) and ((tst'.ntf + tp.fv.v >= tf.ntf) or
         (tst'.ntf - tp.fv.v <= tf.ntf)) and
         ((tst'.nmc + tp.fv.v >= tf.nmc) or
         (tst'.nmc - tp.fv.v <= tf.nmc)) and
         ((tst'.ness + tp.fv.v >= tf.ness) or
         (tst'.ness - tp.fv.v <= tf.ness)) and
         ((tst'.ncde + tp.fv.v >= tf.ncde) or 
         (tst'.ncde - tp.fv.v <= tf.ncde)) and
         ((tst'.nfill + tp.fv.v >= tf.nfill) or
         (tst'.nfill - tp.fv.v <= tf.nfill)));

   description: (*
      Creates a new test using TestFilter to sort out questions in the
   QuestionDatabase
   *);
end CreateTest;

end TestGeneration;