(*The PieChart object models the piechart functionality of grade scaling*)
module PieChart;

from GradeTable import all;
from histogram import all;
from class import all;
export all;

object GradeScale is
   components: piechart:PieChart, histogram:Histogram, gradetable:GradeTable;
end GradeScale;

object PieChart is
   components: piesector:PieSector*;
end PieChart;

object PieSector is
   components: Color, lettergrade:string, percentage:integer;
end PieSector;

object Color is
   components: Red:integer, Green:integer, Blue:integer;
end Color;

operation ModifyPieChart is
   inputs: gs:GradeScale, class:Class;
   outputs: gs':GradeScale;
   precondition: (*The PieChart should never be in a state where input has be checked. No precondition.*);
   postcondition: (*The new gradescale's data matches that of the modified piechart.*)
      (SumOfPercentageInSector(gs'.piechart, 1) = 100) 
         
        and 

      (forall (i:integer | i >= 1 and (i < #(gs'.piechart.piesector)))
         (gs'.piechart.piesector[i].lettergrade = 
	    gs'.histogram.histogramsector[i].lettergrade) 
	 
	       and 
	       
	 (gs'.piechart.piesector[i].percentage = 
	     (gs'.histogram.histogramsector[i].studentcount / #(class.studs) * 100)) 
	 
	       and 

	 (gs'.piechart.piesector[i].lettergrade = 
	     gs'.gradetable.rga[i].lettergrade) 
	   
	       and 

	 (gs'.piechart.piesector[i].percentage = 
	     gs'.gradetable.rga[i].percentage)
      );

   description: (*Modifies the displayed piechart, histogram, gradetable and the gradescale given the modified piechart.*); 
end ModifyPieChart;

operation SavePieChart is
   inputs: gs:GradeScale, class:Class;
   outputs: class':Class;
   description: (*Saves the modified gradescale given the modified piechart.*);
   precondition: (*The input of GradeScale should never be in a state where a check is needed. No precondition.*);
   postcondition: (*The new class's gradescale is the inputted gradescale.*)
      class'.gradescale = gs;
end SavePieChart;

operation CreatePieChart is
   inputs: gradescale:GradeScale;
   outputs: piechart':PieChart;
   description: (*Creates the piechart from gradescale when the gradescale functionality is first called*);
   precondition: (*The input of GradeScale should never be in a state where a check is needed. No precondition.*);
   postcondition: (*The created piechart is the piechart in gradescale*)
      piechart' = gradescale.piechart;
end CreatePieChart;

function SumOfPercentageInSector(piechart:PieChart, index:integer) -> integer =
   (if (piechart.piesector[index] != nil)
   then piechart.piesector[index].percentage + SumOfPercentageInSector(piechart, index + 1)
   else 0);

end PieChart;