module Syncing;
from QuestionManagement import all;
export all;

object SyncCriteria is
	components: crit:Criteria*;
	description: 
	(*
		Contains all of the criteria for searching for questions to sync.
	*);
end SyncCriteria;
	
obj RemoteAddress is string;

object Criteria is
	components: au:Author or cl:Class or ty:Type or dif:Difficulty or Keyword*;
	description:
	(*
		a criteria that a question can be checked against
	*);
end Criteria;


object QuestionsToRetrieve is
	components: q:Question* ;
	description:
	(*
		The list of questions to retrieve from question db server
	*);
end QuestionsToRetrieve;


object QuestionsToSend is
	components: q:Question* ;
	description:
	(*
		The list of questions to be sent to the question db server
	*);
end QuestionstoSend;


operation FindQuestionsToRetrieve is
	inputs: syncCrit:SyncCriteria, qdb:QuestionDatabase, orig_qdb:QuestionDatabase;
	outputs: qtr:QuestionsToRetrieve ;
	description:
	(*
		finds the questions that match the search criteria on the central qdb server
	*);
	precondition: ;
	postcondition: 

	(forall(q in qdb.qs)
		q in qtr.q iff 
			(forall(crit in syncCrit.crit)
				meetsCriteria(crit, q)))
	and (forall (q' in qtr.q)
		(q' in qdb.qs))
	and (forall (q' in qtr.q)
		(not(q' in orig_qdb.qs)));

end FindQuestionsToRetrieve;



operation FindQuestionsToSend is
	inputs: syncCrit:SyncCriteria, qdb:QuestionDatabase, remote_qdb:QuestionDatabase;
	outputs: qts:QuestionsToSend ;
	description:
	(*
		seaches local question DB for questions to load to server
	*);
	precondition: ;
	postcondition: 

	(forall(q in qdb.qs)
		q in qts.q iff 
			(forall(crit in syncCrit.crit)
				meetsCriteria(crit, q)))
	and (forall (q' in qts.q) q' in qdb.qs)
	and (forall (q' in qts.q)
		not(q' in remote_qdb.qs));

end FindQuestionsToSend;


operation RetrieveQuestions is
	inputs: qtr:QuestionsToRetrieve, qdb:QuestionDatabase;
	outputs: qdb':QuestionDatabase;
	description:
	(*
		adds the retrieved questions to the local question database
	*);
	precondition: 
		forall(q in qtr.q)
			not(q in qdb.qs) ;
	postcondition:

	(forall (q in qdb.qs) 
		(q in qdb'.qs))
	and (forall (q in qtr.q)
		(q in qdb'.qs))
	and (forall (q' in qdb'.qs)
		(q' in qdb.qs or q' in qtr.q))
	and (#qdb'.qs = #qtr.q + #qdb.qs);

end RetrieveQuestions;


operation SendQuestions is
	inputs: qts:QuestionsToSend, RemoteAddress, qdb:QuestionDatabase;
	outputs: qdb':QuestionDatabase;
	description:
	(*
		adds the sent questions to the remote question database
	*);
	precondition: 
		forall(q in qts.q)
			not(q in qdb.qs);
	postcondition:
	(forall (q in qdb.qs) 
		(q in qdb'.qs))
	and (forall (q in qts.q)
		(q in qdb'.qs))
	and (forall (q' in qdb'.qs)
		(q' in qdb.qs or q' in qts.q))
	and (#qdb'.qs = #qts.q + #qdb.qs);
end SendQuestions;

function meetsCriteria(Criteria, Question)
	(* I'm unsure how to do this in RSL because I or'ed the different categories of criteria, but this means true if the given questions meets the given criteria*)
end meetsCriteria;

function questionEquality(q:Question, q':Question)=
	q.author = q'.author
	and q.t = q'.t
	and q.qt = q'.qt
	and q.qa = q'.qa
	and q.time = q'.time
	and q.diff = q'.diff
	and q.keywords = q'.keywords
	and q.class = q'.class;

end Syncing;