package org.ggp.base.util.gdl.transforms;
import java.util.ArrayList;
import java.util.List;
import org.ggp.base.util.gdl.grammar.Gdl;
import org.ggp.base.util.gdl.grammar.GdlConstant;
import org.ggp.base.util.gdl.grammar.GdlDistinct;
import org.ggp.base.util.gdl.grammar.GdlFunction;
import org.ggp.base.util.gdl.grammar.GdlLiteral;
import org.ggp.base.util.gdl.grammar.GdlNot;
import org.ggp.base.util.gdl.grammar.GdlOr;
import org.ggp.base.util.gdl.grammar.GdlPool;
import org.ggp.base.util.gdl.grammar.GdlProposition;
import org.ggp.base.util.gdl.grammar.GdlRelation;
import org.ggp.base.util.gdl.grammar.GdlRule;
import org.ggp.base.util.gdl.grammar.GdlVariable;
/**
* As a GDL transformer, this class takes in a GDL description of a game,
* transforms it in some way, and outputs a new GDL descriptions of a game
* which is functionally equivalent to the original game.
*
* DeORer removes OR rules from the GDL. Technically, these rules shouldn't
* be in the GDL in the first place, but it's very straightforward to remove
* them, so we do that so that we can handle GDL descriptions that use OR.
*
* @author Ethan Dreyfuss
*/
public class DeORer {
public static List<Gdl> run(List<Gdl> description)
{
List<Gdl> newDesc = new ArrayList<Gdl>();
for(Gdl gdl : description)
{
if(gdl instanceof GdlRule)
{
GdlRule rule = (GdlRule)gdl;
List<List<GdlLiteral>> newBodies = deOr(rule.getBody());
for(List<GdlLiteral> body : newBodies)
{
newDesc.add(GdlPool.getRule(rule.getHead(), body));
}
}
else
newDesc.add(gdl);
}
return newDesc;
}
private static List<List<GdlLiteral>> deOr(List<GdlLiteral> rhs) {
List<List<GdlLiteral>> wrapped = new ArrayList<List<GdlLiteral>>();
wrapped.add(rhs);
return deOr2(wrapped);
}
private static List<List<GdlLiteral>> deOr2(List<List<GdlLiteral>> rhsList) {
List<List<GdlLiteral>> rval = new ArrayList<List<GdlLiteral>>();
boolean expandedSomething = false;
for(List<GdlLiteral> rhs : rhsList)
{
int i=0;
if(!expandedSomething)
{
for(GdlLiteral lit : rhs)
{
if(!expandedSomething)
{
List<Gdl> expandedList = expandFirstOr(lit);
if(expandedList.size() > 1)
{
for(Gdl replacement : expandedList)
{
List<GdlLiteral> newRhs = new ArrayList<GdlLiteral>(rhs);
if(!(replacement instanceof GdlLiteral)) throw new RuntimeException("Top level return value is different type of gdl.");
GdlLiteral newLit = (GdlLiteral)replacement;
newRhs.set(i, newLit);
rval.add(newRhs);
}
expandedSomething = true;
break;
}
}
i++;
}
if(!expandedSomething) //If I didn't find anything to expand
rval.add(rhs);
}
else
rval.add(rhs); //If I've already expanded this function call
}
if(!expandedSomething)
return rhsList;
else
return deOr2(rval);
}
private static List<Gdl> expandFirstOr(Gdl gdl) {
List<Gdl> rval;
List<Gdl> expandedChild;
if(gdl instanceof GdlDistinct)
{
//Can safely be ignored, won't contain 'or'
rval = new ArrayList<Gdl>();
rval.add(gdl);
return rval;
}
else if(gdl instanceof GdlNot)
{
GdlNot not = (GdlNot)gdl;
expandedChild = expandFirstOr(not.getBody());
rval = new ArrayList<Gdl>();
for(Gdl g : expandedChild)
{
if(!(g instanceof GdlLiteral)) throw new RuntimeException("Not must have literal child.");
GdlLiteral lit = (GdlLiteral)g;
rval.add(GdlPool.getNot(lit));
}
return rval;
}
else if(gdl instanceof GdlOr)
{
GdlOr or = (GdlOr)gdl;
rval = new ArrayList<Gdl>();
for(int i=0; i<or.arity(); i++)
{
rval.add(or.get(i));
}
return rval;
}
else if(gdl instanceof GdlProposition)
{
//Can safely be ignored, won't contain 'or'
rval = new ArrayList<Gdl>();
rval.add(gdl);
return rval;
}
else if(gdl instanceof GdlRelation)
{
//Can safely be ignored, won't contain 'or'
rval = new ArrayList<Gdl>();
rval.add(gdl);
return rval;
}
else if(gdl instanceof GdlRule)
{
throw new RuntimeException("This should be used to remove 'or's from the body of a rule, and rules can't be nested");
}
else if(gdl instanceof GdlConstant)
{
//Can safely be ignored, won't contain 'or'
rval = new ArrayList<Gdl>();
rval.add(gdl);
return rval;
}
else if(gdl instanceof GdlFunction)
{
//Can safely be ignored, won't contain 'or'
rval = new ArrayList<Gdl>();
rval.add(gdl);
return rval;
}
else if(gdl instanceof GdlVariable)
{
//Can safely be ignored, won't contain 'or'
rval = new ArrayList<Gdl>();
rval.add(gdl);
return rval;
}
else
{
throw new RuntimeException("Uh oh, gdl hierarchy must have been extended without updating this code.");
}
}
}