GdlFactory.java

package org.ggp.base.util.gdl.factory;

import java.util.ArrayList;
import java.util.List;

import org.ggp.base.util.gdl.factory.exceptions.GdlFormatException;
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.GdlSentence;
import org.ggp.base.util.gdl.grammar.GdlTerm;
import org.ggp.base.util.gdl.grammar.GdlVariable;
import org.ggp.base.util.symbol.factory.SymbolFactory;
import org.ggp.base.util.symbol.factory.exceptions.SymbolFormatException;
import org.ggp.base.util.symbol.grammar.Symbol;
import org.ggp.base.util.symbol.grammar.SymbolAtom;
import org.ggp.base.util.symbol.grammar.SymbolList;


public final class GdlFactory
{

    public static Gdl create(String string) throws GdlFormatException, SymbolFormatException
    {
        return create(SymbolFactory.create(string));
    }

    public static Gdl create(Symbol symbol) throws GdlFormatException
    {
        try
        {
            return createGdl(symbol);
        }
        catch (Exception e)
        {
            throw new GdlFormatException(symbol);
        }
    }

    private static GdlConstant createConstant(SymbolAtom atom)
    {
        return GdlPool.getConstant(atom.getValue());
    }

    private static GdlDistinct createDistinct(SymbolList list)
    {
        GdlTerm arg1 = createTerm(list.get(1));
        GdlTerm arg2 = createTerm(list.get(2));

        return GdlPool.getDistinct(arg1, arg2);
    }

    private static GdlFunction createFunction(SymbolList list)
    {
        GdlConstant name = createConstant((SymbolAtom) list.get(0));

        List<GdlTerm> body = new ArrayList<GdlTerm>();
        for (int i = 1; i < list.size(); i++)
        {
            body.add(createTerm(list.get(i)));
        }

        return GdlPool.getFunction(name, body);
    }

    private static Gdl createGdl(Symbol symbol)
    {
        if (symbol instanceof SymbolList)
        {
            SymbolList list = (SymbolList) symbol;
            SymbolAtom type = (SymbolAtom) list.get(0);

            if (type.getValue().equals("<="))
            {
                return createRule(list);
            }
        }

        return createSentence(symbol);
    }

    private static GdlLiteral createLiteral(Symbol symbol)
    {
        if (symbol instanceof SymbolList)
        {
            SymbolList list = (SymbolList) symbol;
            SymbolAtom type = (SymbolAtom) list.get(0);

            if (type.getValue().toLowerCase().equals("distinct"))
            {
                return createDistinct(list);
            }
            else if (type.getValue().toLowerCase().equals("not"))
            {
                return createNot(list);
            }
            else if (type.getValue().toLowerCase().equals("or"))
            {
                return createOr(list);
            }
        }

        return createSentence(symbol);
    }

    private static GdlNot createNot(SymbolList list)
    {
        return GdlPool.getNot(createLiteral(list.get(1)));
    }

    private static GdlOr createOr(SymbolList list)
    {
        List<GdlLiteral> disjuncts = new ArrayList<GdlLiteral>();
        for (int i = 1; i < list.size(); i++)
        {
            disjuncts.add(createLiteral(list.get(i)));
        }

        return GdlPool.getOr(disjuncts);
    }

    private static GdlProposition createProposition(SymbolAtom atom)
    {
        return GdlPool.getProposition(createConstant(atom));
    }

    private static GdlRelation createRelation(SymbolList list)
    {
        GdlConstant name = createConstant((SymbolAtom) list.get(0));

        List<GdlTerm> body = new ArrayList<GdlTerm>();
        for (int i = 1; i < list.size(); i++)
        {
            body.add(createTerm(list.get(i)));
        }

        return GdlPool.getRelation(name, body);
    }

    private static GdlRule createRule(SymbolList list)
    {
        GdlSentence head = createSentence(list.get(1));

        List<GdlLiteral> body = new ArrayList<GdlLiteral>();
        for (int i = 2; i < list.size(); i++)
        {
            body.add(createLiteral(list.get(i)));
        }

        return GdlPool.getRule(head, body);
    }

    private static GdlSentence createSentence(Symbol symbol)
    {
        if (symbol instanceof SymbolAtom)
        {
            return createProposition((SymbolAtom) symbol);
        }
        else
        {
            return createRelation((SymbolList) symbol);
        }
    }

    public static GdlTerm createTerm(String string) throws SymbolFormatException
    {
        return createTerm(SymbolFactory.create(string));
    }

    public static GdlTerm createTerm(Symbol symbol)
    {
        if (symbol instanceof SymbolAtom)
        {
            SymbolAtom atom = (SymbolAtom) symbol;
            if (atom.getValue().charAt(0) == '?')
            {
                return createVariable(atom);
            }
            else
            {
                return createConstant(atom);
            }
        }
        else
        {
            return createFunction((SymbolList) symbol);
        }
    }

    private static GdlVariable createVariable(SymbolAtom atom)
    {
        return GdlPool.getVariable(atom.getValue());
    }

}