GdlUtils.java

package org.ggp.base.util.gdl;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

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.GdlProposition;
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;


public class GdlUtils {
    private GdlUtils() {
    }

    //TODO (AL): Check if we can switch over to just having this return a set.
    public static List<GdlVariable> getVariables(Gdl gdl) {
        final List<GdlVariable> variablesList = new ArrayList<GdlVariable>();
        final Set<GdlVariable> variables = new HashSet<GdlVariable>();
        GdlVisitors.visitAll(gdl, new GdlVisitor() {
            @Override
            public void visitVariable(GdlVariable variable) {
                if (!variables.contains(variable)) {
                    variablesList.add(variable);
                    variables.add(variable);
                }
            }
        });
        return variablesList;
    }

    public static Set<GdlVariable> getVariablesSet(Gdl gdl) {
        final Set<GdlVariable> variables = new HashSet<GdlVariable>();
        GdlVisitors.visitAll(gdl, new GdlVisitor() {
            @Override
            public void visitVariable(GdlVariable variable) {
                variables.add(variable);
            }
        });
        return variables;
    }

    public static List<String> getVariableNames(Gdl gdl) {
        List<GdlVariable> variables = getVariables(gdl);
        List<String> variableNames = new ArrayList<String>();
        for (GdlVariable variable : variables) {
            variableNames.add(variable.getName());
        }
        return variableNames;
    }

    public static List<GdlSentence> getSentencesInRuleBody(GdlRule rule) {
        List<GdlSentence> result = new ArrayList<GdlSentence>();
        for(GdlLiteral literal : rule.getBody()) {
            addSentencesInLiteral(literal, result);
        }
        return result;
    }

    private static void addSentencesInLiteral(GdlLiteral literal,
            Collection<GdlSentence> sentences) {
        if(literal instanceof GdlSentence) {
            sentences.add((GdlSentence) literal);
        } else if(literal instanceof GdlNot) {
            GdlNot not = (GdlNot) literal;
            addSentencesInLiteral(not.getBody(), sentences);
        } else if(literal instanceof GdlOr) {
            GdlOr or = (GdlOr) literal;
            for(int i = 0; i < or.arity(); i++)
                addSentencesInLiteral(or.get(i), sentences);
        } else if(!(literal instanceof GdlDistinct)) {
            throw new RuntimeException("Unexpected GdlLiteral type encountered: " + literal.getClass().getSimpleName());
        }
    }

    public static List<GdlTerm> getTupleFromSentence(
            GdlSentence sentence) {
        if(sentence instanceof GdlProposition)
            return Collections.emptyList();

        //A simple crawl through the sentence.
        List<GdlTerm> tuple = new ArrayList<GdlTerm>();
        try {
            addBodyToTuple(sentence.getBody(), tuple);
        } catch(RuntimeException e) {
            throw new RuntimeException(e.getMessage() + "\nSentence was " + sentence);
        }
        return tuple;
    }
    private static void addBodyToTuple(List<GdlTerm> body, List<GdlTerm> tuple) {
        for(GdlTerm term : body) {
            if(term instanceof GdlConstant) {
                tuple.add(term);
            } else if(term instanceof GdlVariable) {
                tuple.add(term);
            } else if(term instanceof GdlFunction){
                GdlFunction function = (GdlFunction) term;
                addBodyToTuple(function.getBody(), tuple);
            } else {
                throw new RuntimeException("Unforeseen Gdl tupe in SentenceModel.addBodyToTuple()");
            }
        }
    }

    public static List<GdlConstant> getTupleFromGroundSentence(
            GdlSentence sentence) {
        if(sentence instanceof GdlProposition)
            return Collections.emptyList();

        //A simple crawl through the sentence.
        List<GdlConstant> tuple = new ArrayList<GdlConstant>();
        try {
            addBodyToGroundTuple(sentence.getBody(), tuple);
        } catch(RuntimeException e) {
            throw new RuntimeException(e.getMessage() + "\nSentence was " + sentence);
        }
        return tuple;
    }
    private static void addBodyToGroundTuple(List<GdlTerm> body, List<GdlConstant> tuple) {
        for(GdlTerm term : body) {
            if(term instanceof GdlConstant) {
                tuple.add((GdlConstant) term);
            } else if(term instanceof GdlVariable) {
                throw new RuntimeException("Asking for a ground tuple of a non-ground sentence");
            } else if(term instanceof GdlFunction){
                GdlFunction function = (GdlFunction) term;
                addBodyToGroundTuple(function.getBody(), tuple);
            } else {
                throw new RuntimeException("Unforeseen Gdl tupe in SentenceModel.addBodyToTuple()");
            }
        }
    }

    public static Map<GdlVariable, GdlConstant> getAssignmentMakingLeftIntoRight(
            GdlSentence left, GdlSentence right) {
        Map<GdlVariable, GdlConstant> assignment = new HashMap<GdlVariable, GdlConstant>();
        if(!left.getName().equals(right.getName()))
            return null;
        if(left.arity() != right.arity())
            return null;
        if(left.arity() == 0)
            return Collections.emptyMap();
        if(!fillAssignmentBody(assignment, left.getBody(), right.getBody()))
            return null;
        return assignment;
    }

    private static boolean fillAssignmentBody(
            Map<GdlVariable, GdlConstant> assignment, List<GdlTerm> leftBody,
            List<GdlTerm> rightBody) {
        //left body contains variables; right body shouldn't
        if(leftBody.size() != rightBody.size()) {
            return false;
        }
        for(int i = 0; i < leftBody.size(); i++) {
            GdlTerm leftTerm = leftBody.get(i);
            GdlTerm rightTerm = rightBody.get(i);
            if(leftTerm instanceof GdlConstant) {
                if(!leftTerm.equals(rightTerm)) {
                    return false;
                }
            } else if(leftTerm instanceof GdlVariable) {
                if(assignment.containsKey(leftTerm)) {
                    if(!assignment.get(leftTerm).equals(rightTerm)) {
                        return false;
                    }
                } else {
                    if(!(rightTerm instanceof GdlConstant)) {
                        return false;
                    }
                    assignment.put((GdlVariable)leftTerm, (GdlConstant)rightTerm);
                }
            } else if(leftTerm instanceof GdlFunction) {
                if(!(rightTerm instanceof GdlFunction))
                    return false;
                GdlFunction leftFunction = (GdlFunction) leftTerm;
                GdlFunction rightFunction = (GdlFunction) rightTerm;
                if(!leftFunction.getName().equals(rightFunction.getName()))
                    return false;
                if(!fillAssignmentBody(assignment, leftFunction.getBody(), rightFunction.getBody()))
                    return false;
            }
        }
        return true;
    }

    public static boolean containsTerm(GdlSentence sentence, GdlTerm term) {
        if(sentence instanceof GdlProposition)
            return false;
        return containsTerm(sentence.getBody(), term);
    }

    private static boolean containsTerm(List<GdlTerm> body, GdlTerm term) {
        for(GdlTerm curTerm : body) {
            if(curTerm.equals(term))
                return true;
            if(curTerm instanceof GdlFunction) {
                if(containsTerm(((GdlFunction) curTerm).getBody(), term))
                    return true;
            }
        }
        return false;
    }

}