Path.java

package org.aksw.jena_sparql_api.concepts;

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

import org.apache.jena.graph.NodeFactory;
import org.apache.jena.graph.Triple;
import org.apache.jena.sdb.core.Generator;
import org.apache.jena.sparql.core.Var;
import org.apache.jena.sparql.syntax.Element;
import org.apache.jena.sparql.syntax.ElementTriplesBlock;

import com.google.common.base.Joiner;


public class Path {
    private List<Step> steps;

    public Path() {
        this(new ArrayList<Step>());
    }

    public Path(List<Step> steps) {
        this.steps = steps;
    }

    public List<Step> getSteps() {
        return steps;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((steps == null) ? 0 : steps.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Path other = (Path) obj;
        if (steps == null) {
            if (other.steps != null)
                return false;
        } else if (!steps.equals(other.steps))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "Path [steps=" + steps + "]";
    }


    public static List<Element> pathToElements(Path path, Var start, Var end, Generator generator) {
        List<Element> result = new ArrayList<Element>();

        ElementTriplesBlock tmp = new ElementTriplesBlock();

        List<Triple> triples = pathToTriples(path, start, end, generator);

        if(!triples.isEmpty()) {
            for(Triple triple : triples) {
                tmp.addTriple(triple);
            }

            result.add(tmp);
        }

        return result;
    }


    public static List<Triple> pathToTriples(Path path, Var start, Var end, Generator generator) {
        List<Triple> result = new ArrayList<Triple>();

        Var a = start;

        Iterator<Step> it = path.getSteps().iterator();
        while(it.hasNext()) {
            Step step = it.next();

            Var b;
            if(it.hasNext()) {
                b = Var.alloc(generator.next());
            } else {
                b = end;
            }

            Triple t;
            if(!step.isInverse()) {
                t = new Triple(a, NodeFactory.createURI(step.getPropertyName()), b);
            }
            else {
                t = new Triple(b, NodeFactory.createURI(step.getPropertyName()), a);
            }

            result.add(t);

            a = b;
        }

        return result;
    }

    public String toPathString() {
        String result = Joiner.on(' ').join(steps);
        return result;

        /*
        String result = "";

        for(Step step : steps) {
            if(!result.isEmpty()) {
                result += " ";
            }

            if(step.isInverse()) {
                result += "<";
            }

            result += step.getPropertyName();
        }


        return result;
        */
    }
}