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Core Implementation of LD Path a simple path-based query language similar to XPath or SPARQL Property Paths that is particularly well-suited for querying and retrieving resources from the Linked Data Cloud by following RDF links between resources and servers.

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/*
 * Copyright (c) 2011 Salzburg Research.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package at.newmedialab.ldpath.model.tests;

import java.util.Collection;

import at.newmedialab.ldpath.api.backend.RDFBackend;
import at.newmedialab.ldpath.api.selectors.NodeSelector;
import at.newmedialab.ldpath.api.tests.NodeTest;

/**
 * Checks whether a path selector contains a certain node.  Used for the syntax construct
 *
 *  is 
 *
 * e.g.
 *
 * rdf:type is skos:Concept
 *
 * 
 * Author: Sebastian Schaffert 
 */
public class PathEqualityTest implements NodeTest {

    private NodeSelector path;
    private Node node;


    public PathEqualityTest(NodeSelector path, Node node) {
        this.node = node;
        this.path = path;
    }

    /**
     * Apply the function to the list of nodes passed as arguments and return the result as type T.
     * Throws IllegalArgumentException if the function cannot be applied to the nodes passed as argument
     * or the number of arguments is not correct.
     *
     * @param args a nested list of KiWiNodes
     * @return
     */
    @Override
    public Boolean apply(RDFBackend rdfBackend, Collection... args) throws IllegalArgumentException {
        if (args.length != 1 || args[0].isEmpty()) { 
            throw new IllegalArgumentException("path equality test only takes one parameter"); 
        }
        if (args[0].size() != 1) {
            throw new IllegalArgumentException("path equality test can only be applied to a single node");
        }

        Node candidate = args[0].iterator().next();
        return path.select(rdfBackend, candidate).contains(node);
    }

    /**
     * Return the representation of the NodeFunction or NodeSelector in the RDF Path Language
     *
     * @param rdfBackend
     * @return
     */
    @Override
    public String getPathExpression(RDFBackend rdfBackend) {
        if (rdfBackend.isURI(node)) {
            return String.format("%s is <%s>", path.getPathExpression(rdfBackend), rdfBackend.stringValue(node));
        } else {
            // TODO Can this happen?
            return String.format("%s is %s", path.getPathExpression(rdfBackend), rdfBackend.stringValue(node));
        }
    }


    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        @SuppressWarnings("rawtypes")
        PathEqualityTest that = (PathEqualityTest) o;

        if (node != null ? !node.equals(that.node) : that.node != null) return false;
        if (path != null ? !path.equals(that.path) : that.path != null) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = path != null ? path.hashCode() : 0;
        result = 31 * result + (node != null ? node.hashCode() : 0);
        return result;
    }
}