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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;

/**
 * Tests whether the path given as argument for the constructor yields at least one node when evaluated
 * from the context node to which the test is applied.
 * 
 * Author: Sebastian Schaffert 
 */
public class PathTest implements NodeTest {

    private NodeSelector path;

    public PathTest(NodeSelector path) {
        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 test only takes one parameter"); 
        }
        if (args[0].size() != 1) {
            throw new IllegalArgumentException("path test can only be applied to a single node");
        }

        Node node = args[0].iterator().next();

        if (rdfBackend.isURI(node) || rdfBackend.isBlank(node)) {
            Collection testResult = path.select(rdfBackend, node);
            return testResult.size() > 0;
        } else {
            return false;
        }

    }

    /**
     * Return the representation of the NodeFunction or NodeSelector in the RDF Path Language
     *
     * @param rdfBackend
     * @return
     */
    @Override
    public String getPathExpression(RDFBackend rdfBackend) {
        return path.getPathExpression(rdfBackend);
    }


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

        @SuppressWarnings("rawtypes")
        PathTest pathTest = (PathTest) o;

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

        return true;
    }

    @Override
    public int hashCode() {
        return path != null ? path.hashCode() : 0;
    }
}