at.newmedialab.ldpath.model.selectors.FunctionSelector Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of ldpath-core-bundle Show documentation

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.

There is a newer version: 0.9.7

Show newest version

/*
 * 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.selectors;

import at.newmedialab.ldpath.api.backend.RDFBackend;
import at.newmedialab.ldpath.api.functions.NodeFunction;
import at.newmedialab.ldpath.api.selectors.NodeSelector;

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

/**
 * Add file description here!
 * 
 * Author: Sebastian Schaffert 
 */
public class FunctionSelector implements NodeSelector {

    private List> selectors;
    private NodeFunction,Node> function;


    public FunctionSelector(NodeFunction,Node> function, List> selectors) {
        this.function  = function;
        this.selectors = selectors;
    }

    /**
     * Apply the selector to the context node passed as argument and return the collection
     * of selected nodes in appropriate order.
     *
     * @param context the node where to start the selection
     * @return the collection of selected nodes
     */
    @Override
    public Collection select(RDFBackend rdfBackend, Node context) {
        ArrayList> args = new ArrayList>();
        for(NodeSelector selector : selectors) {
            Collection param = selector.select(rdfBackend, context);
            args.add(param);
        }
        return function.apply(rdfBackend, args.toArray(new Collection[0]));
    }

    /**
     * Return the name of the NodeSelector for registration in the selector registry
     *
     * @return
     * @param backend
     */
    @Override
    public String getPathExpression(RDFBackend backend) {
        final StringBuilder format = new StringBuilder();
        format.append(String.format("fn:%s(", function.getPathExpression(backend)));
        boolean first = true;
        for (NodeSelector ns : selectors) {
            if (!first) {
                format.append(", ");
            }
            format.append(ns.getPathExpression(backend));
            first = false;
        }
        return format.append(")").toString();
    }

    /**
     * Return a name for this selector to be used as the name for the whole path if not explicitly
     * specified. In complex selector expressions, this is typically delegated to the first
     * occurrence of an atomic selector.
     */
    @Override
    public String getName(RDFBackend nodeRDFBackend) {
        throw new UnsupportedOperationException("cannot use functions in unnamed field definitions because the name is ambiguous");
    }


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

        FunctionSelector that = (FunctionSelector) o;

        if (function != null ? !function.equals(that.function) : that.function != null) return false;
        if (selectors != null ? !selectors.equals(that.selectors) : that.selectors != null) return false;

        return true;
    }

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