io.wcm.caravan.pipeline.extensions.hal.crawler.LinkExtractors.java Source code

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Here is the source code for io.wcm.caravan.pipeline.extensions.hal.crawler.LinkExtractors.java

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/*
 * #%L
 * wcm.io
 * %%
 * Copyright (C) 2014 wcm.io
 * %%
 * 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.
 * #L%
 */
package io.wcm.caravan.pipeline.extensions.hal.crawler;

import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.tuple.Pair;
import org.osgi.annotation.versioning.ProviderType;

import com.damnhandy.uri.template.UriTemplate;
import com.google.common.base.Predicate;
import com.google.common.collect.ImmutableListMultimap;
import com.google.common.collect.ImmutableListMultimap.Builder;
import com.google.common.collect.ListMultimap;

import io.wcm.caravan.hal.resource.HalResource;
import io.wcm.caravan.hal.resource.Link;
import io.wcm.caravan.hal.resource.util.HalUtil;

/**
 * Common link extractors.
 */
@ProviderType
public final class LinkExtractors {

    private LinkExtractors() {
        // nothing to do
    }

    /**
     * Returns all relations and links in a HAL resource except CURI links.
     * @return All links
     */
    public static LinkExtractor all() {
        return new LinkExtractor() {

            @Override
            public ListMultimap<String, Link> extract(HalResource hal) {
                return HalUtil.getAllLinks(hal);
            }

            @Override
            public String getId() {
                return "ALL";
            }

        };
    }

    /**
     * Returns all relations and links in a HAL resource having no URI template expressions.
     * @return Filtered links
     */
    public static LinkExtractor noUriTemplates() {
        return new LinkExtractor() {

            @Override
            public ListMultimap<String, Link> extract(HalResource hal) {
                return HalUtil.getAllLinks(hal, new Predicate<Pair<String, Link>>() {

                    @Override
                    public boolean apply(Pair<String, Link> input) {
                        return UriTemplate.fromTemplate(input.getValue().getHref()).expressionCount() == 0;
                    }
                });
            }

            @Override
            public String getId() {
                return "NO-URI-TEMPLATES";
            }

        };
    }

    /**
     * Returns all relations and links provided by the {@code delegate}d {@link LinkExtractor} where the URI starts with
     * the given prefix.
     * @param prefix URI prefix
     * @param delegate Delegated link extractor
     * @return Link extractor for prefixed URIs
     */
    public static LinkExtractor filterByPrefix(String prefix, LinkExtractor delegate) {
        return new LinkExtractor() {

            @Override
            public String getId() {
                return "ONLY-STARTING-WITH('" + prefix + "', " + delegate.getId() + ")";
            }

            @Override
            public ListMultimap<String, Link> extract(HalResource hal) {

                ListMultimap<String, Link> fromDelegate = delegate.extract(hal);
                Builder<String, Link> builder = ImmutableListMultimap.builder();
                fromDelegate.entries().stream()
                        .filter(entry -> StringUtils.startsWith(entry.getValue().getHref(), prefix))
                        .forEach(entry -> builder.put(entry));
                return builder.build();

            }
        };
    }

}