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    * Copyright (C) 2015 wcm.io
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    * Licensed under the Apache License, Version 2.0 (the "License");
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    * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
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   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
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  package io.wcm.caravan.hal.docs.impl.augmenter;
  
  import static io.wcm.caravan.hal.docs.impl.augmenter.CurieUtil.LINK_RELATION_CURIES;
  
  import java.util.Collections;
  import java.util.List;
  import java.util.Set;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import org.apache.commons.lang3.StringUtils;
  
  import com.google.common.collect.Sets;
  
  import io.wcm.caravan.hal.resource.HalResource;
  import io.wcm.caravan.hal.resource.Link;
  
  /**
   * Checks if the HAL resource contains link relations with curies without documentaiton links.
   * Add documentation links referencing the HAL documentation generated by this bundle.
   */
  class CurieAugmenter {
  
    private final DocsMetadata metadata;
  
    CurieAugmenter(DocsMetadata metadata) {
      this.metadata = metadata;
    }
  
    public void augment(HalResource resource) {
      Set<String> existingCurieNames = getExistingCurieNames(resource);
      Set<Link> curieLinks = getCurieLinks(resource, existingCurieNames);
      resource.addLinks(LINK_RELATION_CURIES, curieLinks);
    }
  
    private Set<String> getExistingCurieNames(HalResource hal) {
      if (!hal.hasLink(LINK_RELATION_CURIES)) {
        return Collections.emptySet();
      }
      return Stream.of(hal.getLink(LINK_RELATION_CURIES))
          .map(link -> link.getName())
          .collect(Collectors.toSet());
    }
  
    private Set<Link> getCurieLinks(HalResource resource, Set<String> existingCurieNames) {
      Set<Link> curiLinks = Sets.newLinkedHashSet();
      curiLinks.addAll(getCurieLinksForCurrentHalResource(resource, existingCurieNames));
      curiLinks.addAll(getCurieLinksForEmbeddedResources(resource, existingCurieNames));
      return curiLinks;
    }
  
    private List<Link> getCurieLinksForCurrentHalResource(HalResource resource, Set<String> existingCurieNames) {
      return resource.getLinks().keySet().stream()
          // get CURI name for relation
          .map(CurieUtil::getCurieName)
          // filter CURIE being empty or exist in HAL resource
          .filter(curieName -> StringUtils.isNotEmpty(curieName) && !existingCurieNames.contains(curieName))
          // get link for CURI name
          .map(this::toCurieLink)
          // filter non existing links
          .filter(link -> link != null)
          .collect(Collectors.toList());
    }
  
    private List<Link> getCurieLinksForEmbeddedResources(HalResource resource, Set<String> existingCurieNames) {
      return resource.getEmbedded().values().stream()
          .flatMap(embeddedResource -> getCurieLinks(embeddedResource, existingCurieNames).stream())
          .collect(Collectors.toList());
    }
  
    private Link toCurieLink(String curieName) {
      String docLink = metadata.getCurieLink(curieName);
      if (docLink == null) {
        return null;
      }
      else {
        return new Link(docLink).setName(curieName).setTitle("Documentation link");
      }
    }
  
 }