/*
    * SPDX-FileCopyrightText: none
    * SPDX-License-Identifier: CC0-1.0
    */
   
   package gov.nist.secauto.oscal.lib;
   
   import gov.nist.secauto.metaschema.core.util.ObjectUtils;
   import gov.nist.secauto.oscal.lib.model.BackMatter.Resource;
  import gov.nist.secauto.oscal.lib.model.BackMatter.Resource.Rlink;
  
  import java.net.URI;
  import java.util.List;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  
  public final class OscalUtils {
    private static final Pattern INTERNAL_REFERENCE_FRAGMENT_PATTERN = Pattern.compile("^#(.+)$");
  
    private OscalUtils() {
      // disable construction
    }
  
    @SuppressWarnings("PMD.OnlyOneReturn") // readability
    public static boolean isInternalReference(@NonNull URI uri) {
      if (uri.isAbsolute()) {
        return false;
      }
  
      String schemeSpecificPart = uri.getSchemeSpecificPart();
      return uri.getScheme() == null && (schemeSpecificPart == null || schemeSpecificPart.isEmpty())
          && uri.getFragment() != null;
    }
  
    /**
     * Get the id based on a URI's fragment.
     *
     * @param fragment
     *          the URI to extract the identifier from
     * @return the identifier
     * @throws IllegalArgumentException
     *           if the fragment does not contain an identifier
     */
    @NonNull
    public static String internalReferenceFragmentToId(@NonNull URI fragment) {
      return internalReferenceFragmentToId(ObjectUtils.notNull(fragment.toString()));
    }
  
    /**
     * Get the id based on a URI's fragment.
     *
     * @param fragment
     *          the URI to extract the identifier from
     * @return the identifier
     * @throws IllegalArgumentException
     *           if the fragment does not contain an identifier
     */
    @NonNull
    public static String internalReferenceFragmentToId(@NonNull String fragment) {
      Matcher matcher = INTERNAL_REFERENCE_FRAGMENT_PATTERN.matcher(fragment);
      String retval;
      if (matcher.matches()) {
        retval = ObjectUtils.notNull(matcher.group(1));
      } else {
        throw new IllegalArgumentException(String.format("The fragment '%s' does not match the pattern '%s'", fragment,
            INTERNAL_REFERENCE_FRAGMENT_PATTERN.pattern()));
      }
      return retval;
    }
  
    @Nullable
    public static Rlink findMatchingRLink(@NonNull Resource resource, @Nullable String preferredMediaType) {
      // find a suitable rlink reference
      List<Rlink> rlinks = resource.getRlinks();
  
      Rlink retval = null;
      if (rlinks != null) {
        // check if there is a matching rlink for the mime type
        if (preferredMediaType != null) {
          // find preferred mime type first
          retval = rlinks.stream().filter(rlink -> preferredMediaType.equals(rlink.getMediaType())).findFirst()
              .orElse(null);
        } else {
          // use the first one instead
          retval = rlinks.stream().findFirst().orElse(null);
        }
      }
      return retval;
    }
  }