package eu.fbk.dkm.pikes.eval;
   
   import java.util.Objects;
   
   import javax.annotation.Nullable;
   
   import org.eclipse.rdf4j.model.IRI;
   
   public final class Relation implements Comparable<Relation> {
  
      private final IRI first;
  
      private final IRI second;
  
      private final boolean extra;
  
      public Relation(final IRI first, final IRI second, final boolean extra) {
          final boolean swap = Util.VALUE_ORDERING.compare(first, second) > 0;
          this.first = swap ? second : first;
          this.second = swap ? first : second;
          this.extra = extra;
      }
  
      public IRI getFirst() {
          return this.first;
      }
  
      public IRI getSecond() {
          return this.second;
      }
  
      public boolean isExtra() {
          return this.extra;
      }
  
      @Override
      public int compareTo(final Relation other) {
          int result = Util.VALUE_ORDERING.compare(this.first, other.first);
          if (result == 0) {
              result = Util.VALUE_ORDERING.compare(this.second, other.second);
          }
          return result;
      }
  
      @Override
      public boolean equals(final Object object) {
          if (object == this) {
              return true;
          }
          if (!(object instanceof Relation)) {
              return false;
          }
          final Relation other = (Relation) object;
          return this.first.equals(other.first) && this.second.equals(other.second);
      }
  
      @Override
      public int hashCode() {
          return Objects.hash(this.first, this.second);
      }
  
      public String toString(@Nullable final IRI baseIRI) {
          return "(" + Util.format(baseIRI, this.first) + ", " + Util.format(baseIRI, this.second)
                  + ")";
      }
  
      @Override
      public String toString() {
          return toString(null);
      }
  
  }