package com.atlassian.plugins.rest.common;
   
   import com.google.common.base.Preconditions;
   import org.apache.commons.lang.builder.EqualsBuilder;
   import org.apache.commons.lang.builder.HashCodeBuilder;
   
   import javax.xml.bind.annotation.XmlAttribute;
   import javax.xml.bind.annotation.XmlRootElement;
   import java.net.URI;
  
  /**
   * Represents a link to a given entity. The {@link #href}
   *
   * @since 1.0
   */
  @XmlRootElement
  public class Link {
      @XmlAttribute
      private final URI href;
  
      @XmlAttribute
      private final String type;
  
      @XmlAttribute
      private final String rel;
  
      // For JAXB's usage
  
      private Link() {
          this.href = null;
          this.rel = null;
          this.type = null;
      }
  
      private Link(URI href, String rel, String type) {
          this.href = Preconditions.checkNotNull(href);
          this.rel = Preconditions.checkNotNull(rel);
          this.type = type;
      }
  
      /**
       * Creates a link using the specified uri and rel values
       *
       * @param uri the {@link URI} to use for the link URI,
       * @param rel the rel attribute of the link.
       * @return a link
       */
      public static Link link(URI uri, String rel) {
          return new Link(uri, rel, null);
      }
  
      /**
       * Creates a link using the given URI builder to build the URI.
       *
       * @param uri  the {@link URI} to use for the link URI,
       * @param rel  the rel attribute of the link.
       * @param type the type attribute of the link.
       * @return a link
       */
      public static Link link(URI uri, String rel, String type) {
          return new Link(uri, rel, type);
      }
  
      /**
       * Creates a link using the given URI builder to build the URI.
       * The {@code rel} attribute of the link is set to {@code self}.
       *
       * @param uri the {@link URI} to use for the link URI.
       * @return a link
       */
      public static Link self(URI uri) {
          return link(uri, "self");
      }
  
      /**
       * Creates a link using the given URI builder to build the URI.
       * The {@code rel} attribute of the link is set to {@code edit}.
       *
       * @param uri the {@link URI} to use for the link URI.
       * @return a link
       */
      public static Link edit(URI uri) {
          return link(uri, "edit");
      }
  
      /**
       * Creates a link using the given URI builder to build the URI.
       * The {@code rel} attribute of the link is set to {@code add}.
       *
       * @param uri the {@link URI} to use for the link URI.
       * @return a link
       */
      public static Link add(URI uri) {
          return link(uri, "add");
      }
  
      /**
       * Creates a link using the given URI builder to build the URI.
       * The {@code rel} attribute of the link is set to {@code delete}.
      *
      * @param uri the {@link URI} to use for the link URI.
      * @return a link
      */
     public static Link delete(URI uri) {
         return link(uri, "delete");
     }
 
     public URI getHref() {
         return href;
     }
 
     public String getRel() {
         return rel;
     }
 
     @Override
     public int hashCode() {
         return new HashCodeBuilder(3, 7).append(href).append(rel).toHashCode();
     }
 
     @Override
     public boolean equals(Object obj) {
         if (obj == null) {
             return false;
         }
         if (obj == this) {
             return true;
         }
         if (obj.getClass() != getClass()) {
             return false;
         }
         final Link link = (Link) obj;
         return new EqualsBuilder().append(href, link.href).append(rel, link.rel).isEquals();
     }
 
     @Override
     public String toString() {
         return "Link{" +
                 "href=" + href +
                 ", type='" + type + '\'' +
                 ", rel='" + rel + '\'' +
                 '}';
     }
 }