package net.sf.saxon.om;

import java.io.Serializable;

/**
 * A qualified name.
 */
@SuppressWarnings("serial")
public class QualifiedName implements Serializable
{
  /**
   * Creates a {@link QualifiedName} instance.
   * @param prefix a prefix.
   * @param localName a local name.
   * @param namespace a namespace.
   */
  public QualifiedName(String prefix, String localName, String namespace)
  {
    this(prefix, new QualifiedName(localName, namespace), 0);
  }
  
  /**
   * Creates a {@link QualifiedName} instance.
   * @param prefix a prefix.
   * @param localName a local name.
   * @param namespace a namespace.
   * @param id an associated identifier.
   */
  public QualifiedName(
    String prefix, 
    String localName, 
    String namespace, 
    int id)
  {
    this(prefix, new QualifiedName(localName, namespace), id);
  }
  
  /**
   * Creates a {@link QualifiedName} instance.
   * @param prefix a prefix.
   * @param name an expanded name.
   */
  public QualifiedName(String prefix, QualifiedName name)
  {
    this(prefix, name, 0);
  }

  /**
   * Creates a {@link QualifiedName} instance.
   * @param prefix a prefix.
   * @param name an expanded name.
   * @param id an associated identifier.
   */
  public QualifiedName(String prefix, QualifiedName name, int id)
  {
    this.prefix = prefix;
    this.localName = name.localName;
    this.namespace = name.namespace;
    this.expandedName = name.expandedName;
    this.id = id;
  }

  /**
   * Creates a {@link QualifiedName} instance.
   * @param localName a local name.
   * @param namespace an namespace.
   */
  public QualifiedName(String localName, String namespace)
  {
    this(localName, namespace, 0);
  }

  /**
   * Creates a {@link QualifiedName} instance.
   * @param localName a local name.
   * @param namespace an namespace.
   * @param id an associated identifier.
   */
  public QualifiedName(String localName, String namespace, int id)
  {
    this.prefix = "";
    this.localName = localName;
    this.namespace = namespace;
    this.expandedName = this;
    this.id = 0;
  }

  /**
   * Gets a prefix.
   * @return a prefix.
   */
  public final String getPrefix()
  {
    return prefix; 
  }
  
  /**
   * Gets a local name.
   * @return a local name.
   */
  public final String getLocalName()
  {
    return localName; 
  }
  
  /**
   * Gets a namespace.
   * @return a namespace.
   */
  public final String getNamespace()
  {
    return namespace; 
  }
  
  /**
   * Gets an expanded name.
   * @return an expanded name.
   */
  public final QualifiedName getExpandedName()
  {
    return expandedName; 
  }

  /**
   * Gets an associated identifier.
   * @return an associated identifier.
   */
  public final int getId()
  {
    return id;
  }

  /**
   * Gets a display name.
   * @return
   */
  public final String getQName()
  {
    if (qname == null)
    {
      if (prefix.length() == 0)
      {
        qname = localName;
      }
      else
      {
        qname = prefix + ":" + localName;
      }
    }
    
    return qname;
  }
  
  /**
   * Gets a hash code.
   */
  @Override
  public int hashCode()
  {
    return localName.hashCode() ^
      Integer.rotateLeft(namespace.hashCode(), 13) ^
      Integer.rotateLeft(prefix.hashCode(), 26);
  }

  /**
   * Compares qualified name with other instance.
   */
  @Override
  public final boolean equals(Object other)
  {
    if (other instanceof QualifiedName)
    {
      QualifiedName that = (QualifiedName)other;
      
      return equal(this, that);
    }
    
    return false;
  }
  
  /**
   * Compares two expanded names. 
   * @param first a first instance.
   * @param second a second instance.
   * @return true if instances are equal, and false otherwise.
   */
  public static boolean equal(QualifiedName first, QualifiedName second)
  {
    if (first == second)
    {
      return true;
    }
    
    return first.localName.equals(second.localName) &&
      first.namespace.equals(second.namespace) &&
      first.prefix.equals(second.prefix);
  }
  
  /**
   * A prefix.
   */
  private final String prefix;
  
  /**
   * A local name.
   */
  private final String localName;
  
  /**
   * A namespace.
   */
  private final String namespace;
  
  /**
   * An expanded name.
   */
  private final QualifiedName expandedName;
  
  /**
   * An associated identifier.
   */
  private final int id; 
  
  /**
   * A display name.
   */
  private transient String qname;
}