/*
 * @(#)Attribute.java	1.9 01/02/09
 *
 * Copyright 1999-2001 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the proprietary information of Sun Microsystems, Inc.  
 * Use is subject to license terms.
 * 
 */

package javax.naming.directory;

import java.util.Vector;
import java.util.Enumeration;
import java.util.NoSuchElementException;

import javax.naming.NamingException;
import javax.naming.NamingEnumeration;
import javax.naming.OperationNotSupportedException;

/**
  * This interface represents an attribute associated with a named object.
  *<p>
  * In a directory, named objects can have associated with them
  * attributes.  The <tt>Attribute</tt> interface represents an attribute associated
  * with a named object.  An attribute contains 0 or more, possibly null, values.
  * The attribute values can be ordered or unordered (see <tt>isOrdered()</tt>).
  * If the values are unordered, no duplicates are allowed.
  * If the values are ordered, duplicates are allowed.
  *<p>
  * The content and representation of an attribute and its values is defined by
  * the attribute's <em>schema</em>. The schema contains information
  * about the attribute's syntax and other properties about the attribute.
  * See <tt>getAttributeDefinition()</tt> and
  * <tt>getAttributeSyntaxDefinition()</tt>
  * for details regarding how to get schema information about an attribute
  * if the underlying directory service supports schemas.
  *<p>
  * Equality of two attributes is determined by the implementation class.
  * A simple implementation can use <tt>Object.equals()</tt> to determine equality 
  * of attribute values, while a more sophisticated implementation might
  * make use of schema information to determine equality.
  * Similarly, one implementation might provide a static storage
  * structure which simply returns the values passed to its
  * constructor, while another implementation might define <tt>get()</tt> and 
  * <tt>getAll()</tt>.
  * to get the values dynamically from the directory.
  *<p>
  * Note that updates to <tt>Attribute</tt> (such as adding or removing a
  * value) do not affect the corresponding representation of the attribute
  * in the directory.  Updates to the directory can only be effected
  * using operations in the <tt>DirContext</tt> interface.
  *
  * @author Rosanna Lee
  * @author Scott Seligman
  * @version 1.9 01/02/09
  *
  * @see BasicAttribute
  * @since 1.3
  */
public interface Attribute extends Cloneable, java.io.Serializable {
    /**
      * Retrieves an enumeration of the attribute's values.
      * The behaviour of this enumeration is unspecified
      * if the attribute's values are added, changed,
      * or removed while the enumeration is in progress.
      * If the attribute values are ordered, the enumeration's items
      * will be ordered.
      *
      * @return A non-null enumeration of the attribute's values.
      * Each element of the enumeration is a possibly null Object. The object's
      * class is the class of the attribute value. The element is null
      * if the attribute's value is null.
      * If the attribute has zero values, an empty enumeration 
      * is returned.
      * @exception NamingException
      *		If a naming exception was encountered while retrieving
      *		the values.
      * @see #isOrdered
      */
    NamingEnumeration getAll() throws NamingException;

    /**
      * Retrieves one of this attribute's values.
      * If the attribute has more than one value and is unordered, any one of
      * the values is returned.
      * If the attribute has more than one value and is ordered, the
      * first value is returned.
      *
      * @return A possibly null object representing one of 
      *        the attribute's value. It is null if the attribute's value
      *	       is null.
      * @exception NamingException
      *		If a naming exception was encountered while retrieving
      *		the value.
      * @exception java.util.NoSuchElementException
      *		If this attribute has no values.
      */
    Object get() throws NamingException;

    /** 
      * Retrieves the number of values in this attribute.
      *
      * @return The nonnegative number of values in this attribute.
      */
    int size();

    /**
      * Retrieves the id of this attribute.
      *
      * @return The id of this attribute. It cannot be null.
      */
    String getID();

    /**
      * Determines whether a value is in the attribute.
      * Equality is determined by the implementation, which may use
      * <tt>Object.equals()</tt> or schema information to determine equality.
      *
      * @param attrVal The possibly null value to check. If null, check
      *  whether the attribute has an attribute value whose value is null.
      * @return true if attrVal is one of this attribute's values; false otherwise.
      * @see java.lang.Object#equals
      * @see BasicAttribute#equals
      */
    boolean contains(Object attrVal);
    /**
      * Adds a new value to the attribute. 
      * If the attribute values are unordered and
      * <tt>attrVal</tt> is already in the attribute, this method does nothing.
      * If the attribute values are ordered, <tt>attrVal</tt> is added to the end of
      * the list of attribute values.
      *<p>
      * Equality is determined by the implementation, which may use
      * <tt>Object.equals()</tt> or schema information to determine equality.
      *
      * @param attrVal The new possibly null value to add. If null, null
      *  is added as an attribute value.
      * @return true if a value was added; false otherwise.
      */
    boolean add(Object attrVal);

    /**
      * Removes a specified value from the attribute.
      * If <tt>attrval</tt> is not in the attribute, this method does nothing.
      * If the attribute values are ordered, the first occurrence of 
      * <tt>attrVal</tt> is removed and attribute values at indices greater 
      * than the removed
      * value are shifted up towards the head of the list (and their indices
      * decremented by one).
      *<p>
      * Equality is determined by the implementation, which may use
      * <tt>Object.equals()</tt> or schema information to determine equality.
      *
      * @param attrval The possibly null value to remove from this attribute.
      * If null, remove the attribute value that is null.
      * @return true if the value was removed; false otherwise.
      */
    boolean remove(Object attrval);

    /**
      * Removes all values from this attribute.
      */
    void clear();

    /**
      * Retrieves the syntax definition associated with the attribute.
      * An attribute's syntax definition specifies the format
      * of the attribute's value(s). Note that this is different from 
      * the attribute value's representation as a Java object. Syntax 
      * definition refers to the directory's notion of <em>syntax</em>.
      *<p>
      * For example, even though a value might be
      * a Java String object, its directory syntax might be "Printable String"
      * or "Telephone Number". Or a value might be a byte array, and its
      * directory syntax is "JPEG" or "Certificate".
      * For example, if this attribute's syntax is "JPEG",
      * this method would return the syntax definition for "JPEG".
      * <p>
      * The information that you can retrieve from a syntax definition
      * is directory-dependent.
      *<p>
      * If an implementation does not support schemas, it should throw
      * OperationNotSupportedException. If an implementation does support
      * schemas, it should define this method to return the appropriate
      * information.
      * @return The attribute's syntax definition. Null if the implementation
      *	   supports schemas but this particular attribute does not have
      *    any schema information.
      * @exception OperationNotSupportedException If getting the schema
      * 	is not supported.
      * @exception NamingException If a naming exception occurs while getting
      *		the schema.
      */

    DirContext getAttributeSyntaxDefinition() throws NamingException;

    /**
      * Retrieves the attribute's schema definition.
      * An attribute's schema definition contains information
      * such as whether the attribute is multivalued or single-valued,
      * the matching rules to use when comparing the attribute's values.
      *
      * The information that you can retrieve from an attribute definition
      * is directory-dependent.
      *
      *<p>
      * If an implementation does not support schemas, it should throw
      * OperationNotSupportedException. If an implementation does support
      * schemas, it should define this method to return the appropriate
      * information.
      * @return This attribute's schema definition. Null if the implementation
      *	    supports schemas but this particular attribute does not have
      *	    any schema information.
      * @exception OperationNotSupportedException If getting the schema
      * 	is not supported.
      * @exception NamingException If a naming exception occurs while getting
      *		the schema.
      */ 
    DirContext getAttributeDefinition() throws NamingException;

    /**
      * Makes a copy of the attribute. 
      * The copy contains the same attribute values as the original attribute:
      * the attribute values are not themselves cloned.
      * Changes to the copy will not affect the original and vice versa.
      *
      * @return A non-null copy of the attribute.
      */
    Object clone();

    //----------- Methods to support ordered multivalued attributes

    /**
      * Determines whether this attribute's values are ordered.
      * If an attribute's values are ordered, duplicate values are allowed.
      * If an attribute's values are unordered, they are presented
      * in any order and there are no duplicate values.
      * @return true if this attribute's values are ordered; false otherwise.
      * @see #get(int)
      * @see #remove(int)
      * @see #add(int, java.lang.Object)
      * @see #set(int, java.lang.Object)
      */
    boolean isOrdered();

    /**
     * Retrieves the attribute value from the ordered list of attribute values.
     * This method returns the value at the <tt>ix</tt> index of the list of
     * attribute values.
     * If the attribute values are unordered,
     * this method returns the value that happens to be at that index.
     * @param ix The index of the value in the ordered list of attribute values.
     * 0 <= <tt>ix</tt> < <tt>size()</tt>.
     * @return The possibly null attribute value at index <tt>ix</tt> 
     *   null if the attribute value is null.
     * @exception NamingException If a naming exception was encountered while
     * retrieving the value.
     * @exception IndexOutOfBoundsException If <tt>ix</tt> is outside the specified range.
     */
    Object get(int ix) throws NamingException;

    /**
     * Removes an attribute value from the ordered list of attribute values.
     * This method removes the value at the <tt>ix</tt> index of the list of
     * attribute values. 
     * If the attribute values are unordered,
     * this method removes the value that happens to be at that index.
     * Values located at indices greater than <tt>ix</tt> are shifted up towards
     * the front of the list (and their indices decremented by one).
     *
     * @param ix The index of the value to remove.
     * 0 <= <tt>ix</tt> < <tt>size()</tt>.
     * @return The possibly null attribute value at index <tt>ix</tt> that was removed; 
     *   null if the attribute value is null.
     * @exception IndexOutOfBoundsException If <tt>ix</tt> is outside the specified range.
     */
    Object remove(int ix);

    /**
     * Adds an attribute value to the ordered list of attribute values.
     * This method adds <tt>attrVal</tt> to the list of attribute values at
     * index <tt>ix</tt>.
     * Values located at indices at or greater than <tt>ix</tt> are 
     * shifted down towards the end of the list (and their indices incremented 
     * by one).
     * If the attribute values are unordered and already have <tt>attrVal</tt>,
     * <tt>IllegalStateException</tt> is thrown.
     *
     * @param ix The index in the ordered list of attribute values to add the new value.
     * 0 <= <tt>ix</tt> <= <tt>size()</tt>.
     * @param attrVal The possibly null attribute value to add; if null, null is
     * the value added.
     * @exception IndexOutOfBoundsException If <tt>ix</tt> is outside the specified range.
     * @exception IllegalStateException If the attribute values are unordered and
     * <tt>attrVal</tt> is one of those values.
     */
    void add(int ix, Object attrVal);


    /**
     * Sets an attribute value in the ordered list of attribute values.
     * This method sets the value at the <tt>ix</tt> index of the list of
     * attribute values to be <tt>attrVal</tt>. The old value is removed.
     * If the attribute values are unordered,
     * this method sets the value that happens to be at that index
     * to <tt>attrVal</tt>, unless <tt>attrVal</tt> is already one of the values.
     * In that case, <tt>IllegalStateException</tt> is thrown.
     *
     * @param ix The index of the value in the ordered list of attribute values.
     * 0 <= <tt>ix</tt> < <tt>size()</tt>.
     * @param attrVal The possibly null attribute value to use. 
     * If null, 'null' replaces the old value.
     * @return The possibly null attribute value at index ix that was replaced. 
     *   Null if the attribute value was null.
     * @exception IndexOutOfBoundsException If <tt>ix</tt> is outside the specified range.
     * @exception IllegalStateException If <tt>attrVal</tt> already exists and the
     *    attribute values are unordered.
     */
    Object set(int ix, Object attrVal);

    /**
     * Use serialVersionUID from JNDI 1.1.1 for interoperability.
     */
    static final long serialVersionUID = 8707690322213556804L;
}