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   package com.bonevich.erj.model;
   
   import com.bonevich.erj.ErjConstants;
   import com.bonevich.util.dependency.Dynamic;
   import com.bonevich.java.util.ImmutableIterator;
   
   import java.util.*;
   
   /*** A class that represents an attribute of a relation
   *  (i.e. a column in a table).  Attributes must have a type
   *  (which may be a predefined {@link DataType DataType} or
   *  a user-defined {@link Domain Domain}, both of which 
   *  implement the {@link AttributeType AttributeType}
   *  typing interface) and a constraint (NULL or NOTNULL as
   *  defined by {@link AttributeConstraint AttributeConstraint}).
   *  Attributes also may optionally have a default value and
   *  a set of associated keys.
   * 
   * @see Relation
   * @see AttributeType
   * @see AttributeConstraint
   * @see KeyConstraint 
   * @author Jeffrey D. Bonevich <bonevich@telocity.com>
   */
  public final class Attribute extends ModelElement
  {
  	//////////////////////////////////////////////////////////
  	// Constants
  	public static final String NEW_ATTRIBUTE_STR = "attr_";
  
  	/////////////////////////////////////////////////////////
  	// Attributes
  	// defined in super-class, initialized here
  	{
  		_name        = ErjConstants.EMPTY_STR;
  		_identifier  = ErjConstants.EMPTY_STR;
  		_description = ErjConstants.EMPTY_STR;
  	}
  
  	/////////////////////////////////////////////////////////
  	// Associations
  	private Relation            _relation;
  	private AttributeType       _type       = (AttributeType)DataType.SQL92_CHAR_VARYING.clone();
  	private DefaultValue        _default    = DefaultValue.NULL;
  	private AttributeConstraint _constraint = AttributeConstraint.DEFAULT;
  	private List                _keys       = new LinkedList(); //of KeyConstraints
  
  	/////////////////////////////////////////////////////////
  	// Dynamic Sentries
  	private Dynamic _dyn_type        = new Dynamic();
  	private Dynamic _dyn_default     = new Dynamic();
  	private Dynamic _dyn_constraint  = new Dynamic();
  	private Dynamic _dyn_keys        = new Dynamic();
  
  	//////////////////////////////////////////////////////////
  	// Constructors
  	/*** Create a new attribute for a given <code>Relation</code>.
  	 *  You should use <code>Relation.createAttribute()</code>
  	 */
  	public Attribute(Relation relation)
  	{
  		setRelation(relation);
  		setIdentifier(NEW_ATTRIBUTE_STR + _relation.getAttributeCount()); 
  		setName(getIdentifier());
  	}
  
  	protected Attribute(Relation relation, Attribute that)
  	{
  		this(relation);
  		if (that != null)
  		{
  			String id = that.getIdentifier();
  			String anotherId = id;
  			int uniquifier = 0;
  			Attribute another = null;
  			while ((another = relation.getAttribute(anotherId)) != null)
  			{
  				anotherId = id + "_" + (++uniquifier);
  			}
  			setIdentifier(anotherId); 
  			setName(that.getName());
  			setDescription(that.getDescription());
  			setType(that.getType());
  			setConstraint(that.getConstraint());
  		}
  	}
  
  	/*** Default constructor needed for diagram loading. */
  	public Attribute() { }
  
  	/////////////////////////////////////////////////////////
  	// Getter/Setters
  	public AttributeType getType()
  	{
  		_dyn_type.onGet();
  		return _type;
  	}
  	public void setType(AttributeType type)
  	{
 		if (_type != type)
 		{
 			_dyn_type.onSet();
 			_type = type;
 		}
 	}
 
 	public DefaultValue getDefaultValue()
 	{
 		_dyn_default.onGet();
 		return _default;
 	}
 	public void setDefaultValue(DefaultValue value)
 	{
 		if (!_default.equals(value))
 		{
 			_dyn_default.onSet();
 			_default = value;
 		}
 	}
 
 	public void setConstraint(AttributeConstraint constraint)
 	{
 		if (_constraint != constraint)
 		{
 			_dyn_constraint.onSet();
 			_constraint = constraint;
 			if (_constraint == AttributeConstraint.NOTNULL &&
 					_default == DefaultValue.NULL)
 			{
 				setDefaultValue(DefaultValue.EMPTY);
 			}
 		}
 	}
 	public AttributeConstraint getConstraint()
 	{
 		_dyn_constraint.onGet();
 		return _constraint;
 	}
 
 	public Relation getRelation()
 	{
 		return _relation;
 	}
 	private void setRelation(Relation relation)
 	{
 		_relation = relation;
 	}
 
 	/////////////////////////////////////////////////////////
 	// Operations
 	public void addKey(KeyConstraint key)
 	{
 		if (!_keys.contains(key))
 		{
 			_dyn_keys.onSet();
 			_keys.add(key);
 		}
 	}
 	public void removeKey(KeyConstraint key)
 	{
 		_dyn_keys.onSet();
 		_keys.remove(key);
 	}
 	public Iterator getKeyIterator()
 	{
 		_dyn_keys.onGet();
 		return new ImmutableIterator(_keys.iterator());
 	}
 
 	//FIXME: cache info on first iteration so we don't have to iter every time?
 	public boolean isPrimaryKey()
 	{
 		Iterator keys = getKeyIterator();
 		boolean found = false;
 		while (keys.hasNext())
 		{
 			if (keys.next() instanceof PrimaryKey)
 			{
 				found = true;
 				break;
 			}
 		}
 		return found;
 	}
 	public boolean isUniqueKey()
 	{
 		Iterator keys = getKeyIterator();
 		boolean found = false;
 		while (keys.hasNext())
 		{
 			if (keys.next() instanceof UniqueKey)
 			{
 				found = true;
 				break;
 			}
 		}
 		return found;
 	}
 	public boolean isForeignKey()
 	{
 		Iterator keys = getKeyIterator();
 		boolean found = false;
 		while (keys.hasNext())
 		{
 			if (keys.next() instanceof ForeignKey)
 			{
 				found = true;
 				break;
 			}
 		}
 		return found;
 	}
 
 	/***
 	 * Delete all keys of which this attribute is a member.
 	 */
 	public void dispose()
 	{
 		Relation relation = getRelation();
 		Iterator itr = getKeyIterator();
 		while (itr.hasNext())
 		{
 			relation.deleteKey((KeyConstraint) itr.next());
 		}
 		_keys.clear();
 	}
 
 	public boolean equals(Object rhs)
 	{
 		if (rhs != null && rhs instanceof Attribute)
 		{
 			Attribute that = (Attribute)rhs;
 			if (getRelation() == that.getRelation() &&
 					that.getIdentifier().equals(getIdentifier())
 					)
 			{
 				return true;
 			}
 		}
 		return false;
 	}
 
 	public void accept(ModelElementVisitor visitor)
 	{
 		visitor.visitAttribute(this);
 	}
 
 } /* end class Attribute */