package net.wotonomy.control;

import java.util.Collection;
import java.util.Iterator;

import net.wotonomy.foundation.NSArray;
import net.wotonomy.foundation.NSMutableArray;

/**
 * A data source that automates the process of creating a child editing context
 * and copying objects from a parent context into it. Attach this data source to
 * a display group that represents a "detail" or "drill-down" view. <br>
 * <br>
 * 
 * Once created, editingContext() will return the child context, and fetch()
 * will return the objects that were copied into the child context.
 */
public class ChildDataSource extends EODataSource {
	private EODataSource parent;
	private EOEditingContext context;
	private EOClassDescription classDescription;
	private NSMutableArray objects;

	/**
	 * Creates a child editing context for the specified parent's context and copies
	 * the specified object into the child context. The object must exist in the
	 * parent context. fetch() will return the child's object.
	 */
	public ChildDataSource(EODataSource aParentSource, Object anObject) {
		this(aParentSource, new NSArray((Object) anObject));
	}

	/**
	 * Creates a child editing context for the specified parent's context and copies
	 * the specified objects into the child context. The objects must exist in the
	 * parent context. The order of the parent's objects in the collection will
	 * determine the order in which the child objects are returned from fetch().
	 */
	public ChildDataSource(EODataSource aParentSource, Collection anObjectList) {
		EOEditingContext parentContext = aParentSource.editingContext();

		parent = aParentSource;
		context = new EOEditingContext(parentContext);
//!new net.wotonomy.ui.swing.util.ObjectInspector( context );        
		objects = new NSMutableArray();
		classDescription = null;

		Object o;
		Object copy;
		boolean allSameClass = true;
		Iterator it = anObjectList.iterator();
		while (it.hasNext()) {
			o = it.next();

			// determine class
			if (allSameClass == true) {
				Class c = o.getClass();
				if (classDescription == null) {
					classDescription = EOClassDescription.classDescriptionForClass(c);
				} else {
					if (c != classDescription.getDescribedClass()) {
						allSameClass = false;
						classDescription = null;
					}
				}
			}

			// copy and add to list
			objects.addObject(parentContext.faultForGlobalID(parentContext.globalIDForObject(o), context));
		}
	}

	/**
	 * Returns the editing context for this data source, which was created in the
	 * constructor and whose parent is the editing context specified in the
	 * constructor.
	 */
	public EOEditingContext editingContext() {
		return context;
	}

	/**
	 * This implementation does nothing.
	 */
	public void insertObject(Object anObject) {

	}

	/**
	 * This implementation does nothing.
	 */
	public void deleteObject(Object anObject) {

	}

	/**
	 * Returns a List containing the objects in this data source. This
	 * implementation returns all TestObjects that have been persisted to the
	 * datastore in the data directory.
	 */
	public NSArray fetchObjects() {
		return new NSArray((Collection) objects);
	}

	/**
	 * Returns a data source that is capable of manipulating objects of the type
	 * returned by applying the specified key to objects vended by this data source.
	 * This implementation forwards the call to the parent data source.
	 * 
	 * @see #qualifyWithRelationshipKey
	 */
	public EODataSource dataSourceQualifiedByKey(String aKey) {
		// FIXME: This is fundamentally broken.
		// Objects vended from the returned source
		// are not registered in our editing context.
		// We probably need yet another utility data
		// source class that would wrap another source
		// and convert vended objects into a different
		// context.

		return parent.dataSourceQualifiedByKey(aKey);
	}

	/**
	 * Restricts this data source to vend those objects that are associated with the
	 * specified key on the specified object. This implementation forwards the call
	 * to the parent data source.
	 */
	public void qualifyWithRelationshipKey(String aKey, Object anObject) {
		parent.qualifyWithRelationshipKey(aKey, anObject);
	}

	/**
	 * Returns the description of the class of the objects that is vended by this
	 * data source, or null if this cannot be determined. This implementation
	 * returns the class of the objects passed to the constructor if they are all
	 * the same class, otherwise returns null.
	 */
	public EOClassDescription classDescriptionForObjects() {
		return classDescription;
	}

}