// Copyright 2007, 2008 The Apache Software Foundation

 //

 // Licensed under the Apache License, Version 2.0 (the "License");

 // you may not use this file except in compliance with the License.

 // You may obtain a copy of the License at

 //

 //     http://www.apache.org/licenses/LICENSE-2.0

 //

 // Unless required by applicable law or agreed to in writing, software

 // distributed under the License is distributed on an "AS IS" BASIS,

 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 // See the License for the specific language governing permissions and

 // limitations under the License.

 package org.apache.tapestry5.internal.grid;

 import org.apache.tapestry5.PropertyConduit;

 import org.apache.tapestry5.grid.ColumnSort;

 import org.apache.tapestry5.grid.GridDataSource;

 import org.apache.tapestry5.grid.SortConstraint;

 import org.apache.tapestry5.ioc.internal.util.CollectionFactory;

 import org.apache.tapestry5.ioc.internal.util.Defense;

 import java.util.Collection;

 import java.util.Collections;

 import java.util.Comparator;

 import java.util.List;

 public class CollectionGridDataSource implements GridDataSource

 {

     private final List list;

     @SuppressWarnings("unchecked")

     public CollectionGridDataSource(final Collection collection)

     {

         Defense.notNull(collection, "collection");

         // Copy the collection so that we can sort it without disturbing the original

         list = CollectionFactory.newList(collection);

     }

     public int getAvailableRows()

     {

         return list.size();

     }

     public void prepare(int startIndex, int endIndex, List<SortConstraint> sortConstraints)

     {

         for (SortConstraint constraint : sortConstraints)

         {

             final ColumnSort sort = constraint.getColumnSort();

             if (sort == ColumnSort.UNSORTED) continue;

             final PropertyConduit conduit = constraint.getPropertyModel().getConduit();

             final Comparator valueComparator = new Comparator<Comparable>()

             {

                 public int compare(Comparable o1, Comparable o2)

                 {

                     // Simplify comparison, and handle case where both are nulls.

                     if (o1 == o2) return 0;

                     if (o2 == null) return 1;

                     if (o1 == null) return -1;

                     return o1.compareTo(o2);

                 }

             };

             final Comparator rowComparator = new Comparator()

             {

                 public int compare(Object row1, Object row2)

                 {

                     Comparable value1 = (Comparable) conduit.get(row1);

                     Comparable value2 = (Comparable) conduit.get(row2);

                     return valueComparator.compare(value1, value2);

                 }

             };

             final Comparator reverseComparator = new Comparator()

             {

                 public int compare(Object o1, Object o2)

                 {

                     int modifier = sort == ColumnSort.ASCENDING ? 1 : -1;

                     return modifier * rowComparator.compare(o1, o2);

                 }

             };

             // We can freely sort this list because its just a copy.

             Collections.sort(list, reverseComparator);

         }

     }

     /**

      * Returns the type of the first element in the list, or null if the list is empty.

      */

     public Class getRowType()

     {

         return list.isEmpty() ? null : list.get(0).getClass();

     }

     public Object getRowValue(int index)

     {

         return list.get(index);

     }

 }