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/*
 * Copyright (C) 2014 The droitated DB Authors
 *
 * 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.droitateddb;

import android.content.ContentProvider;
import android.content.ContentResolver;
import android.database.Cursor;
import android.database.CursorWrapper;

import org.droitateddb.cursor.ObjectCursor;

/**
 * Provides utility methods for cursors.
 *
 * @author Falk Appel
 * @author Alexander Frank
 */
public class CursorUtil {

	/**
	 * Convert a standard Android {@link Cursor} into a {@link org.droitateddb.cursor.ObjectCursor}.

	 * This is only possible for {@link Cursor}s that where queried over a {@link ContentResolver} from a
	 * {@link ContentProvider} derived by {@link BaseContentProvider}.
	 *
	 * @param     Entity class represented within the Cursor
	 * @param cursor Android {@link Cursor}
	 * @return The {@link org.droitateddb.cursor.ObjectCursor} representation of the given Android {@link Cursor}
	 * @throws NullPointerException     When the given cursor is null
	 * @throws IllegalArgumentException When the given cursor is not of the type {@link CursorWrapper}, which will be returned by a
	 *                                  {@link ContentResolver}
	 * @throws IllegalStateException    When the wrapped cursor within the given cursor is not of type {@link org.droitateddb.cursor.ObjectCursor}. This indicates
	 *                                  that the given cursor was not queried from a derivation {@link BaseContentProvider}
	 */
	@SuppressWarnings("unchecked")
	public static  ObjectCursor getObjectCursor(final Cursor cursor) {
		if (cursor == null) {
			throw new NullPointerException("The given cursor is null");
		}
		if (!(cursor instanceof CursorWrapper)) {
			throw new IllegalArgumentException(
					"The given cursor is not of type " + CursorWrapper.class.getCanonicalName() + ". It has type " + cursor.getClass().getCanonicalName() +
							". Was it queried with a ContentResolver?");
		}

		CursorWrapper wrapper = (CursorWrapper) cursor;
		Cursor wrappedCursor = wrapper.getWrappedCursor();

		if (!(wrappedCursor instanceof ObjectCursor)) {
			throw new IllegalStateException(
					"The wrapped cursor of the given CursorWrapper is not of type " + ObjectCursor.class.getCanonicalName() + ". It has type " +
							wrappedCursor.getClass().getCanonicalName() +
							". Was it queried over a ContentResolver from BaseContentProvider derived ContentProvider?");
		}
		return (ObjectCursor) wrappedCursor;
	}

}