/*
 * Copyright 2002-2016 the original author or 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.springframework.test.context.web.socket;

import java.util.List;

import org.springframework.beans.BeanUtils;
import org.springframework.core.annotation.AnnotatedElementUtils;
import org.springframework.lang.Nullable;
import org.springframework.test.context.ContextConfigurationAttributes;
import org.springframework.test.context.ContextCustomizer;
import org.springframework.test.context.ContextCustomizerFactory;
import org.springframework.util.ClassUtils;

/**
 * {@link ContextCustomizerFactory} which creates a {@link MockServerContainerContextCustomizer}
 * if WebSocket support is present in the classpath and the test class is annotated
 * with {@code @WebAppConfiguration}.
 *
 * @author Sam Brannen
 * @since 4.3.1
 */
class MockServerContainerContextCustomizerFactory implements ContextCustomizerFactory {

	private static final String WEB_APP_CONFIGURATION_ANNOTATION_CLASS_NAME =
			"org.springframework.test.context.web.WebAppConfiguration";

	private static final String MOCK_SERVER_CONTAINER_CONTEXT_CUSTOMIZER_CLASS_NAME =
			"org.springframework.test.context.web.socket.MockServerContainerContextCustomizer";

	private static final boolean webSocketPresent = ClassUtils.isPresent("javax.websocket.server.ServerContainer",
			MockServerContainerContextCustomizerFactory.class.getClassLoader());


	@Override
	@Nullable
	public ContextCustomizer createContextCustomizer(Class<?> testClass,
			List<ContextConfigurationAttributes> configAttributes) {

		if (webSocketPresent && isAnnotatedWithWebAppConfiguration(testClass)) {
			try {
				Class<?> clazz = ClassUtils.forName(MOCK_SERVER_CONTAINER_CONTEXT_CUSTOMIZER_CLASS_NAME,
						getClass().getClassLoader());
				return (ContextCustomizer) BeanUtils.instantiateClass(clazz);
			}
			catch (Throwable ex) {
				throw new IllegalStateException("Failed to enable WebSocket test support; could not load class: " +
						MOCK_SERVER_CONTAINER_CONTEXT_CUSTOMIZER_CLASS_NAME, ex);
			}
		}

		// Else, nothing to customize
		return null;
	}

	private static boolean isAnnotatedWithWebAppConfiguration(Class<?> testClass) {
		return (AnnotatedElementUtils.findMergedAnnotationAttributes(testClass,
				WEB_APP_CONFIGURATION_ANNOTATION_CLASS_NAME, false, false) != null);
	}

}
