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/*
 * Copyright © 2015 The Gravitee team (http://gravitee.io)
 *
 * 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 io.gravitee.common.spring.factory;

import java.lang.reflect.Constructor;
import java.util.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;

/**
 * @author David BRASSELY (david.brassely at graviteesource.com)
 * @author GraviteeSource Team
 */
public abstract class SpringFactoriesLoader implements ApplicationContextAware {

    /**
     * Logger.
     */
    protected final Logger logger = LoggerFactory.getLogger(getClass());

    protected ApplicationContext applicationContext;

    private Collection factories;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

    protected abstract Class getObjectType();

    protected Collection getFactoriesInstances() {
        if (factories == null) {
            logger.debug("Loading instances for type {}", getObjectType().getName());
            factories = getSpringFactoriesInstances(getObjectType(), new Class[] {});
        } else {
            logger.debug("Instances for type {} already loaded. Skipping...", getObjectType().getName());
        }

        return factories;
    }

    private Collection getSpringFactoriesInstances(Class type, Class[] parameterTypes, Object... args) {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        // Use names and ensure unique to protect against duplicates
        Set names = new LinkedHashSet<>(
            org.springframework.core.io.support.SpringFactoriesLoader.loadFactoryNames(type, classLoader)
        );
        List instances = createSpringFactoriesInstances(type, parameterTypes, classLoader, args, names);
        AnnotationAwareOrderComparator.sort(instances);
        return instances;
    }

    @SuppressWarnings("unchecked")
    private  List createSpringFactoriesInstances(
        Class type,
        Class[] parameterTypes,
        ClassLoader classLoader,
        Object[] args,
        Set names
    ) {
        List instances = new ArrayList<>(names.size());
        for (String name : names) {
            try {
                Class instanceClass = ClassUtils.forName(name, classLoader);
                Assert.isAssignable(type, instanceClass);
                Constructor constructor = instanceClass.getDeclaredConstructor(parameterTypes);
                T instance = (T) BeanUtils.instantiateClass(constructor, args);
                ((AbstractApplicationContext) applicationContext).getBeanFactory().autowireBean(instance);
                if (instance instanceof ApplicationContextAware) {
                    ((ApplicationContextAware) instance).setApplicationContext(applicationContext);
                }
                instances.add(instance);
            } catch (Throwable ex) {
                throw new IllegalArgumentException("Cannot instantiate " + type + " : " + name, ex);
            }
        }
        return instances;
    }
}