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/*
 * Copyright 2008 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.constretto.spring;

import org.constretto.spring.internal.resolver.DefaultAssemblyContextResolver;
import org.constretto.spring.resolver.AssemblyContextResolver;
import org.springframework.beans.factory.BeanInitializationException;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.annotation.Autowired;

import java.util.Map;

/**
 * A factory bean used to instantiate spring beans depending on the environment you are running in. This factory bean
 * use the {@link org.constretto.spring.resolver.AssemblyContextResolver} to lookup the running environment. the value of this property is used to
 * lookup in the map of beans.
 * 
 * 
Usage :
 * 
 * 
 * <bean id="productionBean" class="com..ProductionTestBean">
 *      <property name="value" value="production value" />
 *  </bean>
 * 
 *  <bean id="developmentBean" class="com..DevelopmentTestBean">
 *      <property name="value" value="development value" />
 *  </bean>
 * 

 *  <bean id="myBean" class="org.constretto.spring.ConstrettoSingletonFactoryBean">
 *      <constructor-arg>
 *          <map>
 *              <entry key="production" value-ref="productionBean" />
 *              <entry key="development" value-ref="developmentBean" />
 *          </map>
 *      </constructor-arg>
 *  </bean>
 * 

 *  <bean id="myBeanOverriddenDefaultPrefix" class="org.constretto.spring.propertyplaceholder.factory.ConstrettoSingletonFactoryBean">
 *    <constructor-arg>
 *          <map>
 *              <entry key="production" value-ref="productionBean" />
 *              <entry key="development" value-ref="developmentBean" />
 *          </map>
 *      </constructor-arg>
 *      <constructor-arg ref="developmentBean" />
 *  </bean>
 * 

 * 
 *
 * @author Kaare Nilsen
 */
public class ConstrettoSingletonFactoryBean implements FactoryBean {
    private Map beans;
    private Object defaultBean;
    private AssemblyContextResolver assemblyContextResolver;

    private ConstrettoSingletonFactoryBean() {
        assemblyContextResolver = new DefaultAssemblyContextResolver();
    }

    public ConstrettoSingletonFactoryBean(Map beans, Object defaultBean) {
        this();
        this.beans = beans;
        this.defaultBean = defaultBean;
    }

    public ConstrettoSingletonFactoryBean(Map beans) {
        this();
        this.beans = beans;
    }

    public ConstrettoSingletonFactoryBean(Map beans, AssemblyContextResolver assemblyContextResolver) {
        this.assemblyContextResolver = assemblyContextResolver;
        this.beans = beans;
    }

    public ConstrettoSingletonFactoryBean(Map beans, Object defaultBean,
                                          AssemblyContextResolver assemblyContextResolver) {
        this.assemblyContextResolver = assemblyContextResolver;
        this.beans = beans;
        this.defaultBean = defaultBean;
    }

    /**
     * Chooses the correct implementation to use given the current environment. if no environment is set. uses the class
     * with the default prefix (production if not set)
     */
    public Object getObject() throws Exception {
        if (null == beans && null == defaultBean) {
            throw new BeanInitializationException("At least one implementation of the service is mandatory");
        }
        return getResolvedBean();
    }

    @Autowired
    public void setAssemblyContextResolver(AssemblyContextResolver assemblyContextResolver) {
        this.assemblyContextResolver = assemblyContextResolver;
    }

    public void setDefaultBean(Object defaultBean) {
        this.defaultBean = defaultBean;
    }

    private Object getResolvedBean() {
        Object bean = null;
        if (!assemblyContextResolver.getAssemblyContext().isEmpty()) {
            for (String currentEnvironment : assemblyContextResolver.getAssemblyContext()) {
                bean = beans.get(currentEnvironment);
                if (null != bean) {
                    break;
                }
            }
        }

        if (bean == null) {
            bean = defaultBean;
        }

        if (bean == null) {
            throw new BeanInitializationException("No bean assosiated with the prefix " + assemblyContextResolver.getAssemblyContext()
                    + ", and no default bean could be found");
        }
        return bean;
    }

    public Class getObjectType() {
        if (null == beans) {
            throw new BeanInitializationException("At least one implementation of the service is mandatory");
        }

        return getResolvedBean().getClass();
    }

    public boolean isSingleton() {
        return false;
    }
}