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/**********************************************************************************
Copyright (c) 2018 Apereo Foundation

Licensed under the Educational Community 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://opensource.org/licenses/ecl2

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.sakaiproject.jsf2.app;

import javax.faces.context.FacesContext;
import javax.faces.el.EvaluationException;
import javax.faces.el.VariableResolver;
import javax.servlet.ServletContext;

import lombok.extern.slf4j.Slf4j;

import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

import org.sakaiproject.component.cover.ComponentManager;

/**
 * 
 * SakaiVariableResolver extends the standard variable resolved of the selected faced implementation. Special Sakai features include the ability to name any Sakai component (or Spring bean) by component (bean) name.
 * 
 */
@Slf4j
public class SakaiVariableResolver extends VariableResolver
{
	/** The VariableResolver already in place that we add features to. */
	protected VariableResolver m_resolver = null;

	/**
	 * Construct taking the VariableResolver alreay in place that we decorate.
	 * 
	 * @param other
	 *        The VariableResolver already in place.
	 */
	public SakaiVariableResolver(VariableResolver other)
	{
		m_resolver = other;
		if (log.isDebugEnabled()) log.debug("constructed around: " + m_resolver);
	}

	/**
	 * @inheritDoc
	 */
	public Object resolveVariable(FacesContext context, String name) throws EvaluationException
	{
		if (log.isDebugEnabled()) log.debug("resolving: " + name);

		Object rv = null;

		// first, give the other a shot
		if (m_resolver != null)
		{
			rv = m_resolver.resolveVariable(context, name);
			if (rv != null)
			{
				if (log.isDebugEnabled()) log.debug("resolving: " + name + " with other to: " + rv);
				return rv;
			}
		}

		// now, we extend. Check for a component/bean, using the local Spring method to pick up local and global definitions.
		WebApplicationContext wac = null;
		
		try
		{
			wac	 = WebApplicationContextUtils.getWebApplicationContext((ServletContext) context
				.getExternalContext().getContext());
		}
		catch (Exception e)
		{
			log.error(e.getMessage(), e);
		}
		
		if (wac != null)
		{
			// try the name as given
			try
			{
				rv = wac.getBean(name);
				if (rv != null)
				{
					if (log.isDebugEnabled()) log.debug("resolving: " + name + " via spring to : " + rv);
					return rv;
				}
			}
			catch (NoSuchBeanDefinitionException ignore)
			{
				// the bean doesn't exist, but its not necessarily an error
			}

			// since the jsf environment does not allow a dot in the name, convert from underbar to dot and try again
			if (name.indexOf('_') != -1)
			{
				String alternate = name.replace('_', '.');
				try
				{
					rv = wac.getBean(alternate);
	
					if (rv != null)
					{
						if (log.isDebugEnabled()) log.debug("resolving: " + alternate + " via spring to : " + rv);
						return rv;
					}
				}
				catch (NoSuchBeanDefinitionException ignore)
				{
					// the bean doesn't exist, but its not necessarily an error
				}
			}
		}

		// if no wac, try using the component manager
		else
			rv = ComponentManager.get(name);
		{
			if (rv != null)
			{
				if (log.isDebugEnabled()) log.debug("resolving: " + name + " via component manager to : " + rv);
				return rv;
			}

			// since the jsf environment does not allow a dot in the name, convert from underbar to dot and try again
			if (name.indexOf('_') != -1)
			{
				String alternate = name.replace('_', '.');
				rv = ComponentManager.get(alternate);

				if (rv != null)
				{
					if (log.isDebugEnabled()) log.debug("resolving: " + alternate + " via component manager to : " + rv);
					return rv;
				}
			}
		}

		if (log.isDebugEnabled()) log.debug("resolving: " + name + " unresolved!");
		return null;
	}
}