/* Copyright 2012 Tacit Knowledge
*
* 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 com.tacitknowledge.flip.context;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.tacitknowledge.flip.Environment;
import com.tacitknowledge.flip.exceptions.UnknownContextException;
/**
* The central point to access all context providers.
*
* @author Serghei Soloviov <ssoloviov@tacitknowledge.com>
* @author Petric Coroli <pcoroli@tacitknowledge.com>
*/
public class ContextManager
{
private final Map<String, ContextDescriptor> contexts = new HashMap<String, ContextDescriptor>();
private final List<ContextDescriptor> contextList = new ArrayList<ContextDescriptor>();
/**
* Constructs the context manager and adds the context providers set in {@link Environment#getContextProviders() }.
*
* @param environment the environment used to construct this context manager.
*/
public ContextManager(final Environment environment)
{
final ContextDescriptorFactory contextDescriptorFactory = new ContextDescriptorFactory();
for (final Object contextProvider : environment.getContextProviders())
{
if (contextProvider == null)
{
continue;
}
final ContextDescriptor contextDescriptor = contextDescriptorFactory
.createContextDescriptor(contextProvider);
contexts.put(contextDescriptor.getName(), contextDescriptor);
contextList.add(contextDescriptor);
}
}
/**
* Returns the map view used to access the context properties. If the context
* name is {@code "_all"} then it is created a map view this all properties
* available from all contexts. In the resulting map if two contexts
* has the property with the same name it is used that which was set
* in {@link Environment#getContextProviders()} closer to the start of the list.
* If the context name is the name of one existent context (there is a context
* provider whose annotation value {@link FlipContext#name()} equals to the
* contextName parameter) then that context map is returned.
*
* @param contextName the context
* @return the map view of properties of that context.
* @throws UnknownContextException throws where no context with such name was found.
*/
public Map<String, Object> getContext(final String contextName)
{
if (ContextMap.GLOBAL.equals(contextName))
{
return new ContextMap(contextList);
}
else
{
final ContextDescriptor descriptor = contexts.get(contextName);
if (descriptor == null)
{
throw new UnknownContextException(String.format("Cannot find context with name [%s].", contextName));
}
return new ContextMap(Collections.singletonList(descriptor));
}
}
}