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/* 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.activiti.engine.impl.el;

import java.beans.FeatureDescriptor;
import java.util.Iterator;
import java.util.List;

import javax.el.ELContext;
import javax.el.ELResolver;

import org.activiti.engine.delegate.VariableScope;
import org.activiti.engine.impl.context.Context;
import org.activiti.engine.impl.identity.Authentication;
import org.activiti.engine.impl.persistence.entity.ExecutionEntity;
import org.activiti.engine.impl.persistence.entity.TaskEntity;
import org.activiti.engine.impl.persistence.entity.VariableInstance;

import com.fasterxml.jackson.databind.JsonNode;

/**
 * Implementation of an {@link ELResolver} that resolves expressions with the
 * process variables of a given {@link VariableScope} as context. 

 * Also exposes the currently logged in username to be used in expressions (if
 * any)
 * 
 * 
 * 
 */
public class VariableScopeElResolver extends ELResolver {

	public static final String EXECUTION_KEY = "execution";
	public static final String TASK_KEY = "task";
	public static final String LOGGED_IN_USER_KEY = "authenticatedUserId";

	protected VariableScope variableScope;

	public VariableScopeElResolver(VariableScope variableScope) {
		this.variableScope = variableScope;
	}

	@Override
	public Object getValue(ELContext context, Object base, Object property) {

		if (base == null) {
			String variable = (String) property; // according to javadoc, can
													// only be a String

			if ((EXECUTION_KEY.equals(property) && variableScope instanceof ExecutionEntity)
					|| (TASK_KEY.equals(property) && variableScope instanceof TaskEntity)) {
				context.setPropertyResolved(true);
				return variableScope;
			} else if (EXECUTION_KEY.equals(property) && variableScope instanceof TaskEntity) {
				context.setPropertyResolved(true);
				return ((TaskEntity) variableScope).getExecution();
			} else if (LOGGED_IN_USER_KEY.equals(property)) {
				context.setPropertyResolved(true);
				return Authentication.getAuthenticatedUserId();
			} else {
				if (variableScope.hasVariable(variable)) {
					context.setPropertyResolved(true); // if not set, the next
														// elResolver in the
														// CompositeElResolver
														// will be called
					VariableInstance variableInstance = variableScope.getVariableInstance(variable);
					Object value = variableInstance.getValue();
					if (("json".equals(variableInstance.getTypeName())
							|| "longJson".equals(variableInstance.getTypeName())) && (value instanceof JsonNode)
							&& ((JsonNode) value).isArray()) {
						return Context.getProcessEngineConfiguration().getObjectMapper().convertValue(value,
								List.class);
					} else {
						return value;
					}
				}
			}
		}

		// property resolution (eg. bean.value) will be done by the
		// BeanElResolver (part of the CompositeElResolver)
		// It will use the bean resolved in this resolver as base.

		return null;
	}

	@Override
	public boolean isReadOnly(ELContext context, Object base, Object property) {
		if (base == null) {
			String variable = (String) property;
			return !variableScope.hasVariable(variable);
		}
		return true;
	}

	@Override
	public void setValue(ELContext context, Object base, Object property, Object value) {
		if (base == null) {
			String variable = (String) property;
			if (variableScope.hasVariable(variable)) {
				variableScope.setVariable(variable, value);
			}
		}
	}

	@Override
	public Class getCommonPropertyType(ELContext arg0, Object arg1) {
		return Object.class;
	}

	@Override
	public Iterator getFeatureDescriptors(ELContext arg0, Object arg1) {
		return null;
	}

	@Override
	public Class getType(ELContext arg0, Object arg1, Object arg2) {
		return Object.class;
	}

}