/**

  * Copyright 2005-2011 The Kuali 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://www.opensource.org/licenses/ecl2.php

  *

  * 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.kuali.rice.krms.framework.engine;

 import java.util.Map;

 import org.joda.time.DateTime;

 import org.kuali.rice.krms.api.engine.Engine;

 import org.kuali.rice.krms.api.engine.EngineResults;

 import org.kuali.rice.krms.api.engine.ExecutionEnvironment;

 import org.kuali.rice.krms.api.engine.ExecutionOptions;

 import org.kuali.rice.krms.api.engine.Facts;

 import org.kuali.rice.krms.api.engine.ResultEvent;

 import org.kuali.rice.krms.api.engine.SelectionCriteria;

 import org.kuali.rice.krms.api.engine.Term;

 import org.kuali.rice.krms.framework.engine.result.TimingResult;

 public class ProviderBasedEngine implements Engine {

         private static final Term effectiveExecutionTimeTerm = new Term("effectiveExecutionTime", null);

         private static final org.apache.log4j.Logger LOG = org.apache.log4j.Logger.getLogger(ProviderBasedEngine.class);

         private static final ResultLogger KLog = ResultLogger.getInstance();

         private ContextProvider contextProvider;

     @Override

     public EngineResults execute(SelectionCriteria selectionCriteria, Map<String, Object> facts,

             ExecutionOptions executionOptions) {

         return execute(selectionCriteria,

                 Facts.Builder.create().addFactsByName(facts).build(),

                 executionOptions);

     }

     @Override

         public EngineResults execute(SelectionCriteria selectionCriteria, Facts facts, ExecutionOptions executionOptions) {

                 DateTime start, end;

                 start = new DateTime();

                 ExecutionEnvironment environment = establishExecutionEnvironment(selectionCriteria, facts.getFactMap(), executionOptions);

                 // set execution time

                 Long effectiveExecutionTime = environment.getSelectionCriteria().getEffectiveExecutionTime();

                 if (effectiveExecutionTime == null) { effectiveExecutionTime = System.currentTimeMillis(); }

                 environment.publishFact(effectiveExecutionTimeTerm, effectiveExecutionTime);

                 Context context = selectContext(selectionCriteria, facts.getFactMap(), executionOptions);

                 if (context == null) {

                         LOG.info("Failed to locate a Context for the given qualifiers, skipping rule engine execution: " + selectionCriteria.getContextQualifiers());

                         return null;

                 }

                 context.execute(environment);

                 end = new DateTime();

                 if (KLog.isEnabled(environment)){

                         KLog.logResult(new TimingResult(ResultEvent.TimingEvent, this, environment, start, end));

                 }

                 return environment.getEngineResults();

         }

         protected ExecutionEnvironment establishExecutionEnvironment(SelectionCriteria selectionCriteria, Map<Term, Object> facts, ExecutionOptions executionOptions) {

                 return new BasicExecutionEnvironment(selectionCriteria, facts, executionOptions, new TermResolutionEngineImpl());

         }

         protected Context selectContext(SelectionCriteria selectionCriteria, Map<Term, Object> facts, ExecutionOptions executionOptions) {

                 if (contextProvider == null) {

                         throw new IllegalStateException("No ContextProvider was configured.");

                 }

                 return contextProvider.loadContext(selectionCriteria, facts, executionOptions);

         }

         public void setContextProvider(ContextProvider contextProvider) {

                 this.contextProvider = contextProvider;

         }

 }