/*

  * Copyright 2007 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.kew.rule;

 import java.text.ParseException;

 import org.apache.commons.lang.StringUtils;

 import org.apache.log4j.Logger;

 import org.kuali.rice.kew.engine.RouteContext;

 import org.kuali.rice.kew.exception.WorkflowException;

 import org.kuali.rice.kew.service.KEWServiceLocator;

 /**

  * Implements the KRA meta-rule processing and state machine engine 

  * 

  * @author Kuali Rice Team (rice.collab@kuali.org)

  */

 public class KRAMetaRuleEngine {

     private static final Logger LOG = Logger.getLogger(KRAMetaRuleEngine.class);

     /**

      * KRA meta-rule processing flag

      */

     private static enum KRA_RULE_FLAG {

         NEXT, TRUE, FALSE

     }

     private final String expression;

     private final String[] statements;

     private int curStatement = 0;

     /**

      * Whether processing has indicated that we should stop

      */

     private boolean stop = false;

     public KRAMetaRuleEngine(String expression) throws ParseException {

         this.expression = expression;

         statements = expression.split("\\s*[;\r\n]\\s*");

         if (statements.length == 0) {

             throw new ParseException("No statements parsed in expression: " + expression, 0);

         }

     }

     /**

      * @return the expression the engine was initialized with

      */

     public String getExpression() {

         return expression;

     }

     /**

      * @return the parsed statements

      */

     public String[] getStatements() {

         return statements;

     }

     /**

      * @return the next statement the engine will process

      */

     public int getCurStatement() {

         return curStatement;

     }

     /**

      * @param statementNo the statement index at which to resume processing 

      */

     public void setCurStatement(int statementNo) {

         this.curStatement = statementNo;

     }

     /**

      * @return whether we are done processing

      */

     public boolean isDone() {

         return curStatement >= statements.length || stop;

     }

     /**

      * Processes a single statement and returns the result

      * @param context the current RouteContext

      * @return the expression result that resulted from the evaluation of a single statement

      * @throws ParseException if the statement could not be parsed

      */

     public RuleExpressionResult processSingleStatement(RouteContext context) throws ParseException, WorkflowException {

         if (isDone()) {

             return null;

         }

         int stmtNum = curStatement + 1;

         String statement = statements[curStatement];

         LOG.debug("Processing statement: " + statement);

         String[] words = statement.split("\\s*:\\s*");

         if (words.length < 2) {

             throw new ParseException("Invalid statement (#" + stmtNum + "): " + statement, 0);

         }

         String ruleName = words[0];

         if (StringUtils.isEmpty(ruleName)) {

             throw new ParseException("Invalid rule in statement (#" + stmtNum + "): " + statement, 0);

         }

         String flag = words[1];

         LOG.debug(flag.toUpperCase());

         KRA_RULE_FLAG flagCode = KRA_RULE_FLAG.valueOf(flag.toUpperCase());

         if (flagCode == null) {

             throw new ParseException("Invalid flag in statement (#" + stmtNum + "): " + statement, 0);

         }

         RuleBaseValues nestedRule = KEWServiceLocator.getRuleService().getRuleByName(ruleName);

         if (nestedRule == null) {

             throw new ParseException("Rule '" + ruleName + "' in statement (#" + stmtNum + ") not found: " + statement, 0);

         }

         Rule rule = new RuleImpl(nestedRule);

         RuleExpressionResult result;

         switch (flagCode) {

             case NEXT:

                 result = rule.evaluate(rule, context);

                 break;

             case TRUE:

                 result = rule.evaluate(rule, context);

                 if (!result.isSuccess()) {

                     stop = true;

                 }

                 break;

             case FALSE:

                 result = rule.evaluate(rule, context);

                 if (result.isSuccess()) {

                     stop = true;

                     // we need to just invert the ultimate expression result success, because in this case

                     // we wanted the expression to fail but it didn't

                     result = new RuleExpressionResult(rule, false, result.getResponsibilities());

                 }

                 break;

             default:

                 throw new WorkflowException("Unhandled statement flag: " + flagCode);

         }

         curStatement++;

         LOG.debug("Result of statement '" + statement + "': " + result);

         return result;

     }

 }