/*

  * Copyright 2011 The Kuali Foundation

  *

  * Licensed under the Educational Community License, Version 1.0 (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/ecl1.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.impl.provider.repository;

 import java.util.ArrayList;

 import java.util.LinkedList;

 import java.util.List;

 import java.util.Map;

 import java.util.TreeMap;

 import org.apache.commons.collections.CollectionUtils;

 import org.apache.commons.lang.StringUtils;

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

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

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

 import org.kuali.rice.krms.api.repository.RepositoryDataException;

 import org.kuali.rice.krms.api.repository.function.FunctionDefinition;

 import org.kuali.rice.krms.api.repository.function.FunctionParameterDefinition;

 import org.kuali.rice.krms.api.repository.function.FunctionRepositoryService;

 import org.kuali.rice.krms.api.repository.proposition.PropositionDefinition;

 import org.kuali.rice.krms.api.repository.proposition.PropositionParameter;

 import org.kuali.rice.krms.api.repository.proposition.PropositionParameterType;

 import org.kuali.rice.krms.api.repository.term.TermDefinition;

 import org.kuali.rice.krms.api.repository.term.TermParameterDefinition;

 import org.kuali.rice.krms.api.repository.term.TermSpecificationDefinition;

 import org.kuali.rice.krms.framework.engine.Function;

 import org.kuali.rice.krms.framework.engine.Proposition;

 import org.kuali.rice.krms.framework.engine.expression.BinaryOperatorExpression;

 import org.kuali.rice.krms.framework.engine.expression.BooleanValidatingExpression;

 import org.kuali.rice.krms.framework.engine.expression.ComparisonOperator;

 import org.kuali.rice.krms.framework.engine.expression.ConstantExpression;

 import org.kuali.rice.krms.framework.engine.expression.Expression;

 import org.kuali.rice.krms.framework.engine.expression.ExpressionBasedProposition;

 import org.kuali.rice.krms.framework.engine.expression.FunctionExpression;

 import org.kuali.rice.krms.framework.engine.expression.TermExpression;

 import org.kuali.rice.krms.framework.type.FunctionTypeService;

 import org.kuali.rice.krms.framework.type.PropositionTypeService;

 import org.kuali.rice.krms.impl.repository.TermBoService;

 import org.kuali.rice.krms.impl.type.KrmsTypeResolver;

 /**

  * A default implementation of {@link PropositionTypeService} for propositions

  * which are composed of terms, operators, and functions.  A simple proposition

  * is self-contained and has no compound "sub" propositions.  However, it's

  * behavior is defined by the set of parameters on the {@link PropositionDefinition}.

  * 

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

  *

  */

 public class SimplePropositionTypeService implements PropositionTypeService {

         private TermBoService termBoService;

         private FunctionRepositoryService functionRepositoryService;

         private KrmsTypeResolver typeResolver;

         @Override

         public Proposition loadProposition(PropositionDefinition propositionDefinition) {

                 return new ExpressionBasedProposition(translateToExpression(propositionDefinition));

         }

         /**

          * Translates the parameters on the given proposition definition to create an expression for evaluation.

          * The proposition parameters are defined in a reverse-polish notation so a stack is used for

          * evaluation purposes.

          * 

          * @param propositionDefinition the proposition definition to translate

          * 

          * @return the translated expression for the given proposition, this

          * expression, when evaluated, will return a Boolean.

          */

         protected Expression<Boolean> translateToExpression(PropositionDefinition propositionDefinition) {

                 LinkedList<Expression<? extends Object>> stack = new LinkedList<Expression<? extends Object>>();

                 for (PropositionParameter parameter : propositionDefinition.getParameters()) {

                         PropositionParameterType parameterType = PropositionParameterType.fromCode(parameter.getParameterType());

                         if (parameterType == PropositionParameterType.CONSTANT) {

                                 // TODO - need some way to define data type on the prop parameter as well?  Not all constants will actually be String values!!!

                                 stack.addFirst(new ConstantExpression<String>(parameter.getValue()));

                         } else if (parameterType == PropositionParameterType.FUNCTION) {

                                 String functionId = parameter.getValue();

                                 FunctionDefinition functionDefinition = functionRepositoryService.getFunction(functionId);

                                 if (functionDefinition == null) {

                                         throw new RepositoryDataException("Unable to locate function with the given id: " + functionId);

                                 }

                                 FunctionTypeService functionTypeService = typeResolver.getFunctionTypeService(functionDefinition);

                                 Function function = functionTypeService.loadFunction(functionDefinition);

                                 // TODO throw an exception if function is null?

                                 List<FunctionParameterDefinition> parameters = functionDefinition.getParameters();

                                 if (stack.size() < parameters.size()) {

                                         throw new RepositoryDataException("Failed to initialize custom function '" + functionDefinition.getNamespace() + " " + functionDefinition.getName() +

                                                         "'.  There were only " + stack.size() + " values on the stack but function requires at least " + parameters.size());

                                 }

                                 List<Expression<? extends Object>> arguments = new ArrayList<Expression<? extends Object>>();

                                 // work backward through the list to match params to the stack

                                 for (int index = parameters.size() - 1; index >= 0; index--) {

                                         FunctionParameterDefinition parameterDefinition = parameters.get(index);

                                         // TODO need to check types here? expression object probably needs a getType on it so that we can confirm that the types will be compatible?

                                         Expression<? extends Object> argument = stack.removeFirst();

                                         arguments.add(argument);

                                 }

                                 stack.addFirst(new FunctionExpression(function, arguments));

                         } else if (parameterType == PropositionParameterType.OPERATOR) {

                                 ComparisonOperator operator = ComparisonOperator.fromCode(parameter.getValue());

                                 if (stack.size() < 2) {

                                         throw new RepositoryDataException("Failed to initialize expression for comparison operator " + operator + " because a sufficient number of arguments was not available on the stack.  Current contents of stack: " + stack.toString());

                                 }

                                 Expression<? extends Object> rhs = stack.removeFirst();

                                 Expression<? extends Object> lhs = stack.removeFirst();

                                 stack.addFirst(new BinaryOperatorExpression(operator, lhs, rhs));

                         } else if (parameterType == PropositionParameterType.TERM) {

                                 String termId = parameter.getValue();

                                 TermDefinition termDefinition = termBoService.getTermById(termId);

                                 if (termDefinition == null) { throw new RepositoryDataException("unable to load term with id " + termId);}

                                 Term term = translateTermDefinition(termDefinition);

                                 stack.addFirst(new TermExpression(term));

                         }

                 }

                 if (stack.size() != 1) {

                         throw new RepositoryDataException("Final contents of expression stack are incorrect, there should only be one entry but was " + stack.size() +".  Current contents of stack: " + stack.toString());

                 }

                 return new BooleanValidatingExpression(stack.removeFirst());

         }

         protected Term translateTermDefinition(TermDefinition termDefinition) {

                 if (termDefinition == null) {

                         throw new RepositoryDataException("Given TermDefinition is null");

                 }

                 TermSpecificationDefinition termSpecificationDefinition = termDefinition.getSpecification();

                 if (termSpecificationDefinition == null) { throw new RepositoryDataException("term with id " + termDefinition.getId() + " has a null specification"); } 

                 List<TermParameterDefinition> params = termDefinition.getParameters();

                 Map<String,String> paramsMap = new TreeMap<String,String>();

                 if (!CollectionUtils.isEmpty(params)) for (TermParameterDefinition param : params) {

                         if (StringUtils.isBlank(param.getName())) { 

                                 throw new RepositoryDataException("TermParameterDefinition.name may not be blank"); 

                         }

                         paramsMap.put(param.getName(), param.getValue());

                 }

                 return new Term(new TermSpecification(termSpecificationDefinition.getName(), termSpecificationDefinition.getType()), paramsMap);

         }

         /**

          * @param termBoService the termBoService to set

          */

         public void setTermBoService(TermBoService termBoService) {

                 this.termBoService = termBoService;

         }

         public void setFunctionRepositoryService(FunctionRepositoryService functionRepositoryService) {

                 this.functionRepositoryService = functionRepositoryService;

         }

         public void setTypeResolver(KrmsTypeResolver typeResolver) {

                 this.typeResolver = typeResolver;

         }

 }