/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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.apache.commons.scxml2.env.minimal;
  
  import java.io.Serializable;
  
  import org.apache.commons.scxml2.Builtin;
  import org.apache.commons.scxml2.Context;
  import org.apache.commons.scxml2.Evaluator;
  import org.apache.commons.scxml2.EvaluatorProvider;
  import org.apache.commons.scxml2.SCXMLExpressionException;
  import org.apache.commons.scxml2.model.SCXML;
  
  /**
   * Minimal Evaluator implementing and providing support for the SCXML Null Data Model.
   * <p>
   * The SCXML Null Data Model only supports the SCXML "In(stateId)" builtin function.
   * </p>
   */
  public class MinimalEvaluator implements Evaluator, Serializable {
  
      /** Serial version UID. */
      private static final long serialVersionUID = 1L;
  
      public static final String SUPPORTED_DATA_MODEL = Evaluator.NULL_DATA_MODEL;
  
      public static class MinimalEvaluatorProvider implements EvaluatorProvider {
  
          @Override
          public String getSupportedDatamodel() {
              return SUPPORTED_DATA_MODEL;
          }
  
          @Override
          public Evaluator getEvaluator() {
              return new MinimalEvaluator();
          }
  
          @Override
          public Evaluator getEvaluator(final SCXML document) {
              return new MinimalEvaluator();
          }
      }
  
      @Override
      public String getSupportedDatamodel() {
          return SUPPORTED_DATA_MODEL;
      }
  
      @Override
      public Object eval(final Context ctx, final String expr) throws SCXMLExpressionException {
          return expr;
      }
  
      @Override
      public Boolean evalCond(final Context ctx, final String expr) throws SCXMLExpressionException {
          // only support the "In(stateId)" predicate
          String predicate = expr != null ? expr.trim() : "";
          if (predicate.startsWith("In(") && predicate.endsWith(")")) {
              String stateId = predicate.substring(3, predicate.length()-1);
              return Builtin.isMember(ctx, stateId);
          }
          return false;
      }
  
      @Override
      public Object evalLocation(final Context ctx, final String expr) throws SCXMLExpressionException {
          return expr;
      }
  
      @Override
      public void evalAssign(final Context ctx, final String location, final Object data, final AssignType type, final String attr) throws SCXMLExpressionException {
          throw new UnsupportedOperationException("Assign expressions are not supported by the \"null\" datamodel");
      }
  
      @Override
      public Object evalScript(final Context ctx, final String script) throws SCXMLExpressionException {
          throw new UnsupportedOperationException("Scripts are not supported by the \"null\" datamodel");
      }
  
      @Override
      public Context newContext(final Context parent) {
          return parent instanceof MinimalContext ? parent : new MinimalContext(parent);
      }
  }