/*
    * 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;
  
  import java.io.Serializable;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.commons.scxml2.Context;
  import org.apache.commons.scxml2.SCXMLSystemContext;
  
  /**
   * Simple Context wrapping a map of variables.
   *
   */
  public class SimpleContext implements Context, Serializable {
  
      /** Serial version UID. */
      private static final long serialVersionUID = 1L;
      /** Implementation independent log category. */
      private static final Log DEFAULT_LOG = LogFactory.getLog(Context.class);
      private Log log = DEFAULT_LOG;
      /** The parent Context to this Context. */
      private Context parent;
      /** The Map of variables and their values in this Context. */
      private Map<String, Object> vars;
  
      protected final SCXMLSystemContext systemContext;
  
      /**
       * Constructor.
       *
       */
      public SimpleContext() {
          this(null, null);
      }
  
      /**
       * Constructor.
       *
       * @param parent A parent Context, can be null
       */
      public SimpleContext(final Context parent) {
          this(parent, null);
      }
  
      /**
       * Constructor.
       *
       * @param parent A parent Context, can be null
       * @param initialVars A pre-populated initial variables map
       */
      public SimpleContext(final Context parent, final Map<String, Object> initialVars) {
          this.parent = parent;
          this.systemContext = parent instanceof SCXMLSystemContext ?
                  (SCXMLSystemContext) parent : parent != null ? parent.getSystemContext() : null;
          if (initialVars == null) {
              setVars(new HashMap<String, Object>());
          } else {
              setVars(this.vars = initialVars);
          }
      }
  
      /**
       * Assigns a new value to an existing variable or creates a new one.
       * The method searches the chain of parent Contexts for variable
       * existence.
       *
       * @param name The variable name
       * @param value The variable value
       * @see org.apache.commons.scxml2.Context#set(String, Object)
       */
      public void set(final String name, final Object value) {
          if (getVars().containsKey(name)) { //first try to override local
              setLocal(name, value);
          } else if (parent != null && parent.has(name)) { //then check for global
              parent.set(name, value);
          } else { //otherwise create a new local variable
              setLocal(name, value);
          }
      }
  
      /**
      * Get the value of this variable; delegating to parent.
      *
      * @param name The variable name
      * @return Object The variable value
      * @see org.apache.commons.scxml2.Context#get(java.lang.String)
      */
     public Object get(final String name) {
         Object localValue = getVars().get(name);
         if (localValue != null) {
             return localValue;
         } else if (parent != null) {
             return parent.get(name);
         } else {
             return null;
         }
     }
 
     /**
      * Check if this variable exists, delegating to parent.
      *
      * @param name The variable name
      * @return boolean true if this variable exists
      * @see org.apache.commons.scxml2.Context#has(java.lang.String)
      */
     public boolean has(final String name) {
         return (hasLocal(name) || (parent != null && parent.has(name)));
     }
 
     /**
      * Check if this variable exists, only checking this Context
      *
      * @param name The variable name
      * @return boolean true if this variable exists
      * @see org.apache.commons.scxml2.Context#hasLocal(java.lang.String)
      */
     public boolean hasLocal(final String name) {
         return (getVars().containsKey(name));
     }
 
     /**
      * Clear this Context.
      *
      * @see org.apache.commons.scxml2.Context#reset()
      */
     public void reset() {
         getVars().clear();
     }
 
     /**
      * Get the parent Context, may be null.
      *
      * @return Context The parent Context
      * @see org.apache.commons.scxml2.Context#getParent()
      */
     public Context getParent() {
         return parent;
     }
 
     /**
      * Get the SCXMLSystemContext for this Context, should not be null unless this is the root Context
      *
      * @return The SCXMLSystemContext in a chained Context environment
      */
     public final SCXMLSystemContext getSystemContext() {
         return systemContext;
     }
 
     /**
      * Assigns a new value to an existing variable or creates a new one.
      * The method allows to shaddow a variable of the same name up the
      * Context chain.
      *
      * @param name The variable name
      * @param value The variable value
      * @see org.apache.commons.scxml2.Context#setLocal(String, Object)
      */
     public void setLocal(final String name, final Object value) {
         getVars().put(name, value);
         if (log.isDebugEnabled()) {
             log.debug(name + " = " + String.valueOf(value));
         }
     }
 
     /**
      * Set the variables map.
      *
      * @param vars The new Map of variables.
      */
     protected void setVars(final Map<String, Object> vars) {
         this.vars = vars;
     }
 
     /**
      * Get the Map of all local variables in this Context.
      *
      * @return Returns the vars.
      */
     public Map<String, Object> getVars() {
         return vars;
     }
 
     /**
      * Set the log used by this <code>Context</code> instance.
      *
      * @param log The new log.
      */
     protected void setLog(final Log log) {
         this.log = log;
     }
 
     /**
      * Get the log used by this <code>Context</code> instance.
      *
      * @return Log The log being used.
      */
     protected Log getLog() {
         return log;
     }
 
 }