/*
    * 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.jexl2.scripting;
  
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.List;
  
  import javax.script.ScriptEngine;
  import javax.script.ScriptEngineFactory;
  import org.apache.commons.jexl2.JexlEngine;
  import org.apache.commons.jexl2.parser.StringParser;
  
  /**
   * Implements the Jexl ScriptEngineFactory for JSF-223.
   * <p>
   * Supports the following:<br.>
   * Language short names: "JEXL", "Jexl", "jexl", "JEXL2", "Jexl2", "jexl2" <br/>
   * File Extensions: ".jexl", ".jexl2"<br/>
   * "jexl2" etc. were added for engineVersion="2.0".
   * </p>
   * <p>
   * See
   * <a href="http://java.sun.com/javase/6/docs/api/javax/script/package-summary.html">Java Scripting API</a>
   * Javadoc.
   * @since 2.0
   */
  public class JexlScriptEngineFactory implements ScriptEngineFactory {
  
      /** {@inheritDoc} */
      public String getEngineName() {
          return "JEXL Engine";
      }
  
      /** {@inheritDoc} */
      public String getEngineVersion() {
          return "2.0"; // ensure this is updated if function changes are made to this class
      }
  
      /** {@inheritDoc} */
      public String getLanguageName() {
          return "JEXL";
      }
  
      /** {@inheritDoc} */
      public String getLanguageVersion() {
          return "2.0"; // TODO this should be derived from the actual version
      }
  
      /** {@inheritDoc} */
      public String getMethodCallSyntax(String obj, String m, String[] args) {
          StringBuilder sb = new StringBuilder();
          sb.append(obj);
          sb.append('.');
          sb.append(m);
          sb.append('(');
          boolean needComma = false;
          for(String arg : args){
              if (needComma) {
                  sb.append(',');
              }
              sb.append(arg);
              needComma = true;
          }
          sb.append(')');
          return sb.toString();
      }
  
      /** {@inheritDoc} */
      public List<String> getExtensions() {
          return Collections.unmodifiableList(Arrays.asList("jexl", "jexl2"));
      }
  
      /** {@inheritDoc} */
      public List<String> getMimeTypes() {
          return Collections.unmodifiableList(Arrays.asList("application/x-jexl", "application/x-jexl2"));
      }
  
      /** {@inheritDoc} */
      public List<String> getNames() {
          return Collections.unmodifiableList(Arrays.asList("JEXL", "Jexl", "jexl", "JEXL2", "Jexl2", "jexl2"));
      }
  
      /** {@inheritDoc} */
     public String getOutputStatement(String toDisplay) {
         if (toDisplay == null) {
             return "JEXL.out.print(null)";
         } else {
             return "JEXL.out.print("+StringParser.escapeString(toDisplay, '\'')+")";
         }
     }
 
     /** {@inheritDoc} */
     public Object getParameter(String key) {
         if (key.equals(ScriptEngine.ENGINE)) {
             return getEngineName();
         } else if (key.equals(ScriptEngine.ENGINE_VERSION)) {
             return getEngineVersion();
         } else if (key.equals(ScriptEngine.NAME)) {
             return getNames();
         } else if (key.equals(ScriptEngine.LANGUAGE)) {
             return getLanguageName();
         } else if(key.equals(ScriptEngine.LANGUAGE_VERSION)) {
             return getLanguageVersion();
         } else if (key.equals("THREADING")) {
             /*
              * To implement multithreading, the scripting engine context (inherited from AbstractScriptEngine)
              * would need to be made thread-safe; so would the setContext/getContext methods.
              * It is easier to share the underlying Uberspect and JEXL engine instance, especially
              * with an expression cache.
              */
             return null;
         }
         return null;
     }
 
     /** {@inheritDoc} */
     public String getProgram(String[] statements) {
         StringBuilder sb = new StringBuilder();
         for(String statement : statements){
             sb.append(JexlEngine.cleanExpression(statement));
             if (!statement.endsWith(";")){
                 sb.append(';');
             }
         }
         return sb.toString();
     }
 
     /** {@inheritDoc} */
     public ScriptEngine getScriptEngine() {
         JexlScriptEngine engine = new JexlScriptEngine(this);
         return engine;
     }
 
 }