/*
    * 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
    *
    *      https://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.jexl3.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.jexl3.JexlBuilder;
  import org.apache.commons.jexl3.JexlEngine;
  import org.apache.commons.jexl3.introspection.JexlPermissions;
  import org.apache.commons.jexl3.parser.StringParser;
  
  /**
   * Implements the JEXL ScriptEngineFactory for JSF-223.
   * <p>
   * Supports the following:<br>
   * </p>
   * <ul>
   * <li>Language short names: "JEXL", "Jexl", "jexl", "JEXL2", "Jexl2", "jexl2", "JEXL3", "Jexl3", "jexl3"</li>
   * <li>File Extensions: ".jexl", ".jexl2", ".jexl3"</li>
   * <li>"jexl3" etc. were added for engineVersion="3.0"</li>
   * </ul>
   * <p>
   * See
   * <a href="https://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 {
      /**
       * The engine and language version.
       */
      private static final String JEXL_VERSION = "3.7";
      /**
       * The default factory permissions.
       */
      private static JexlPermissions defaultPermissions;
  
      /**
       * The engine permissions.
       */
      private final JexlPermissions permissions;
  
      /**
       * Default constructor.
       */
      public JexlScriptEngineFactory() { this(null); } // Keep Javadoc happy
  
      /**
       * Constructor with permissions.
       * <p>Meant to reduce dependency to JEXL for extraordinary use case of JSR233.</p>
       * @param jexlPermissions the permissions instance to use or null to use the {@link JexlScriptEngineFactory} default
       */
      public JexlScriptEngineFactory(final JexlPermissions jexlPermissions) {
          permissions = jexlPermissions != null ? jexlPermissions : defaultPermissions;
      }
  
      @Override
      public ScriptEngine getScriptEngine() {
          return new JexlScriptEngine(this);
      }
  
      /**
       * Creates an engine.
       * @return the JexlEngine instance, create it if necessary
       */
      protected JexlEngine getEngine() {
          return createJexlEngine();
      }
  
      /**
       * Creates a new JexlEngine instance.
       * @return a new JexlEngine instance
       */
      protected JexlEngine createJexlEngine() {
          final JexlBuilder builder = new JexlBuilder()
            .strict(true)
            .safe(false)
            .logger(JexlScriptEngine.LOG)
           .cache(JexlScriptEngine.CACHE_SIZE);
         JexlPermissions p = permissions;
         if (p == null) {
             p = defaultPermissions;
             if (p == null) {
                 p = builder.permissions();
                 if (p == null) {
                     p = JexlPermissions.RESTRICTED;
                 }
             }
         }
         final JexlPermissions required = new JexlPermissions.ClassPermissions(p, JexlScriptEngine.JexlScriptObject.class);
         builder.permissions(required);
         return builder.create();
     }
 
     /**
      * Sets the permissions instance used to create the script engine.
      * <p>To restore 3.2 <em>unsafe</em> script behavior:</p>
      * {@code
      *         JexlScriptEngineFactory.setDefaultPermissions(JexlPermissions.UNRESTRICTED);
      * }
      *
      * @param permissions the permissions instance to use or null to use the {@link JexlBuilder} default
      * @since 3.6.3
      */
     public static void setDefaultPermissions(final JexlPermissions permissions) {
         defaultPermissions = permissions;
     }
 
     @Override
     public String getEngineName() {
         return "JEXL Engine";
     }
 
     @Override
     public String getEngineVersion() {
         return JEXL_VERSION;
     }
 
     @Override
     public List<String> getExtensions() {
         return Collections.unmodifiableList(Arrays.asList("jexl", "jexl2", "jexl3"));
     }
 
     @Override
     public String getLanguageName() {
         return "JEXL";
     }
 
     @Override
     public String getLanguageVersion() {
         return JEXL_VERSION;
     }
 
     @Override
     public String getMethodCallSyntax(final String obj, final String m, final String... args) {
         final StringBuilder sb = new StringBuilder();
         sb.append(obj);
         sb.append('.');
         sb.append(m);
         sb.append('(');
         boolean needComma = false;
         for(final String arg : args){
             if (needComma) {
                 sb.append(',');
             }
             sb.append(arg);
             needComma = true;
         }
         sb.append(')');
         return sb.toString();
     }
 
     @Override
     public List<String> getMimeTypes() {
         return Collections.unmodifiableList(Arrays.asList("application/x-jexl",
                                                           "application/x-jexl2",
                                                           "application/x-jexl3"));
     }
 
     @Override
     public List<String> getNames() {
         return Collections.unmodifiableList(Arrays.asList("JEXL", "Jexl", "jexl",
                                                           "JEXL2", "Jexl2", "jexl2",
                                                           "JEXL3", "Jexl3", "jexl3"));
     }
 
     @Override
     public String getOutputStatement(final String toDisplay) {
         if (toDisplay == null) {
             return "JEXL.out.print(null)";
         }
         return "JEXL.out.print("+StringParser.escapeString(toDisplay, '\'')+")";
     }
 
     @Override
     public Object getParameter(final String key) {
         switch (key) {
             case ScriptEngine.ENGINE:
                 return getEngineName();
             case ScriptEngine.ENGINE_VERSION:
                 return getEngineVersion();
             case ScriptEngine.NAME:
                 return getNames();
             case ScriptEngine.LANGUAGE:
                 return getLanguageName();
             case ScriptEngine.LANGUAGE_VERSION:
                 return getLanguageVersion();
             case "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.
                  */
             default:
                 return null;
         }
     }
 
     @Override
     public String getProgram(final String... statements) {
         final StringBuilder sb = new StringBuilder();
         for(final String statement : statements){
             sb.append(statement.trim());
             if (!statement.endsWith(";")){
                 sb.append(';');
             }
         }
         return sb.toString();
     }
 
 }