/* BeanShellDecideRule
   *
   * $Id: BeanShellDecideRule.java 6149 2009-03-02 22:52:51Z gojomo $
   *
   * Created on Aug 7, 2006
   *
   * Copyright (C) 2006 Internet Archive.
   *
   * This file is part of the Heritrix web crawler (crawler.archive.org).
  *
  * Heritrix is free software; you can redistribute it and/or modify
  * it under the terms of the GNU Lesser Public License as published by
  * the Free Software Foundation; either version 2.1 of the License, or
  * any later version.
  *
  * Heritrix is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU Lesser Public License for more details.
  *
  * You should have received a copy of the GNU Lesser Public License
  * along with Heritrix; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
  package org.archive.crawler.deciderules;
  
  import java.io.File;
  import java.io.IOException;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  import org.archive.crawler.settings.SimpleType;
  import org.archive.crawler.settings.Type;
  
  import bsh.EvalError;
  import bsh.Interpreter;
  
  
  /***
   * Rule which runs a groovy script to make its decision. 
   * 
   * Script source may be provided via a file local to the crawler.
   * 
   * Variables available to the script include 'object' (the object to be
   * evaluated, typically a CandidateURI or CrawlURI), 'self' 
   * (this GroovyDecideRule instance), and 'controller' (the crawl's 
   * CrawlController instance). 
   *
   * TODO: reduce copy & paste with GroovyProcessor
   * 
   * @author gojomo
   */
  public class BeanShellDecideRule extends DecideRule {
  
      private static final long serialVersionUID = -8433859929199308527L;
  
      private static final Logger logger =
          Logger.getLogger(BeanShellDecideRule.class.getName());
      
      /*** setting for script file */
      public final static String ATTR_SCRIPT_FILE = "script-file"; 
  
      /*** whether each thread should have its own script runner (true), or
       * they should share a single script runner with synchronized access */
      public final static String ATTR_ISOLATE_THREADS = "isolate-threads";
  
      protected ThreadLocal<Interpreter> threadInterpreter = 
          new ThreadLocal<Interpreter>();;
      protected Interpreter sharedInterpreter;
      public Map<Object,Object> sharedMap = 
          Collections.synchronizedMap(new HashMap<Object,Object>());
      protected boolean initialized = false; 
      
      public BeanShellDecideRule(String name) {
          super(name);
          setDescription("BeanShellDecideRule. Runs the BeanShell script " +
                  "source (supplied via a file path) against " +
                  "the current URI. Source should define a script method " +
                  "'decisionFor(object)' which will be passed the object" +
                  "to be evaluated and returns one of self.ACCEPT, " +
                  "self.REJECT, or self.PASS. " +
                  "The script may access this BeanShellDecideRule via" +
                  "the 'self' variable and the CrawlController via the " +
                  "'controller' variable. Runs the groovy script source " +
                  "(supplied via a file path) against the " +
                  "current URI.");
          Type t = addElementToDefinition(new SimpleType(ATTR_SCRIPT_FILE,
                  "BeanShell script file", ""));
          t.setOverrideable(false);
          t = addElementToDefinition(new SimpleType(ATTR_ISOLATE_THREADS,
                  "Whether each ToeThread should get its own independent " +
                  "script context, or they should share synchronized access " +
                  "to one context. Default is true, meaning each threads " +
                  "gets its own isolated context.", true));
          t.setOverrideable(false);
      }
 
     public Object decisionFor(Object object) {
         // depending on previous configuration, interpreter may 
         // be local to this thread or shared
         Interpreter interpreter = getInterpreter(); 
         synchronized(interpreter) {
             // synchronization is harmless for local thread interpreter,
             // necessary for shared interpreter
             try {
                 interpreter.set("object",object);
                 return interpreter.eval("decisionFor(object)");
             } catch (EvalError e) {
                 // TODO Auto-generated catch block
                 e.printStackTrace();
                 return PASS;
             } 
         }
     }
 
     /***
      * Get the proper Interpreter instance -- either shared or local 
      * to this thread. 
      * @return Interpreter to use
      */
     protected synchronized Interpreter getInterpreter() {
         if(sharedInterpreter==null 
            && !(Boolean)getUncheckedAttribute(null,ATTR_ISOLATE_THREADS)) {
             // initialize
             sharedInterpreter = newInterpreter();
         }
         if(sharedInterpreter!=null) {
             return sharedInterpreter;
         }
         Interpreter interpreter = threadInterpreter.get(); 
         if(interpreter==null) {
             interpreter = newInterpreter(); 
             threadInterpreter.set(interpreter);
         }
         return interpreter; 
     }
 
     /***
      * Create a new Interpreter instance, preloaded with any supplied
      * source file and the variables 'self' (this 
      * BeanShellProcessor) and 'controller' (the CrawlController). 
      * 
      * @return  the new Interpreter instance
      */
     protected Interpreter newInterpreter() {
         Interpreter interpreter = new Interpreter(); 
         try {
             interpreter.set("self", this);
             interpreter.set("controller", getController());
             
             String filePath = (String) getUncheckedAttribute(null, ATTR_SCRIPT_FILE);
             if(filePath.length()>0) {
                 try {
                     File file = getSettingsHandler().getPathRelativeToWorkingDirectory(filePath);
                     interpreter.source(file.getPath());
                 } catch (IOException e) {
                     logger.log(Level.SEVERE,"unable to read script file",e);
                 }
             }
         } catch (EvalError e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
         
         return interpreter; 
     }
     
     
     /***
      * Setup (or reset) Intepreter variables, as appropraite based on 
      * thread-isolation setting. 
      */
     public void kickUpdate() {
         // TODO make it so running state (tallies, etc.) isn't lost on changes
         // unless unavoidable
         if((Boolean)getUncheckedAttribute(null,ATTR_ISOLATE_THREADS)) {
             sharedInterpreter = null; 
             threadInterpreter = new ThreadLocal<Interpreter>(); 
         } else {
             sharedInterpreter = newInterpreter(); 
             threadInterpreter = null;
         }
     }
 }