PrologQueryProxy.java

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/* 
 * Copyright (c) 2010, Moritz Tenorth
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of Willow Garage, Inc. nor the names of its
 *       contributors may be used to endorse or promote products derived from
 *       this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

package edu.tum.cs.ias.knowrob.json_prolog;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.NoSuchElementException;

import ros.RosException;
import ros.pkg.json_prolog_msgs.srv.PrologFinish;
import ros.pkg.json_prolog_msgs.srv.PrologNextSolution;
import ros.pkg.json_prolog_msgs.srv.PrologQuery;

public class PrologQueryProxy implements Iterable<PrologBindings> {

        boolean finished_;
        Prolog prolog_;
        String query_id_;
        ArrayList<PrologBindings> bindings_;
        QueryIterator q_it;
        
        
        public PrologQueryProxy(Prolog prolog, String query_str) {

                this.query_id_ = makeQueryID();
                this.prolog_ = prolog;
                this.finished_ = false;
                this.bindings_ = new ArrayList<PrologBindings>();
                
                PrologQuery.Request req = new PrologQuery.Request();
                PrologQuery.Response resp = new PrologQuery.Response();

                req.id = query_id_;
                req.query = query_str;

                
                try{
                        
                        resp=prolog_.prolog_query.call(req);
                        
                } catch (RosException e) {
                        throw(new QueryError("Service call '" + prolog_.prolog_query.getService() + "' failed"));
                }
                
                if(resp.ok == false) {
                        throw(new QueryError("Prolog query failed: " + resp.message));
                }

                
                // Instantiate the first solution
                q_it = new QueryIterator(this);
                //q_it.requestNextSolution();

        }
        
        public Iterator<PrologBindings> iterator() {
                return q_it;
        }
        

        public boolean isFinished()     {
                return finished_;
        }
        
        
        public void finish()    {

                PrologFinish.Request req = new PrologFinish.Request();

                req.id = query_id_;             
                try{
                        
                        prolog_.prolog_finish.call(req);
                        
                } catch (RosException e) {
                        throw(new QueryError("Service call '" + prolog_.prolog_finish.getService() + "' failed"));
                }
                finished_ = true;
        }

        
        class QueryIterator implements Iterator<PrologBindings> {

                Iterator<PrologBindings> data_;
            PrologQueryProxy query_;
            
            
                public QueryIterator(PrologQueryProxy proxy) {
                        query_ = proxy;
                        data_=proxy.bindings_.iterator(); // initialize iterator to the first element in the bindings list
                }

                
                @Override
                public boolean hasNext() {
                        return requestNextSolution();
                }

                
                @Override
                public PrologBindings next() {
                        
                        if(query_==null)
                                throw( new NullPointerException());
                        
                        // just return the next element if there are still some in bindings_
                        if(data_.hasNext()) {
                                data_ = query_.bindings_.listIterator(query_.bindings_.size()-1);
                                return data_.next();
                        }
  
                        // return last element if the query is finished
                        if(query_.finished_) {
                                data_ = query_.bindings_.listIterator(query_.bindings_.size()-1);
                                return data_.next();
                        }

                        else throw( new NoSuchElementException());
                }

                
                
                @Override
                public void remove() {
                        // do nothing: we do not remove elements from the result set
                        
                        return;
                }
        
        
                protected boolean requestNextSolution() {
                        
                        // just return the next element if there are still some in bindings_
                        if(data_.hasNext()) {
                                return true;
                        }
                        
                          PrologNextSolution.Request req = new PrologNextSolution.Request();
                          PrologNextSolution.Response resp = new PrologNextSolution.Response();

                          req.id = query_.query_id_;
                          
                                try{
                                        
                                        resp=prolog_.next_solution.call(req);
                                        
                                } catch (RosException e) {
                                        throw(new QueryError("Service call '" + prolog_.next_solution.getService() + "' failed"));
                                }

                          switch(resp.status) {
                          
                            case PrologNextSolution.Response.NO_SOLUTION:
                                finish();
                                data_ = query_.bindings_.listIterator(query_.bindings_.size());
                                query_.finished_ = true;
                                return false;
                              
                            case PrologNextSolution.Response.WRONG_ID:
                                finish();
                                query_.finished_ = true;
                                throw(new PrologQueryProxy.QueryError("Wrong id. Maybe the server is already processing a query."));
                              
                            case PrologNextSolution.Response.QUERY_FAILED:
                                finish();
                                query_.finished_ = true;      
                                throw(new PrologQueryProxy.QueryError("Prolog query failed: " + resp.solution));
                              
                            case PrologNextSolution.Response.OK:
                                query_.bindings_.add(PrologBindings.parseJSONBindings(resp.solution));
                                return true;
                              
                            default:
                                finish();
                                query_.finished_ = true;      
                                throw(new PrologQueryProxy.QueryError("Unknow query status."));
                          }
                }
        };


        protected String makeQueryID() {
                SimpleDateFormat sdf = new SimpleDateFormat("yy-MM-dd_HH-mm-ss-SSS");
                return "JAVA_QUERY_"+sdf.format(new Date());
        }
        
        
        class QueryError extends RuntimeException {
                private static final long serialVersionUID = 1190356215893161319L;
                public QueryError(String msg) {
                        super(msg);
                }
        };


}