/* Copyright (c) 2005-2006 Ricebridge. All Rights Reserved.
 *
 * This file is available under the terms and conditions of the
 * Ricebridge "Open Source API" policy; Ricebridge grants use of this
 * copyrighted work under the terms of a BSD-style license only. See
 * http://www.opensource.org/licenses/bsd-license.php for more
 * information.
 * 
 * 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
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 *  disclaimer in the documentation and/or other materials provided
 *  with the distribution.
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 *  from this software without specific prior written permission.
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import com.ricebridge.xmlman.XmlManager;
import com.ricebridge.xmlman.RecordSpec;
import com.ricebridge.xmlman.XmlSpec;
import com.ricebridge.xmlman.RecordListenerSupport;
import com.ricebridge.xmlman.BadRecord;

import com.ricebridge.csvman.CsvManager;
import com.ricebridge.csvman.CsvSpec;

import java.util.*;
import java.io.*;


/** Convert an XML file into a CSV file, as a continuous data stream.
 *    In this example, the entire XML file is NOT loaded into memory. 
 *  Instead, each data record extracted from the XML file is saved 
 *  immediately as a line of the CSv file. This means that you can 
 *  process very large multi-gigabyte files without running out of memory.
 *    The data formats for this example as the same as for the
 *  Xml2CSv.java example. You should review that example first as this one
 *  is based on it.
 */
public class StreamingXml2Csv {

  // public methods

  public static void main( String[] args ) {
    File xml = new File("GetSearchResults.xml");
    File csv = new File("GetSearchResults.csv");

    convert( xml, csv );
  }


  public static void convert( File pXmlFile, File pCsvFile ) {
    
    // Create the XML Manager used to load the data.
    XmlManager xmlman  = new XmlManager();
    XmlSpec    xmlspec = xmlman.getXmlSpec();
    xmlspec.addNamespace("e","urn:ebay:apis:eBLBaseComponents");
    
    String[] fieldpaths 
      = new String[] { 
        "e:Item/e:ItemID",
        "e:Item/e:ListingDetails/e:StartTime",
        "e:Item/e:ListingDetails/e:EndTime",
        "e:Item/e:ListingDetails/e:ViewItemURL",
        "e:Item/e:SellingStatus/e:BidCount",
        "e:Item/e:SellingStatus/e:CurrentPrice/@currencyID",
        "e:Item/e:SellingStatus/e:CurrentPrice",
        "e:Item/e:Site",
        "e:Item/e:Title",
        "e:Item/e:Country",
      };
    
    RecordSpec itemspec
      = new RecordSpec("e:GetSearchResultsResponse/e:SearchResultItemArray/e:SearchResultItem", fieldpaths );
    
    // This is the object that enables us to stream the data.
    StreamingRecordListener streamer = new StreamingRecordListener( pCsvFile ); 

    // Load the XML file as a stream, the CSV data is saved in the
    // StreamingRecordListener object.
    xmlman.load( pXmlFile, itemspec, streamer );
  }


  /** Stream XML records to a CSV file. */
  public static class StreamingRecordListener extends RecordListenerSupport {

    // private instance

    /** The CSV Manager used for output. */
    private CsvManager iCsvManager = null;

    /** The destination CSV file. */
    private File iCsvFile = null;

    /** The CSV file output stream (kept open for appending). */
    private FileOutputStream iCsvOS = null;



    // public methods

    /** Create the stream handler. 
     *  @param pCsvFile the CSV file to create
     */
    public StreamingRecordListener( File pCsvFile ) {
      iCsvFile = pCsvFile;
    }


    /** Called by XML Manager once at start of loading. */
    protected void startProcessImpl() throws Exception {
      iCsvManager = new CsvManager();
      CsvSpec csvspec = iCsvManager.getCsvSpec();
      csvspec.setEncoding( "UTF-8" );      
      csvspec.setCloseOutputStream( false );      
      csvspec.setFlushEachLine( true );      

      // open the file for appending, and keep it open
      iCsvOS = new FileOutputStream( iCsvFile, true );

      ArrayList headers = new ArrayList();
      headers.add( new String[] {"ItemID","StartTime","EndTime","ViewItemURL","BidCount","Currency","Price","Site","Title","Country"} );
      iCsvManager.save( iCsvOS, headers );
    }


    /** Call by XML Manager for each data record extract from the XML file.
     *  @param pRecord record data fields
     *  @param pRecordNumber number of records found so far
     */
    protected BadRecord handleRecordImpl( String[] pRecord, long pRecordNumber ) throws Exception {

      // just create a list with one data record
      // we could buffer the records and only output them
      // every 100 records say, but we'll keep this example simple
      ArrayList row = new ArrayList();
      row.add( pRecord );
      iCsvManager.save( iCsvOS, row );

      // we are not doing any semantic validation, 
      // so return a null BadRecord to indicate that
      // everything was fine
      return null;
    }


    /** Called by XML Manager once at end of loading. */
    protected void endProcessImpl() throws Exception {
      iCsvOS.close();
    }
  } 
}