/** Copyright (c) 2007 Ricebridge. BSD License. */

package com.ricebridge.example.updown;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Properties;

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.commons.fileupload.FileItemIterator;
import org.apache.commons.fileupload.FileItemStream;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.fileupload.util.Streams;


/** A servlet that handles upload and download requests. */
public class UpDownServlet extends HttpServlet {

  private static final long serialVersionUID = 1L;
  
  public static final String NUM_LINES       
    = UpDownServlet.class.getName()+"-NUM_LINES";
  public static final String INPUT_ERRORS    
    = UpDownServlet.class.getName()+"-INPUT_ERRORS";
  public static final String DATABASE_ERRORS 
    = UpDownServlet.class.getName()+"-DATABASE_ERRORS";

  
  private CsvUploader   mCsvUploader    = new CsvUploader();
  private CsvDownloader mCsvDownloader  = new CsvDownloader();

  /** THESE ARE HARDCODED FOR SECURITY. DON'T USE HIDDEN FORM FIELDS. */
  private String        mTableName      = "ClothingItem";
  private String        mIdentityColumn = "SKU";



  /** Start an upload or download depending on the action parameter. */
  public void service( HttpServletRequest pRequest, 
      HttpServletResponse pResponse ) 
  throws IOException 
  {
    try {
      HttpSession session = pRequest.getSession();

      // these are displayed on the JSP page
      session.setAttribute(NUM_LINES, null);
      session.setAttribute(INPUT_ERRORS, null);
      session.setAttribute(DATABASE_ERRORS, null);

      // we use the apache fileupload component
      ServletFileUpload upload = new ServletFileUpload();
      FileItemIterator itemI = upload.getItemIterator( pRequest );
      InputStream in = null;
      
      String action = null;
      Properties props = new Properties();
      
      // get the form fields until we have file
      // note that the file has to be the last form field
      // as multipart data is provided as a stream
      while( itemI.hasNext() ) {
        FileItemStream item = itemI.next();
        String name = item.getFieldName();
        
        if( item.isFormField() ) {
          String value = Streams.asString( item.openStream() );
          if( "action".equals(name) ) {
            action = value;
          }
          else {
            // set other form fields as properties
            // to be used by CsvSpecHandler
            props.setProperty( name, value );
          }
        } 
        else {
          // this is the CSV file
          in = item.openStream();
          break;
        }
      }

      // look at the action
      if( "upload".equals(action) ) {
        doUpload( in, props, pRequest, pResponse );
      }
      else if( "download".equals(action) ) {
        doDownload( props, pRequest, pResponse );
      }
      else {
        throw new Exception("unknown action: ["+action+"]");
      }
    }
    catch( Exception e ) {
      // you'll probably want to put in better logging here
      e.printStackTrace();
      throw new IOException(e.toString());
    }
  }
  

  /** Upload a CSV file. */
  public void doUpload( InputStream pIn, Properties pProperties, 
      HttpServletRequest pRequest, HttpServletResponse pResponse ) 
  throws Exception 
  {
    // get and store database connection
    Connection con = getConnection();
    mCsvUploader.setDatabaseContext(con, mTableName, mIdentityColumn);
    
    // do the actual upload
    mCsvUploader.process(pIn, pProperties);
    
    // set results for display to user
    HttpSession session = pRequest.getSession();
    session.setAttribute(NUM_LINES, new Long(mCsvUploader.getNumLines()));
    session.setAttribute(INPUT_ERRORS, mCsvUploader.getInputErrors());
    session.setAttribute(DATABASE_ERRORS, mCsvUploader.getDatabaseErrors());

    // redirect back to upload page
    pResponse.sendRedirect("upload.htm");
  }

  
  /** Download a CSV file. */
  public void doDownload( Properties pProperties, HttpServletRequest pRequest,
      HttpServletResponse pResponse ) 
  throws Exception 
  {
    // get and store database connection
    Connection con = getConnection();
    mCsvDownloader.setDatabaseContext( con, mTableName );
    
    // setup HTTP response
    // we can't set Content-length since we don't know it in advance
    pResponse.setContentType("text/csv");
    pResponse.setHeader("Content-disposition", "attachment; filename="+
        mTableName+".csv");

    // stream data down 
    mCsvDownloader.process( pResponse.getOutputStream(), pProperties);

    // no need for redirect as browser asks user to save CSV file
  }

  
  /** Get a connection to the database.
   *  You'll want to change this to your own database connection details
   *  and strategy. */
  public static Connection getConnection() throws Exception {
    Class.forName( "com.mysql.jdbc.Driver" );
    return DriverManager.getConnection( "jdbc:mysql://127.0.0.1:3306/test", 
        "root", "");
  }
  
}