// Copyright MageLang Institute; Version $Id: //depot/main/src/edu/modules/Servlets/magercises/FormPostingAndProcessing/solution/FormDisplayServlet.java#3 $
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

/**
 * FormDisplayServlet
 *
 * This servlet will dynamically create a data editing form.
 * Two paramaters are required:
 *
 *    structurefile: The name of a file that contains data structure information
 *
 *    datafile:      The name of a file that dontains the data to be displayed.
 *
 * Because this servlet is used in a Magercise, we will send error messages
 * to the browser. Normally this is not a good idea as the browser user should
 * know nothing about the workings of a servlet.
 *
 * The format of the structure file is:
 * |<name>|<datatype>|<length>|
 *
 * name:      Name of the column of data
 * datatype:  Type of the data in the column (use only text for now)
 * length:    Maximum number of characters in this column of data
 *
 * The format for the data file is:
 * |<data for column1>|<data for column2>|...
 *
 * Each piece of data is stored in a file as a string. For this reason
 * it is best to deal with text fields. A real version of this would
 * work against a database, reading the database structure from the
 * JDBC metadata. It would also handle datatype conversions from the
 * actual data type to text (which is required for display on the HTML form)
 */
public
class FormDisplayServlet extends HttpServlet
{
  private static final int PIXELS_PER_CHAR = 10;

  public void doGet
  (
    HttpServletRequest req,
    HttpServletResponse res
  )
  throws
    ServletException,
    IOException
  {
    Vector     columns = new Vector( 20 );
    ColumnInfo colInfo;

    String paramStructureFile;
    String paramDataFile;
    String inputLine = "";

    int    i;
    int    l;
    int    row;
    String title;

    FileInputStream   fisStructure;
    DataInputStream   disStructure;
    FileInputStream   fisData;
    DataInputStream   disData;

    StringTokenizer   stData;

    // Set the Output Stream to HTML
    res.setContentType("text/html");

    // Get a handle to the OutputStream going back to the client
    ServletOutputStream out = res.getOutputStream();

    // Get the name of the file that contains the form information
    paramStructureFile = req.getParameter( "structurefile"     );
    // Get the name of the file that contains the form data
    paramDataFile      = req.getParameter( "datafile" );


    // Set up files for processing. If there is an error, send
    // information back to the browser.

    if ( null == paramStructureFile )
    {
      sendError( out, "Missing parameter: structurefile" );
      return;
    }

    if ( null == paramDataFile )
    {
      sendError( out, "Missing parameter: datafile" );
      return;
    }

    // Try to open and parse the Structure file
    // Report an error to the browser if we fail
    try
    {
      fisStructure = new FileInputStream( "c:\\JavaWebServer1.1\\servlets\\" + paramStructureFile );
      disStructure = new DataInputStream( fisStructure );
      while ( 0 != disStructure.available() )
      {
        inputLine = disStructure.readLine();
        colInfo =     new ColumnInfo( inputLine );
        if ( null != colInfo )
        {
          columns.addElement( colInfo );
        }
      }
    }
    catch ( Exception e )
    {
      sendError( out, "Could not open and process the file " + paramStructureFile + " Got error " + e );
      return;
    }

    // Try to open and read the data file
    // Store the data in the Vector of ColumnInfo objects.
    // Each ColumnInfo object contains all rows of data for that column
    try
    {
      fisData = new FileInputStream( "c:\\JavaWebServer1.1\\servlets\\" + paramDataFile );
      disData = new DataInputStream( fisData );

      row = 0;
      while ( 0 != disData.available() )
      {
         inputLine = disData.readLine();
         stData    = new StringTokenizer( inputLine, "|" );
         for ( i = 0; i < columns.size(); i++ )
         {
           ((ColumnInfo)columns.elementAt(i)).setNextData( stData.nextToken() );
         }
      }
    }
    catch ( Exception e )
    {
      sendError( out, "Could not open and process the file " + paramDataFile + " Got error " + e );
      return;
    }

    // Now we generate the HTML form

    out.println( "<html>" );
    out.println( "<head><title>Data Editing Form</title></head>" );
    out.println( "<body>" );

    // Notice that the ACTION command sends the data to the FormProcessingServlet 
    // It embeds the datafile and structure file information inside of hidden fields
    // This is done because POST command cannot accept URL embedded parameters
    out.println( "<form method=POST ACTION=\"http://localhost:8080/servlet/FormProcessingServlet\">" );
    out.println( "<input type=hidden name=datafile value=" + paramDataFile + ">" );
    out.println( "<input type=hidden name=structurefile value=" + paramStructureFile + ">" );
    out.println( "<table width=100% border=1>" );
    out.println( "<tr>" );

    // Output the headers for the display table
    for ( i=0; i < columns.size(); i++ )
    {
      colInfo = ((ColumnInfo)columns.elementAt( i ));
      l     = colInfo.getLength();
      title = colInfo.getName();
      if ( l < title.length() )
      {
        l = title.length();
      }
      out.println( "<td width=" + (PIXELS_PER_CHAR * l ) + ">" );
      out.println( colInfo.getName() );
      out.println( "</td>" );
    }

    out.println( "</tr>" );

    // Now display the data from the data file
    int numberOfRows = ((ColumnInfo)columns.elementAt(0)).getNumberOfRows();
    for ( row = 0; row < numberOfRows; row ++ )
    {
      out.println( "<tr>" );
      for ( i=0; i < columns.size(); i++ )
      {
        colInfo = ((ColumnInfo)columns.elementAt( i ));
        out.println( "<td>" );
        out.println( "<input TYPE=\"text\" NAME=\"" + colInfo.getName() + /*  "_" + row + */ "\" SIZE=\"" + (1+colInfo.getLength()) + "\" VALUE=\"" + colInfo.getData( row ) + "\">" );
        out.println( "</td>" );
      }
      out.println( "</tr>" );
     }
    out.println( "</table>" );

    out.println( "<br>" );
    out.println( "<input type=\"submit\" name=\"CMD\" value=\"Submit Changes\">&nbsp;&nbsp;<input type=\"reset\">" );
    out.println( "</form>" );
    out.println( "</body>" );
    out.println( "</html>" );
    }


  public String getServletInfo()
  {
    return "A servlet that sends a form to the browser";
  }


  // Routine to send error message back to the browser
  // in the form of an HTML page.
  private void sendError( ServletOutputStream out, String message ) 
    throws IOException
  {
    out.println( "<html>" );
    out.println( "<head><title>Data Editing Form</title></head>" );
    out.println( "<body>" );

    out.println( "<h1>Error in FormDisplayServlet</h1>" );
    out.println( "<p>" );
    out.println( message );
    out.println( "</p>" );
    out.println( "</body>" );
    out.println( "</html>" );
  }
  

}