/*

  * Created on 28-Apr-2004

  */

 package ca.uhn.hl7v2.preparser;

 import java.util.Arrays;

 import java.util.List;

 import java.util.Properties;

 import java.util.StringTokenizer;

 import ca.uhn.hl7v2.HL7Exception;

 import ca.uhn.hl7v2.parser.EncodingDetector;

 import ca.uhn.hl7v2.util.Terser;

 /**

  * <p>Extracts specified fields from unparsed messages.  This class is a 

  * facade for the ER7 and XML classes.  Use it like this: </p>

  * 

  * <code>

  * String message = null; //... your ER7 or XML message string goes here

  * String[] fieldSpecs = {"MSH-9-1", "MSH-9-2", "MSH-12"};

  * String[] fields = PreParser.getFields(message, fieldSpecs);

  * </code>

  * 

  * @author <a href="mailto:bryan.tripp@uhn.on.ca">Bryan Tripp</a>

  * @version $Revision: 1.1 $ updated on $Date: 2007-02-19 02:24:37 $ by $Author: jamesagnew $

  */

 public class PreParser {

     /**

      * Extracts selected fields from a message.  

      *   

      * @param theMessageText an unparsed message from which to get fields 

      * @param thePathSpecs Terser-like paths to fields in the message.  See documentation

      *      for Terser.  These paths are identical except that they start with the segment

      *      name (search flags and group names are to be omitted as they are not relevant 

      *      with unparsed ER7 messages).  

      * @return field values corresponding to the given paths

      * @throws HL7Exception

      */

     public static String[] getFields(String theMessageText, String... thePathSpecs) throws HL7Exception {

         DatumPath[] paths = new DatumPath[thePathSpecs.length];

         for (int i = 0; i < thePathSpecs.length; i++) {

             StringTokenizer tok = new StringTokenizer(thePathSpecs[i], "-", false);

             String segSpec = tok.nextToken();

             tok = new StringTokenizer(segSpec, "()", false);

             String segName = tok.nextToken();

             if (segName.length() != 3) {

                 throw new HL7Exception("In field path, " + segName + " is not a valid segment name");

             }

             int segRep = 0;

             if (tok.hasMoreTokens()) {

                 String rep = tok.nextToken();

                 try {

                     segRep = Integer.parseInt(rep);

                 } catch (NumberFormatException e) {

                     throw new HL7Exception("In field path, segment rep" + rep + " is not valid", e);

                 }

             }

             int[] indices = Terser.getIndices(thePathSpecs[i]);

             paths[i] = new DatumPath();

             paths[i].add(segName).add(segRep);

             paths[i].add(indices[0]).add(indices[1]).add(indices[2]).add(indices[3]);

         }

         return getFields(theMessageText, paths);

     }

     /** 

      * Gets selected fields from a message, as with String[] arg version but 

      * using DatumPaths. 

      */     

     private static String[] getFields(String theMessageText, DatumPath[] thePaths) throws HL7Exception {

         String[] fields = new String[thePaths.length];

         Properties props = new Properties();

         List<DatumPath> mask = Arrays.asList(thePaths);

         boolean OK = false;

         if (EncodingDetector.isEr7Encoded(theMessageText)) {

             OK = ER7.parseMessage(props, mask, theMessageText);

         } else if (EncodingDetector.isXmlEncoded(theMessageText)) {

             OK = XML.parseMessage(props, theMessageText, null);

         } else {

             throw new HL7Exception("Message encoding is not recognized"); 

         }

         if (!OK) {

             throw new HL7Exception("Parse failed");

         }

         for (int i = 0; i < fields.length; i++) {

             fields[i] = props.getProperty(thePaths[i].toString());

         }

         return fields;

     }    

 }