/*
    * 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.html#DatumPath">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;
          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;
      }    
  
  }