/*
    * Trip Tracker, a real-time position tracking system for the Internet.
    * Copyright (C) 2006  Team Trip Tracker
    *
    * This program is free software; you can redistribute it and/or modify it
    * under the terms of the GNU General Public License as published by the
    * Free Software Foundation; either version 2 of the License, or (at your
    * option) any later version.
    *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License along
   * with this program; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
   */
  
  package triptracker.client.gps.core;
  
  /***
   * Parser for the GPS NMEA-0183 (National Marine Electronics Association) data
   * protocol. NMEA-0183 data is sent at 4800 baud and the max. length of a
   * sentence is 80 ASCII characters including the leading '$' and the trailing
   * CR LF control characters.
   */
  public class NMEASentence {
  	
  //	static {
  //	}
  	
  	public static final char DELIMITER = ',';
  	public static final char START = '$';
  	public static final char CHECKSUM = '*';
  	public static final int MAXLENGTH = 82; 
  	public static final String CRLF = "\r\n";
  	
  	private String checksum;
  	private String sentence;
  	private String[] fields;
  	private NMEATalkerID talkerID;
  	private NMEASentenceID sentenceID;
  	private NMEAManufacturerID manufacturerID;
  	private boolean ignoreChecksum = false;
  	private boolean proprietary = false;
  	
  
  //	Test output from our Garmin GPS:
  //	$GPRMC,105648,A,5856.3026,N,00541.6098,E,0.0,0.0,170106,1.3,W,A*0A
  //	$GPRMB,A,,,,,,,,,,,,A,A*0B
  //	$GPGGA,105648,5856.3026,N,00541.6098,E,1,05,3.8,28.2,M,44.0,M,,*74
  //	$GPGSA,A,3,03,,,13,15,,,21,23,,,,6.5,3.8,4.7*3E
  //	$GPGSV,3,1,11,03,13,262,39,06,46,090,00,10,24,046,00,13,13,325,37*7E
  //	$GPGLL,5856.3026,N,00541.6098,E,105648,A,A*47
  //	Latit, Long
  //	$GPBOD,,T,,M,,*47
  //	$GPVTG,0.0,T,1.3,M,0.0,N,0.0,K*4C
  //	$PGRME,26.2,M,45.0,M,52.0,M*1E
  //	$PGRMZ,93,f,3*21
  //	$PGRMM,WGS 84*06
  //	$GPRTE,1,1,c,*37
  
  	
  	public NMEASentence() {	}
  
  	public NMEASentence(String sentence) {
  		parseSentence(sentence);
  	}
  	
  	/***
  	 * Parses the NMEA-0183 sentence. Fields can then be read from
  	 * {@link #getField(int)}.
  	 * 
  	 * @param sentence NMEA-0183 formatted sentence
  	 * @throws IllegalArgumentException on malformed sentence
  	 * @see #getField(int)
  	 */
  	public void parseSentence(String sentence) throws IllegalArgumentException {
  		// Remove CRLF and everything after.
  		this.sentence = sentence.split(CRLF)[0];
  
  		// Check for $ at start of sentence and remove it.
  		if (sentence.charAt(0) == START) {
  			this.sentence = this.sentence.substring(1);
  		} else {
  			//throw new IllegalArgumentException("Bad NMEA-0183 sentence format: "
  			//		+ "first character is not '" + START + "'");
  		}
  
  		fields = this.sentence.split(DELIMITER + "");
  
  		// Look for checksum.
  		String csField = fields[fields.length - 1];
  		if (this.sentence.matches(".*//*[0-9a-fA-F]{2}$")) {
  			checksum = csField.substring(csField.length() - 2);
  			fields[fields.length - 1]
  			       = csField.substring(0, csField.length() - 3);
  		} else {
 			checksum = null;
 		}
 
 		validateSentence();
 		
 		// Find talker ID.
 		if (fields[0].substring(0, 1).equals(NMEATalkerID.P.name())) {
 			proprietary = true;
 			talkerID = NMEATalkerID.P;
 		} else {
 			proprietary = false;
 			talkerID = NMEATalkerID.valueOf(fields[0].substring(0, 2));
 		}
 		
 		// Find sentence ID.
 		if (proprietary) {
 			sentenceID = NMEASentenceID.valueOf(fields[0].substring(1,5));
 		} else {
 			sentenceID = NMEASentenceID.valueOf(fields[0].substring(2,5));
 		}
 		
 	}
 	
 	private void validateSentence() throws IllegalArgumentException {
 		// Check for max. length which includes $ and CR LF (\r\n).
 		if (sentence.length() > (MAXLENGTH - CRLF.length() - 1))
 			//throw new IllegalArgumentException("Bad NMEA-0183 sentence format: "
 			//		+ "length exceeds " + MAXLENGTH + " characters");
 
 		// Check for 6 character first field.
 		if (fields[0].length() != 5)
 			//throw new IllegalArgumentException("Bad NMEA-0183 sentence format: "
 			//		+ "sentence identification field is wrong length");
 		
 		// Check for more than one field.
 		if (fields.length < 2)
 			//throw new IllegalArgumentException("Bad NMEA-0183 sentence format: "
 			//		+ "no data fields");
 		
 		// Check for non-printable ASCII characters.
         // Under the NMEA-0183 standard, all characters used are printable
         // ASCII text (plus carriage return and line feed).
 		if (!sentence.matches("^[//x20-//x7E]+$"))
 			//throw new IllegalArgumentException("Bad NMEA-0183 sentence format: "
 			//		+ "non-printable ASCII character(s)");
 		
 		
 		
         // The optional checksum field consists of a "*" and two hex digits
         // representing the exclusive OR of all characters between, but not
         // including, the "$" and "*".  A checksum is required on some
 		// sentences.
 
 		// Run checksum test.
 		if (checksum != null && !ignoreChecksum) {
 			int csCalc = 0x00;
 			int csReal;
 
 			//try {
 				csReal = Integer.valueOf(checksum, 16);
 			//} catch (NumberFormatException e) {
 			//	throw new IllegalArgumentException("Bad NMEA-0183 sentence "
 			//			+ "format: checksum not hexadecimal");
 			//}
 
 			// XOR characters in sentence.
 			for (int i = 0; i < sentence.length() - 3; i++) {
 				csCalc ^= sentence.charAt(i);
 			}
 			
 			if (csCalc != csReal) {
 			//	throw new IllegalArgumentException("Bad NMEA-0183 sentence "
 			//			+ "format: checksum failed");
 			}
 		}
 
 		// All tests passed.
 	}
 
 	public String getField(int index) {
 		return fields[index];
 	}
 	
 	public String getField(String fieldName) {
 		return null;
 	}
 	
 	public int getFieldCount() {
 		return fields.length;
 	}
 	
 	public NMEATalkerID getTalkerID() {
 		return talkerID;
 	}
 	
 	public NMEASentenceID getSentenceID() {
 		return sentenceID;
 	}
 	
 	public NMEAManufacturerID getManufacturerID() {
 		return manufacturerID;
 	}
 	
 	public String getSentence() {
 		return sentence;
 	}
 	
 	public boolean isChecksumPresent() {
 		return (checksum != null);
 	}
 
 	public boolean isIgnoreChecksum() {
 		return ignoreChecksum;
 	}
 
 	public void setIgnoreChecksum(boolean ignoreChecksum) {
 		this.ignoreChecksum = ignoreChecksum;
 	}
 
 	public boolean isProprietary() {
 		return proprietary;
 	}
 	
 }