Nmea/GprmcSentence.cs

﻿using System;
using System.Collections.Generic;
using System.Text;

namespace GeoFramework.Gps.Nmea
{
    /// <summary>
    /// Represents the "recommended minimum" GPS sentence.
    /// </summary>
    public sealed class GprmcSentence : NmeaSentence, IPositionSentence, IUtcDateTimeSentence, 
                                        IBearingSentence, ISpeedSentence, IMagneticVariationSentence,
                                        IFixStatusSentence 
    {
        private DateTime _UtcDateTime;
        private FixStatus _FixStatus;
        private Position _Position;
        private Speed _Speed;
        private Azimuth _Bearing;
        private Longitude _MagneticVariation;

        #region Constructors

        internal GprmcSentence(string sentence, string commandWord, string[] words, string validChecksum)
            : base(sentence, commandWord, words, validChecksum)
        { }

        public GprmcSentence(string sentence)
            : base(sentence)
        { }

        public GprmcSentence(DateTime utcDateTime, bool isFixAcquired, Position position, Speed speed, Azimuth bearing, Longitude magneticVariation)
        {
            // Use a string builder to create the sentence text
            StringBuilder builder = new StringBuilder(128);

            /* GPRMC sentences have the following format:
             * 
             * $GPRMC,040302.663,A,3939.7,N,10506.6,W,0.27,358.86,200804,,*1A
             */

            // Append the command word, $GPRMC
            builder.Append("$GPRMC");

            // Append a comma
            builder.Append(',');

            #region Append the UTC time

            builder.Append(utcDateTime.Hour.ToString("0#", NmeaCultureInfo));
            builder.Append(utcDateTime.Minute.ToString("0#", NmeaCultureInfo));
            builder.Append(utcDateTime.Second.ToString("0#", NmeaCultureInfo));
            builder.Append(".");
            builder.Append(utcDateTime.Millisecond.ToString("00#", NmeaCultureInfo));

            #endregion

            // Append a comma
            builder.Append(',');            

            #region Append the fix status

            // Write fix information
            if (isFixAcquired)
                builder.Append("A");
            else
                builder.Append("V");

            #endregion

            // Append a comma
            builder.Append(',');

            #region Append the position

            // Append latitude in the format HHMM.MMMM. 
            builder.Append(position.Latitude.ToString("HHMM.MMMM,I,", NmeaCultureInfo));
            // Append Longitude in the format HHHMM.MMMM.
            builder.Append(position.Longitude.ToString("HHHMM.MMMM,I,", NmeaCultureInfo));

            #endregion

            // Append the speed (in knots)
            builder.Append(speed.ToKnots().ToString("v.v", NmeaCultureInfo));

            // Append a comma
            builder.Append(',');

            // Append the bearing
            builder.Append(bearing.ToString("d.d", NmeaCultureInfo));

            // Append a comma
            builder.Append(',');

            #region Append the UTC date

            // Append UTC date
            builder.Append(utcDateTime.Day.ToString("0#", NmeaCultureInfo));
            builder.Append(utcDateTime.Month.ToString("0#", NmeaCultureInfo));

            // Append the year (year minus 2000)
            int year = utcDateTime.Year - 2000;
            builder.Append(year.ToString("0#", NmeaCultureInfo));

            #endregion

            // Append a comma
            builder.Append(',');

            // Append magnetic variation
            builder.Append(magneticVariation.ToString("d.d", NmeaCultureInfo));

            // Set this object's sentence
            SetSentence(builder.ToString());

            // Finally, append the checksum
            AppendChecksum();
        }

        #endregion

        protected override void OnSentenceChanged()
        {
            // First, process the basic info for the sentence
            base.OnSentenceChanged();

            // Cache the sentence words
            string[] words = base.Words;
            int wordCount = words.Length;

            /*
             * $GPRMC

                 Recommended minimum specific GPS/Transit data

                 eg1. $GPRMC,081836,A,3751.65,S,14507.36,E,000.0,360.0,130998,011.3,E*62
                 eg2. $GPRMC,225446,A,4916.45,N,12311.12,W,000.5,054.7,191194,020.3,E*68


                            225446       Time of fix 22:54:46 UTC
                            A            Navigation receiver warning A = OK, V = warning
                            4916.45,N    Latitude 49 deg. 16.45 min North
                            12311.12,W   Longitude 123 deg. 11.12 min West
                            000.5        Speed over ground, Knots
                            054.7        Course Made Good, True
                            191194       Date of fix  19 November 1994
                            020.3,E      Magnetic variation 20.3 deg East
                            *68          mandatory checksum


                 eg3. $GPRMC,220516,A,5133.82,N,00042.24,W,173.8,231.8,130694,004.2,W*70
                               1    2    3    4    5     6    7    8      9     10  11 12


                       1   220516     Time Stamp
                       2   A          validity - A-ok, V-invalid
                       3   5133.82    current Latitude
                       4   N          North/South
                       5   00042.24   current Longitude
                       6   W          East/West
                       7   173.8      Speed in knots
                       8   231.8      True course
                       9   130694     Date Stamp
                       10  004.2      Variation
                       11  W          East/West
                       12  *70        checksum


                 eg4. $GPRMC,hhmmss.ss,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,ddmmyy,x.x,a*hh
                 1    = UTC of position fix
                 2    = Data status (V=navigation receiver warning)
                 3    = Latitude of fix
                 4    = N or S
                 5    = Longitude of fix
                 6    = E or W
                 7    = Speed over ground in knots
                 8    = Track made good in degrees True
                 9    = UT date
                 10   = Magnetic variation degrees (Easterly var. subtracts from true course)
                 11   = E or W
                 12   = Checksum
             */


            // Do we have enough words to parse the fix status?
            if (wordCount >= 2 && words[1].Length != 0)
            {
                #region Fix status 

                // Get the fix flag
                _FixStatus = words[1].Equals("A", StringComparison.OrdinalIgnoreCase) ? FixStatus.Fix : FixStatus.NoFix;

                #endregion
            }
            else
            {
                // The fix status is invalid
                _FixStatus = FixStatus.Unknown;
            }

            // Do we have enough words to parse the UTC date/time?
            if (wordCount >= 9 && words[0].Length != 0 && words[8].Length != 0)
            {
                #region Parse the UTC time

                string utcTimeWord = words[0];
                int utcHours = int.Parse(utcTimeWord.Substring(0, 2), NmeaCultureInfo);                 // AA
                int utcMinutes = int.Parse(utcTimeWord.Substring(2, 2), NmeaCultureInfo);               // BB
                int utcSeconds = int.Parse(utcTimeWord.Substring(4, 2), NmeaCultureInfo);               // CC
                int utcMilliseconds = 0;
                if(utcTimeWord.Length > 6)
                    utcMilliseconds = Convert.ToInt32(float.Parse(utcTimeWord.Substring(6), NmeaCultureInfo) * 1000, NmeaCultureInfo);    // DDDD

                #endregion

                #region Parse the UTC date

                string utcDateWord = words[8];
                int utcDay = int.Parse(utcDateWord.Substring(0, 2), NmeaCultureInfo);
                int utcMonth = int.Parse(utcDateWord.Substring(2, 2), NmeaCultureInfo);
                int utcYear = int.Parse(utcDateWord.Substring(4, 2), NmeaCultureInfo) + 2000;

                #endregion

                #region Build a UTC date/time

                _UtcDateTime = new DateTime(utcYear, utcMonth, utcDay, utcHours, utcMinutes, utcSeconds, utcMilliseconds, DateTimeKind.Utc);

                #endregion
            }
            else
            {
                // The UTC date/time is invalid
                _UtcDateTime = DateTime.MinValue;
            }

            // Do we have enough data to parse the location?
            if (wordCount >= 6 && words[2].Length != 0 && words[3].Length != 0 && words[4].Length != 0 && words[5].Length != 0)
            {
                #region Parse the latitude

                string latitudeWord = words[2];
                int latitudeHours = int.Parse(latitudeWord.Substring(0, 2), NmeaCultureInfo);
                double latitudeDecimalMinutes = double.Parse(latitudeWord.Substring(2), NmeaCultureInfo);
                LatitudeHemisphere latitudeHemisphere =
                    words[3].Equals("N", StringComparison.Ordinal) ? LatitudeHemisphere.North : LatitudeHemisphere.South;

                #endregion

                #region Parse the longitude

                string longitudeWord = words[4];
                int longitudeHours = int.Parse(longitudeWord.Substring(0, 3), NmeaCultureInfo);
                double longitudeDecimalMinutes = double.Parse(longitudeWord.Substring(3), NmeaCultureInfo);
                LongitudeHemisphere longitudeHemisphere =
                    words[5].Equals("E", StringComparison.Ordinal) ? LongitudeHemisphere.East : LongitudeHemisphere.West;

                #endregion

                #region Build a Position from the latitude and longitude

                _Position = new Position(
                                new Latitude(latitudeHours, latitudeDecimalMinutes, latitudeHemisphere),
                                new Longitude(longitudeHours, longitudeDecimalMinutes, longitudeHemisphere));

                #endregion
            }
            else
            {
                _Position = Position.Invalid;
            }

            // Do we have enough info to process speed?
            if (wordCount >= 7 && words[6].Length != 0)
            {
                #region Speed

                // The speed is the sixth word, expressed in knots                
                _Speed = new Speed(double.Parse(words[6], NmeaCultureInfo), SpeedUnit.Knots);

                #endregion
            }
            else
            {
                // The speed is invalid
                _Speed = Speed.Invalid;
            }

            // do we have enough info to process the bearing?
            if (wordCount >= 8 && words[7].Length != 0)
            {
                #region Bearing

                // The bearing is the seventh word
                _Bearing = new Azimuth(double.Parse(words[7], NmeaCultureInfo));

                #endregion
            }
            else
            {
                // The bearing is invalid
                _Bearing = Azimuth.Invalid;
            }

            // Do we have enough info for magnetic variation?
            if (wordCount >= 10 && words[9].Length != 0)
            {
                // Parse the value
                _MagneticVariation = new Longitude(double.Parse(words[9], NmeaCultureInfo));
            }
            else
            {
                // The magnetic variation is invalid
                _MagneticVariation = Longitude.Invalid;
            }
        }

        #region IPositionSentence Members

        public Position Position
        {
            get { return _Position; }
        }

        #endregion

        #region IUtcDatetimeSentence Members

        public DateTime UtcDateTime
        {
            get { return _UtcDateTime; }
        }

        #endregion

        #region IBearingSentence Members

        public Azimuth Bearing
        {
            get { return _Bearing; }
        }

        #endregion

        #region ISpeedSentence Members

        public Speed Speed
        {
            get { return _Speed; }
        }

        #endregion

        #region IMagneticVariationSentence Members

        public Longitude MagneticVariation
        {
            get { return _MagneticVariation; }
        }

        #endregion

        #region IFixStatusSentence Members

        public FixStatus FixStatus
        {
            get { return _FixStatus; }
        }

        #endregion
    }

}