#
# Copyright (c) 2013-2023, Kalopa Robotics Limited.  All rights
# reserved.
#
# 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.
#
# THIS SOFTWARE IS PROVIDED BY KALOPA ROBOTICS LIMITED "AS IS" AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
# TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
# PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL KALOPA
# ROBOTICS LIMITED BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
# STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
# ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
# ABSTRACT
#

##
# Routines for handling sailboat navigation and route planning.
#
module SGS
  class NMEA
    ##
    # Parse and create NMEA strings for various purposes.
    #
    attr_accessor :args, :valid, :checksum

    def initialize
      @args = Array.new
      @valid = false
      @checksum = 0
    end

    #
    # Parse an NMEA string into its component parts.
    def self.parse(str)
      nmea = new
      if nmea.parse(str) < 0
        nmea = nil
      end
      nmea
    end
    
    #
    # Parse an NMEA string into its component parts.
    def parse(str)
      str.chomp!
      if str[0] != "$"
        return -1
      end
      str, sum = str[1..-1].split('*')
      if sum.nil? or sum.to_i(16) != compute_csum(str)
        return -1
      end
      @args = str.split(',')
      @args.count
    end

    #
    # Is the current line a GPRMC message?
    def is_gprmc?
      @args[0] == "GPRMC"
    end

    #
    # Parse a GPRMC message
    # ["GPRMC", "211321.000", "A", "5309.7743", "N", "00904.5576", "W", "0.17", "78.41", "200813", "", "", "A"]
    def parse_gprmc
      if @args.count < 12 or @args.count > 13
        return nil
      end
      gps = SGS::GPS.new
      gps.is_valid if @args[2] == "A"
      hh = @args[1][0..1].to_i
      mm = @args[1][2..3].to_i
      ss = @args[1][4..-1].to_f
      us = (ss % 1.0 * 1000000)
      ss = ss.to_i
      dd = @args[9][0..1].to_i
      mn = @args[9][2..3].to_i
      yy = @args[9][4..5].to_i + 2000
      gps.time = Time.gm(yy, mn, dd, hh, mm, ss, us)
      pos = {"latitude" => ll_nmea(@args[3,4]),
             "longitude" => ll_nmea(@args[5,6])}
      gps.location = Location.parse pos
      gps.sog = @args[7].to_f
      gps.cmg = Bearing.dtor @args[8].to_f
      gps
    end

    #
    # Output a GPRMC message
    def make_gprmc(gps)
      @valid = true
      @args = Array.new
      @args[0] = "GPRMC"
      @args[1] = gps.time.strftime("%H%M%S.") + "%03d" % (gps.time.usec / 1000)
      @args[2] = 'A'
      @args.concat gps.location.latitude_array
      @args.concat gps.location.longitude_array("%03d%07.4f")
      @args[7] = "%.2f" % gps.sog
      @args[8] = "%.2f" % Bearing.radians_to_d(gps.cmg)
      @args[9] = gps.time.strftime("%d%m%y")
      @args.concat ['', '']
      @args << 'A'
    end

    #
    # Convert an array of component parts into an NMEA string.
    def to_s
      str = @args.join(',')
      "$%s*%02X" % [str, compute_csum(str)]
    end

    #
    # Compute an NMEA checksum
    def compute_csum(str)
      @checksum = 0
      str.each_byte {|ch| @checksum ^= ch}
      @checksum
    end

  private
    #
    # Convert NMEA lat/long to something useful.
    def ll_nmea(args)
      args[0].gsub(/(\d\d\.)/, ' \1') + args[1]
    end
  end
end