#!/usr/bin/env python

#

# Copyright 2005-2007,2011 Free Software Foundation, Inc.

# 

# This file is part of GNU Radio

# 

# GNU Radio 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 3, or (at your option)

# any later version.

# 

# GNU Radio 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 GNU Radio; see the file COPYING.  If not, write to

# the Free Software Foundation, Inc., 51 Franklin Street,

# Boston, MA 02110-1301, USA.

# 

from gnuradio import gr, gru

from gnuradio import eng_notation

from gnuradio import digital

import copy

import sys

# /////////////////////////////////////////////////////////////////////////////

#                              receive path

# /////////////////////////////////////////////////////////////////////////////

class receive_path(gr.hier_block2):

    def __init__(self, demod_class, rx_callback, options):

        gr.hier_block2.__init__(self, "receive_path",

                                gr.io_signature(1, 1, gr.sizeof_gr_complex),

                                gr.io_signature(0, 0, 0))

        options = copy.copy(options)    # make a copy so we can destructively modify

        self._verbose     = options.verbose

        self._bitrate     = options.bitrate  # desired bit rate

        self._rx_callback = rx_callback  # this callback is fired when a packet arrives

        self._demod_class = demod_class  # the demodulator_class we're using

        self._chbw_factor = options.chbw_factor # channel filter bandwidth factor

        # Get demod_kwargs

        demod_kwargs = self._demod_class.extract_kwargs_from_options(options)

        # Build the demodulator

        self.demodulator = self._demod_class(**demod_kwargs)

        # Make sure the channel BW factor is between 1 and sps/2

        # or the filter won't work.

        if(self._chbw_factor < 1.0 or self._chbw_factor > self.samples_per_symbol()/2):

            sys.stderr.write("Channel bandwidth factor ({0}) must be within the range [1.0, {1}].\n".format(self._chbw_factor, self.samples_per_symbol()/2))

            sys.exit(1)

        # Design filter to get actual channel we want

        sw_decim = 1

        chan_coeffs = gr.firdes.low_pass (1.0,                  # gain

                                          sw_decim * self.samples_per_symbol(), # sampling rate

                                          self._chbw_factor,    # midpoint of trans. band

                                          0.5,                  # width of trans. band

                                          gr.firdes.WIN_HANN)   # filter type

        self.channel_filter = gr.fft_filter_ccc(sw_decim, chan_coeffs)

        # receiver

        self.packet_receiver = \

            digital.demod_pkts(self.demodulator,

                               access_code=None,

                               callback=self._rx_callback,

                               threshold=-1)

        # Carrier Sensing Blocks

        alpha = 0.001

        thresh = 30   # in dB, will have to adjust

        self.probe = gr.probe_avg_mag_sqrd_c(thresh,alpha)

        # Display some information about the setup

        if self._verbose:

            self._print_verbage()

        # connect block input to channel filter

        self.connect(self, self.channel_filter)

        # connect the channel input filter to the carrier power detector

        self.connect(self.channel_filter, self.probe)

        # connect channel filter to the packet receiver

        self.connect(self.channel_filter, self.packet_receiver)

    def bitrate(self):

        return self._bitrate

    def samples_per_symbol(self):

        return self.demodulator._samples_per_symbol

    def differential(self):

        return self.demodulator._differential

    def carrier_sensed(self):

        """

        Return True if we think carrier is present.

        """

        #return self.probe.level() > X

        return self.probe.unmuted()

    def carrier_threshold(self):

        """

        Return current setting in dB.

        """

        return self.probe.threshold()

    def set_carrier_threshold(self, threshold_in_db):

        """

        Set carrier threshold.

        @param threshold_in_db: set detection threshold

        @type threshold_in_db:  float (dB)

        """

        self.probe.set_threshold(threshold_in_db)

    def add_options(normal, expert):

        """

        Adds receiver-specific options to the Options Parser

        """

        if not normal.has_option("--bitrate"):

            normal.add_option("-r", "--bitrate", type="eng_float", default=100e3,

                              help="specify bitrate [default=%default].")

        normal.add_option("-v", "--verbose", action="store_true", default=False)

        expert.add_option("-S", "--samples-per-symbol", type="float", default=2,

                          help="set samples/symbol [default=%default]")

        expert.add_option("", "--log", action="store_true", default=False,

                          help="Log all parts of flow graph to files (CAUTION: lots of data)")

        expert.add_option("", "--chbw-factor", type="float", default=1.0,

                          help="Channel bandwidth = chbw_factor x signal bandwidth [defaut=%default]")

    # Make a static method to call before instantiation

    add_options = staticmethod(add_options)

    def _print_verbage(self):

        """

        Prints information about the receive path

        """

        print "\nReceive Path:"

        print "modulation:      %s"    % (self._demod_class.__name__)

        print "bitrate:         %sb/s" % (eng_notation.num_to_str(self._bitrate))

        print "samples/symbol:  %.4f"    % (self.samples_per_symbol())

        print "Differential:    %s"    % (self.differential())