/* -*- c++ -*- */
/*
 * Copyright 2006,2010-2012 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.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "costas_loop_cc_impl.h"
#include <gr_io_signature.h>
#include <gr_expj.h>
#include <gr_sincos.h>
#include <gr_math.h>

namespace gr {
  namespace digital {

    costas_loop_cc::sptr
    costas_loop_cc::make(float loop_bw, int order)
    {
      return gnuradio::get_initial_sptr
	(new costas_loop_cc_impl(loop_bw, order));
    }

    costas_loop_cc_impl::costas_loop_cc_impl(float loop_bw, int order)
      : gr_sync_block("costas_loop_cc",
		      gr_make_io_signature(1, 1, sizeof(gr_complex)),
		      gr_make_io_signature2(1, 2, sizeof(gr_complex), sizeof(float))),
	gri_control_loop(loop_bw, 1.0, -1.0),
	d_order(order), d_phase_detector(NULL)
    {
      // Set up the phase detector to use based on the constellation order
      switch(d_order) {
      case 2:
	d_phase_detector = &costas_loop_cc_impl::phase_detector_2;
	break;

      case 4:
	d_phase_detector = &costas_loop_cc_impl::phase_detector_4;
	break;

      case 8:
	d_phase_detector = &costas_loop_cc_impl::phase_detector_8;
	break;

      default: 
	throw std::invalid_argument("order must be 2, 4, or 8");
	break;
      }
    }

    costas_loop_cc_impl::~costas_loop_cc_impl()
    {
    }

    float
    costas_loop_cc_impl::phase_detector_8(gr_complex sample) const
    {
      /* This technique splits the 8PSK constellation into 2 squashed
	 QPSK constellations, one when I is larger than Q and one
	 where Q is larger than I. The error is then calculated
	 proportionally to these squashed constellations by the const
	 K = sqrt(2)-1.

	 The signal magnitude must be > 1 or K will incorrectly bias
	 the error value.

	 Ref: Z. Huang, Z. Yi, M. Zhang, K. Wang, "8PSK demodulation for
	 new generation DVB-S2", IEEE Proc. Int. Conf. Communications,
	 Circuits and Systems, Vol. 2, pp. 1447 - 1450, 2004.
      */

      float K = (sqrt(2.0) - 1);
      if(fabsf(sample.real()) >= fabsf(sample.imag())) {
	return ((sample.real()>0 ? 1.0 : -1.0) * sample.imag() -
		(sample.imag()>0 ? 1.0 : -1.0) * sample.real() * K);
      }
      else {
	return ((sample.real()>0 ? 1.0 : -1.0) * sample.imag() * K -
		(sample.imag()>0 ? 1.0 : -1.0) * sample.real());
      }
    }

    float
    costas_loop_cc_impl::phase_detector_4(gr_complex sample) const
    {
      return ((sample.real()>0 ? 1.0 : -1.0) * sample.imag() -
	      (sample.imag()>0 ? 1.0 : -1.0) * sample.real());
    }

    float
    costas_loop_cc_impl::phase_detector_2(gr_complex sample) const
    {
      return (sample.real()*sample.imag());
    }

    int
    costas_loop_cc_impl::work(int noutput_items,
			      gr_vector_const_void_star &input_items,
			      gr_vector_void_star &output_items)
    {
      const gr_complex *iptr = (gr_complex *) input_items[0];
      gr_complex *optr = (gr_complex *) output_items[0];
      float *foptr = (float *) output_items[1];

      bool write_foptr = output_items.size() >= 2;

      float error;
      gr_complex nco_out;
  
      if(write_foptr) {
	for(int i = 0; i < noutput_items; i++) {
	  nco_out = gr_expj(-d_phase);
	  optr[i] = iptr[i] * nco_out;
      
	  error = (*this.*d_phase_detector)(optr[i]);
	  error = gr_branchless_clip(error, 1.0);
	
	  advance_loop(error);
	  phase_wrap();
	  frequency_limit();
      
	  foptr[i] = d_freq;
	} 
      }
      else {
	for(int i = 0; i < noutput_items; i++) {
	  nco_out = gr_expj(-d_phase);
	  optr[i] = iptr[i] * nco_out;
      
	  error = (*this.*d_phase_detector)(optr[i]);
	  error = gr_branchless_clip(error, 1.0);

	  advance_loop(error);
	  phase_wrap();
	  frequency_limit();
	}
      }
      return noutput_items;
    }

  } /* namespace digital */
} /* namespace gr */