/* -*- 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 "feedforward_agc_cc_impl.h"
#include <gr_io_signature.h>
#include <stdexcept>

namespace gr {
  namespace analog {

    feedforward_agc_cc::sptr
    feedforward_agc_cc::make(int nsamples, float reference)
    {
      return gnuradio::get_initial_sptr
	(new feedforward_agc_cc_impl(nsamples, reference));
    }

    feedforward_agc_cc_impl::feedforward_agc_cc_impl(int nsamples, float reference)
      : gr_sync_block("feedforward_agc_cc",
		      gr_make_io_signature(1, 1, sizeof(gr_complex)),
		      gr_make_io_signature(1, 1, sizeof(gr_complex))),
	d_nsamples(nsamples), d_reference(reference)
    {
      if(nsamples < 1)
	throw std::invalid_argument("feedforward_agc_cc_impl: nsamples must be >= 1");
  
      set_history(nsamples);
    }

    feedforward_agc_cc_impl::~feedforward_agc_cc_impl()
    {
    }

    inline static float
    mag_squared(gr_complex x)
    {
      return x.real() * x.real() + x.imag() * x.imag();
    }

    // approximate sqrt(x^2 + y^2)
    inline static float
    envelope(gr_complex x)
    {
      float r_abs = std::fabs(x.real());
      float i_abs = std::fabs(x.imag());

      if(r_abs > i_abs)
	return r_abs + 0.4 * i_abs;
      else
	return i_abs + 0.4 * r_abs;
    }

    int
    feedforward_agc_cc_impl::work(int noutput_items,
				  gr_vector_const_void_star &input_items,
				  gr_vector_void_star &output_items)
    {
      const gr_complex *in = (const gr_complex*)input_items[0];
      gr_complex *out = (gr_complex*)output_items[0];
      int nsamples = d_nsamples;
      float gain;

      for(int i = 0; i < noutput_items; i++) {
	//float max_env = 1e-12;	// avoid divide by zero
	float max_env = 1e-4;	// avoid divide by zero, indirectly set max gain
	for(int j = 0; j < nsamples; j++) {
	  max_env = std::max(max_env, envelope(in[i+j]));
	}
	gain = d_reference / max_env;
	out[i] = gain * in[i];
      }
      return noutput_items;
    }

  } /* namespace analog */
} /* namespace gr */