/* -*- c++ -*- */
/*
 * Copyright 2004,2010,2012 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 "packet_sink_impl.h"
#include <gnuradio/blocks/count_bits.h>
#include <gnuradio/io_signature.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <cstdio>
#include <stdexcept>

namespace gr {
namespace digital {

#define VERBOSE 0

// detect access code with up to DEFAULT_THRESHOLD bits wrong
static const int DEFAULT_THRESHOLD = 12;

inline void packet_sink_impl::enter_search()
{
    if (VERBOSE)
        fprintf(stderr, "@ enter_search\n");

    d_state = STATE_SYNC_SEARCH;
    d_shift_reg = 0;
}

inline void packet_sink_impl::enter_have_sync()
{
    if (VERBOSE)
        fprintf(stderr, "@ enter_have_sync\n");

    d_state = STATE_HAVE_SYNC;
    d_header = 0;
    d_headerbitlen_cnt = 0;
}

inline void packet_sink_impl::enter_have_header(int payload_len)
{
    if (VERBOSE)
        fprintf(stderr, "@ enter_have_header (payload_len = %d)\n", payload_len);

    d_state = STATE_HAVE_HEADER;
    d_packetlen = payload_len;
    d_packetlen_cnt = 0;
    d_packet_byte = 0;
    d_packet_byte_index = 0;
}

packet_sink::sptr packet_sink::make(const std::vector<unsigned char>& sync_vector,
                                    msg_queue::sptr target_queue,
                                    int threshold)
{
    return gnuradio::get_initial_sptr(
        new packet_sink_impl(sync_vector, target_queue, threshold));
}

packet_sink_impl::packet_sink_impl(const std::vector<unsigned char>& sync_vector,
                                   msg_queue::sptr target_queue,
                                   int threshold)
    : sync_block("packet_sink",
                 io_signature::make(1, 1, sizeof(float)),
                 io_signature::make(0, 0, 0)),
      d_target_queue(target_queue),
      d_threshold(threshold == -1 ? DEFAULT_THRESHOLD : threshold)
{
    d_sync_vector = 0;
    for (int i = 0; i < 8; i++) {
        d_sync_vector <<= 8;
        d_sync_vector |= sync_vector[i];
    }

    enter_search();
}

packet_sink_impl::~packet_sink_impl() {}

int packet_sink_impl::work(int noutput_items,
                           gr_vector_const_void_star& input_items,
                           gr_vector_void_star& output_items)
{
    float* inbuf = (float*)input_items[0];
    int count = 0;

    if (VERBOSE)
        fprintf(stderr, ">>> Entering state machine\n"), fflush(stderr);

    while (count < noutput_items) {
        switch (d_state) {

        case STATE_SYNC_SEARCH: // Look for sync vector
            if (VERBOSE)
                fprintf(stderr, "SYNC Search, noutput=%d\n", noutput_items),
                    fflush(stderr);

            while (count < noutput_items) {
                if (slice(inbuf[count++]))
                    d_shift_reg = (d_shift_reg << 1) | 1;
                else
                    d_shift_reg = d_shift_reg << 1;

                // Compute popcnt of putative sync vector
                if (gr::blocks::count_bits64(d_shift_reg ^ d_sync_vector) <=
                    d_threshold) {
                    // Found it, set up for header decode
                    enter_have_sync();
                    break;
                }
            }
            break;

        case STATE_HAVE_SYNC:
            if (VERBOSE)
                fprintf(stderr,
                        "Header Search bitcnt=%d, header=0x%08x\n",
                        d_headerbitlen_cnt,
                        d_header),
                    fflush(stderr);

            while (count < noutput_items) { // Shift bits one at a time into header
                if (slice(inbuf[count++]))
                    d_header = (d_header << 1) | 1;
                else
                    d_header = d_header << 1;

                if (++d_headerbitlen_cnt == HEADERBITLEN) {
                    if (VERBOSE)
                        fprintf(stderr, "got header: 0x%08x\n", d_header);

                    // we have a full header, check to see if it has been received
                    // properly
                    if (header_ok()) {
                        int payload_len = header_payload_len();
                        if (payload_len <= MAX_PKT_LEN)     // reasonable?
                            enter_have_header(payload_len); // yes.
                        else
                            enter_search(); // no.
                    } else
                        enter_search(); // no.
                    break;              // we're in a new state
                }
            }
            break;

        case STATE_HAVE_HEADER:
            if (VERBOSE)
                fprintf(stderr, "Packet Build\n"), fflush(stderr);

            while (count <
                   noutput_items) { // shift bits into bytes of packet one at a time
                if (slice(inbuf[count++]))
                    d_packet_byte = (d_packet_byte << 1) | 1;
                else
                    d_packet_byte = d_packet_byte << 1;

                if (d_packet_byte_index++ == 7) { // byte is full so move to next byte
                    d_packet[d_packetlen_cnt++] = d_packet_byte;
                    d_packet_byte_index = 0;

                    if (d_packetlen_cnt == d_packetlen) { // packet is filled
                        // build a message
                        message::sptr msg = message::make(0, 0, 0, d_packetlen_cnt);
                        memcpy(msg->msg(), d_packet, d_packetlen_cnt);

                        d_target_queue->insert_tail(msg); // send it
                        msg.reset();                      // free it up

                        enter_search();
                        break;
                    }
                }
            }
            break;

        default:
            assert(0);
        } // switch
    }     // while

    return noutput_items;
}

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