/*
 *   ALDL Dashboard, core 160 baud handling code
 *
 *   (c) 2019 Solomon Peachy <pizza@shaftnet.org>
 *
 *   The latest version of this program can be found at:
 *
 *     http://git.shaftnet.org/cgit/users/pizza/public/aldl_pi.git
 *
 *   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 3 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 *          [http://www.gnu.org/licenses/gpl-3.0.html]
 *
 *   SPDX-License-Identifier: GPL-3.0+
 *
 */

#include <stdio.h>
#include <stdint.h>
#include <time.h>
#include <unistd.h>

#include <pthread.h>

#include "aldl.h"

/* shift register & sync word */
#define SYNC_WORD 0x1ff
#define DWELL_TIME 1000  /* microseconds after falling edge */
#define DEBOUNCE_TIME 200 /* microseconds */
#define MAX_STREAM_WORDS 255
static uint16_t ALDLSR = 0;
static uint8_t bits = 0;
static int datalen = 0;
static uint8_t data[MAX_STREAM_WORDS];

int gotsync = 0;

static FILE *datalog_handle;

struct stream_common decoded = { 0 };

void (*aldl_callback)(uint8_t *data, int datalen) = NULL;

/* Datalogging */
void datalog_init(char *fname)
{
   datalog_handle = fopen(fname, "a");
   if (!datalog_handle)
       perror("Can't open datalog file!\n");
   fprintf(datalog_handle, "# New session\n");
}

void datalog_close(void)
{
    if (datalog_handle)
	fclose(datalog_handle);
}

static void aldl_datalog(uint8_t *data, int datalen)
{
    int i;

    if (!datalog_handle) return;

    fprintf(datalog_handle, "%ld", time(NULL));

    for (i = 0 ; i < datalen ; i++) {
	    fprintf(datalog_handle, ",%02x", *data++);
    }
    fprintf(datalog_handle, "\n");
}

static void process_bit(int val)
{
  ALDLSR <<= 1;
  ALDLSR |= (val & 1);

  if ((ALDLSR & SYNC_WORD) == SYNC_WORD) {
    /* New sync word, we've finished a sequence */
    printf(" - %d\n", datalen);

    /* Received a sync word.. */
    ALDLSR = 0;
    if (!gotsync) {
        gotsync = 1;
	return;  /* First one, we don't do anything */
    }

    /* Process ALDL payload */
    if (aldl_callback)
	aldl_callback(data, datalen);
    /* Log data */
    if (datalog_handle)
        aldl_datalog(data, datalen);
    /* Reset state */
    bits = 0;
    datalen = 0;
  } else if (++bits == 9) {
    printf(" %02x", ALDLSR & 0xFF);
    /* Just latch in the word */
    data[datalen++] = ALDLSR & 0xff;
    /* Reset state */
    bits = 0;
    ALDLSR = 0;
  }
}

/* ISR */
void isrfn(void)
{
  int val;
  delayfn(DWELL_TIME);  // To handle both variations, minimum of 0.5, max of 1.8ms
  val = !readbit();  // If hi, represents ALDL 0; if low, ALDL1.
  process_bit(val);
}

#include <sys/time.h>

int run_sampler = 1;

long tv_diff(struct timeval *tv1, struct timeval *tv2)
{
  long usecs = (tv2->tv_sec - tv1->tv_sec) * 1000000;
  usecs += (tv2->tv_usec - tv1->tv_usec);
  return usecs;
}

/* Alternatively.. continually poll. */
void poll_gpio(void)
{
  struct timeval tv, last_tv;
  int pin, last_pin;
  long total_us = 0;

  gettimeofday(&last_tv, NULL);
  last_pin = readbit();

  while(run_sampler) {
     /* Read */
     gettimeofday(&tv, NULL);
     pin = readbit();

     /* Work out how long it's been since our last sample */
     total_us += tv_diff(&last_tv, &tv);
     last_tv = tv;

     /* No edge.. or possibly false edge. */
     if (pin == last_pin || total_us < DEBOUNCE_TIME)
        continue;

     if (pin == 1) {  /* ie Rising edge */
//	printf ("%06d\n", total_us);
	/* Rising edge.  tells us when the bit ends */
	if (total_us > DWELL_TIME)
	    process_bit(0);  /* long period high is logical 0 */
        else
	    process_bit(1);  /* short period high is logical 1 */
     }
     /* Edge transition, reset time and record new pin */
     total_us = 0;
     last_pin = pin;
  }
}

static pthread_t poller;
static int polling = 0;

static void *thread_poller(void *arg)
{
   poll_gpio();
   pthread_exit(NULL);
}

int thread_start(void)
{
  polling = 1;
  return pthread_create(&poller, NULL, thread_poller, NULL);
}
void thread_shutdown(void)
{
  if (polling) {
    run_sampler = 0;
    pthread_join(poller, NULL);
    polling = 0;
  }
}