#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <time.h>
#include <sched.h>
#include <inttypes.h>

#define PIN "132"

void init_pin() {
  int fd = open("/sys/class/gpio/export",O_WRONLY);
  char buf[16];
  int len = sprintf(buf,"%s\n",PIN);
  write(fd,buf,len);
  close(fd);
  fd = open("/sys/class/gpio/gpio" PIN "/direction",O_WRONLY);
  write(fd,"out\n",4);
  close(fd);
}

void deinit_pin() {
  int fd = open("/sys/class/gpio/unexport",O_WRONLY);
  char buf[16];
  int len = sprintf(buf,"%s\n",PIN);
  write(fd,buf,len);
  close(fd);
}

int pin_fd;
void write_pin(uint8_t value) {
  if (!pin_fd) {
    pin_fd = open("/sys/class/gpio/gpio" PIN "/value",O_WRONLY);
  }
  char buf[16];
  int len = sprintf(buf,"%d\n",value);
  write(pin_fd,buf,len);
}

void init_sched() {
  struct sched_param sp;
  sp.sched_priority=99;

  // to make this work, sudo setcap CAP_SYS_NICE=eip clock
  sched_setscheduler(0,SCHED_RR,&sp);
}

const int width=520000;
struct timespec next_step;
void send_array(const uint8_t values[],size_t len) {
  if (next_step.tv_sec == 0) {
    clock_gettime(CLOCK_REALTIME,&next_step);
  }
  uint8_t pin_value = 1;
  for (int i=0; i<len; ++i) {
    write_pin(pin_value);
    pin_value = 1 - pin_value;

    next_step.tv_nsec += width * values[i];

    if (next_step.tv_nsec > 1000000000UL) {
      next_step.tv_nsec -= 1000000000UL;
      ++next_step.tv_sec;
    }

    int rc = clock_nanosleep(CLOCK_REALTIME,
                             TIMER_ABSTIME,
                             &next_step,
                             NULL);
    if (rc) {
      printf("problems: %d\n",rc);
    }
  }
}
void my_sleep(uint8_t seconds) {
  next_step.tv_sec += seconds;

  int rc = clock_nanosleep(CLOCK_REALTIME,
                           TIMER_ABSTIME,
                           &next_step,
                           NULL);
  if (rc) {
    printf("problems: %d\n",rc);
  }
}

// alternate HIGH and LOW, first one of each array is HIGH
const uint8_t prologue[] = {
  1,1, 1,1, 1,1, 1,1, 1,1, 1,1,
  2,3, 1,1, 2,2, 1,1, 1,1, 2,1,
  1,1, 1,1, 1,2, 1,1, 1,1, 1,1,
  1,1, 1,1,
};
const size_t prologueSize = sizeof(prologue) / sizeof(uint8_t);

const uint8_t epilogue[] = {
  1,2, 2,2, 1,3, // the last value doesn't much matter
};
const size_t epilogueSize = sizeof(epilogue) / sizeof(uint8_t);

const uint8_t onSignal[] = {
  2,2, 1,1, 1,1, 1,1, 1,1, 2,1, 1,1,
};
const size_t onSize = sizeof(onSignal) / sizeof(uint8_t);

const uint8_t offSignal[] = {
  1,1, 1,1, 1,1, 1,1, 1,1, 2,2, 2,1,
};
const size_t offSize = sizeof(offSignal) / sizeof(uint8_t);

void transmitSignal(const uint8_t signal[], size_t signalSize) {
  send_array(prologue,prologueSize);
  send_array(signal,signalSize);
  send_array(epilogue,epilogueSize);
}

void sendTrain(const uint8_t signal[], size_t signalSize) {
  transmitSignal(offSignal,offSize);
  my_sleep(1);
  transmitSignal(signal,signalSize);
  my_sleep(2);
  transmitSignal(offSignal,offSize);
}

int main(int argc,char **argv) {
  if (argc != 2) {
    fprintf(stderr,"thing 0/1\n");
    return 1;
  }

  init_sched();
  init_pin();
  write_pin(0);

  if (argv[1][0] == '1') {
    sendTrain(onSignal,onSize);
  }
  else {
    sendTrain(offSignal,offSize);
  }

  deinit_pin();

  return 0;
}