/*
 * File Name:       uart_api.c
 * Workflow:        implementation of the uart apis
 * Return Value:    open_port return file describer as successful,
 *                  set_comfig return 0 as successful,
 *                  both function would return -1 as erroneaous
 */

/* Header files */
#include "uart_api.h"

/*
 * Function Name:    open_port
 * Workflow:         get a file describer that follows the under requests:
 *                   1, it must be a terminal device
 *                   2, it is NONBLOCK mode
 */
int open_port(const char *com_port) {
  int fd;
  int flags;

  /* open port in read/write mode */
  fd = open(com_port, O_RDWR, S_IRUSR | S_IWUSR);
  DebugLog("[DEBUG-INFO %s:%d]:Open from \"%s\" get fd: %d\n", __FUNCTION__,
           __LINE__, com_port, fd);

  if (fd < 0) {
    fprintf(stderr, "[%s:%d] open(): %s", __FUNCTION__, __LINE__,
            strerror(errno));
    return -1;
  }

  /* check if fd is associated with a terminal */
  if (isatty(fd) == 0) {
    fprintf(stderr, "[%s:%d] isatty(): %s", __FUNCTION__, __LINE__,
            strerror(errno));
    close(fd);
    return -1;
  }

  /* file describer is set to non-block mode */
  flags = fcntl(fd, F_GETFL);

  if (flags == -1) {
    fprintf(stderr, "[%s:%d] fcntl(): %s", __FUNCTION__, __LINE__,
            strerror(errno));
    close(fd);
    return -1;
  }

  if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
    fprintf(stderr, "[%s:%d] fcntl(): %s", __FUNCTION__, __LINE__,
            strerror(errno));
    close(fd);
    return -1;
  }

  return fd;
}

/*
 * Function Name:    set_comfig
 * Workflow:         use termios to set the port under these requests:
 *                   1, data bit fixed to 8
 *                   2, no parity check
 *                   3, 1 stop bit
 *                   4, no hardware control flow
 *                   5, wait 3 seconds OR read 6 bytes, either reaches read
 * would return 6, buffer must be clean
 */
int set_comfig(int serial_fd, int baud_rate) {
  struct termios term_new, term_old;

  /* save old config */
  if (tcgetattr(serial_fd, &term_old) == -1) {
    fprintf(stderr, "[%s:%d] tcgetattr(): %s", __FUNCTION__, __LINE__,
            strerror(errno));
    return -1;
  }

  /* prepare new config struct to be used */
  cfmakeraw(&term_new);
  term_new.c_cflag &= ~CSIZE;

  /* set  baud rate */
  switch (baud_rate) {
  case 9600:
    cfsetispeed(&term_new, B9600);
    cfsetospeed(&term_new, B9600);
    break;
  case 115200:
    cfsetispeed(&term_new, B115200);
    cfsetospeed(&term_new, B115200);
    break;
  default:
    fprintf(stderr, "[%s:%d] switch(baud_rate): %s", __FUNCTION__, __LINE__,
            strerror(errno));
    return -1;
  }

  /* set data bit to 8 */
  term_new.c_cflag &= ~CSIZE;
  term_new.c_cflag |= CS8;

  /* set no parity check */
  term_new.c_cflag &= ~PARENB;
  term_new.c_iflag &= ~INPCK;

  /* set stop bit to 1 */
  term_new.c_cflag &= ~CSTOPB;

  /* disable hardware flow control
   * term_new.c_cflag &= ~CRTSCTS; */

  /* set to line buffered */
  term_new.c_lflag |= ICANON;

  /* set EOF and EOF */
  term_new.c_cc[VEOL] = '\0';

  /* read() function would wait 3 seconds before return */
  term_new.c_cc[VTIME] = 30;

  /* read() fuction would return if 6 bytes read */
  term_new.c_cc[VMIN] = 6;

  /* flush IO buffer area */
  tcflush(serial_fd, TCIFLUSH);
  tcflush(serial_fd, TCOFLUSH);

  /* enable setting */
  if (tcsetattr(serial_fd, TCSANOW, &term_new) == -1) {
    fprintf(stderr, "[%s:%d] tcsetattr: %s", __FUNCTION__, __LINE__,
            strerror(errno));
    return -1;
  }

  return 0;
}