#define _DEFAULT_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <signal.h>

#define SER_SPEED       B19200
#define SER_BITS        CS7
#define SER_PARITY      (PARENB | PARODD)

int quit_flag = 0;

void handle_sigint(int a) {
    quit_flag = 1; 
}

int sercat(char *dev) {
    int fd;
    struct termios tty, orig_tty;
    int tio, orig_tio;
    int r;
    char buffer[14];

    signal(SIGINT, handle_sigint);

    fd = open(dev, O_RDWR | O_NOCTTY);
    if (fd < 0) {
        perror("open():");
        return fd;
    }

    memset(&orig_tty, 0, sizeof(orig_tty));

    r = tcgetattr(fd, &orig_tty);
    if (r < 0) {
        close(fd);
        perror("tcgetattr():");
        return r;
    }

    memcpy(&tty, &orig_tty, sizeof(orig_tty));

    cfsetospeed(&tty, SER_SPEED);
    cfsetispeed(&tty, SER_SPEED);

    tty.c_cflag = (tty.c_cflag & ~CSIZE) | SER_BITS;

    tty.c_cflag = (tty.c_cflag & ~(PARENB | PARODD)) | SER_PARITY;

    tty.c_cflag &= ~CSTOPB;
    tty.c_cflag &= ~CRTSCTS;

    tty.c_iflag &= ~ICRNL;

    r = tcsetattr(fd, TCSANOW, &tty);
    if (r < 0) {
        perror("tcsetattr():");
        close(fd);
        return r;
    }

    ioctl(fd, TIOCMGET, &orig_tio);

    // To power the adapter we need DTR high and RTS low
    tio = (orig_tio & ~TIOCM_RTS) | TIOCM_DTR;

    ioctl(fd, TIOCMSET, &tio);

    while ((r = read(fd, buffer, sizeof(buffer))) > 0) {
        write(STDOUT_FILENO, buffer, r);
        if (quit_flag)
            break;
    }

    close(STDOUT_FILENO);

    if (r < 0) {
        perror("read():");
    }

    r = tcsetattr(fd, TCSANOW, &orig_tty);
    if (r < 0) {
        perror("tcsetattr(restore):");
    }

    ioctl(fd, TIOCMSET, &orig_tio);

    close(fd);
    return 0;
}

void usage(char *bin) {
    fprintf(stderr, "Symtax: %s SERIAL_PORT\n", bin);
}

int main(int argc, char *argp[]) {
    if (argc < 2)
        usage(argp[0]);
    else {
        if (sercat(argp[1]) < 0)
            return EXIT_FAILURE;
    }
    return EXIT_SUCCESS;
}