#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>

#define DEFAULT_PORT "/dev/ttyESP32_A"
#define DEFAULT_BAUD B1500000

int open_serial(const char *path, speed_t baud) {
    int fd = open(path, O_RDONLY | O_NOCTTY);
    if (fd < 0) { perror("open"); return -1; }

    struct termios tio;
    if (tcgetattr(fd, &tio) != 0) { perror("tcgetattr"); close(fd); return -1; }

    cfsetispeed(&tio, baud);
    cfsetospeed(&tio, baud);

    // Raw mode
    tio.c_iflag &= ~(IGNBRK | BRKINT | ICRNL | INLCR | IXON | IXOFF | IXANY |
                     PARMRK | INPCK | ISTRIP);
    tio.c_oflag &= ~(OPOST);
    tio.c_lflag &= ~(ECHO | ECHONL | ICANON | IEXTEN | ISIG);
    tio.c_cflag &= ~(CSIZE | PARENB | CSTOPB | CRTSCTS);
    tio.c_cflag |= (CS8 | CLOCAL | CREAD);

    tio.c_cc[VMIN]  = 1;
    tio.c_cc[VTIME] = 0;

    if (tcsetattr(fd, TCSANOW, &tio) != 0) { perror("tcsetattr"); close(fd); return -1; }

    return fd;
}

int main(int argc, char *argv[]) {
    const char *port = (argc > 1) ? argv[1] : DEFAULT_PORT;
    speed_t baud = DEFAULT_BAUD;

    int fd = open_serial(port, baud);
    if (fd < 0) return 1;

    uint8_t buf[8192];
    while (1) {
        ssize_t n = read(fd, buf, sizeof(buf));
        if (n > 0) {
            fwrite(buf, 1, n, stdout);
            fflush(stdout);
        }
    }

    close(fd);
    return 0;
}