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

int set_serial_device(int fd){
    struct termios serial_cnf;

    if (tcgetattr(fd, &serial_cnf) < 0){
        printf("It's a TTY device\n");
        close(fd);
        return -1;
    }

    cfsetispeed(&serial_cnf, B115200);
    cfsetospeed(&serial_cnf, B115200);

    serial_cnf.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
    serial_cnf.c_iflag &= ~(IXON | IXOFF | IXANY); // Disable software flow control
    serial_cnf.c_iflag &= ~(INLCR | ICRNL | IGNCR);
    serial_cnf.c_cflag &= ~CRTSCTS; // Disable hardware control

    serial_cnf.c_cflag |= CREAD | CLOCAL;

    /* Set 8N1 (8 bits, no parity, 1 stop bit) */
    serial_cnf.c_cflag &= ~PARENB; // No parity
    serial_cnf.c_cflag &= ~CSTOPB; // 1 stop bit
    serial_cnf.c_cflag &= ~CSIZE;  // clear data
    serial_cnf.c_cflag |= CS8; // 8 data bits
    serial_cnf.c_oflag &= ~OPOST; // Disable output processing

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

    tcflush(fd, TCIFLUSH);
    if (tcsetattr(fd, TCSANOW/*TCSAFLUSH*/, &serial_cnf) < 0) {
        printf("Failed to serial_cnfure the serial port\n");
        close(fd);
        return -1;
    }
    return 0;
}



static unsigned short csum(unsigned short *buf, int nwords) {
    unsigned long sum = 0;
    while (nwords > 0) {
        sum += *buf++;
        nwords--;
    }   
    sum = (sum >> 16) + (sum & 0xFFFF);
    sum += (sum >> 16);
    return (unsigned short)(~sum);
}

int send_uart(struct prng **s_prng){
    int fd;

    if ((fd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY)) < 0){
        printf("Failed to read the device\n");
        exit(-1);
    }

    set_serial_device(fd);

    char buffer[sizeof(struct prng)];
    char buf_cmd[sizeof(struct cmd)];

    struct cmd s_cmd = {0};
    s_cmd.version = CSPRNG_VERS;
    s_cmd.cmd = CSPRNG_CMD_GET_RNG;
    memcpy(buf_cmd, &s_cmd, sizeof(struct cmd));

    //printf("Sending command...\n");
    size_t len = write(fd, &buf_cmd, sizeof(struct cmd));
    //printf("Data sent: %ld\n\n", len);

    // Read data
    //printf("Receiving data...\n");
    int total_len = 0;
    while (total_len < sizeof(struct prng)){
        len = read(fd, buffer + total_len, sizeof(struct prng));
        //printf("Len recv: %ld\n", len);
        total_len += len;
    }
    *s_prng = (struct prng *)buffer;
    close(fd);
    return 0;
}