#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <termios.h>
#include <errno.h>
#include <string.h>
#include <assert.h>

#include <cstdlib>

#include "Uart.h"

Uart::Uart(const char* name)
{
    assert(name != nullptr);
    serial_device = open(name, O_RDWR);
    if (serial_device < 0)
    {
        printf("unable to open serial port\r\n");
        exit(1);
    }

    // Create new termios struct, we call it 'tty' for convention
    // No need for "= {0}" at the end as we'll immediately write the existing
    // config to this struct
    struct termios tty;

    // Read in existing settings, and handle any error
    // NOTE: This is important! POSIX states that the struct passed to tcsetattr()
    // must have been initialized with a call to tcgetattr() overwise behaviour
    // is undefined
    if (tcgetattr(serial_device, &tty) != 0)
    {
        printf("Error %i from tcgetattr: %s\n", errno, strerror(errno));
        close(serial_device);
        exit(2);
    }

    tty.c_cflag |= PARENB; // Clear parity bit, disabling parity (most common)
    tty.c_cflag &= ~PARODD;
    tty.c_cflag &= ~CSTOPB; // Clear stop field, only one stop bit used in communication (most common)

    tty.c_cflag &= ~CSIZE; // First clear all the size bits
    tty.c_cflag |= CS8;    // 8 bits per byte (most common)

    tty.c_cflag &= ~CRTSCTS;       // Disable RTS/CTS hardware flow control (most common)
    tty.c_cflag |= CREAD | CLOCAL; // Turn on READ & ignore ctrl lines (CLOCAL = 1)

    tty.c_lflag &= ~ICANON;
    tty.c_lflag &= ~ECHO;   // Disable echo
    tty.c_lflag &= ~ECHOE;  // Disable erasure
    tty.c_lflag &= ~ECHONL; // Disable new-line echo
    tty.c_lflag &= ~ISIG;   // Disable interpretation of INTR, QUIT and SUSP

    tty.c_iflag &= ~(IXON | IXOFF | IXANY);                                      // Turn off s/w flow ctrl
    tty.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL); // Disable any special handling of received bytes

    tty.c_oflag &= ~OPOST; // Prevent special interpretation of output bytes (e.g. newline chars)
    tty.c_oflag &= ~ONLCR; // Prevent conversion of newline to carriage return/line feed

    tty.c_cc[VTIME] = 10; // Wait for up to 1s (10 deciseconds), returning as soon as any data is received.
    tty.c_cc[VMIN] = 0;

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

    // Save tty settings, also checking for error
    if (tcsetattr(serial_device, TCSANOW, &tty) != 0)
    {
        printf("Error %i from tcsetattr: %s\n", errno, strerror(errno));
        close(serial_device);
        exit(3);
    }
}

Uart::~Uart()
{
    close(serial_device);
}

int Uart::transmit(const unsigned char *buffer, size_t len)
{
    return write(serial_device, buffer, len);
}

int Uart::receive(unsigned char *buffer, size_t len)
{
    return read(serial_device, buffer, len);
}