/**************************************************************
 * Class::  CSC-415-01 Fall 2024
 * Name::  Uzair Hamed Mohammed
 * Student ID::  920142896
 * GitHub-Name::  gamersekofy
 * Project:: Assignment 6 - Device Driver

 *
 * File:: Mohammed_UzairHamed_HW6_main.c
 *
 * Description::  This file contains a very easy to use and application that
 reads and writes data
 * to the tempMonitor kernel module.
 **************************************************************/

#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <unistd.h>

#define IOCTL_GET_TEMP _IOR('t', 1, int)

#define GREEN "\033[1;32m"
#define RESET "\033[0m"

void read_temp(int fd, const char *unit) {
  char buffer[128];
  ssize_t bytes_read;

  /* Declare this variable because /sys/class/thermal/thermal_zonex/ isn't
   available on virtual machines. In case of a virtual machine, set this flag
   that will make the kernel module return a simulated temperature. */
  int is_simulated = 0;

  // Writing the desired unit or "simulate" command to the device
  ssize_t bytes_written = write(fd, unit, strlen(unit));
  if (bytes_written < 0) {
    return;
  }

  // Reading the temperature
  bytes_read = read(fd, buffer, sizeof(buffer));
  if (bytes_read < 0) {
    return;
  } else {
    buffer[bytes_read] = '\0';

    // Check if the temperature is simulated. If it is, set flag here.
    if (strstr(buffer, "(simulated temperature)") != NULL) {
      is_simulated = 1;
    }

    if (is_simulated) {
      printf(GREEN "CPU Temperature\n--- -----------\n" RESET "%s\n", buffer);
    } else {
      printf(GREEN "CPU Temperature\n--- -----------\n" RESET "%s\n", buffer);
    }
  }
}

int main() {
  int fd;
  char choice;

  // Access kernel module here
  fd = open("/dev/temp_monitor", O_RDWR);
  if (fd < 0) {
    perror("Failed to open the device");
    return -1;
  }

  // Ask the user for the preferred temperature unit
  printf("Choose temperature unit (C/F): ");
  scanf(" %c", &choice);

  if (choice == 'C' || choice == 'c') {
    // Request the kernel module provide temperature in Celsius
    read_temp(fd, "C");
  } else if (choice == 'F' || choice == 'f') {
    // Request the kernel module provide the temperature in Fahrenheit
    read_temp(fd, "F");
  } else {
    printf("Invalid choice. Please choose 'C' or 'F'.\n");
    close(fd);
    return -1;
  }

  close(fd);
  return 0;
}