#include <errno.h>
#include <fcntl.h> 
#include <string.h>
#include <termios.h>
#include <stdio.h>
#include <stdlib.h>

#define NO_ERROR_EXIT_CODE 0
#define PARAMETER_ERROR_EXIT_CODE 1
#define PORT_OPEN_ERROR_EXIT_CODE 2
#define WRITE_ERROR_EXIT_CODE 4
#define READ_ERROR_EXIT_CODE 5

int set_interface_attribs (int fUSBPort, int speed)
{
	/* Set up the control structure */
	struct termios toptions;

	/* Get currently set options for the tty */
	tcgetattr(fUSBPort, &toptions);

	/* Set custom options */

	/* 9600 baud */
	cfsetispeed(&toptions, speed);
	cfsetospeed(&toptions, speed);
	
	/* 8 bits, no parity, no stop bits */
	toptions.c_cflag &= ~PARENB;
	toptions.c_cflag &= ~CSTOPB;
	toptions.c_cflag &= ~CSIZE;
	toptions.c_cflag |= CS8;
	
	/* no hardware flow control */
	toptions.c_cflag &= ~CRTSCTS;
	
	/* enable receiver, ignore status lines */
	toptions.c_cflag |= CREAD | CLOCAL;
	
	/* disable input/output flow control, disable restart chars */
	toptions.c_iflag &= ~(IXON | IXOFF | IXANY);
	
	/* disable canonical input, disable echo,
	disable visually erase chars,
	disable terminal-generated signals */
	toptions.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
	toptions.c_lflag |= ICANON;
	
	/* disable output processing */
	toptions.c_oflag &= ~OPOST;

	/* wait for 1 character to come in before read returns */
	toptions.c_cc[VMIN] = 1;
	
	// 20 = 2 sec 
	toptions.c_cc[VTIME] = 20; 

	/* commit the options */
	tcsetattr(fUSBPort, TCSANOW, &toptions);
}

int main(int argc, char *argv[]) {
	if (argc<2) {
		printf("Proper usage:  upsmon [full_port_name]\n");
		printf("Exit codes:\n");
		printf("  %d=success\n", NO_ERROR_EXIT_CODE);
		printf("  %d=parameter error\n", PARAMETER_ERROR_EXIT_CODE);
		printf("  %d=port open fail\n", PORT_OPEN_ERROR_EXIT_CODE);
		printf("  %d=write error\n", WRITE_ERROR_EXIT_CODE);
		printf("  %d=read error\n", READ_ERROR_EXIT_CODE);
		exit(PARAMETER_ERROR_EXIT_CODE);
	}

//FILE* f=fopen("/share/Installers/QNAPUPSMon/UPSMonLog.txt", "a");
//// use \r\n so it'll be windows-friendly
//fprintf(f, "starting  PID=%d\r\n", getpid());
//fclose(f);

	char* sUSBPortName = (char*) malloc(50);
	strcpy(sUSBPortName, argv[1]);
	printf("MONITORING %s\n", sUSBPortName);
	int fUSBPort = open(sUSBPortName, O_RDWR | O_NOCTTY);
	if (fUSBPort < 0)
	{
		printf("Error %d opening %s: %s\n", errno, sUSBPortName, strerror(errno));
		free(sUSBPortName);
		exit(PORT_OPEN_ERROR_EXIT_CODE);
	}

	free(sUSBPortName);

	// internally handled:  8n1 (no parity)
	set_interface_attribs(fUSBPort, B9600);  

	/* Flush anything already in the serial buffer */
	tcflush(fUSBPort, TCIFLUSH);

	int n = write(fUSBPort, "HowAreThings?\n", 14); 
	if (n < 0) {
	  printf("Write error %d.\n", n);
	  exit(WRITE_ERROR_EXIT_CODE);
	}

	const int icBufferLen = 100;
	char* sReadBuffer = (char*) malloc(icBufferLen);

	n = read(fUSBPort, sReadBuffer, icBufferLen); 

	if (n < 0) {
	  printf("Read error %d.\n", n);
	  exit(READ_ERROR_EXIT_CODE);
	}

	printf("Received %d bytes buffer contains [%s]\n", n, sReadBuffer);

	int bOK = (strstr(sReadBuffer, "OK") != 0);
	int bShutdown = (strstr(sReadBuffer, "NASShutdown") != 0);
	
	free(sReadBuffer);

	if (bOK) 
		printf("Power is on!\n");

	if (bShutdown) {
		printf("Starting power-off now!\n");
		system("/sbin/poweroff");
	}

	close(fUSBPort);

	exit(NO_ERROR_EXIT_CODE);
}