/**
 * Copyright (c) 2010-2023 Contributors to the openHAB project
 *
 * See the NOTICE file(s) distributed with this work for additional
 * information.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * ----------------------------------------------------------------------------
 *
 *	This application listening data from various Nibe heat pumps (RS485 bus)
 *	and send valid frames to configurable IP/port address by UDP packets.
 *	Application also acknowledge the valid packets to heat pump.
 *
 *	Serial settings: 9600 baud, 8 bits, Parity: none, Stop bits 1
 *
 *	MODBUS module support should be turned ON from the heat pump.
 *
 *	Frame format:
 *	+----+------+------+-----+-----+----+----+-----+
 *	| 5C | ADDR | ADDR | CMD | LEN |  DATA   | CHK |
 *	+----+------+------+-----+-----+----+----+-----+
 *
 *	     |------------ CHK ------------------|
 *
 *	Address: 
 *		0x0016 = SMS40
 *		0x0019 = RMU40
 *		0x0020 = MODBUS40
 *
 *	Checksum: XOR
 *
 *	When valid data is received (checksum ok),
 *	 ACK (0x06) should be sent to the heat pump.
 *	When checksum mismatch,
 *	 NAK (0x15) should be sent to the heat pump.
 *
 *	If heat pump does not receive acknowledge in certain time period,
 *	pump will raise an alarm and alarm mode is activated.
 *
 *	Author: pauli.anttila@gmail.com
 *
 *	Build: gcc -std=gnu99 -o nibegw nibegw.c
 *
 *	3.2.2013    v1.00   Initial version
 *	5.2.2013    v1.01   
 *	4.11.2013   v1.02   Support cheksum and data special cases.
 *	20.12.2013  v1.03   Fixed compiling error.
 *	3.6.2014    v1.04   
 *	4.6.2014    v1.10   More options.
 *	10.9.2014   v1.20   Bidirectional support.
 *	30.6.2015   v1.21   Some fixes.
 *	20.2.2017   v1.22   Separated read and write token support.
 *	7.2.2021    v1.23   Fixed compile error in RasPi.
 *	19.11.2022  v1.30   Support 16-bit addressing.
 */

#include <signal.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <termios.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <time.h>

#define VERSION	"1.23"

#define FALSE	0
#define TRUE	1

#define MIN(a,b) (((a)<(b))?(a):(b))
#define MAX(a,b) (((a)>(b))?(a):(b))

int verbose = 0;
int testmode = FALSE;

void signalCallbackHandler(int signum)
{
	if (verbose) printf("\nExit...caught by signal %d\n", signum);
	exit(1);
}

int initSerialPort(int fd, int hwflowctrl)
{
	struct termios options;
	
	// Get the current options for the port...
	
	tcgetattr(fd, &options);
	
	// Set the baud rates
	cfsetispeed(&options, B9600);
	cfsetospeed(&options, B9600);
	
	// Enable the receiver and set local mode...
	options.c_cflag |= (CLOCAL | CREAD);
	
	// 8 data bits, no parity, 1 stop bit
	options.c_cflag &= ~PARENB;
	options.c_cflag &= ~CSTOPB;
	options.c_cflag &= ~CSIZE;
	options.c_cflag |= CS8;
	
	// Flow control
	options.c_iflag &= ~(IXON | IXOFF | IXANY);
	
	if (hwflowctrl)
		options.c_cflag |= CRTSCTS;		// Enable hardware flow control
	else
		options.c_cflag &= ~CRTSCTS;	// Disable hardware flow control
	
	options.c_cc[VMIN] = 1;				// Min character to be read
	options.c_cc[VTIME] = 1;			// Time to wait for data (tenth of seconds)
	
	// Set the new options
	if (tcsetattr(fd, TCSANOW, &options) < 0 )
	{
		return -1;
	}
	
	return 0;
}

void printMessage(const unsigned char* const message, int msglen)
{
	printf("Data: ");
	for (int l = 0; l < msglen; l++)
		printf("%02X", message[l]);
	printf("\n");
}

int writeDataToSerialPort(int fd, const unsigned char* const message, int msglen)
{
	int retval = -1;
	
	if (verbose > 2) printf("Write data to serial port\n");
	if (verbose > 2) printMessage(message, msglen);
	
	if( write( fd, message, msglen) == msglen)
	{
		tcdrain (fd);
		retval = 0;
	}
	
	return retval;
}

int forwardUdpMsgToSerial(int udpfd, int serialfd)
{
	#define MAX_UDP_MSG_SIZE 50
	unsigned char udp_packet[MAX_UDP_MSG_SIZE];
	int udplen;
	
	if ((udplen = recv(udpfd, udp_packet, MAX_UDP_MSG_SIZE, 0)) > 0)
	{
		if (verbose > 1) printf("Received UDP message...relay message to serial port\n");
		if (verbose > 2) printMessage( udp_packet, udplen);
		
		writeDataToSerialPort(serialfd, udp_packet, udplen);
		return FALSE;
	}
	return TRUE;
}

int sendAck(int fd)
{
	unsigned char ack = 0x06;
	if (verbose > 1) printf("Send ACK (0x06)\n");
	return writeDataToSerialPort(fd, &ack, 1);
}

int sendNak(int fd)
{
	unsigned char nack = 0x15;
	if (verbose > 1) printf("Send NAK (0x15)\n");
	return writeDataToSerialPort(fd, &nack, 1);
}

char* getTimeStamp(char* buffer)
{
	struct timeval  tv;
	struct timezone tz;
	struct tm*      tm;
 
	gettimeofday(&tv, &tz);
	tm = localtime(&tv.tv_sec);
 
	sprintf(buffer, "%d.%d.%d %d:%02d:%02d:%d", 
		   tm->tm_year + 1900,
		   tm->tm_mon + 1,
		   tm->tm_mday,
		   tm->tm_hour,
		   tm->tm_min, tm->tm_sec, tv.tv_usec
		   );
	return buffer;
}

ssize_t readData(int fildes, void *buf, size_t nbyte)
{
	if (testmode)
	{
		unsigned char testdata[] = 
					/* Junk */
					"\x01\x02" \
					
					/* Frame from MODBUS40 */
					"\x5C\x00\x20\x6B\x00\x4B" \
					
					/* Frame from RMU40 */
					"\x5C\x00\x19\x60\x00\x79" \
					
					/* Frame from RMU40 */
					"\x5C\x00\x19\x62\x18\x00\x80\x00\x80\x00\x00\x00\x00\x00"
					"\x80\x00\x00\x00\x00\x00\x0B\x0B\x00\x00\x00\x01\x00\x00"
					"\x05\xE7" \
					
					/* Data frame from MODBUS40 */
					"\x5C\x00\x20\x68\x50\x01\xA8\x1F\x01\x00\xA8\x64\x00\xFD" \
					"\xA7\xD0\x03\x44\x9C\x1E\x00\x4F\x9C\xA0\x00\x50\x9C\x78" \
					"\x00\x51\x9C\x03\x01\x52\x9C\x1B\x01\x87\x9C\x14\x01\x4E" \
					"\x9C\xC6\x01\x47\x9C\x01\x01\x15\xB9\xB0\xFF\x3A\xB9\x4B" \
					"\x00\xC9\xAF\x00\x00\x48\x9C\x0D\x01\x4C\x9C\xE7\x00\x4B" \
					"\x9C\x00\x00\xFF\xFF\x00\x00\xFF\xFF\x00\x00\xFF\xFF\x00" \
					"\x00\x45" \
					
					/* Token Frame from MODBUS40 */
					"\x5C\x00\x20\x69\x00\x49" \
					;
		
		int len = sizeof(testdata);

		if (len > nbyte)
		{
			fprintf(stderr, "Too much test data, limiting %u to %u\n", len, (unsigned int)nbyte);
		}

		len = MIN(len, nbyte);
		memcpy( buf, testdata, len);
		
		static int delay = FALSE;
		if (delay)
			sleep(2); // slow down little bit after first round
		
		delay = TRUE;
		return len;
	}

	return read(fildes, buf, nbyte);
}

/*
 * Return:
 *	>0 if valid message received (return message len)
 *	 0 if OK but message not ready
 *	-1 if invalid message
 *	-2 if checksum fails
 */
int checkMessage(const unsigned char* const data, int len)
{
	if (len >= 1)
	{
		if (data[0] != 0x5C)
			return -1;
		
		if (len >= 6)
		{
			int datalen = data[4];
			
			if (len < datalen + 6)
				return 0;
			
			unsigned char calc_checksum = 0;
			
			// calculate XOR checksum
			for(int i = 1; i < (datalen + 5); i++)
				calc_checksum ^= data[i];
			
			unsigned char msg_checksum = data[datalen + 5];
			
			if (verbose) printf("(calc/recv checksum %02X/%02X = ", calc_checksum, msg_checksum);
			
			if (calc_checksum != msg_checksum)
			{
				// check special case, if checksum is 0x5C (start character), 
				// heat pump seems to send 0xC5 checksum
				if (calc_checksum != 0x5C && msg_checksum != 0xC5)
				{
					if (verbose) printf("ERROR)\n");
					return -2;
				}
			}
			
			if (verbose) printf("OK)\n");
			return datalen + 6;
		}
		
	}
	
	return 0;
}

void printUsage(char* appname)
{
	char* usage = "%s usage:\n\n" \
	"\t-h                 Print help\n" \
	"\t-v                 Print debug information\n" \
	"\t-d <device name>   Serial port device (default: /dev/ttyS0)\n" \
	"\t-a <address>       Remote host address (default: 127.0.0.1)\n" \
	"\t-p <port>          Remote UDP port (default: 9999)\n" \
	"\t-f                 Disable flow control (default: HW)\n" \
	"\t-r <address>       RS-485 address to listen (default: 0x20)\n" \
	"\t-i                 Send all messages by UDP (default: only modbus data)\n" \
	"\t-n                 Don't send acknowledge at all\n" \
	"\t-o                 Send acknowledge to all addresses\n" \
	"\t-t                 Test mode\n" \
	"\t-l <port>          Local UDP port for read commands (default: 10000)\n" \
	"\t-w <port>          Local UDP port for write commands (default: 10001)\n" \
	"\t-q                 Print data in log format\n" \
	;
	
	fprintf (stderr, usage, appname);
}
 
int main(int argc, char **argv)
{
	char *device = "/dev/ttySO";
	char *remoteHost = "127.0.0.1";
	int remotePort = 9999;
	int localPort4readCmds = 10000;
	int localPort4writeCmds = 10001;
	unsigned char rs485addr = 0x20;
	int sendall = FALSE;
	int sendack = TRUE;
	int ackall = FALSE;
	int hwflowctrl = TRUE;
	int log = FALSE;
	
	int c;
	opterr = 0;
	
	while ((c = getopt (argc, argv, "hvd:a:p:r:infotql:w:")) != -1)
	{
		switch (c)
		{
		case 'v':
			verbose++;
			break;

		case 'i':
			sendall = TRUE;
			break;

		case 'n':
			sendack = FALSE;
			break;

		case 'f':
			hwflowctrl = FALSE;
			break;

		case 'o':
			ackall = TRUE;
			break;

		case 't':
			testmode = TRUE;
			break;

		case 'q':
			log = TRUE;
			break;
			
		case 'd':
			device = optarg;
			break;
			
		case 'a':
			remoteHost = optarg;
			break;
			
		case 'p':
			remotePort = atoi(optarg);
			break;

		case 'l':
			localPort4readCmds = atoi(optarg);
			break;

		case 'w':
			localPort4writeCmds = atoi(optarg);
			break;

		case 'r':
			rs485addr = atoi(optarg);
			break;
			
		case '?':
			if (optopt == 'd' || optopt == 'a' || optopt == 'p')
				fprintf (stderr, "Option -%c requires an argument.\n", optopt);
			else if (isprint (optopt))
				fprintf (stderr, "Unknown option `-%c'.\n", optopt);
			else
				fprintf (stderr,
						 "Unknown option character `\\x%x'.\n",
						 optopt);
			return 1;
			
		case 'h':
		default:
			printUsage(argv[0]);
			return 1;
		}
	}
	
	if (verbose)
	{
		printf("NibeGW version:                    %s\n", VERSION);
		printf("Verbose level:                     %i\n", verbose);
		printf("Test mode:                         %s\n", testmode ? "TRUE" : "FALSE");
		printf("Serial port:                       %s\n", device);
		printf("Flow control:                      %s\n", hwflowctrl ? "HW" : "None");
		printf("remote UDP address:                %s:%u\n", remoteHost, remotePort);
		printf("server UDP address for read cmds:  %u\n", localPort4readCmds);
		printf("server UDP address for write cmds: %u\n", localPort4writeCmds);
		printf("RS-485 address to listen:          0x%02X\n", rs485addr);
		printf("Send all messages by UDP:          %s\n", sendall ? "TRUE" : "FALSE");
		printf("Send acknowledge:                  %s\n", sendack ? "TRUE" : "FALSE");
		printf("Send acknowledge to all addresses: %s\n", ackall ? "TRUE" : "FALSE");
	}
	
	// Install signal handlers
	signal(SIGINT, signalCallbackHandler);
	
	int serialport_fd = -1;
	int udp_fd = -1;
	int udp4writeCmds_fd = -1;
	
	// Initialize destination address
	struct sockaddr_in dest;
	memset((char *)&dest, 0, sizeof(dest));
	dest.sin_family = AF_INET;
	dest.sin_addr.s_addr = inet_addr(remoteHost);
	dest.sin_port = htons(remotePort);
	
	// Initialize server address for read commands
	struct sockaddr_in server4read;
	memset((char *)&server4read, 0, sizeof(server4read));
	server4read.sin_family = AF_INET;
	server4read.sin_addr.s_addr = htonl(INADDR_ANY);
	server4read.sin_port = htons(localPort4readCmds);

	// Initialize server address for write commands
	struct sockaddr_in server4write;
	memset((char *)&server4write, 0, sizeof(server4write));
	server4write.sin_family = AF_INET;
	server4write.sin_addr.s_addr = htonl(INADDR_ANY);
	server4write.sin_port = htons(localPort4writeCmds);
	
	int maxdatalen = 200;
	
	if (testmode)
	{
		maxdatalen = 1000;
	}
	
	unsigned char buffer[maxdatalen];
	unsigned char message[maxdatalen];

	for (;;)
	{

		if (testmode == FALSE && serialport_fd < 0)
		{
			if (strncmp(device, "stdin" , 5) == 0)
			{
				if (verbose) printf("Use stdin as virtual serial port\n");
				serialport_fd = STDIN_FILENO;
			}
			else
			{
				// Open the serial port
				if (verbose) printf("Open serial port: %s\n", device);
				serialport_fd = open(device, O_RDWR | O_NOCTTY); // | O_NDELAY
			
				if (serialport_fd < 0)
				{
					fprintf(stderr, "Failed to open %s: %s\n", device, strerror(errno));
				}
			
				// Initialize serial port
				if (initSerialPort(serialport_fd, hwflowctrl) == -1)
				{
					fprintf(stderr, "Failed to set serial port: %s\n", strerror(errno));
				}
			}
		}
		
		
		if ( udp_fd < 0 )
		{
			// Open UDP socket
			udp_fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
			
			if (udp_fd < 0)
			{
				fprintf(stderr, "Failed to open UDP socket for read commands: %s\n", strerror(errno));
			}
			
			if (verbose) printf("Initialize UDP server\n");
			
			// Set non blocking flag to UDP socket
			int flags = fcntl(udp_fd, F_GETFL, 0);
			fcntl(udp_fd, F_SETFL, flags | O_NONBLOCK);

			//bind socket to port
			if( bind(udp_fd, (struct sockaddr*)&server4read, sizeof(server4read) ) == -1)
			{
				fprintf(stderr, "Failed to bind UDP port for read commands: %s\n", strerror(errno));
			}
		}
		
		if ( udp4writeCmds_fd < 0 )
		{
			// Open UDP socket
			udp4writeCmds_fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

			if (udp4writeCmds_fd < 0)
			{
				fprintf(stderr, "Failed to open UDP socket for write commands: %s\n", strerror(errno));
			}

			if (verbose) printf("Initialize UDP server\n");

			// Set non blocking flag to UDP socket
			int flags = fcntl(udp4writeCmds_fd, F_GETFL, 0);
			fcntl(udp4writeCmds_fd, F_SETFL, flags | O_NONBLOCK);

			//bind socket to port
			if( bind(udp4writeCmds_fd, (struct sockaddr*)&server4write, sizeof(server4write) ) == -1)
			{
				fprintf(stderr, "Failed to bind UDP port for write commands: %s\n", strerror(errno));
			}
		}

		if (testmode || serialport_fd >= 0)
		{
			char timestamp[80];
			ssize_t len = 0;

			int startfound = FALSE;
			int index = 0;
			
			// read all available bytes from serial port
			while ((len = readData(serialport_fd, buffer, maxdatalen)) > 0)
			{
				// go throw all bytes read from serial port
				for (int i = 0; i < len; i++)
				{
					if (log) printf("\\x%02X", buffer[i]);
					
					if (startfound == FALSE)
					{
						if (verbose) printf("\n%s: ", getTimeStamp(timestamp));
					}
					
					if (verbose) printf("%02X ", buffer[i]);
					if (verbose > 3) printf("(%c) ", buffer[i]);
					
					if (startfound == FALSE && buffer[i] == 0x5C)
					{
						startfound = TRUE;
						index = 0;
					}
					
					if (startfound)
					{
						if ((index+1) >= maxdatalen)
						{
							// too long message, try to find new start char
							startfound = FALSE;
						}
						else
						{
							message[index++] = buffer[i];
							
							int msglen = checkMessage(message, index);
							
							switch (msglen)
							{
								case 0: // Message ok so far, but not ready
									break;
									
								case -1: // Invalid message
									startfound = FALSE;
									break;
									
								case -2: // Checksum error
									if (message[2] == rs485addr || ackall)
									{
										if (sendack) sendNak(serialport_fd);
									}	
									startfound = FALSE;
									break;
									
								default:
									if (verbose > 1) printf("Valid message received, len=%u\n", msglen);
									
									if (message[2] == rs485addr || ackall)
									{
										// send ack to nibe or read/write messages if token received
										
										int nothingToSend = TRUE;
										
										if (message[3] == 0x69 && message[4] == 0x00)
										{
											if (verbose > 1) printf("Read token received\n");
											nothingToSend = forwardUdpMsgToSerial(udp_fd, serialport_fd);
										}
										else if (message[3] == 0x6b && message[4] == 0x00) {
										  	if (verbose > 1) printf("Write token received\n");
										  	nothingToSend = forwardUdpMsgToSerial(udp4writeCmds_fd, serialport_fd);
										}
										
										if (nothingToSend)
										{
											if (verbose > 1) printf("Nothing to send...");
											if (sendack) sendAck(serialport_fd);
										}
									}
									
									if (message[2] == rs485addr || sendall)
									{
										// send message to remote
										
										if (verbose > 1) printf("Send UDP data to %s:%u\n", remoteHost, remotePort);
										if (verbose > 2) printMessage( message, msglen);
									
										if (sendto(udp_fd, message, msglen + 1, 0 , (struct sockaddr *)&dest, sizeof(dest)) == -1)
										{
											fprintf(stderr, "Failed to send udp packet: %s\n", strerror(errno));
										}
									}
									
									// Wait new message
									startfound = FALSE;
									break;
							}	
						}
					}
				}
			}
			
			if (len < 0)
			{
				if (errno == EINTR)
				{
					if (verbose) printf("Interrupted\n");
					break;
				}
				else
				{
					fprintf(stderr, "Read failed: %s\n", strerror(errno));
					sleep(1);
				}
			}
			
			if (log) fflush(stdout);

		}
		else
		{
			sleep(1);
		}
	}
	
	close(serialport_fd);
	close(udp_fd);
	close(udp4writeCmds_fd);
	
	return 0;
}