/* Copyright 2019 King Kévin <kingkevin@cuvoodoo.info>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
/* This program connects to the WEB/WITRN/Qway U2(p) USB meter using the USB HID interface and reads the measurement values.
 *
 * The device's USB VID:PID is 0716:5030.
 * Don't forget to grant USB permission to connect to the device.
 * This program does not support connecting to multiple devices, and will only connect to the first it finds.
 */
#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>
#include <signal.h>
#include <hidapi/hidapi.h>
#include <netdb.h>

#define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))

static void die(const char* format, ...)
{
	va_list args;
	va_start(args, format);
	vfprintf(stderr, format, args);
	va_end(args);
	exit(1);
}

/* watchdog called after alarm timeout
 * @param[in] sig alarm signal
 */
static void watchdog(int sig)
{
	(void)sig; // argument not used
	die("exiting due to inactivity\n");
}

/* original trigger message from vendor software
"\xff\x55\x58\x8a\x13\x79\x06\x57\x1a\x01\x0a\x02\x00\x00\x00\x00" \
"\x5e\x00\x00\x00\xff\x55\x2f\xb2\x8b\xdc\x5a\xd4\x1a\x2c\xa4\x00" \
"\xa4\x40\x00\x00\x00\x00\x00\x00\x00\x00\x0e\x74\x21\x4f\x40\x75" \
"\x23\x19\x40\x75\xcc\x01\x01\x00\x02\x04\x00\x00\x5e\x00\xe7\x06";
*/
// simplified trigger message (without checksum) to get a couple of measurements
static char trigger[] = \
"\xff\x55\x00\x00\x00\x00\x00\x00\x1a\x01\x0a\x00\x00\x00\x00\x00" \
"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" \
"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" \
"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00";

static hid_device *handle = NULL;

struct u2_measurement_t {
	uint8_t payload[64];
	uint8_t seconds;
	uint8_t increment1;
	uint8_t increment2;
	float increment3;
	uint8_t increment4;
	float vbus_voltage1; // in V
	float vbus_current1; // in A
	float vbus_current2; // in A
	float vbus_current3; // in A
	float vbus_power; // in W
	float dp_voltage; // in V
	float dm_voltage; // in V
	float temperature_internal; // in °C
	float temperature_external; // in °C
	float vbus_voltage2; // in V
	float vbus_current4; // in A
	bool checksum1;
	bool checksum2;
};

static void trigger_mesurement(void)
{
	if (NULL == handle) {
		die("open a HID device first\n");
	}
	// update checksum
	uint8_t checksum = 0;
	for (uint8_t i = 8; i < 62; i++) {
		checksum += trigger[i];
	}
	trigger[62] = checksum;
	checksum = 0;
	for (uint8_t i = 0; i < 62; i++) {
		checksum += trigger[i];
	}
	trigger[63] = checksum;
	// add report ID prefix to message
	unsigned char report[65] = {0};
	memcpy(&report[1], trigger, 64);
	int rc = hid_write(handle, report, ARRAY_SIZE(report));
	if (rc < 0) {
		die("could not write\n");
	}
}

int main(int argc, char* argv[])
{
	int rc; // return code
	char str[200]; // general strings
	wchar_t wstr[100]; // wide strings (used by hidapi)
	bool debug = false; // print debug information

	if (argc >= 2) {
		if (0 == strcmp(argv[1],"-h")) {
			printf("%s [-d|-h] [host port]\n", argv[0]);
			printf("connect to WEB/WITRN/QWay U2 over USB and output measurements as CSV\n\n");
			printf("\t-h\tprint help\n");
			printf("\t-d\tenable debug output (disables CSV output)\n");
			printf("\thost port\tinfluxDB UDP host and port to send voltage/current measurements to\n");
			exit(0);
		} if (0 == strcmp(argv[1],"-d")) {
			debug = true;
		}
	}

	signal(SIGALRM, watchdog); // setup watchdog
	alarm(10); // start watchdog (in case connecting to the U2 gets stuck)

	// UDP socket to send data to influxdb
	int influxdb_fd = 0;
	struct addrinfo* res = 0;
	if (argc >= 3) {
		struct addrinfo hints;
		memset(&hints, 0, sizeof(hints));
		hints.ai_family = AF_UNSPEC;
		hints.ai_socktype = SOCK_DGRAM;
		hints.ai_protocol = 0;
		hints.ai_flags = AI_ADDRCONFIG;
		if (0 != getaddrinfo(argv[argc -2], argv[argc - 1], &hints, &res)) {
			die("failed to resolve remote socket address\n");
		}
		influxdb_fd = socket(res->ai_family,res->ai_socktype,res->ai_protocol);
		if (0 == influxdb_fd) {
			die("could not create UDP socket\n");
		}
	}

	rc = hid_init();
	if (rc < 0) {
		die("could not initialize HID\n");
	}

	handle = hid_open(0x0716, 0x5030, NULL); // open Qway/WITRN.U2
	if (handle) {
		if (debug) {
			printf("WEB-U2 opened\n");
		}
	} else {
		die("could not open WEB-U2 (make sure it is connected and you have access rights)\n");
	}

	rc = hid_get_manufacturer_string(handle, wstr, ARRAY_SIZE(wstr));
	if (rc < 0) {
		die("could not get manufacturer string\n");
	}
	if (debug) {
		wcstombs(str, wstr, ARRAY_SIZE(str));
		printf("manufacturer: %s\n", str);
	}

	rc = hid_get_product_string(handle, wstr, ARRAY_SIZE(wstr));
	if (rc < 0) {
		die("could not get product string\n");
	}
	if (debug) {
		wcstombs(str, wstr, ARRAY_SIZE(str));
		printf("product: %s\n", str);
	}

	// Read the Serial Number String
	rc = hid_get_serial_number_string(handle, wstr, ARRAY_SIZE(wstr));
	if (rc < 0) {
		die("could not get serial string\n");
	}
	if (debug) {
		wcstombs(str, wstr, ARRAY_SIZE(str));
		printf("serial: %s\n", str);
	}

	if (!debug) { // print CSV header
		printf("timer (in s),super fast timer,fast timer,timer,slow timer,VBUS voltage 1 (in V),VBUS current 1 (in A),VBUS current 2 (in A),VBUS current 3 (in A),VBUS power (in W),D+ voltage (in V),D- voltage (in V),internal temperature (in °C),external temperature (in °C),VBUS voltage 2 (in V),VBUS current 4 (in A)\n");
	}

	bool run = true; // read from USB as long as true
	struct u2_measurement_t meas; // to store the parsed measurement values
	// line containing values for influxdb
	char line[22 * 2];
	int line_len;
	while (run) {
		rc = hid_read_timeout(handle, meas.payload, ARRAY_SIZE(meas.payload), 50); // wait for max 50 ms for a measurement
		if (rc < 0) {
			die("could not read\n");
		} else if (0 == rc) { // timeout
			trigger_mesurement();
			if (debug) {
				printf("trigger measurement\n");
			}
			continue;
		}

		alarm(10); // restart watchdog

		// parse measurement values
		meas.seconds = meas.payload[2];
		meas.increment1 = meas.payload[3];
		meas.increment2 = meas.payload[4];
		meas.increment3 = meas.payload[5] + meas.payload[6] / 100.0;
		meas.increment4 = meas.payload[7];
		meas.vbus_voltage1 = *(float*)(&meas.payload[10]); // in V
		meas.vbus_current1 = *(float*)(&meas.payload[14]); // in A
		meas.vbus_current2 = *(float*)(&meas.payload[18]); // in A
		meas.vbus_current3 = *(float*)(&meas.payload[22]); // in A
		meas.vbus_power = *(float*)(&meas.payload[26]); // in W
		meas.dp_voltage = *(float*)(&meas.payload[30]); // in V
		meas.dm_voltage = *(float*)(&meas.payload[34]); // in V
		meas.temperature_internal = *(float*)(&meas.payload[38]); // in °C
		meas.temperature_external = *(float*)(&meas.payload[42]); // in °C
		meas.vbus_voltage2 = *(float*)(&meas.payload[46]); // in V
		meas.vbus_current4 = *(float*)(&meas.payload[50]); // in A

		// calculate checksums
		// the 64th byte is the sum of the first 62 bytes
		uint8_t checksum = 0;
		for (uint8_t i = 0; i < 62; i++) {
			checksum += meas.payload[i];
		}
		meas.checksum2 = (checksum == meas.payload[63]);
		// the 63th byte is the sum of bytes 8 to 62 (without the timer information)
		checksum = 0;
		for (uint8_t i = 8; i < 62; i++) {
			checksum += meas.payload[i];
		}
		meas.checksum1 = (checksum == meas.payload[62]);

		if (debug) { // print payload and values aligned
			for (uint8_t i = 0; i < ARRAY_SIZE(meas.payload); i++) {
				printf("%02x ", meas.payload[i]);
			}
			printf("\n");

			if (meas.checksum1 && meas.checksum2) {
				printf("const ");
				printf("%03us  ", meas.seconds);
				//printf("++"); // meas.increment1 is simply incrementing
				printf("++"); // meas.increment2 is simply incrementing
				printf("%03u.%02u ", (uint8_t)meas.increment3, (uint8_t)(meas.increment3 * 100) % 100);
				printf("++"); // meas.increment4 is simply incrementing
				printf(" const ");
				printf("U:%.04fV   ", meas.vbus_voltage1);
				printf("I:%.04fA   ", meas.vbus_current1);
				printf("I:%.04fA   ", meas.vbus_current2);
				printf("I:%.04fA   ", meas.vbus_current3);
				printf("P:%.04fW   ", meas.vbus_power);
				printf("D+:%.04fV  ", meas.dp_voltage);
				printf("D-:%.04fV  ", meas.dm_voltage);
				printf("Int:%.02fC  ", meas.temperature_internal);
				printf("Ext:%.02fC ", meas.temperature_external);
				printf("U:%.04fV   ", meas.vbus_voltage2);
				printf("I:%.04fA   ", meas.vbus_current4);
				printf("\n");
			} else {
				printf("invalid checksum\n");
			}
		} else { // print CSV line
			if (meas.checksum1 && meas.checksum2) {
				printf("%u,", meas.seconds);
				printf("%u,", meas.increment1);
				printf("%u,", meas.increment2);
				printf("%.02f,", meas.increment3);
				printf("%u,", meas.increment4);
				printf("%.04f,", meas.vbus_voltage1);
				printf("%.04f,", meas.vbus_current1);
				printf("%.04f,", meas.vbus_current2);
				printf("%.04f,", meas.vbus_current3);
				printf("%.04f,", meas.vbus_power);
				printf("%.04f,", meas.dp_voltage);
				printf("%.04f,", meas.dm_voltage);
				printf("%.02f,", meas.temperature_internal);
				printf("%.02f,", meas.temperature_external);
				printf("%.04f,", meas.vbus_voltage2);
				printf("%.04f", meas.vbus_current4);
				printf("\n");
			}
		}
		if (influxdb_fd) {
			line_len = snprintf(line, sizeof(line), "voltage value=%.04f\ncurrent value=%.04f\n", meas.vbus_voltage1, meas.vbus_current1);
			if (-1 == sendto(influxdb_fd, line, line_len, 0, res->ai_addr, res->ai_addrlen)) {
				die("could not send UDP packet\n");
				goto close;
			}
		}
	}

close:
	hid_close(handle);
	handle = NULL;
	rc = hid_exit();
	if (rc < 0) {
		die("could not exit HID\n");
	}

	return 0;
}