/*
 * visomat-data-downloader - download data from Visomat Double Comfort
 *
 * The Visomat Double Comfort is a blood pressure meter with a USB port.
 *
 * Copyright (C) 2013  Antonio Ospite <ospite@studenti.unina.it>
 *
 * 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 <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <libusb.h>

#define STX 0x02
#define ETX 0x03

#define DEVICE_VID 0x1247
#define DEVICE_PID 0x00f8

#define EP_IN 0x82
#define EP_OUT 0x03

#define BASE_YEAR 2000

typedef enum {
	VISOMAT_CMD_DUMP_EEPROM,
	VISOMAT_CMD_UNKNOWN1, /* maybe the firmware revision */
	VISOMAT_CMD_GET_DATETIME,
	VISOMAT_CMD_START_MEASURE1,
	VISOMAT_CMD_UNKNOWN2, /* XXX transmission hangs */
	VISOMAT_CMD_UNKNOWN3,
} visomat_command;

static char command_codes[][3] = {
	[VISOMAT_CMD_DUMP_EEPROM]    = "R00",
	[VISOMAT_CMD_UNKNOWN1]       = "R01",
	[VISOMAT_CMD_GET_DATETIME]   = "R02",
	[VISOMAT_CMD_START_MEASURE1] = "R03",
	[VISOMAT_CMD_UNKNOWN2]       = "R04",
	[VISOMAT_CMD_UNKNOWN3]       = "R05",
};

struct datetime  {
	unsigned int year;
	unsigned int month;
	unsigned int day;
	unsigned int hour;
	unsigned int minute;
};

struct pressure  {
	unsigned int systolic;
	unsigned int diastolic;
	unsigned int pulses;
};

static inline int extract_datetime(unsigned char *buffer, struct datetime *d)
{
	int ret;

	ret = sscanf((char *)buffer, "%02u%02u%02u%02u%02u",
		     &d->year,
		     &d->month,
		     &d->day,
		     &d->hour,
		     &d->minute);
	if (ret != 5)
		return -EINVAL;

	d->year += BASE_YEAR;

	return 0;
}

/* 
 * NOTE: the CSV output is meant to be compatible with one from the Windows
 * program, which uses the %d/%m/%Y date format, so that's not my fault.
 */
static void print_record_csv_compat(struct datetime *d, struct pressure *p)
{
	unsigned int pulse_pressure;

	printf("%02u/%02u/%04u;%02u.%02u;",
	       d->day, d->month, d->year, d->hour, d->minute);

	printf("%u;%u;%u;", p->systolic, p->diastolic, p->pulses);

	pulse_pressure = p->systolic - p->diastolic;
	printf("%u;", pulse_pressure);

	if (p->pulses > 100)
		printf("tachycardia");
	else if (p->pulses < 60)
		printf("bradycardia");

	printf("\n");
}

/* TODO separate better decoding data from printing it */
static int decode_eeprom(unsigned char *buffer, unsigned int len)
{
	int ret;
	unsigned int n;
	unsigned int i;
	unsigned int j;
	unsigned int user_id;
	unsigned int num_records;
	struct datetime d;
	struct pressure p;

	if (buffer[0] != STX || buffer[1] != 'M' || buffer[len - 1] != ETX)
		return -EINVAL;

	/* skip the initial STX */
	i = 1;

	/* and the final ETX */
	n = len - 1;

	while (i < n) {
		/* Each user record begins with 'M', maybe for "Memory" */
		if (buffer[i] == 'M') {
			/* i tracks the bytes consumed */
			i += 1;


			ret = sscanf((char *)(buffer + i), "%1u%02u",
				     &user_id, &num_records);
			if (ret != 2)
				return -EINVAL;

			/* user_id and num_records take 3 bytes */
			i += 3;

			printf("# User: %d\n", user_id);

			for (j = 0; j < num_records; j++) {
				ret = extract_datetime(buffer + i, &d);
				if (ret < 0)
					return ret;

				/* datetime takes 10 bytes */
				i += 10;

				ret = sscanf((char *)(buffer + i),
					     "%04u%03u%03u",
					     &p.systolic,
					     &p.diastolic,
					     &p.pulses);
				if (ret != 3)
					return -EINVAL;

				/* pressure data is 10 bytes */
				i += 10;

				print_record_csv_compat(&d, &p);
			}
		}
	}

	return 0;
}

static int decode_datetime(unsigned char *buffer, unsigned int len)
{
	int ret;
	unsigned char code[4] = { 0 };
	struct datetime d;
	unsigned char *pbuffer = buffer;

	if (len != 15)
		return -EINVAL;

	code[0] = buffer[1];
	code[1] = buffer[2];
	code[2] = buffer[3];

	ret = extract_datetime(pbuffer + 4, &d);
	if (ret < 0)
		return ret;

	printf("# (%s) Date: %04d/%02d/%02d %02d:%02d\n",
	       code, d.year, d.month, d.day, d.hour, d.minute);

	return 0;
}

static int send_command(libusb_device_handle *dev, visomat_command cmd)
{
	int ret;
	int transferred;
	unsigned char request[5];

	request[0] = STX;
	request[1] = command_codes[cmd][0];
	request[2] = command_codes[cmd][1];
	request[3] = command_codes[cmd][2];
	request[4] = ETX;

	transferred = 0;
	ret = libusb_bulk_transfer(dev, EP_OUT, request, sizeof(request), &transferred, 0);
	if (ret != 0 || transferred != sizeof(request)) {
		fprintf(stderr, "Error: sending request: %d (%s)\ttransferred: %d (expected %zu)\n",
			ret, libusb_error_name(ret), transferred, sizeof(request));
		return ret;
	}
	return 0;
}

static int get_response(libusb_device_handle *dev,
			unsigned char *buffer,
			unsigned int len)
{
	int ret;
	int transferred;
	unsigned char response[64] = { 0 };
	unsigned int i;

	i = 0;
	do {
		unsigned int j;

		transferred = 0;
		ret = libusb_bulk_transfer(dev, EP_IN, response, sizeof(response), &transferred, 5000);
		if (ret != 0) {
			fprintf(stderr, "Error getting response: %d (%s)\ttransferred: %d (expected %zu)\n",
				ret, libusb_error_name(ret), transferred, sizeof(response));
			return ret;
		}

		for (j = 0; j < (unsigned int)transferred; j++) {
			buffer[i] = response[j];
			i += 1;
		}

	} while (buffer[i - 1] != ETX && i < len);

	/* Check the buffer is a valid response packet */
	if (buffer[0] != STX || buffer[i - 1] != ETX)
		return -EINVAL;

	return i;
}

/* Candidates for a future public API, if a shared library will ever be made */
#define visomat_device libusb_device_handle
static int visomat_dump_eeprom(visomat_device *dev)
{
	/* Assuming an EEPROM of 1 KiB  */
	unsigned char buffer[1024] = { 0 };
	int ret;

	ret = send_command(dev, VISOMAT_CMD_DUMP_EEPROM);
	if (ret < 0)
		return ret;

	ret = get_response(dev, buffer, sizeof(buffer));
	if (ret < 0)
		return ret;

	ret = decode_eeprom(buffer, ret);
	if (ret < 0)
		return ret;

	return 0;
}

static int visomat_get_datetime(visomat_device *dev)
{
	unsigned char buffer[255] = { 0 };
	int ret;

	ret = send_command(dev, VISOMAT_CMD_GET_DATETIME);
	if (ret < 0)
		return ret;

	ret = get_response(dev, buffer, sizeof(buffer));
	if (ret < 0)
		return ret;

	ret = decode_datetime(buffer, ret);
	if (ret < 0)
		return ret;

	return 0;
}

int main(void)
{
	int ret;
	libusb_device_handle *dev;

	libusb_init(NULL);
	libusb_set_debug(NULL, LIBUSB_LOG_LEVEL_INFO);

	dev = libusb_open_device_with_vid_pid(NULL, DEVICE_VID, DEVICE_PID);
	if (dev == NULL) {
		fprintf(stderr, "Couldn't open device.\n");
		ret = -ENODEV;
		goto out_libusb_exit;
	}

	libusb_set_configuration(dev, 1);
	libusb_detach_kernel_driver(dev, 1);
	libusb_claim_interface(dev, 1);

	ret = visomat_get_datetime(dev);
	if (ret < 0)
		goto out;

	ret = visomat_dump_eeprom(dev);

out:
	libusb_close(dev);
out_libusb_exit:
	libusb_exit(NULL);
	return ret;
}