/**
 * collectd - src/multimeter.c
 * Copyright (C) 2005,2006  Peter Holik
 *
 * 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 2 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, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 *
 * Authors:
 *   Peter Holik <peter at holik.at>
 *
 * Used multimeter: Metex M-4650CR
 **/

#include "collectd.h"

#include "plugin.h"
#include "utils/common/common.h"

#if HAVE_TERMIOS_H && HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#include <termios.h>
#else
#error "No applicable input method."
#endif

static int fd = -1;

#define LINE_LENGTH 14
static int multimeter_read_value(double *value) {
  int retry = 3; /* sometimes we receive garbadge */

  do {
    struct timeval time_end;

    tcflush(fd, TCIFLUSH);

    if (gettimeofday(&time_end, NULL) < 0) {
      ERROR("multimeter plugin: gettimeofday failed: %s", STRERRNO);
      return -1;
    }
    time_end.tv_sec++;

    while (1) {
      char buf[LINE_LENGTH];
      char *range;
      int status;
      fd_set rfds;
      struct timeval timeout;
      struct timeval time_now;

      status = swrite(fd, "D", 1);
      if (status != 0) {
        ERROR("multimeter plugin: swrite failed.");
        return -1;
      }

      FD_ZERO(&rfds);
      FD_SET(fd, &rfds);

      if (gettimeofday(&time_now, NULL) < 0) {
        ERROR("multimeter plugin: "
              "gettimeofday failed: %s",
              STRERRNO);
        return -1;
      }
      if (timeval_cmp(time_end, time_now, &timeout) < 0)
        break;

      status = select(fd + 1, &rfds, NULL, NULL, &timeout);

      if (status > 0) /* usually we succeed */
      {
        status = read(fd, buf, LINE_LENGTH);

        if ((status < 0) && ((errno == EAGAIN) || (errno == EINTR)))
          continue;

        /* Format: "DC 00.000mV  \r" */
        if (status > 0 && status == LINE_LENGTH) {
          *value = strtod(buf + 2, &range);

          if (range > (buf + 6)) {
            range = buf + 9;

            switch (*range) {
            case 'p':
              *value *= 1.0E-12;
              break;
            case 'n':
              *value *= 1.0E-9;
              break;
            case 'u':
              *value *= 1.0E-6;
              break;
            case 'm':
              *value *= 1.0E-3;
              break;
            case 'k':
              *value *= 1.0E3;
              break;
            case 'M':
              *value *= 1.0E6;
              break;
            case 'G':
              *value *= 1.0E9;
              break;
            }
          } else
            return -1; /* Overflow */

          return 0; /* value received */
        } else
          break;
      } else if (!status) /* Timeout */
      {
        break;
      } else if ((status == -1) && ((errno == EAGAIN) || (errno == EINTR))) {
        continue;
      } else /* status == -1 */
      {
        ERROR("multimeter plugin: "
              "select failed: %s",
              STRERRNO);
        break;
      }
    }
  } while (--retry);

  return -2; /* no value received */
} /* int multimeter_read_value */

static int multimeter_init(void) {
  char device[] = "/dev/ttyS ";

  for (int i = 0; i < 10; i++) {
    device[strlen(device) - 1] = i + '0';

    if ((fd = open(device, O_RDWR | O_NOCTTY)) != -1) {
      struct termios tios = {0};
      int rts = TIOCM_RTS;
      double value;

      tios.c_cflag = B1200 | CS7 | CSTOPB | CREAD | CLOCAL;
      tios.c_iflag = IGNBRK | IGNPAR;
      tios.c_oflag = 0;
      tios.c_lflag = 0;
      tios.c_cc[VTIME] = 3;
      tios.c_cc[VMIN] = LINE_LENGTH;

      tcflush(fd, TCIFLUSH);
      tcsetattr(fd, TCSANOW, &tios);
      ioctl(fd, TIOCMBIC, &rts);

      if (multimeter_read_value(&value) < -1) {
        close(fd);
        fd = -1;
      } else {
        INFO("multimeter plugin: Device "
             "found at %s",
             device);
        return 0;
      }
    }
  }

  ERROR("multimeter plugin: No device found");
  return -1;
}
#undef LINE_LENGTH

static void multimeter_submit(double value) {
  value_list_t vl = VALUE_LIST_INIT;

  vl.values = &(value_t){.gauge = value};
  vl.values_len = 1;
  sstrncpy(vl.plugin, "multimeter", sizeof(vl.plugin));
  sstrncpy(vl.type, "multimeter", sizeof(vl.type));

  plugin_dispatch_values(&vl);
}

static int multimeter_read(void) {
  double value;

  if (fd < 0)
    return -1;

  if (multimeter_read_value(&value) != 0)
    return -1;

  multimeter_submit(value);
  return 0;
} /* int multimeter_read */

static int multimeter_shutdown(void) {
  if (fd >= 0) {
    close(fd);
    fd = -1;
  }

  return 0;
}

void module_register(void) {
  plugin_register_init("multimeter", multimeter_init);
  plugin_register_read("multimeter", multimeter_read);
  plugin_register_shutdown("multimeter", multimeter_shutdown);
} /* void module_register */