/**
 * collectd - src/ted.c
 * Copyright (C) 2009  Eric Reed
 *
 * 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:
 *   Eric Reed <ericr at reedhome.net>
 *
 *  This is a collectd module for The Energy Detective: A low-cost whole
 * house energy monitoring system. For more information on TED, see
 * http://theenergydetective.com
 *
 * This module was not created by Energy, Inc. nor is it supported by
 * them in any way. It was created using information from two sources:
 * David Satterfield's TED module for Misterhouse, and Micah Dowty's TED
 * Python Module.
 *
 * This has only tested with the model 1001 RDU, with
 * firmware version 9.01U. The USB port is uses the very common FTDI
 * USB-to-serial chip, so the RDU will show up as a serial device on
 * Windows, Mac OS, or Linux.
 **/

#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

#define EXPECTED_PACKAGE_LENGTH 278
#define ESCAPE 0x10
#define PKT_BEGIN 0x04
#define PKT_END 0x03

#define DEFAULT_DEVICE "/dev/ttyUSB0"

static char *conf_device;
static int conf_retries;

static int fd = -1;

static const char *config_keys[] = {"Device", "Retries"};
static int config_keys_num = STATIC_ARRAY_SIZE(config_keys);

static int ted_read_value(double *ret_power, double *ret_voltage) {
  unsigned char receive_buffer[300];
  unsigned char package_buffer[300];
  unsigned char pkt_request[1] = {0xAA};
  int package_buffer_pos;

  fd_set input;

  /* Initialize timeout structure, set to 2 seconds */
  struct timeval timeout = {.tv_sec = 2};

  int end_flag;
  int escape_flag;

  int status;

  assert(fd >= 0);

  /* Initialize the input set*/
  FD_ZERO(&input);
  FD_SET(fd, &input);

  /* clear out anything in the buffer */
  tcflush(fd, TCIFLUSH);

  status = write(fd, pkt_request, sizeof(pkt_request));
  if (status <= 0) {
    ERROR("ted plugin: write failed.");
    return -1;
  }

  /* Loop until we find the end of the package */
  end_flag = 0;
  package_buffer_pos = 0;
  while (end_flag == 0) {
    ssize_t receive_buffer_length;

    /* check for timeout or input error*/
    status = select(fd + 1, &input, NULL, NULL, &timeout);
    if (status == 0) /* Timeout */
    {
      WARNING("ted plugin: Timeout while waiting for file descriptor "
              "to become ready.");
      return -1;
    } else if ((status < 0) && ((errno == EAGAIN) || (errno == EINTR))) {
      /* Some signal or something. Start over.. */
      continue;
    } else if (status < 0) {
      ERROR("ted plugin: select failed: %s", STRERRNO);
      return -1;
    }

    receive_buffer_length = read(fd, receive_buffer, sizeof(receive_buffer));
    if (receive_buffer_length < 0) {
      if ((errno == EAGAIN) || (errno == EINTR))
        continue;
      ERROR("ted plugin: read(2) failed: %s", STRERRNO);
      return -1;
    } else if (receive_buffer_length == 0) {
      /* Should we close the FD in this case? */
      WARNING("ted plugin: Received EOF from file descriptor.");
      return -1;
    } else if (((size_t)receive_buffer_length) > sizeof(receive_buffer)) {
      ERROR("ted plugin: read(2) returned invalid value %zi.",
            receive_buffer_length);
      return -1;
    }

    /*
     * packet filter loop
     *
     * Handle escape sequences in `receive_buffer' and put the
     * result in `package_buffer'.
     */
    /* We need to see the begin sequence first. When we receive `ESCAPE
     * PKT_BEGIN', we set `package_buffer_pos' to zero to signal that
     * the beginning of the package has been found. */

    escape_flag = 0;
    for (ssize_t i = 0; i < receive_buffer_length; i++) {
      /* Check if previous byte was the escape byte. */
      if (escape_flag == 1) {
        escape_flag = 0;
        /* escape escape = single escape */
        if ((receive_buffer[i] == ESCAPE) && (package_buffer_pos >= 0)) {
          package_buffer[package_buffer_pos] = ESCAPE;
          package_buffer_pos++;
        } else if (receive_buffer[i] == PKT_BEGIN) {
          package_buffer_pos = 0;
        } else if (receive_buffer[i] == PKT_END) {
          end_flag = 1;
          break;
        } else {
          DEBUG("ted plugin: Unknown escaped byte: %#x",
                (unsigned int)receive_buffer[i]);
        }
      } else if (receive_buffer[i] == ESCAPE) {
        escape_flag = 1;
      }
      /* if we are in a package add byte to buffer
       * otherwise throw away */
      else if (package_buffer_pos >= 0) {
        package_buffer[package_buffer_pos] = receive_buffer[i];
        package_buffer_pos++;
      }
    } /* for (i = 0; i < receive_buffer_length; i++) */
  }   /* while (end_flag == 0) */

  /* Check for errors inside the loop. */
  if ((end_flag == 0) || (package_buffer_pos != EXPECTED_PACKAGE_LENGTH))
    return -1;

  /*
   * Power is at positions 247 and 248 (LSB first) in [10kW].
   * Voltage is at positions 251 and 252 (LSB first) in [.1V].
   *
   * Power is in 10 Watt steps
   * Voltage is in volts
   */
  *ret_power = 10.0 * (double)((((int)package_buffer[248]) * 256) +
                               ((int)package_buffer[247]));
  *ret_voltage = 0.1 * (double)((((int)package_buffer[252]) * 256) +
                                ((int)package_buffer[251]));

  /* success */
  return 0;
} /* int ted_read_value */

static int ted_open_device(void) {
  const char *dev;
  struct termios options;

  if (fd >= 0)
    return 0;

  dev = DEFAULT_DEVICE;
  if (conf_device != NULL)
    dev = conf_device;

  fd = open(dev, O_RDWR | O_NOCTTY | O_NDELAY | O_NONBLOCK);
  if (fd < 0) {
    ERROR("ted plugin: Unable to open device %s.", dev);
    return -1;
  }

  /* Get the current options for the port... */
  tcgetattr(fd, &options);
  options.c_cflag = B19200 | CS8 | CSTOPB | CREAD | CLOCAL;
  options.c_iflag = IGNBRK | IGNPAR;
  options.c_oflag = 0;
  options.c_lflag = 0;
  options.c_cc[VTIME] = 20;
  options.c_cc[VMIN] = 250;

  /* Set the new options for the port... */
  tcflush(fd, TCIFLUSH);
  tcsetattr(fd, TCSANOW, &options);

  INFO("ted plugin: Successfully opened %s.", dev);
  return 0;
} /* int ted_open_device */

static void ted_submit(const char *type, double value) {
  value_list_t vl = VALUE_LIST_INIT;

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

  plugin_dispatch_values(&vl);
}

static int ted_config(const char *key, const char *value) {
  if (strcasecmp("Device", key) == 0) {
    sfree(conf_device);
    conf_device = sstrdup(value);
  } else if (strcasecmp("Retries", key) == 0) {
    int tmp;

    tmp = atoi(value);
    if (tmp < 0) {
      ERROR("ted plugin: Invalid retry count: %i", tmp);
      return 1;
    }
    conf_retries = tmp;
  } else {
    ERROR("ted plugin: Unknown config option: %s", key);
    return -1;
  }

  return 0;
} /* int ted_config */

static int ted_read(void) {
  double power;
  double voltage;
  int status;

  status = ted_open_device();
  if (status != 0)
    return -1;

  power = NAN;
  voltage = NAN;
  for (int i = 0; i <= conf_retries; i++) {
    status = ted_read_value(&power, &voltage);
    if (status == 0)
      break;
  }

  if (status != 0)
    return -1;

  ted_submit("power", power);
  ted_submit("voltage", voltage);

  return 0;
} /* int ted_read */

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

  return 0;
} /* int ted_shutdown */

void module_register(void) {
  plugin_register_config("ted", ted_config, config_keys, config_keys_num);
  plugin_register_read("ted", ted_read);
  plugin_register_shutdown("ted", ted_shutdown);
} /* void module_register */