farmOS/modules/farm/farm_quantity/farm_quantity.module

<?php
/**
 * @file
 * Farm quantity module.
 */

// Include Features code.
include_once 'farm_quantity.features.inc';

/**
 * Implements hook_permission().
 */
function farm_quantity_permission() {
  $perms = array(
    'administer farm_quantity module' => array(
      'title' => t('Administer farm quantity module'),
    ),
  );
  return $perms;
}

/**
 * Implements hook_farm_access_perms().
 */
function farm_quantity_farm_access_perms($role) {

  // Assemble a list of entity types provided by this module.
  $types = array(
    'taxonomy' => array(
      'farm_quantity_units',
    ),
  );

  // Grant different CRUD permissions based on the role.
  $perms = array();
  switch ($role) {

    // Farm Manager and Worker
    case 'Farm Manager':
    case 'Farm Worker':
      $perms = farm_access_entity_perms($types);
      break;

    // Farm Viewer
    case 'Farm Viewer':
      $perms = farm_access_entity_perms($types, array('view'));
      break;
  }

  // If the role is "Farm Manager", grant access to quantity configuration.
  if ($role == 'Farm Manager') {
    $perms[] = 'administer farm_quantity module';
  }

  return $perms;
}

/**
 * Implements hook_menu().
 */
function farm_quantity_menu() {

  // Quantity configuration form.
  $items['admin/config/farm/quantity'] = array(
    'title' => 'Quantity',
    'description' => 'Quantity configuration settings.',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('farm_quantity_settings_form'),
    'access arguments' => array('administer farm_quantity module'),
  );

  return $items;
}

/**
 * Quantity settings form.
 */
function farm_quantity_settings_form($form, &$form_state) {

  // Metric or US/Imperial.
  $form['farm_quantity_unit_system'] = array(
    '#type' => 'radios',
    '#title' => t('System of measurement'),
    '#description' => t('Select the system of measurement you would like to use in farmOS.'),
    '#options' => array(
      'metric' => t('Metric'),
      'us' => t('US/Imperial'),
    ),
    '#default_value' => variable_get('farm_quantity_unit_system', 'metric'),
  );

  // Return it as a system settings form.
  return system_settings_form($form);
}

/**
 * Define information about available quantity measures.
 *
 * @return array
 *   Returns an array of measure information.
 */
function farm_quantity_measures() {
  return array(
    'count' => array(
      'label' => t('Count'),
    ),
    'length' => array(
      'label' => t('Length'),
    ),
    'weight' => array(
      'label' => t('Weight'),
    ),
    'volume' => array(
      'label' => t('Volume'),
    ),
    'time' => array(
      'label' => t('Time'),
    ),
    'temperature' => array(
      'label' => t('Temperature'),
    ),
    'water_content' => array(
      'label' => t('Water content'),
    ),
    'value' => array(
      'label' => t('Value'),
    ),
    'rating' => array(
      'label' => t('Rating'),
    ),
    'ratio' => array(
      'label' => t('Ratio'),
    ),
    'probability' => array(
      'label' => t('Probability'),
    ),
  );
}

/**
 * Define available options for the Measure field.
 */
function farm_quantity_measure_options() {

  // Start an empty options array.
  $options = array();

  // Load information about measures.
  $measures = farm_quantity_measures();

  // Iterate through the measures and build a list of options.
  foreach ($measures as $measure => $data) {
    $options[$measure] = $data['label'];
  }

  // Return the array of options.
  return $options;
}

/**
 * Extract quantity data from a log, with optional filters for measure/label.
 *
 * @param Log $log
 *   The log object to extract quantity information from.
 * @param string $measure
 *   The quantity measure to search for (ie: weight).
 * @param string $label
 *   The quantity label to search for.
 *
 * @return array
 *   Returns a structured array of information about the quantities recorded
 *   on the log.
 */
function farm_quantity_log_data(Log $log, $measure = NULL, $label = NULL) {

  // Start with an empty data array.
  $data = array();

  // Load the log entity metadata wrapper.
  $log_wrapper = entity_metadata_wrapper('log', $log);

  // If there are no quantities, bail.
  if (empty($log_wrapper->field_farm_quantity)) {
    return $data;
  }

  // Iterate over the quantities.
  foreach ($log_wrapper->field_farm_quantity as $quantity) {

    // If a measure is specified, and it doesn't match, skip this one.
    if (!empty($measure) && $quantity->field_farm_quantity_measure->value() != $measure) {
      continue;
    }

    // If a label is specified, and it doesn't match, skip this one.
    if (!empty($label) && $quantity->field_farm_quantity_label->value() != $measure) {
      continue;
    }

    // Get the quantity value and convert to a decimal.
    $value = '';
    if (!empty($quantity->field_farm_quantity_value->value())) {
      if (!empty($quantity->field_farm_quantity_value->value()['fraction'])) {
        $value = $quantity->field_farm_quantity_value->value()['fraction']->toDecimal(0, TRUE);
      }
    }

    // Get the quantity units name.
    $units = '';
    if (!empty($quantity->field_farm_quantity_units->value())) {
      if (!empty($quantity->field_farm_quantity_units->value()->name)) {
        $units = $quantity->field_farm_quantity_units->value()->name;
      }
    }

    // Add quantity data to the array.
    $data[] = array(
      'measure' => $quantity->field_farm_quantity_measure->value(),
      'value' => $value,
      'units' => $units,
      'label' => $quantity->field_farm_quantity_label->value(),
    );
  }

  // Return the data.
  return $data;
}

/**
 * Load an asset's latest log with a given quantity measure and/or label.
 *
 * @param FarmAsset $asset
 *   The farm_asset object to look for.
 * @param string $measure
 *   The quantity measure to search for (ie: weight).
 * @param string $label
 *   The quantity label to search for.
 * @param int $time
 *   Unix timestamp limiter. Only logs before this time will be included.
 *   Defaults to the current time. Set to 0 to load the absolute last.
 * @param bool $done
 *   Whether or not to only show logs that are marked as "done". Defaults to
 *   TRUE.
 *
 * @return Log|bool
 *   Returns a log entity. FALSE if something goes wrong.
 */
function farm_quantity_asset_log(FarmAsset $asset, $measure = NULL, $label = NULL, $time = REQUEST_TIME, $done = TRUE) {

  // If the asset doesn't have an ID (for instance if it is new and hasn't been
  // saved yet), bail.
  if (empty($asset->id)) {
    return FALSE;
  }

  // Make a query for loading the latest quantity log.
  $query = farm_quantity_asset_log_query($asset->id, $measure, $label, $time, $done);

  // Execute the query and gather the log id.
  $result = $query->execute();
  $log_id = $result->fetchField();

  // If a log id exists, load and return it.
  if (!empty($log_id)) {
    return log_load($log_id);
  }
  return FALSE;
}

/**
 * Build a query to find the latest log of an asset that defines a quantity.
 *
 * @param int $asset_id
 *   The asset id to search for.
 * @param string $measure
 *   The quantity measure to search for (ie: weight).
 * @param string $label
 *   The quantity label to search for.
 * @param int $time
 *   Unix timestamp limiter. Only logs before this time will be included.
 *   Defaults to the current time. Set to 0 to load the absolute last.
 * @param bool $done
 *   Whether or not to only show logs that are marked as "done". Defaults to
 *   TRUE.
 *
 * @return \SelectQuery
 *   Returns a SelectQuery object.
 */
function farm_quantity_asset_log_query($asset_id, $measure = NULL, $label = NULL, $time = REQUEST_TIME, $done = TRUE) {

  /**
   * Please read the comments in farm_log_asset_query() to understand how this
   * works, and to be aware of the limitations and responsibilities we have in
   * this function with regard to sanitizing query inputs.
   */

  // Ensure that $measure and $label are valid strings, because we use them
  // directly in the query's WHERE statements below. This is defensive code.
  // See note about views_join_subquery in farm_log_asset_query().
  if (!is_null($measure)) {
    $measures = farm_quantity_measure_options();
    if (!array_key_exists($measure, $measures)) {
      $measure = '';
    }
  }
  if (!is_null($label)) {
    $label = db_escape_field($label);
  }

  // Use the farm_log_asset_query() helper function to start a query object.
  $query = farm_log_asset_query($asset_id, $time, $done);

  // Join in the Quantity field collection and filter to only include logs that
  // have quantities.
  $query->join('field_data_field_farm_quantity', 'ss_fdffq', "ss_fdffq.entity_type = 'log' AND ss_fdffq.entity_id = ss_log.id AND ss_fdffq.deleted = 0");
  $query->where('ss_fdffq.field_farm_quantity_value IS NOT NULL');

  // Filter to only include logs with a matching measure.
  if (!empty($measure)) {
    $query->join('field_data_field_farm_quantity_measure', 'ss_fdffqm', "ss_fdffqm.entity_id = ss_fdffq.field_farm_quantity_value AND ss_fdffqm.deleted = 0");
    $query->where("ss_fdffqm.field_farm_quantity_measure_value = '" . $measure . "'");
  }

  // Filter to only include logs with a matching label.
  if (!empty($label)) {
    $query->join('field_data_field_farm_quantity_label', 'ss_fdffql', "ss_fdffql.entity_id = ss_fdffq.field_farm_quantity_value AND ss_fdffql.deleted = 0");
    $query->where("ss_fdffql.field_farm_quantity_label_value = '" . $label . "'");
  }

  // Return the query object.
  return $query;
}