farmOS/modules/farm/farm_soil/farm_soil_nrcs/farm_soil_nrcs.module

<?php
/**
 * @file
 * Code for the Farm Soil NRCS feature.
 */

/**
 * Implements hook_menu().
 */
function farm_soil_nrcs_menu() {
  $items['farm/soil/nrcs/stir/autocomplete'] = array(
    'page callback' => 'farm_soil_nrcs_stir_autocomplete',
    'page arguments' => array(5),
    'access callback' => TRUE,
    'type' => MENU_CALLBACK,
  );
  return $items;
}

/**
 * Autocomplete callback for STIR operations.
 */
function farm_soil_nrcs_stir_autocomplete($string) {
  $matches = array();
  $query = db_select('farm_soil_nrcs_stir', 'fsns');
  $query->fields('fsns', array('operation'));
  $query->condition('fsns.operation', '%' . db_like($string) . '%', 'LIKE');
  $query->range(0, 10);
  $result = $query->execute();
  foreach ($result as $row) {
    $matches[$row->operation] = check_plain($row->operation);
  }
  drupal_json_output($matches);
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function farm_soil_nrcs_form_farm_soil_disturbance_form_alter(&$form, &$form_state, $form_id) {

  // Alter the "Activity" field.
  if (!empty($form['disturbance']['disturbance']['activity'])) {

    // Add to the description.
    $description = t('As you type, a list of pre-defined operations will be available to select from. Click on the operation from the dropdown to select it and the "STIR" field below will be filled in automatically.');
    $form['disturbance']['disturbance']['activity']['#description'] = $form['disturbance']['disturbance']['activity']['#description'] . ' ' . $description;

    // Add autocomplete to the "Activity" field that shows operations from
    // the {farm_soil_nrcs_stir} table.
    $form['disturbance']['disturbance']['activity']['#autocomplete_path'] = 'farm/soil/nrcs/stir/autocomplete';

    // Add ajax to regenerate the stir field below.
    $form['disturbance']['disturbance']['activity']['#ajax'] = array(
      'callback' => 'farm_soil_nrcs_stir_value_ajax',
      'wrapper' => 'stir-value',
    );
  }

  // Add a field for the STIR value, auto-populated based on the activity.
  $stir = '';
  if (!empty($form_state['values']['disturbance']['disturbance']['activity'])) {
    $result = db_query('SELECT stir FROM {farm_soil_nrcs_stir} WHERE operation = :operation', array(':operation' => $form_state['values']['disturbance']['disturbance']['activity']))->fetchField();
    if (!empty($result)) {
      $stir = $result;

      // Remove trailing zeros by converting to a PHP float.
      $stir = (float)$stir;

      // Unset the STIR field input value so that it can be replaced via ajax.
      unset($form_state['input']['disturbance']['disturbance']['stir']);
    }
  }
  $form['disturbance']['disturbance']['stir'] = array(
    '#type' => 'textfield',
    '#title' => t('STIR value'),
    '#description' => t('Enter the Soil Tillage Intensity Rating (STIR), calculated using the Revised Universal Soil Loss Equation, Version 2 (RUSLE2). This will be automatically populated if you select a pre-determined operation in the activity field above.'),
    '#element_validate' => array('element_validate_number'),
    '#default_value' => $stir,
    '#prefix' => '<div id="stir-value">',
    '#suffix' => '</div>',
  );

  // Add a submit function to save the STIR value to the log.
  $form['#submit'][] = 'farm_soil_nrcs_disturbance_form_stir_submit';
}

/**
 * Ajax callback for STIR value lookup.
 */
function farm_soil_nrcs_stir_value_ajax($form, &$form_state) {
  return $form['disturbance']['disturbance']['stir'];
}

/**
 * Submit function for saving the STIR value in soil disturbance quick form.
 */
function farm_soil_nrcs_disturbance_form_stir_submit($form, &$form_state) {

  // If no STIR value was entered, bail.
  if (empty($form_state['values']['disturbance']['disturbance']['stir'])) {
    return;
  }

  // Get the log that was saved by the quick form. Bail if not found.
  if (empty($form_state['storage']['log'])) {
    return;
  }
  $log = $form_state['storage']['log'];

  // Create a measurement for the STIR value.
  $measurements = array();
  $measurements[] = array(
    'measure' => 'rating',
    'value' => $form_state['values']['disturbance']['disturbance']['stir'],
    'units' => '',
    'label' => 'STIR',
  );

  // Add the measurement to the log.
  farm_quantity_log_add_measurements($log, $measurements);
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function farm_soil_nrcs_form_log_form_alter(&$form, &$form_state, $form_id) {

  // Only act on the soil test log form.
  if ($form['#bundle'] != 'farm_soil_test') {
    return;
  }

  // Add the Farm Soil NRCS soil name lookup button.
  farm_soil_nrcs_soil_name_lookup_button($form, $form_state);
}

/**
 * Adds a "Look up soil names" button to a form. The form should contain a
 * geofield and a text field for storing the names.
 *
 * This can be added to a form that has the necessary fields via
 * hook_form_alter(). See the this module's hook_form_alter() for an example,
 * which adds the button to the soil test log form.
 *
 * @param array $form
 *   The form array to be altered.
 * @param array $form_state
 *   The form state array.
 */
function farm_soil_nrcs_soil_name_lookup_button(&$form, &$form_state) {

  // Define the field names.
  $geofield = 'field_farm_geofield';
  $textfield = 'field_farm_soil_names';

  // If the geofield or textfield don't exist, bail.
  if (empty($form[$geofield]) || empty($form[$textfield])) {
    return;
  }

  // Add a wrapper around the text field so we can replace it with AJAX.
  $form[$textfield]['#prefix'] = '<div id="soil-names">';
  $form[$textfield]['#suffix'] = '</div>';

  // Add an AJAX button below the text field.
  $form[$textfield]['soil_name_lookup'] = array(
    '#type' => 'submit',
    '#value' => t('Look up soil names'),
    '#submit' => array('farm_soil_nrcs_soil_name_lookup_submit'),
    // No need to validate when submitting this.
    '#limit_validation_errors' => array(),
    '#ajax' => array(
      'callback' => 'farm_soil_nrcs_soil_name_lookup_ajax',
      'wrapper' => 'soil-names',
    ),
  );
}

/**
 * Ajax callback for soil name lookup.
 *
 * @param array $form
 *   The form array.
 * @param array $form_state
 *   The form state array.
 *
 * @return array
 *   Returns the part of the form that will be replaced via AJAX.
 */
function farm_soil_nrcs_soil_name_lookup_ajax($form, $form_state) {
  $textfield = 'field_farm_soil_names';
  return $form[$textfield];
}

/**
 * Submit function for auto-populating the Soil Names field.
 *
 * @param array $form
 *   The form array.
 * @param array $form_state
 *   The form state array.
 */
function farm_soil_nrcs_soil_name_lookup_submit($form, &$form_state) {

  // Start with an empty array of soil names.
  $soil_names = array();

  // Grab the geometry from the geofield input.
  if (!empty($form_state['input']['field_farm_geofield'][LANGUAGE_NONE][0]['geom'])) {
    $wkt = $form_state['input']['field_farm_geofield'][LANGUAGE_NONE][0]['geom'];
  }

  // Request soil names from the NRCS.
  if (!empty($wkt)) {
    $soil_names = farm_soil_nrcs_soil_name_lookup($wkt);
  }

  // If no soil names were returned, print a message.
  if (empty($soil_names)) {
    drupal_set_message(t('Soil names could not be found. Add points to the "Sample points" map above and try again.'), 'warning');
  }

  // If any of the soil names contain commas, wrap them in double-quotes.
  foreach ($soil_names as &$name) {
    if (strpos($name, ',') !== FALSE) {
      $name = '"' . $name . '"';
    }
  }

  // Add the soil names to the input.
  $form_state['input']['field_farm_soil_names'][LANGUAGE_NONE] = implode(', ', $soil_names);

  // Rebuild the form.
  $form_state['rebuild'] = TRUE;
}

/**
 * Send a request to the NRCS server to get names of soils, given a string of
 * Well-Known Text.
 *
 * @param string $wkt
 *   The Well-Known Text representation of the geometry to query.
 *
 * @return array
 *   Returns an array of soil names.
 */
function farm_soil_nrcs_soil_name_lookup($wkt) {

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

  // Assemble the query.
  $query = "SELECT MU.muname, MU.musym, MU.nationalmusym FROM SDA_Get_Mukey_from_intersection_with_WktWgs84('" . $wkt . "') K LEFT JOIN mapunit MU ON K.mukey = MU.mukey";

  // Build the request.
  $url = 'http://sdmdataaccess.sc.egov.usda.gov/tabular/post.rest';
  $params = array(
    'query' => $query,
    'format' => 'json',
  );
  $options = array(
    'method' => 'POST',
    'data' => json_encode($params),
    'headers' => array(
      'Content-Type' => 'application/json',
      'Accept' => 'application/json',
    ),
  );

  // Send the request and get a response.
  $response = drupal_http_request($url, $options);

  // Decode the JSON data.
  $data = json_decode($response->data);

  // If the data is empty, bail.
  if (empty($data) || empty($data->Table) || !is_array($data->Table)) {
    return $soil_names;
  }

  // Process the data into an array of soil names.
  foreach ($data->Table as $row) {
    $soil_name = '';
    $soil_symbols = array();
    if (!empty($row[0])) {
      $soil_name .= $row[0];
    }
    if (!empty($row[1])) {
      $soil_symbols[] = $row[1];
    }
    if (!empty($row[2])) {
      $soil_symbols[] = $row[2];
    }
    if (!empty($soil_symbols)) {
      $soil_name .= ' (' . implode('/', $soil_symbols) . ')';
    }
    if (!empty($soil_name)) {
      $soil_names[] = $soil_name;
    }
  }

  // Return the array of soil names.
  return $soil_names;
}