gpn.php

<?php 

function commerce_group_sku_form_alter(&$form, &$form_state, $form_id) {
  if(strstr($form_id, 'commerce_cart_add_to_cart_form_')) {

    $group = get_user_groups();
    $custom_label = get_custom_label($group);
    $gpn = get_custom_sku($form_state['default_product']->product_id, $group);

    if (!empty($gpn)) {
      $form_state['default_product']->field_gpn_placeholder[LANGUAGE_NONE][0]['value'] = "<div class='field-label'>" . $custom_label . ":</div> <div class='gpn'>" . $gpn . "</div>"; 
      $form_state['default_product']->field_gpn_placeholder[LANGUAGE_NONE][0]['format'] = "full_html"; 
    }
  }
}

function get_custom_sku($product_id, $group) {
  $query = new EntityFieldQuery();
  
  $query->entityCondition('entity_type', 'group_part_number')
    ->entityCondition('bundle', 'group_part_number')
    ->fieldCondition('field_product_gpn_ref', 'product_id', $product_id, '=')
    ->fieldCondition('field_group_gpn_ref', 'target_id', $group, '=');
 
  $result = $query->execute();
  
  if (isset($result['group_part_number'])) {
    $group_part_numbers = array_keys($result['group_part_number']);
    $gpn = entity_load('group_part_number', $group_part_numbers);
  }

  $gpn = reset($gpn);
  return $gpn->field_group_sku_gpn_ref[LANGUAGE_NONE][0]['value'];
}

function get_custom_label($group) {
  $group = node_load($group);

  if (isset($group->field_custom_pn_label[LANGUAGE_NONE][0]['value'])) {
    $custom_label = $group->field_custom_pn_label[LANGUAGE_NONE][0]['value'];
  } else {
    $custom_label = 'Customer PN';
  }

  return $custom_label;
}

function get_user_groups() {
  $groups = og_get_groups_by_user();
  if (is_array($groups)) {
    $group = array_values($groups['node']);
    $group = $group[0];

    return $group;
  }
}