module.php

<?php 

/*
 * Gets logged in user's Organic Group ID
 */
function og_taxonomy_menu_get_user_group() {
  $groups = og_get_groups_by_user();

  if (is_array($groups)) {
    $group = array_values($groups['node']);
    $group = $group[0];
    $group = node_load($group);
  } else {
    // load default DT group
    $group = node_load('2456');
  }

  return $group->nid;
}

/*
 * 
 */
function og_taxonomy_menu_get_terms($vocabulary) {
  $vocabulary = taxonomy_vocabulary_machine_name_load($vocabulary);
  $terms = entity_load('taxonomy_term', FALSE, array('vid' => $vocabulary->vid));
  return $terms;
}

function og_taxonomy_menu_get_term_nodes($tid) {
  // seems this will only query what the current user has access to
  $query = new EntityFieldQuery();
  $query->entityCondition('entity_type', 'node')
    ->entityCondition('bundle', 'commerce_product')
    ->fieldCondition('field_product_category', 'tid', $tid);

  $result = $query->execute();

  if (is_array($result['node'])) {
    $nids = array_keys($result['node']);
  }

  return $nids;
}

/*
 * Makes menu block available in block management.
 */
function og_taxonomy_menu_block_info() {
  $blocks['og_taxonomy_menu'] = array(
    'info' => t('Browse by Category'),
  );

  $blocks['og_taxonomy_menu_fire'] = array(
    'info' => t('Browse by Category'),
  );

  return $blocks;
}

/*
 * 
 */
function og_taxonomy_menu_filter_results($vocabulary) {

  $tids = og_taxonomy_menu_get_terms($vocabulary);

  foreach ($tids as $tid) {
    // get array of NIDs for this TID
    $nids = og_taxonomy_menu_get_term_nodes($tid->tid);

    if ($nids) {
      // add the NIDs to the flat array structure
      foreach ($nids as $nid) {
        $nid_list[] = $nid;
      }
    }
  }

  foreach ($nid_list AS $nid) {
    // query all taxonomy reference fields
    // @TODO abstract to allow vocabulary arg filter to be passed
    // @TODO add Published == true
    // @TODO add node type check? MAYBE
    $results = db_query('SELECT tid FROM {taxonomy_index} WHERE nid = :nid', array(':nid' => $nid));

    foreach ($results as $result) {

      $term = taxonomy_term_load($result->tid);

      if ($term->vocabulary_machine_name == $vocabulary) {
        $terms[] = $term->tid;
      }
    }
  }

  $children = array_unique($terms);
  $tree = array();
  $html = '';

  foreach ($children as $child) {
    $parent_tid = taxonomy_get_parents($child);
    $parent_tid = array_values($parent_tid);
    $parent_tid = $parent_tid[0]->tid;

    $tree[$parent_tid]['items'][preg_replace("/[^A-Za-z0-9 ]/", '', taxonomy_term_load($child)->name)] = $child;
    $tree[$parent_tid]['weight']  = taxonomy_term_load($parent_tid)->weight;
  }

  // sort parent items by weight
  uasort($tree, 'og_taxonomy_menu_sort_by_weight');

  $html .= '<ul class="menu">';

  foreach($tree as $parent_tid => $children) {
    $parent_link = og_taxonomy_menu_build_link($parent_tid);

    $html .= '<li class="menu__item">' . $parent_link;
    $html .= '<ul class="menu">';

    // sort children alphabetically, since weights are non-unique
    ksort($children['items']);

    foreach($children['items'] as $child_tid) {
      $child_link = og_taxonomy_menu_build_link($child_tid);

      $html .= '<li class="menu__item is-leaf leaf">' . $child_link . '</li>';
    }
    $html .= '</ul>';
    $html .= '</li>';
  }
  $html .= '</ul>';

  return $html;
}

function og_taxonomy_menu_sort_by_weight($a, $b) {
      return $a['weight'] - $b['weight'];
}

function og_taxonomy_menu_build_link($tid) {
  $tid  = taxonomy_term_load($tid);
  $uri  = taxonomy_term_uri($tid);
  $path = drupal_get_path_alias($uri['path']);
  $link = "<a href='/" . $path . "'>" . $tid->name . "</a>";

  return $link;
}

function og_taxonomy_menu_block_view($delta) {

  $block = array();

  switch ($delta) {
    //$nids = og_taxonomy_menu_filter_results();
    case 'og_taxonomy_menu':
      $block['subject'] = t('Browse by Category');
      $block['content'] = og_taxonomy_menu_filter_results('catalog');
    break;

    case 'og_taxonomy_menu_fire':
      $block['subject'] = t('Browse by Fire Category');
      $block['content'] = og_taxonomy_menu_filter_results('fire_catalog');
    break;
  }

  return $block;
}