From f3af2baef086b31436430f6602a0cca0a7ea4479 Mon Sep 17 00:00:00 2001
From: Jon Mifsud <info@jonmifsud.com>
Date: Mon, 15 Aug 2016 08:34:59 +0200
Subject: [PATCH] add support to filter by related field (regex etc depending
 on field support)

---
 fields/field.association.php | 47 +++++++++++++++++++++++++++++++++++-
 1 file changed, 46 insertions(+), 1 deletion(-)

diff --git a/fields/field.association.php b/fields/field.association.php
index e02269a..781fbbe 100755
--- a/fields/field.association.php
+++ b/fields/field.association.php
@@ -511,6 +511,12 @@ public function checkPostFieldData($data, &$message, $entry_id = null)
     {
         $message = null;
 
+        if (isset($data['relation_id']) && !is_array($data['relation_id'])){
+            var_dump($data);
+            var_dump($this->get('id'));
+            var_dump($entry_id);die;
+        }
+
         $data = is_array($data) && isset($data['relation_id'])
                 ? array_filter($data['relation_id'])
                 : $data;
@@ -910,6 +916,11 @@ public function fetchFilterableOperators()
                 'filter' => ' ',
                 'help' => __('Find values that are an exact match for the given string.')
             ),
+            array(
+                'title' => 'related:',
+                'filter' => 'related: ',
+                'help' => __('Find values by filtering on the associated field, can use regexp.')
+            ),
             array(
                 'filter' => 'sql: NOT NULL',
                 'title' => 'is not empty',
@@ -937,7 +948,41 @@ public function buildDSRetrievalSQL($data, &$joins, &$where, $andOperation = fal
     {
         $field_id = $this->get('id');
 
-        if (preg_match('/^sql:\s*/', $data[0], $matches)) {
+        if (preg_match('/^related:\s*/', $data[0], $matches)) {
+
+            $data[0] = preg_replace('/^related: /', null, $data[0]);
+
+            $related_field_id = current($this->get('related_field_id'));
+            $related_field = FieldManager::fetch($related_field_id);
+
+            $newJoin = '';
+            $newWhere = '';
+
+            $related_field->buildDSRetrievalSQL($data,$newJoin,$newWhere);
+
+            if (empty($newWhere)){
+                // the filter is empty eg an empty regexp so no need to continue
+                return true;
+            }
+        
+            $relatedTableName = "t{$related_field_id}";
+            if ($related_field->_key){
+                $relatedTableName .= '_'.$related_field->_key;
+            }
+
+            // Join the main field
+            $joins .= " LEFT JOIN
+                            `tbl_entries_data_{$field_id}` AS `t{$field_id}`
+                        ON (`e`.`id` = `t{$field_id}`.`entry_id`)";
+
+            // Join the related field
+            $joins .= " LEFT JOIN
+                            `tbl_entries_data_{$related_field_id}` AS `$relatedTableName`
+                        ON (`t{$field_id}`.`relation_id` = `$relatedTableName`.`entry_id`)";
+
+            $where .= $newWhere;
+
+        } else if (preg_match('/^sql:\s*/', $data[0], $matches)) {
             $data = trim(array_pop(explode(':', $data[0], 2)));
 
             if (strpos($data, "NOT NULL") !== false) {