From ffa596f4bbc31d1396b027221ed045b0ca4c11f5 Mon Sep 17 00:00:00 2001
From: John van Breda <john.vanbreda@biodiverseit.co.uk>
Date: Thu, 3 Aug 2023 15:49:30 +0100
Subject: [PATCH 1/2] Coalesce function ES special field handler.

---
 .../libraries/RestApiElasticsearch.php        | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/modules/rest_api/libraries/RestApiElasticsearch.php b/modules/rest_api/libraries/RestApiElasticsearch.php
index 6b34f2133..1d23fea16 100644
--- a/modules/rest_api/libraries/RestApiElasticsearch.php
+++ b/modules/rest_api/libraries/RestApiElasticsearch.php
@@ -555,6 +555,34 @@ private function esGetSpecialFieldAttrValue(array $doc, array $params) {
     return implode('; ', $r);
   }
 
+  /**
+   * Special field handler returns the value for the first non-empty field.
+   *
+   * Provide a comma-separated list of field names as the parameter. The value
+   * of the first field in the list to have a non-empty value is returned.
+   *
+   * @param array $doc
+   *   Elasticsearch document.
+   * @param array $params
+   *   Parameters defined for the special field.
+   *
+   * @return string
+   *   Field value.
+   */
+  private function esGetSpecialFieldCoalesce(array $doc, array $params) {
+    if (count($params) !== 1) {
+      return 'Incorrect params for coalesce field';
+    }
+    $fields = explode(',', $params[0]);
+    foreach ($fields as $field) {
+      $value = $this->getRawEsFieldValue($doc, $field);
+      if ($value !== '') {
+        return $value;
+      }
+    }
+    return '';
+  }
+
   /**
    * Special field handler which returns a constant value.
    *
@@ -1918,6 +1946,9 @@ private function getEsPostData($postObj, $format, $file, $isSearch) {
         elseif (preg_match('/^#query(.*)#$/', $field)) {
           $fields[] = 'identification.query';
         }
+        elseif (preg_match('/^#coalesce:(.*)#$/', $field, $matches)) {
+          $fields = array_merge($fields, explode(',', $matches[1]));
+        }
         elseif (preg_match('/^#attr_value:(event|sample|parent_event|occurrence):(\d+)#$/', $field, $matches)) {
           $key = $matches[1] === 'parent_event' ? 'parent_attributes' : 'attributes';
           // Tolerate sample or event for entity parameter.

From aa75ba34e23c6856942db358a4f195407f6b10ef Mon Sep 17 00:00:00 2001
From: John van Breda <john.vanbreda@biodiverseit.co.uk>
Date: Thu, 3 Aug 2023 15:51:08 +0100
Subject: [PATCH 2/2] Changelog and version

---
 CHANGELOG.md                   | 6 ++++++
 application/config/version.php | 4 ++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ba65877eb..850304adf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+# Version 8.22.0
+*2023-08-03*
+
+* Adds a special field handler for Elasticsearch data that supports a coalesce function, returning
+  the value of the first field that has a non-empty value, selected from a list of provided fields.
+
 # Version 8.21.0
 *2023-06-28*
 
diff --git a/application/config/version.php b/application/config/version.php
index fe9b8135a..5d71ae7e6 100644
--- a/application/config/version.php
+++ b/application/config/version.php
@@ -29,14 +29,14 @@
  *
  * @var string
  */
-$config['version'] = '8.21.9';
+$config['version'] = '8.22.0';
 
 /**
  * Version release date.
  *
  * @var string
  */
-$config['release_date'] = '2023-08-01';
+$config['release_date'] = '2023-08-03';
 
 /**
  * Link to the code repository downloads page.