Basic support for negative searches with parentheses (#4503)

* Basic support for negative searches with parentheses
* `!((author:Alice intitle:hello) OR (author:Bob intitle:world))`
* `(author:Alice intitle:hello) !(author:Bob intitle:world)`
* `!(S:1 OR S:2)`

* Minor documentation / comment

* Remove syslog debug line

3 files changed, 22 insertions, 4 deletions

diff --git a/app/Models/BooleanSearch.php b/app/Models/BooleanSearch.php
index 332757556..b1c7bbd3b 100644
--- a/app/Models/BooleanSearch.php
+++ b/app/Models/BooleanSearch.php
@@ -10,7 +10,7 @@ class FreshRSS_BooleanSearch {
 	/** @var array<FreshRSS_BooleanSearch|FreshRSS_Search> */
 	private $searches = array();
 
-	/** @var string 'AND' or 'OR' */
+	/** @var string 'AND' or 'OR' or 'AND NOT' */
 	private $operator;
 
 	public function __construct(string $input, int $level = 0, $operator = 'AND') {
@@ -123,7 +123,20 @@ class FreshRSS_BooleanSearch {
 				$hasParenthesis = true;
 
 				$before = trim($before);
-				if (preg_match('/\bOR$/i', $before)) {
+				if (preg_match('/[!-]$/i', $before)) {
+					// Trim trailing negation
+					$before = substr($before, 0, -1);
+
+					// The text prior to the negation is a BooleanSearch
+					$searchBefore = new FreshRSS_BooleanSearch($before, $level + 1, $nextOperator);
+					if (count($searchBefore->searches()) > 0) {
+						$this->searches[] = $searchBefore;
+					}
+					$before = '';
+
+					// The next BooleanSearch will have to be combined with AND NOT instead of default AND
+					$nextOperator = 'AND NOT';
+				} elseif (preg_match('/\bOR$/i', $before)) {
 					// Trim trailing OR
 					$before = substr($before, 0, -2);
 
diff --git a/app/Models/Entry.php b/app/Models/Entry.php
index d20f5f2a7..8d20e5412 100644
--- a/app/Models/Entry.php
+++ b/app/Models/Entry.php
@@ -364,10 +364,12 @@ class FreshRSS_Entry extends Minz_Model {
 		$ok = true;
 		foreach ($booleanSearch->searches() as $filter) {
 			if ($filter instanceof FreshRSS_BooleanSearch) {
-				// BooleanSearches are combined by AND (default) or OR (special case) operator and are recursive
+				// BooleanSearches are combined by AND (default) or OR or AND NOT (special cases) operators and are recursive
 				if ($filter->operator() === 'OR') {
 					$ok |= $this->matches($filter);
-				} else {
+				} elseif ($filter->operator() === 'AND NOT') {
+					$ok &= !$this->matches($filter);
+				} else {	// AND
 					$ok &= $this->matches($filter);
 				}
 			} elseif ($filter instanceof FreshRSS_Search) {
diff --git a/app/Models/EntryDAO.php b/app/Models/EntryDAO.php
index d69702c60..02552affe 100644
--- a/app/Models/EntryDAO.php
+++ b/app/Models/EntryDAO.php
@@ -770,6 +770,9 @@ SQL;
 				if ($filterSearch !== '') {
 					if ($search !== '') {
 						$search .= $filter->operator();
+					} elseif ($filter->operator() === 'AND NOT') {
+						// Special case if we start with a negation (there is already the default AND before)
+						$search .= ' NOT';
 					}
 					$search .= ' (' . $filterSearch . ') ';
 					$values = array_merge($values, $filterValues);