From 421e08dffef55240fec5f0ebb379cdcef43fef6a Mon Sep 17 00:00:00 2001
From: Torsten Landsiedel <torsten.landsiedel@gmx.de>
Date: Tue, 23 Jan 2024 11:36:11 +0100
Subject: [PATCH 1/9] First draft of adding regexp_replace function to SQLite

Fixes #47
---
 ...s-wp-sqlite-pdo-user-defined-functions.php | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php b/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
index 7d4ac5ee..646c3c4d 100644
--- a/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
+++ b/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
@@ -68,6 +68,7 @@ public function __construct( $pdo ) {
 		'isnull'         => 'isnull',
 		'if'             => '_if',
 		'regexp'         => 'regexp',
+		'regexp_replace' => 'regexp_replace',
 		'field'          => 'field',
 		'log'            => 'log',
 		'least'          => 'least',
@@ -492,6 +493,43 @@ public function regexp( $pattern, $field ) {
 		return preg_match( $pattern, $field );
 	}
 
+	/**
+	 * Method to emulate MySQL REGEXP_REPLACE() function.
+	 *
+	 * @param string|array $pattern     Regular expression to search for (or array of strings).
+	 * @param string|array $replacement The string or an array with strings to replace.
+	 * @param string|array $field       Haystack.
+	 *
+	 * @return Array if the field parameter is an array, or a string otherwise.
+	 */
+	public function regexp_replace( $pattern, $replacement, $field ) {
+		/*
+		 * If the original query says REGEXP BINARY
+		 * the comparison is byte-by-byte and letter casing now
+		 * matters since lower- and upper-case letters have different
+		 * byte codes.
+		 *
+		 * The REGEXP function can't be easily made to accept two
+		 * parameters, so we'll have to use a hack to get around this.
+		 *
+		 * If the first character of the pattern is a null byte, we'll
+		 * remove it and make the comparison case-sensitive. This should
+		 * be reasonably safe since PHP does not allow null bytes in
+		 * regular expressions anyway.
+		 */
+		if ( "\x00" === $pattern[0] ) {
+			$pattern = substr( $pattern, 1 );
+			$flags   = '';
+		} else {
+			// Otherwise, the search is case-insensitive.
+			$flags = 'i';
+		}
+		$pattern = str_replace( '/', '\/', $pattern );
+		$pattern = '/' . $pattern . '/' . $flags;
+
+		return preg_replace( $pattern, $replacement, $field );
+	}
+
 	/**
 	 * Method to emulate MySQL FIELD() function.
 	 *

From ddc87fa7e707c93e3860121c15f6c3d7eb05f969 Mon Sep 17 00:00:00 2001
From: Torsten Landsiedel <torsten.landsiedel@gmx.de>
Date: Thu, 13 Jun 2024 12:01:06 +0200
Subject: [PATCH 2/9] Add first stub for unit test

---
 tests/WP_SQLite_Translator_Tests.php | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tests/WP_SQLite_Translator_Tests.php b/tests/WP_SQLite_Translator_Tests.php
index 260689c1..9dd1eeae 100644
--- a/tests/WP_SQLite_Translator_Tests.php
+++ b/tests/WP_SQLite_Translator_Tests.php
@@ -117,6 +117,18 @@ public function regexpOperators() {
 		);
 	}
 
+	public function testRegexpReplace() {
+		$this->assertQuery(
+			"INSERT INTO _options (option_name, option_value) VALUES ('first', 'test');"
+		);
+		$this->assertQuery(
+			"INSERT INTO _options (option_name, option_value) VALUES ('second', 'ignore test');"
+		);
+
+		$this->assertQuery( "SELECT FROM _options WHERE REGEXP_REPLACE(option_value, 'ignore ', '') = 'test'" );
+		$this->assertCount( 2, $this->engine->get_query_results() );
+	}
+
 	public function testInsertDateNow() {
 		$this->assertQuery(
 			"INSERT INTO _dates (option_name, option_value) VALUES ('first', now());"

From 7ff503563cf5708b29569ea5c0afbdafac012e43 Mon Sep 17 00:00:00 2001
From: Torsten Landsiedel <torsten.landsiedel@gmx.de>
Date: Thu, 13 Jun 2024 14:49:48 +0200
Subject: [PATCH 3/9] Fix unit test - 2nd attempt

---
 .../sqlite/class-wp-sqlite-pdo-user-defined-functions.php       | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php b/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
index e11653a4..50987d29 100644
--- a/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
+++ b/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
@@ -503,7 +503,7 @@ public function regexp( $pattern, $field ) {
 	 *
 	 * @return Array if the field parameter is an array, or a string otherwise.
 	 */
-	public function regexp_replace( $pattern, $replacement, $field ) {
+	public function regexp_replace( $field, $pattern, $replacement ) {
 		/*
 		 * If the original query says REGEXP BINARY
 		 * the comparison is byte-by-byte and letter casing now

From 05d20b2fce80301772ef86d8b3f44ad3f761ba4f Mon Sep 17 00:00:00 2001
From: Torsten Landsiedel <torsten.landsiedel@gmx.de>
Date: Thu, 13 Jun 2024 15:09:06 +0200
Subject: [PATCH 4/9] Fixing unit test - third attempt

---
 tests/WP_SQLite_Translator_Tests.php | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tests/WP_SQLite_Translator_Tests.php b/tests/WP_SQLite_Translator_Tests.php
index bb3b362a..43a68d13 100644
--- a/tests/WP_SQLite_Translator_Tests.php
+++ b/tests/WP_SQLite_Translator_Tests.php
@@ -120,13 +120,13 @@ public static function regexpOperators() {
 
 	public function testRegexpReplace() {
 		$this->assertQuery(
-			"INSERT INTO _options (option_name, option_value) VALUES ('first', 'test');"
+			"INSERT INTO _options (option_name, option_value) VALUES ('test-ignore', '1');"
 		);
 		$this->assertQuery(
-			"INSERT INTO _options (option_name, option_value) VALUES ('second', 'ignore test');"
+			"INSERT INTO _options (option_name, option_value) VALUES ('test-remove', '2');"
 		);
 
-		$this->assertQuery( "SELECT FROM _options WHERE REGEXP_REPLACE(option_value, 'ignore ', '') = 'test'" );
+		$this->assertQuery( "SELECT * FROM _options WHERE REGEXP_REPLACE(option_name, '(-ignore|-remove)', '') = 'test'" );
 		$this->assertCount( 2, $this->engine->get_query_results() );
 	}
 

From 28d2b76c9bdf8a890379c6451fb61ade2c9b9e4a Mon Sep 17 00:00:00 2001
From: Torsten Landsiedel <torsten.landsiedel@gmx.de>
Date: Thu, 13 Jun 2024 15:19:14 +0200
Subject: [PATCH 5/9] Add additional tests to show the value is not modified

---
 tests/WP_SQLite_Translator_Tests.php | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tests/WP_SQLite_Translator_Tests.php b/tests/WP_SQLite_Translator_Tests.php
index 43a68d13..f7821d4b 100644
--- a/tests/WP_SQLite_Translator_Tests.php
+++ b/tests/WP_SQLite_Translator_Tests.php
@@ -128,6 +128,11 @@ public function testRegexpReplace() {
 
 		$this->assertQuery( "SELECT * FROM _options WHERE REGEXP_REPLACE(option_name, '(-ignore|-remove)', '') = 'test'" );
 		$this->assertCount( 2, $this->engine->get_query_results() );
+
+		$result1 = $this->engine->query( "SELECT option_value FROM _options WHERE option_name='test-ignore';" );
+		$result2 = $this->engine->query( "SELECT option_value FROM _options WHERE option_name='test-remove';" );
+		$this->assertEquals( '1', $result1[0]->option_value );
+		$this->assertEquals( '2', $result2[0]->option_value );
 	}
 
 	public function testInsertDateNow() {

From f521f5afd339855a05bff3e46f31c12e12b5f027 Mon Sep 17 00:00:00 2001
From: Torsten Landsiedel <torsten.landsiedel@gmx.de>
Date: Thu, 13 Jun 2024 15:24:28 +0200
Subject: [PATCH 6/9] Update tests/WP_SQLite_Translator_Tests.php

---
 tests/WP_SQLite_Translator_Tests.php | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/tests/WP_SQLite_Translator_Tests.php b/tests/WP_SQLite_Translator_Tests.php
index f7821d4b..43a68d13 100644
--- a/tests/WP_SQLite_Translator_Tests.php
+++ b/tests/WP_SQLite_Translator_Tests.php
@@ -128,11 +128,6 @@ public function testRegexpReplace() {
 
 		$this->assertQuery( "SELECT * FROM _options WHERE REGEXP_REPLACE(option_name, '(-ignore|-remove)', '') = 'test'" );
 		$this->assertCount( 2, $this->engine->get_query_results() );
-
-		$result1 = $this->engine->query( "SELECT option_value FROM _options WHERE option_name='test-ignore';" );
-		$result2 = $this->engine->query( "SELECT option_value FROM _options WHERE option_name='test-remove';" );
-		$this->assertEquals( '1', $result1[0]->option_value );
-		$this->assertEquals( '2', $result2[0]->option_value );
 	}
 
 	public function testInsertDateNow() {

From cfb123c8678e52a10d9c003cd6b6a1821306e865 Mon Sep 17 00:00:00 2001
From: Torsten Landsiedel <torsten.landsiedel@gmx.de>
Date: Thu, 13 Jun 2024 16:07:19 +0200
Subject: [PATCH 7/9] Add additional check to copy MySQL behavior

---
 tests/WP_SQLite_Translator_Tests.php                 | 12 ++++++++++++
 .../class-wp-sqlite-pdo-user-defined-functions.php   |  6 ++++++
 2 files changed, 18 insertions(+)

diff --git a/tests/WP_SQLite_Translator_Tests.php b/tests/WP_SQLite_Translator_Tests.php
index 43a68d13..21118fba 100644
--- a/tests/WP_SQLite_Translator_Tests.php
+++ b/tests/WP_SQLite_Translator_Tests.php
@@ -128,6 +128,18 @@ public function testRegexpReplace() {
 
 		$this->assertQuery( "SELECT * FROM _options WHERE REGEXP_REPLACE(option_name, '(-ignore|-remove)', '') = 'test'" );
 		$this->assertCount( 2, $this->engine->get_query_results() );
+
+		$this->assertQuery( 'SELECT REGEXP_REPLACE( null, 'a', 'x') as result' );
+		$results = $this->engine->get_query_results();
+		$this->assertEquals( null, $results[0]->result );
+
+		$this->assertQuery( 'SELECT REGEXP_REPLACE( 'abc', null, 'x') as result' );
+		$results = $this->engine->get_query_results();
+		$this->assertEquals( null, $results[0]->result );
+
+		$this->assertQuery( 'SELECT REGEXP_REPLACE( 'abc', 'a', null) as result' );
+		$results = $this->engine->get_query_results();
+		$this->assertEquals( null, $results[0]->result );
 	}
 
 	public function testInsertDateNow() {
diff --git a/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php b/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
index 50987d29..9030d81e 100644
--- a/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
+++ b/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
@@ -518,6 +518,12 @@ public function regexp_replace( $field, $pattern, $replacement ) {
 		 * be reasonably safe since PHP does not allow null bytes in
 		 * regular expressions anyway.
 		 */
+		
+		/* Return null if one of the required parameter is null */
+		if ( is_null( $field ) || is_null( $pattern ) || is_null( $replacement ) ) {
+			return null;
+		}
+
 		if ( "\x00" === $pattern[0] ) {
 			$pattern = substr( $pattern, 1 );
 			$flags   = '';

From 0ade800be33baba09b232dc3f35be5e2b2a5aa7c Mon Sep 17 00:00:00 2001
From: Torsten Landsiedel <torsten.landsiedel@gmx.de>
Date: Thu, 13 Jun 2024 16:10:18 +0200
Subject: [PATCH 8/9] Fix quotes and coding standards issue

---
 tests/WP_SQLite_Translator_Tests.php                        | 6 +++---
 .../sqlite/class-wp-sqlite-pdo-user-defined-functions.php   | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/WP_SQLite_Translator_Tests.php b/tests/WP_SQLite_Translator_Tests.php
index 21118fba..f9899723 100644
--- a/tests/WP_SQLite_Translator_Tests.php
+++ b/tests/WP_SQLite_Translator_Tests.php
@@ -129,15 +129,15 @@ public function testRegexpReplace() {
 		$this->assertQuery( "SELECT * FROM _options WHERE REGEXP_REPLACE(option_name, '(-ignore|-remove)', '') = 'test'" );
 		$this->assertCount( 2, $this->engine->get_query_results() );
 
-		$this->assertQuery( 'SELECT REGEXP_REPLACE( null, 'a', 'x') as result' );
+		$this->assertQuery( "SELECT REGEXP_REPLACE( null, 'a', 'x') as result" );
 		$results = $this->engine->get_query_results();
 		$this->assertEquals( null, $results[0]->result );
 
-		$this->assertQuery( 'SELECT REGEXP_REPLACE( 'abc', null, 'x') as result' );
+		$this->assertQuery( "SELECT REGEXP_REPLACE( 'abc', null, 'x') as result" );
 		$results = $this->engine->get_query_results();
 		$this->assertEquals( null, $results[0]->result );
 
-		$this->assertQuery( 'SELECT REGEXP_REPLACE( 'abc', 'a', null) as result' );
+		$this->assertQuery( "SELECT REGEXP_REPLACE( 'abc', 'a', null) as result" );
 		$results = $this->engine->get_query_results();
 		$this->assertEquals( null, $results[0]->result );
 	}
diff --git a/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php b/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
index 9030d81e..e8c00a04 100644
--- a/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
+++ b/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
@@ -518,7 +518,7 @@ public function regexp_replace( $field, $pattern, $replacement ) {
 		 * be reasonably safe since PHP does not allow null bytes in
 		 * regular expressions anyway.
 		 */
-		
+
 		/* Return null if one of the required parameter is null */
 		if ( is_null( $field ) || is_null( $pattern ) || is_null( $replacement ) ) {
 			return null;

From 380e5412d158028312b8e1ea53295162aea4b685 Mon Sep 17 00:00:00 2001
From: Torsten Landsiedel <torsten.landsiedel@gmx.de>
Date: Thu, 13 Jun 2024 17:04:07 +0200
Subject: [PATCH 9/9] Adding more inline comments and add a check for an empty
 pattern

---
 tests/WP_SQLite_Translator_Tests.php                      | 8 +++++++-
 .../sqlite/class-wp-sqlite-pdo-user-defined-functions.php | 5 +++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/tests/WP_SQLite_Translator_Tests.php b/tests/WP_SQLite_Translator_Tests.php
index f9899723..71070eca 100644
--- a/tests/WP_SQLite_Translator_Tests.php
+++ b/tests/WP_SQLite_Translator_Tests.php
@@ -119,16 +119,17 @@ public static function regexpOperators() {
 	}
 
 	public function testRegexpReplace() {
+		/* Testing if an actual replacment works correctly */
 		$this->assertQuery(
 			"INSERT INTO _options (option_name, option_value) VALUES ('test-ignore', '1');"
 		);
 		$this->assertQuery(
 			"INSERT INTO _options (option_name, option_value) VALUES ('test-remove', '2');"
 		);
-
 		$this->assertQuery( "SELECT * FROM _options WHERE REGEXP_REPLACE(option_name, '(-ignore|-remove)', '') = 'test'" );
 		$this->assertCount( 2, $this->engine->get_query_results() );
 
+		/* If one of the required parameters is null, the return value is null, copying the MYSQL/MariaDB behavior */
 		$this->assertQuery( "SELECT REGEXP_REPLACE( null, 'a', 'x') as result" );
 		$results = $this->engine->get_query_results();
 		$this->assertEquals( null, $results[0]->result );
@@ -140,6 +141,11 @@ public function testRegexpReplace() {
 		$this->assertQuery( "SELECT REGEXP_REPLACE( 'abc', 'a', null) as result" );
 		$results = $this->engine->get_query_results();
 		$this->assertEquals( null, $results[0]->result );
+
+		/* Providing an empty pattern should produce an error - but we changed that to null to avoid breaking things */
+		$this->assertQuery( "SELECT REGEXP_REPLACE( 'abc', '', 'x') as result" );
+		$results = $this->engine->get_query_results();
+		$this->assertEquals( null, $results[0]->result );
 	}
 
 	public function testInsertDateNow() {
diff --git a/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php b/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
index e8c00a04..816ccb86 100644
--- a/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
+++ b/wp-includes/sqlite/class-wp-sqlite-pdo-user-defined-functions.php
@@ -524,6 +524,11 @@ public function regexp_replace( $field, $pattern, $replacement ) {
 			return null;
 		}
 
+		/* Return null if the pattern is empty - this changes MySQL/MariaDB behavior! */
+		if ( empty( $pattern ) ) {
+			return null;
+		}
+
 		if ( "\x00" === $pattern[0] ) {
 			$pattern = substr( $pattern, 1 );
 			$flags   = '';