[ticket/17516] Remove dependency on topological sort library

PHPBB-17516

phpBB/phpbb/db/migration/schema_generator.php

@@ -14,21 +14,17 @@
 namespace phpbb\db\migration;
 
 use Closure;
-use LogicException;
 use phpbb\config\config;
 use phpbb\db\driver\driver_interface;
 use phpbb\db\migrator;
 use phpbb\db\tools\tools_interface;
 use UnexpectedValueException;
-use CHItA\TopologicalSort\TopologicalSort;
 
 /**
 * The schema generator generates the schema based on the existing migrations
 */
 class schema_generator
 {
-	use TopologicalSort;
-
 	/** @var config */
 	protected $config;
 
@@ -103,24 +99,56 @@ class schema_generator
 			return $this->tables;
 		}
 
-		$migrations = $this->class_names;
-		$filter = function($class_name) {
-			return !migrator::is_migration($class_name);
-		};
-
-		$edges = function($class_name) {
-			return $class_name::depends_on();
-		};
-
-		$apply_for_each = function($class_name) {
-			$this->apply_migration_to_schema($class_name);
-		};
-
-		try
+		$dependency_counts = [];
+		$dependencies = [];
+		$applicable_migrations = [];
+		$migration_count = 0;
+		foreach ($this->class_names as $class_name)
 		{
-			$this->topologicalSort($migrations, $edges, true, $apply_for_each, $filter);
+			if (!migrator::is_migration($class_name))
+			{
+				continue;
+			}
+
+			$migration_count++;
+			$migration_dependencies = $class_name::depends_on();
+			if (empty($migration_dependencies))
+			{
+				$applicable_migrations[] = $class_name;
+				continue;
+			}
+
+			$dependency_counts[$class_name] = count($migration_dependencies);
+			foreach ($migration_dependencies as $migration_dependency)
+			{
+				$dependencies[$migration_dependency][] = $class_name;
+			}
 		}
-		catch (LogicException $e)
+
+		$applied_migrations = 0;
+		while (!empty($applicable_migrations))
+		{
+			$migration = array_pop($applicable_migrations);
+			$this->apply_migration_to_schema($migration);
+			++$applied_migrations;
+
+			if (!array_key_exists($migration, $dependencies))
+			{
+				continue;
+			}
+
+			$dependents = $dependencies[$migration];
+			foreach ($dependents as $dependent)
+			{
+				$dependency_counts[$dependent]--;
+				if ($dependency_counts[$dependent] === 0)
+				{
+					$applicable_migrations[] = $dependent;
+				}
+			}
+		}
+
+		if ($migration_count !== $applied_migrations)
 		{
 			throw new UnexpectedValueException(
 				"Migrations either have circular dependencies or unsatisfiable dependencies."