CFile::processDuplicates

static function processDuplicates($ID)
{
	$result = self::DELETE_ALL;

	//Part 1: the file is a duplicate of another file, including referenses to itself
	$original = InternalFileDuplicateTable::query()
		->addSelect("*")
		->where("DUPLICATE_ID", $ID)
		->fetch();

	//Part 2: find duplicates of the file
	$duplicates = InternalFileDuplicateTable::query()
		->where("ORIGINAL_ID", $ID)
		->setLimit(1)
		->fetch();

	//Part 1
	if($original)
	{
		if($original["COUNTER"] > 1)
		{
			//decrease references counter
			InternalFileDuplicateTable::update(
				[
					"DUPLICATE_ID" => $ID,
					"ORIGINAL_ID" => $original["ORIGINAL_ID"],
				],
				[
					"COUNTER" => new MainDBSqlExpression("?# - 1", "COUNTER"),
				]
			);

			//there are references still
			$result = self::DELETE_NONE;
		}
		else
		{
			//delete referense
			InternalFileDuplicateTable::delete([
				"DUPLICATE_ID" => $ID,
				"ORIGINAL_ID" => $original["ORIGINAL_ID"],
			]);

			//delete only if the file is a duplicate of *another* file
			if($original["DUPLICATE_ID"] <> $original["ORIGINAL_ID"])
			{
				if($original["ORIGINAL_DELETED"] === "Y")
				{
					//try and delete the original
					static::Delete($original["ORIGINAL_ID"]);
				}

				//there is the original somewhere, we shouldn't delete its file
				$result = self::DELETE_DB;
			}
		}
	}

	//Part 2
	if($duplicates)
	{
		//mark the original as deleted for future deletion
		InternalFileDuplicateTable::markDeleted($ID);

		//duplicates found, should keep the original
		$result = self::DELETE_NONE;
	}

	return $result;
}