use types::c;

export type pthread_t = [8]u8;
type pthread_attr_t = opaque;
type pthread_fn = fn(nullable *opaque) nullable *opaque;
export type thread_fn = fn(nullable *opaque) void;

@symbol("pthread_create") fn pthread_create(thread: nullable *pthread_t, attr: nullable *pthread_attr_t, start_routine: *pthread_fn, arg: nullable *opaque) int;
@symbol("pthread_join") fn pthread_join(thread: pthread_t, nullable *nullable *opaque) int;
@symbol("pthread_detach") fn pthread_detach(thread: pthread_t) int;

type data_wrapper = struct {
	f: *thread_fn,
	data: nullable *opaque,
};

fn thread_spawn_wrapper(arg: nullable *opaque) nullable *opaque = {
	let data = arg: *data_wrapper;
	data.f(data.data);
	free(data);
	return null;
};

export type error = !void;
export type join_handle = struct {
	thread: pthread_t,
};

// spawn a thread
//
// returns a handle or an error
export fn spawn(f: *thread_fn, data: nullable *opaque) (join_handle | error) = {
	let data: *data_wrapper = alloc(data_wrapper {
		f = f,
		data = data,
	});

	let tid: pthread_t = [0...];
	let ret = pthread_create(&tid, null, &thread_spawn_wrapper, data);
	if (ret != 0) {
		return error;
	};

	return join_handle {
		thread = tid
	};
};

// join a thread
//
// no return value or an error on join
export fn join(handle: join_handle) (void | error) = {
	let ret = pthread_join(handle.thread, null);
	if (ret != 0) {
		return error;
	};
};

// detach a thread.
export fn detach(handle: join_handle) (void | error) = {
	let ret = pthread_detach(handle.thread);
	if (ret != 0) {
		return error;
	};
};