//go:build linux

package runtime

import "unsafe"

// spawnDomain creates a new isolated domain by forking the current process.
// The child process executes fn(args) with its own cooperative scheduler.
// Communication between parent and child happens over a Unix socketpair.
func spawnDomain(fn uintptr, args unsafe.Pointer) {
	// Create a socketpair for IPC between parent and child.
	var fds [2]int32
	r := moxie_socketpair(1, 1, 0, unsafe.Pointer(&fds[0])) // AF_UNIX=1, SOCK_STREAM=1
	if r < 0 {
		runtimePanic("spawn: socketpair failed")
	}

	pid := moxie_fork()
	if pid < 0 {
		runtimePanic("spawn: fork failed")
	}

	if pid == 0 {
		// Child process — run the spawned function directly.
		moxie_close(fds[0]) // close parent's end

		// Call the function directly. With no scheduler, the child
		// domain is single-threaded and runs to completion.
		spawnCall(fn, args)

		// Exit child process.
		exit(0)
	}

	// Parent process.
	moxie_close(fds[1]) // close child's end

	domainRegister(pid, fds[0])
}

// spawnCall invokes fn(args) directly. The function pointer fn
// is a $gowrapper that takes a single pointer argument.
func spawnCall(fn uintptr, args unsafe.Pointer) {
	// The function pointer is a wrapper generated by the compiler
	// that unpacks args and calls the real function.
	type funcType func(unsafe.Pointer)
	(*(*funcType)(unsafe.Pointer(&fn)))(args)
}

// C functions defined in spawn_unix.c

//export moxie_fork
func moxie_fork() int32

//export moxie_close
func moxie_close(fd int32) int32

//export moxie_socketpair
func moxie_socketpair(domain, typ, protocol int32, fds unsafe.Pointer) int32