//go:build js && wasm

package runtime

import "unsafe"

// Bridge imports for spawn-boundary SAB channels and domain creation.
// These are provided by wasm-worker-host.mjs in the JS host.

//go:wasmimport bridge channel_create
func bridgeChannelCreate(slotSize, slotCount int32) int32

//go:wasmimport bridge channel_send
func bridgeChannelSend(handle int32, srcPtr *byte, srcLen int32)

//go:wasmimport bridge channel_recv
func bridgeChannelRecv(handle int32, dstPtr *byte, dstCap int32) int32

//go:wasmimport bridge channel_close
func bridgeChannelClose(handle int32)

//go:wasmimport bridge spawn_domain
func bridgeSpawnDomain(fnIdx int32, argPtr *byte, argLen int32, chanHandlesPtr *byte, nChans int32)

//go:wasmimport bridge is_worker_context
func bridgeIsWorkerContext() int32

// SpawnChannelCreate creates a SAB-backed channel for use across a spawn
// boundary. slotSize and slotCount must both be powers of two; slotSize
// >= 64. Returns an opaque int32 handle stored as a uintptr.
func SpawnChannelCreate(slotSize, slotCount int32) uintptr {
	return uintptr(bridgeChannelCreate(slotSize, slotCount))
}

// SpawnChannelSend sends bytes to a SAB channel identified by handle.
func SpawnChannelSend(handle uintptr, data unsafe.Pointer, n int32) {
	bridgeChannelSend(int32(handle), (*byte)(data), n)
}

// SpawnChannelRecv receives into dst from a SAB channel. Returns byte count
// or -1 if the channel is closed.
func SpawnChannelRecv(handle uintptr, dst unsafe.Pointer, cap int32) int32 {
	return bridgeChannelRecv(int32(handle), (*byte)(dst), cap)
}

// SpawnChannelClose marks a SAB channel as closed.
func SpawnChannelClose(handle uintptr) {
	bridgeChannelClose(int32(handle))
}

// SpawnDomain creates a new Worker running the spawned function at fnIdx.
// argPtr/argLen carry serialized scalar args; chanHandlesPtr/nChans carry
// int32 SAB handles. Called by compiler-emitted spawn site code.
//
// Panics if not running inside a Web Worker: channel_recv uses Atomics.wait
// which is forbidden on the main browser thread. See moxie/wasm deployment docs.
func SpawnDomain(fnIdx int32, argPtr unsafe.Pointer, argLen int32, chanHandlesPtr unsafe.Pointer, nChans int32) {
	if bridgeIsWorkerContext() == 0 {
		runtimePanic("moxie/spawn: wasm binary must be loaded inside a Web Worker — channel_recv uses Atomics.wait which is blocked on the main thread")
	}
	bridgeSpawnDomain(fnIdx, (*byte)(argPtr), argLen, (*byte)(chanHandlesPtr), nChans)
}