Lua to Go function handling

functions.go

@@ -22,6 +22,12 @@ import (
 // GoFunction defines the signature for Go functions callable from Lua
 type GoFunction func(*State) int
 
+// LuaFunction represents a Lua function callable from Go
+type LuaFunction struct {
+	state *State
+	ref   int
+}
+
 // Static registry size reduces resizing operations
 const initialRegistrySize = 64
 
@@ -35,6 +41,14 @@ var (
 		funcs: make(map[unsafe.Pointer]GoFunction, initialRegistrySize),
 	}
 
+	// luaFunctionRegistry stores Lua function references
+	luaFunctionRegistry = struct {
+		sync.RWMutex
+		refs map[int]*State
+	}{
+		refs: make(map[int]*State),
+	}
+
 	// statePool reuses State structs to avoid allocations
 	statePool = sync.Pool{
 		New: func() any {
@@ -103,14 +117,188 @@ func (s *State) UnregisterGoFunction(name string) {
 	s.SetGlobal(name)
 }
 
-// Cleanup frees all function pointers and clears the registry
-func (s *State) Cleanup() {
-	functionRegistry.Lock()
-	defer functionRegistry.Unlock()
+// StoreLuaFunction stores a Lua function from the stack and returns a reference
+func (s *State) StoreLuaFunction(index int) (*LuaFunction, error) {
+	if !s.IsFunction(index) {
+		return nil, fmt.Errorf("value at index %d is not a function", index)
+	}
 
-	// Free all allocated pointers
+	s.PushCopy(index)
+	ref := int(C.luaL_ref(s.L, C.LUA_REGISTRYINDEX))
+	if ref == C.LUA_REFNIL {
+		return nil, fmt.Errorf("failed to store function reference")
+	}
+
+	luaFunc := &LuaFunction{
+		state: s,
+		ref:   ref,
+	}
+
+	luaFunctionRegistry.Lock()
+	luaFunctionRegistry.refs[ref] = s
+	luaFunctionRegistry.Unlock()
+
+	return luaFunc, nil
+}
+
+// GetLuaFunction gets a global Lua function and stores it
+func (s *State) GetLuaFunction(name string) (*LuaFunction, error) {
+	s.GetGlobal(name)
+	defer s.Pop(1)
+
+	if !s.IsFunction(-1) {
+		return nil, fmt.Errorf("global '%s' is not a function", name)
+	}
+
+	return s.StoreLuaFunction(-1)
+}
+
+// Call executes the Lua function with given arguments and returns results
+func (lf *LuaFunction) Call(args ...any) ([]any, error) {
+	s := lf.state
+
+	// Push function from registry
+	C.lua_rawgeti(s.L, C.LUA_REGISTRYINDEX, C.int(lf.ref))
+
+	// Push arguments
+	for i, arg := range args {
+		if err := s.PushValue(arg); err != nil {
+			s.Pop(i + 1) // Clean up function and pushed args
+			return nil, fmt.Errorf("failed to push argument %d: %w", i+1, err)
+		}
+	}
+
+	// Call function
+	baseTop := s.GetTop() - len(args) - 1
+	if err := s.Call(len(args), C.LUA_MULTRET); err != nil {
+		return nil, err
+	}
+
+	// Extract results
+	newTop := s.GetTop()
+	nresults := newTop - baseTop
+
+	results := make([]any, nresults)
+	for i := 0; i < nresults; i++ {
+		val, err := s.ToValue(baseTop + i + 1)
+		if err != nil {
+			results[i] = nil
+		} else {
+			results[i] = val
+		}
+	}
+
+	s.SetTop(baseTop)
+	return results, nil
+}
+
+// CallSingle calls the function and returns only the first result
+func (lf *LuaFunction) CallSingle(args ...any) (any, error) {
+	results, err := lf.Call(args...)
+	if err != nil {
+		return nil, err
+	}
+	if len(results) == 0 {
+		return nil, nil
+	}
+	return results[0], nil
+}
+
+// CallTyped calls the function and converts the first result to the specified type
+func CallTyped[T any](lf *LuaFunction, args ...any) (T, error) {
+	var zero T
+	result, err := lf.CallSingle(args...)
+	if err != nil {
+		return zero, err
+	}
+	if result == nil {
+		return zero, nil
+	}
+	if converted, ok := ConvertValue[T](result); ok {
+		return converted, nil
+	}
+	return zero, fmt.Errorf("cannot convert result to %T", zero)
+}
+
+// Release releases the Lua function reference
+func (lf *LuaFunction) Release() {
+	if lf.ref != C.LUA_NOREF && lf.ref != C.LUA_REFNIL {
+		luaFunctionRegistry.Lock()
+		delete(luaFunctionRegistry.refs, lf.ref)
+		luaFunctionRegistry.Unlock()
+
+		C.luaL_unref(lf.state.L, C.LUA_REGISTRYINDEX, C.int(lf.ref))
+		lf.ref = C.LUA_NOREF
+	}
+}
+
+// IsValid checks if the function reference is still valid
+func (lf *LuaFunction) IsValid() bool {
+	return lf.ref != C.LUA_NOREF && lf.ref != C.LUA_REFNIL
+}
+
+// ToGoFunction converts to a standard Go function signature
+func (lf *LuaFunction) ToGoFunction() func(...any) ([]any, error) {
+	return func(args ...any) ([]any, error) {
+		return lf.Call(args...)
+	}
+}
+
+// CreateCallback creates a reusable callback function
+func (s *State) CreateCallback(luaCode string) (*LuaFunction, error) {
+	if err := s.LoadString(luaCode); err != nil {
+		return nil, fmt.Errorf("failed to load callback code: %w", err)
+	}
+
+	luaFunc, err := s.StoreLuaFunction(-1)
+	s.Pop(1) // Remove function from stack
+	return luaFunc, err
+}
+
+// Cleanup frees all function pointers and clears registries
+func (s *State) Cleanup() {
+	// Clean up Go function registry
+	functionRegistry.Lock()
 	for ptr := range functionRegistry.funcs {
 		C.free(ptr)
 		delete(functionRegistry.funcs, ptr)
 	}
+	functionRegistry.Unlock()
+
+	// Clean up Lua function registry for this state
+	luaFunctionRegistry.Lock()
+	for ref, state := range luaFunctionRegistry.refs {
+		if state == s {
+			C.luaL_unref(s.L, C.LUA_REGISTRYINDEX, C.int(ref))
+			delete(luaFunctionRegistry.refs, ref)
+		}
+	}
+	luaFunctionRegistry.Unlock()
+}
+
+// BatchRegisterGoFunctions registers multiple Go functions at once
+func (s *State) BatchRegisterGoFunctions(funcs map[string]GoFunction) error {
+	for name, fn := range funcs {
+		if err := s.RegisterGoFunction(name, fn); err != nil {
+			return fmt.Errorf("failed to register function '%s': %w", name, err)
+		}
+	}
+	return nil
+}
+
+// GetAllLuaFunctions gets multiple global Lua functions by name
+func (s *State) GetAllLuaFunctions(names ...string) (map[string]*LuaFunction, error) {
+	funcs := make(map[string]*LuaFunction, len(names))
+	for _, name := range names {
+		if fn, err := s.GetLuaFunction(name); err == nil {
+			funcs[name] = fn
+		} else {
+			// Clean up any successfully created functions
+			for _, f := range funcs {
+				f.Release()
+			}
+			return nil, fmt.Errorf("failed to get function '%s': %w", name, err)
+		}
+	}
+	return funcs, nil
 }