From 701d73e4a47964ea40100ab2f329ef1dcc0a6f83 Mon Sep 17 00:00:00 2001
From: unwox <me@unwox.com>
Date: Mon, 17 Jun 2024 14:28:27 +0600
Subject: make it possible to push go functions onto the lua stack

---
 lua.go    | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++----------
 main.go   |  1 +
 worker.go | 12 +++++++++++-
 3 files changed, 65 insertions(+), 11 deletions(-)

diff --git a/lua.go b/lua.go
index f13a8cb..199f13a 100644
--- a/lua.go
+++ b/lua.go
@@ -6,12 +6,24 @@ package main
 #include <lua.h>
 #include <lualib.h>
 #include <lauxlib.h>
+
+extern int luna_run_go_func(uintptr_t);
+
+static inline int luna_run(lua_State *l) {
+	return luna_run_go_func(lua_tonumber(l, lua_upvalueindex(1)));
+}
+
+static inline void luna_push_function(lua_State *l, uintptr_t f) {
+	lua_pushinteger(l, f);
+	lua_pushcclosure(l, luna_run, 1);
+}
 */
 import "C"
 import (
 	"errors"
-	"unsafe"
 	"log"
+	"runtime/cgo"
+	"unsafe"
 )
 
 type LuaRef C.longlong
@@ -19,6 +31,13 @@ type Lua struct {
 	l *C.lua_State
 }
 
+//export luna_run_go_func
+func luna_run_go_func(f C.uintptr_t) C.int {
+	log.Println(f)
+	fn := cgo.Handle(f).Value().(func() int)
+	return C.int(fn())
+}
+
 func (l *Lua) Start() {
 	l.l = C.luaL_newstate()
 	C.luaL_openlibs(l.l)
@@ -89,8 +108,26 @@ func (l *Lua) PushString(str string) {
 	C.lua_pushstring(l.l, cstr)
 }
 
-func (l *Lua) PushTable(table map[string]string) {
-	C.lua_createtable(l.l, 0, C.int(len(table)))
+// You may need to delete handle with .Delete() method later.
+func (l *Lua) PushGoFunction(f func (l *Lua) int) cgo.Handle {
+	h := cgo.NewHandle(func () int {
+		return f(l)
+	})
+	C.luna_push_function(l.l, C.uintptr_t(h))
+	return h
+}
+
+// CreateTable pushes a new table onto the stack.
+func (l *Lua) CreateTable(len int) {
+	C.lua_createtable(l.l, 0, C.int(len))
+}
+func (l *Lua) SetTableItem(key string) {
+	cstr := C.CString(key)
+	defer C.free(unsafe.Pointer(cstr))
+	C.lua_setfield(l.l, -2, C.CString(key))
+}
+func (l *Lua) PushStringTable(table map[string]string) {
+	l.CreateTable(len(table))
 	for k, v := range table {
 		l.PushString(v)
 		C.lua_setfield(l.l, -2, C.CString(k))
@@ -101,6 +138,13 @@ func (l *Lua) PushFromRef(ref LuaRef) {
 	C.lua_rawgeti(l.l, C.LUA_REGISTRYINDEX, C.longlong(ref));
 }
 
+func (l *Lua) PushTableItem(key string) {
+	ckey := C.CString(key)
+	defer C.free(unsafe.Pointer(ckey))
+	C.lua_pushstring(l.l, ckey);
+	C.lua_gettable(l.l, -2);
+}
+
 func (l *Lua) IsString(index int) bool {
 	return C.lua_isstring(l.l, C.int(index)) == 1
 }
@@ -138,13 +182,6 @@ func (l *Lua) LoadString(code string) error {
 	return nil
 }
 
-func (l *Lua) PushTableItem(key string) {
-	ckey := C.CString(key)
-	defer C.free(unsafe.Pointer(ckey))
-	C.lua_pushstring(l.l, ckey);
-	C.lua_gettable(l.l, -2);
-}
-
 func (l *Lua) RestoreStackFunc() func () {
 	before := l.StackLen()
 	return func () {
@@ -162,3 +199,9 @@ func (l *Lua) RestoreStackFunc() func () {
 		C.lua_settop(l.l, C.int(before))
 	}
 }
+
+func (l *Lua) SetGlobal(name string) {
+	cstr := C.CString(name)
+	defer C.free(unsafe.Pointer(cstr))
+	C.lua_setglobal(l.l, cstr)
+}
diff --git a/main.go b/main.go
index 6c993fb..793928d 100644
--- a/main.go
+++ b/main.go
@@ -55,6 +55,7 @@ func main() {
 		go wrk.Listen()
 		defer wrk.Stop()
 	}
+
 	go func () {
 		reader := bufio.NewReader(os.Stdin)
 		for {
diff --git a/worker.go b/worker.go
index 2b563ef..646efea 100644
--- a/worker.go
+++ b/worker.go
@@ -85,7 +85,7 @@ func (w *Worker) Listen() {
 			for k := range r.request.Header {
 				fh[k] = r.request.Header.Get(k)
 			}
-			w.lua.PushTable(fh)
+			w.lua.PushStringTable(fh)
 			
 			body, err := io.ReadAll(r.request.Body)
 			if err != nil {
@@ -173,6 +173,16 @@ func (w *Worker) Stop() {
 	w.lua.Close()
 }
 
+func (w *Worker) initLunaModule() {
+	w.lua.CreateTable(1)
+	w.lua.PushGoFunction(func (l *Lua) int {
+		l.PushString("Hello, " + l.ToString(-1))
+		return 1
+	})
+	w.lua.SetTableItem("helloFromGo")
+	w.lua.SetGlobal("luna")
+}
+
 func (w *Worker) initRoutes() error {
 	defer w.lua.RestoreStackFunc()()
 	w.lua.PushFromRef(w.api)
-- 
cgit v1.2.3