make evaluation of custom lua code thread-safe

1 files changed, 100 insertions, 64 deletions

diff --git a/worker.go b/worker.go
index 01b55e3..2b563ef 100644
--- a/worker.go
+++ b/worker.go
@@ -7,27 +7,33 @@ import (
 	"net/http"
 )
 
-type WorkerRequest struct {
-	Request *http.Request
-	Route string
-	result chan *WorkerResponse
+type HTTPRequest struct {
+	request *http.Request
+	route string
+	debug bool
+	result chan *HTTPResponse
 }
 
-type WorkerResponse struct {
+type EvalRequest struct {
+	code string
+	result chan error
+}
+
+type HTTPResponse struct {
 	Code int
 	Headers map[string]string
 	Body string
 }
 
 type Worker struct {
-	read chan *WorkerRequest
+	read chan interface{}
 	lua *Lua
 	api LuaRef
 	routes map[string]LuaRef
 	started bool
 }
 
-func NewWorker(read chan *WorkerRequest) *Worker {
+func NewWorker(read chan interface{}) *Worker {
 	return &Worker {
 		read: read,
 		routes: make(map[string]LuaRef),
@@ -35,7 +41,7 @@ func NewWorker(read chan *WorkerRequest) *Worker {
 	}
 }
 
-func (w *Worker) Start (filename string) error {
+func (w *Worker) Start(filename string) error {
 	if w.started {
 		return errors.New("already started")
 	}
@@ -54,74 +60,107 @@ func (w *Worker) Start (filename string) error {
 	return nil
 }
 
-func (w *Worker) Listen () {
+func (w *Worker) Listen() {
 	for {
-		r := <- w.read
 		resStack := w.lua.RestoreStackFunc()
-		handlerRef := w.routes[r.Route]
-		w.lua.PushFromRef(handlerRef)
-		w.lua.PushString(r.Request.Method)
-		w.lua.PushString(r.Request.URL.Path)
-
-		fh := make(map[string]string)
-		for k := range r.Request.Header {
-			fh[k] = r.Request.Header.Get(k)
-		}
-		w.lua.PushTable(fh)
-		
-		body, err := io.ReadAll(r.Request.Body)
-		if err != nil {
-			resStack()
-			r.result <- &WorkerResponse {
-				Code: 500,
-				Headers: make(map[string]string),
-				Body: "server error",
+		r := <- w.read
+
+		switch r.(type) {
+		case *HTTPRequest:
+			r := r.(*HTTPRequest)
+			// If in debug mode always use handlers from api table
+			// instead of cached references. Makes it much easier
+			// to hot-replace route handlers.
+			if r.debug {
+				w.lua.PushFromRef(w.api)
+				w.lua.PushTableItem("routes")
+				w.lua.PushTableItem(r.route)
+			} else {
+				w.lua.PushFromRef(w.routes[r.route])
 			}
-			log.Println("could not read a request body")
-			continue
-		}
-		w.lua.PushString(string(body))
-
-		w.lua.PCall(4, 3)
-		code := w.lua.ToInt(-3)
-		rbody := w.lua.ToString(-1)
-
-		// parse headers
-		headers := make(map[string]string)
-		w.lua.Pop(1)
-		w.lua.PushNil()
-		for w.lua.Next() {
-			if !w.lua.IsString(-2) || !w.lua.IsString(-2) {
-				w.lua.Pop(1)
+			w.lua.PushString(r.request.Method)
+			w.lua.PushString(r.request.URL.Path)
+
+			fh := make(map[string]string)
+			for k := range r.request.Header {
+				fh[k] = r.request.Header.Get(k)
+			}
+			w.lua.PushTable(fh)
+			
+			body, err := io.ReadAll(r.request.Body)
+			if err != nil {
+				r.result <- &HTTPResponse {
+					Code: 500,
+					Headers: make(map[string]string),
+					Body: "server error",
+				}
+				log.Println("could not read a request body")
+				resStack()
 				continue
 			}
-			v := w.lua.ToString(-1)
+			w.lua.PushString(string(body))
+
+			w.lua.PCall(4, 3)
+			code := w.lua.ToInt(-3)
+			rbody := w.lua.ToString(-1)
+
+			// Parse headers.
+			headers := make(map[string]string)
 			w.lua.Pop(1)
-			// we must not pop the item key from the stack because
-			// otherwise C.lua_next won't work properly
-			k := w.lua.ToString(-1)
-			headers[k] = v
-		}
-		resStack()
+			w.lua.PushNil()
+			for w.lua.Next() {
+				if !w.lua.IsString(-2) || !w.lua.IsString(-2) {
+					w.lua.Pop(1)
+					continue
+				}
+				v := w.lua.ToString(-1)
+				w.lua.Pop(1)
+				// We must not pop the item key from the stack
+				// because otherwise C.lua_next won't work
+				// properly.
+				k := w.lua.ToString(-1)
+				headers[k] = v
+			}
+			r.result <- &HTTPResponse {
+				Code: int(code),
+				Headers: headers,
+				Body: rbody,
+			}
+
+		case *EvalRequest:
+			r := r.(*EvalRequest)
+			err := w.lua.LoadString(r.code)
+			r.result <- err
 
-		r.result <- &WorkerResponse {
-			Code: int(code),
-			Headers: headers,
-			Body: rbody,
+		default:
+			log.Fatal("unknown request")
 		}
+
+		resStack()
 	}
 }
 
-func (w *Worker) Request (route string, r *http.Request) chan *WorkerResponse {
-	res := make(chan *WorkerResponse)
-	w.read <- &WorkerRequest{
-		Request: r,
-		Route: route,
+func (w *Worker) Request(
+	route string,
+	r *http.Request,
+	debug bool,
+) chan *HTTPResponse {
+	res := make(chan *HTTPResponse)
+	w.read <- &HTTPRequest{
+		request: r,
+		route: route,
+		debug: debug,
 		result: res,
 	}
 	return res
 }
 
+func (w *Worker) Eval(code string) chan error {
+	res := make(chan error)
+	w.read <- &EvalRequest{code: code, result: res}
+	return res
+}
+
 func (w *Worker) ListRoutes() []string {
 	res := []string{}
 	for route, _ := range w.routes {
@@ -130,15 +169,12 @@ func (w *Worker) ListRoutes() []string {
 	return res
 }
 
-func (w *Worker) Eval(code string) error {
-	return w.lua.LoadString(code)
-}
-
 func (w *Worker) Stop() {
 	w.lua.Close()
 }
 
 func (w *Worker) initRoutes() error {
+	defer w.lua.RestoreStackFunc()()
 	w.lua.PushFromRef(w.api)
 	w.lua.PushTableItem("routes")
 	if !w.lua.IsTable(-1) {