Refactor interceptor chain functions (#220)

Author: jun06t

chain.go

@@ -19,35 +19,19 @@ import (
 func ChainUnaryServer(interceptors ...grpc.UnaryServerInterceptor) grpc.UnaryServerInterceptor {
 	n := len(interceptors)
 
-	if n > 1 {
-		lastI := n - 1
-		return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
-			var (
-				chainHandler grpc.UnaryHandler
-				curI         int
-			)
-
-			chainHandler = func(currentCtx context.Context, currentReq interface{}) (interface{}, error) {
-				if curI == lastI {
-					return handler(currentCtx, currentReq)
-				}
-				curI++
-				resp, err := interceptors[curI](currentCtx, currentReq, info, chainHandler)
-				curI--
-				return resp, err
+	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
+		chainer := func(currentInter grpc.UnaryServerInterceptor, currentHandler grpc.UnaryHandler) grpc.UnaryHandler {
+			return func(currentCtx context.Context, currentReq interface{}) (interface{}, error) {
+				return currentInter(currentCtx, currentReq, info, currentHandler)
 			}
-
-			return interceptors[0](ctx, req, info, chainHandler)
 		}
-	}
 
-	if n == 1 {
-		return interceptors[0]
-	}
+		chainedHandler := handler
+		for i := n - 1; i >= 0; i-- {
+			chainedHandler = chainer(interceptors[i], chainedHandler)
+		}
 
-	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
-	return func(ctx context.Context, req interface{}, _ *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
-		return handler(ctx, req)
+		return chainedHandler(ctx, req)
 	}
 }
 
@@ -59,35 +43,19 @@ func ChainUnaryServer(interceptors ...grpc.UnaryServerInterceptor) grpc.UnarySer
 func ChainStreamServer(interceptors ...grpc.StreamServerInterceptor) grpc.StreamServerInterceptor {
 	n := len(interceptors)
 
-	if n > 1 {
-		lastI := n - 1
-		return func(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
-			var (
-				chainHandler grpc.StreamHandler
-				curI         int
-			)
-
-			chainHandler = func(currentSrv interface{}, currentStream grpc.ServerStream) error {
-				if curI == lastI {
-					return handler(currentSrv, currentStream)
-				}
-				curI++
-				err := interceptors[curI](currentSrv, currentStream, info, chainHandler)
-				curI--
-				return err
+	return func(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
+		chainer := func(currentInter grpc.StreamServerInterceptor, currentHandler grpc.StreamHandler) grpc.StreamHandler {
+			return func(currentSrv interface{}, currentStream grpc.ServerStream) error {
+				return currentInter(currentSrv, currentStream, info, currentHandler)
 			}
-
-			return interceptors[0](srv, stream, info, chainHandler)
 		}
-	}
 
-	if n == 1 {
-		return interceptors[0]
-	}
+		chainedHandler := handler
+		for i := n - 1; i >= 0; i-- {
+			chainedHandler = chainer(interceptors[i], chainedHandler)
+		}
 
-	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
-	return func(srv interface{}, stream grpc.ServerStream, _ *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
-		return handler(srv, stream)
+		return chainedHandler(srv, ss)
 	}
 }
 
@@ -98,35 +66,19 @@ func ChainStreamServer(interceptors ...grpc.StreamServerInterceptor) grpc.Stream
 func ChainUnaryClient(interceptors ...grpc.UnaryClientInterceptor) grpc.UnaryClientInterceptor {
 	n := len(interceptors)
 
-	if n > 1 {
-		lastI := n - 1
-		return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
-			var (
-				chainHandler grpc.UnaryInvoker
-				curI         int
-			)
-
-			chainHandler = func(currentCtx context.Context, currentMethod string, currentReq, currentRepl interface{}, currentConn *grpc.ClientConn, currentOpts ...grpc.CallOption) error {
-				if curI == lastI {
-					return invoker(currentCtx, currentMethod, currentReq, currentRepl, currentConn, currentOpts...)
-				}
-				curI++
-				err := interceptors[curI](currentCtx, currentMethod, currentReq, currentRepl, currentConn, chainHandler, currentOpts...)
-				curI--
-				return err
+	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+		chainer := func(currentInter grpc.UnaryClientInterceptor, currentInvoker grpc.UnaryInvoker) grpc.UnaryInvoker {
+			return func(currentCtx context.Context, currentMethod string, currentReq, currentRepl interface{}, currentConn *grpc.ClientConn, currentOpts ...grpc.CallOption) error {
+				return currentInter(currentCtx, currentMethod, currentReq, currentRepl, currentConn, currentInvoker, currentOpts...)
 			}
-
-			return interceptors[0](ctx, method, req, reply, cc, chainHandler, opts...)
 		}
-	}
 
-	if n == 1 {
-		return interceptors[0]
-	}
+		chainedInvoker := invoker
+		for i := n - 1; i >= 0; i-- {
+			chainedInvoker = chainer(interceptors[i], chainedInvoker)
+		}
 
-	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
-	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
-		return invoker(ctx, method, req, reply, cc, opts...)
+		return chainedInvoker(ctx, method, req, reply, cc, opts...)
 	}
 }
 
@@ -137,35 +89,19 @@ func ChainUnaryClient(interceptors ...grpc.UnaryClientInterceptor) grpc.UnaryCli
 func ChainStreamClient(interceptors ...grpc.StreamClientInterceptor) grpc.StreamClientInterceptor {
 	n := len(interceptors)
 
-	if n > 1 {
-		lastI := n - 1
-		return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
-			var (
-				chainHandler grpc.Streamer
-				curI         int
-			)
-
-			chainHandler = func(currentCtx context.Context, currentDesc *grpc.StreamDesc, currentConn *grpc.ClientConn, currentMethod string, currentOpts ...grpc.CallOption) (grpc.ClientStream, error) {
-				if curI == lastI {
-					return streamer(currentCtx, currentDesc, currentConn, currentMethod, currentOpts...)
-				}
-				curI++
-				stream, err := interceptors[curI](currentCtx, currentDesc, currentConn, currentMethod, chainHandler, currentOpts...)
-				curI--
-				return stream, err
+	return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
+		chainer := func(currentInter grpc.StreamClientInterceptor, currentStreamer grpc.Streamer) grpc.Streamer {
+			return func(currentCtx context.Context, currentDesc *grpc.StreamDesc, currentConn *grpc.ClientConn, currentMethod string, currentOpts ...grpc.CallOption) (grpc.ClientStream, error) {
+				return currentInter(currentCtx, currentDesc, currentConn, currentMethod, currentStreamer, currentOpts...)
 			}
-
-			return interceptors[0](ctx, desc, cc, method, chainHandler, opts...)
 		}
-	}
 
-	if n == 1 {
-		return interceptors[0]
-	}
+		chainedStreamer := streamer
+		for i := n - 1; i >= 0; i-- {
+			chainedStreamer = chainer(interceptors[i], chainedStreamer)
+		}
 
-	// n == 0; Dummy interceptor maintained for backward compatibility to avoid returning nil.
-	return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
-		return streamer(ctx, desc, cc, method, opts...)
+		return chainedStreamer(ctx, desc, cc, method, opts...)
 	}
 }