chain.go

package grpcserver

import (
	"context"

	"google.golang.org/grpc"
)

// ChainUnaryServer creates a single interceptor out of a chain of many interceptors.
//
// Copy from grpc-ecosystem/go-grpc-middleware.
//
// Execution is done in left-to-right order, including passing of context.
// For example ChainUnaryServer(one, two, three) will execute one before two before three, and three
// will see context changes of one and two.
func ChainUnaryServer(interceptors ...grpc.UnaryServerInterceptor) grpc.UnaryServerInterceptor {
	n := len(interceptors)

	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)
			}
		}

		chainedHandler := handler
		for i := n - 1; i >= 0; i-- {
			chainedHandler = chainer(interceptors[i], chainedHandler)
		}

		return chainedHandler(ctx, req)
	}
}

// ChainStreamServer creates a single interceptor out of a chain of many interceptors.
//
// Copy from grpc-ecosystem/go-grpc-middleware.
//
// Execution is done in left-to-right order, including passing of context.
// For example ChainUnaryServer(one, two, three) will execute one before two before three.
// If you want to pass context between interceptors, use WrapServerStream.
func ChainStreamServer(interceptors ...grpc.StreamServerInterceptor) grpc.StreamServerInterceptor {
	n := len(interceptors)

	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)
			}
		}

		chainedHandler := handler
		for i := n - 1; i >= 0; i-- {
			chainedHandler = chainer(interceptors[i], chainedHandler)
		}

		return chainedHandler(srv, ss)
	}
}