proxy: support standalone mode

[zchee]

Support standalone mode.

protoc -I . -I ${HOME}/src/github.com/googleapis/googleapis --proxy_out=standalone=true,out=github.com/protobuf-tools/protoc-gen-proxy:./testdata ${HOME}/src/github.com/googleapis/googleapis/google/spanner/v1/*.proto

// Code generated by protoc-gen-proxy. DO NOT EDIT.

package spanner

import (
	context "context"
	errors "errors"
	v1 "google.golang.org/genproto/googleapis/spanner/v1"
	grpc "google.golang.org/grpc"
	emptypb "google.golang.org/protobuf/types/known/emptypb"
	net "net"
)

var _ emptypb.Empty

var ErrNotSupported = errors.New("operation not supported")

type spannerServer struct {
	proxy *Proxy
}

func (s *spannerServer) BatchCreateSessions(ctx context.Context, req *v1.BatchCreateSessionsRequest) (*v1.BatchCreateSessionsResponse, error) {
	fn := s.proxy.BatchCreateSessions
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) BeginTransaction(ctx context.Context, req *v1.BeginTransactionRequest) (*v1.Transaction, error) {
	fn := s.proxy.BeginTransaction
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) Commit(ctx context.Context, req *v1.CommitRequest) (*v1.CommitResponse, error) {
	fn := s.proxy.Commit
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) CreateSession(ctx context.Context, req *v1.CreateSessionRequest) (*v1.Session, error) {
	fn := s.proxy.CreateSession
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) DeleteSession(ctx context.Context, req *v1.DeleteSessionRequest) (*emptypb.Empty, error) {
	fn := s.proxy.DeleteSession
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) ExecuteBatchDml(ctx context.Context, req *v1.ExecuteBatchDmlRequest) (*v1.ExecuteBatchDmlResponse, error) {
	fn := s.proxy.ExecuteBatchDml
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) ExecuteSql(ctx context.Context, req *v1.ExecuteSqlRequest) (*v1.ResultSet, error) {
	fn := s.proxy.ExecuteSql
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) ExecuteStreamingSql(req *v1.ExecuteSqlRequest, srv v1.Spanner_ExecuteStreamingSqlServer) {
	fn := s.proxy.ExecuteStreamingSql
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) GetSession(ctx context.Context, req *v1.GetSessionRequest) (*v1.Session, error) {
	fn := s.proxy.GetSession
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) ListSessions(ctx context.Context, req *v1.ListSessionsRequest) (*v1.ListSessionsResponse, error) {
	fn := s.proxy.ListSessions
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) PartitionQuery(ctx context.Context, req *v1.PartitionQueryRequest) (*v1.PartitionResponse, error) {
	fn := s.proxy.PartitionQuery
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) PartitionRead(ctx context.Context, req *v1.PartitionReadRequest) (*v1.PartitionResponse, error) {
	fn := s.proxy.PartitionRead
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) Read(ctx context.Context, req *v1.ReadRequest) (*v1.ResultSet, error) {
	fn := s.proxy.Read
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) Rollback(ctx context.Context, req *v1.RollbackRequest) (*emptypb.Empty, error) {
	fn := s.proxy.Rollback
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

func (s *spannerServer) StreamingRead(req *v1.ReadRequest, srv v1.Spanner_StreamingReadServer) {
	fn := s.proxy.StreamingRead
	if fn == nil {
		return nil, ErrNotSupported
	}

	return fn(ctx, req)
}

// Proxy allows to create Spanner proxy servers.
type Proxy struct {
	BatchCreateSessions func(ctx context.Context, req *v1.BatchCreateSessionsRequest) (*v1.BatchCreateSessionsResponse, error)
	BeginTransaction    func(ctx context.Context, req *v1.BeginTransactionRequest) (*v1.Transaction, error)
	Commit              func(ctx context.Context, req *v1.CommitRequest) (*v1.CommitResponse, error)
	CreateSession       func(ctx context.Context, req *v1.CreateSessionRequest) (*v1.Session, error)
	DeleteSession       func(ctx context.Context, req *v1.DeleteSessionRequest) (*emptypb.Empty, error)
	ExecuteBatchDml     func(ctx context.Context, req *v1.ExecuteBatchDmlRequest) (*v1.ExecuteBatchDmlResponse, error)
	ExecuteSql          func(ctx context.Context, req *v1.ExecuteSqlRequest) (*v1.ResultSet, error)
	ExecuteStreamingSql func(req *v1.ExecuteSqlRequest, srv v1.Spanner_ExecuteStreamingSqlServer)
	GetSession          func(ctx context.Context, req *v1.GetSessionRequest) (*v1.Session, error)
	ListSessions        func(ctx context.Context, req *v1.ListSessionsRequest) (*v1.ListSessionsResponse, error)
	PartitionQuery      func(ctx context.Context, req *v1.PartitionQueryRequest) (*v1.PartitionResponse, error)
	PartitionRead       func(ctx context.Context, req *v1.PartitionReadRequest) (*v1.PartitionResponse, error)
	Read                func(ctx context.Context, req *v1.ReadRequest) (*v1.ResultSet, error)
	Rollback            func(ctx context.Context, req *v1.RollbackRequest) (*emptypb.Empty, error)
	StreamingRead       func(req *v1.ReadRequest, srv v1.Spanner_StreamingReadServer)
}

// Serve starts serving the proxy server on the given listener with the specified options.
func (p *Proxy) Serve(l net.Listener, opts ...grpc.ServerOption) error {
	srv := grpc.NewServer(opts...)
	v1.RegisterSpannerServer(srv, &spannerServer{proxy: p})

	return srv.Serve(l)
}