httpgrpc.go

package httpgrpc

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io/ioutil"
	"net/http"

	"github.com/golang/protobuf/proto"
	"google.golang.org/grpc"
)

// Assert *Client implements ClientConnInterface.
var _ grpc.ClientConnInterface = (*ClientConn)(nil)

type ClientConn struct {
	BaseURI            string
	AuthorizationToken string
}

type StatusError struct {
	Body     string
	Response *http.Response
}

func (e *StatusError) Error() string {
	if e.Body != "" {
		return e.Body
	} else {
		return fmt.Sprintf("HTTP status code: %v", e.Response.StatusCode)
	}
}

func (client *ClientConn) Invoke(ctx context.Context, method string, in interface{}, out interface{}, _ ...grpc.CallOption) error {
	msg, err := proto.Marshal(in.(proto.Message))
	body := bytes.NewBuffer(msg)

	req, err := http.NewRequestWithContext(ctx, "POST", client.BaseURI+method, body)
	if err != nil {
		return err
	}

	req.Header.Set("Content-Type", "application/grpc")
	if client.AuthorizationToken != "" {
		req.Header.Set("Authorization", "Bearer "+client.AuthorizationToken)
	}

	res, err := http.DefaultClient.Do(req)
	if err != nil {
		return err
	}

	responseBody, _ := ioutil.ReadAll(res.Body)
	if res.StatusCode < 200 || res.StatusCode >= 300 {
		return &StatusError{Body: string(responseBody), Response: res}
	}

	err = proto.Unmarshal(responseBody, out.(proto.Message))

	return err
}

func (client *ClientConn) NewStream(_ context.Context, _ *grpc.StreamDesc, _ string, _ ...grpc.CallOption) (grpc.ClientStream, error) {
	return nil, errors.New("streaming not implemented")
}