//
// This Source Code Form is subject to the terms of the MIT License.
// If a copy of the MIT was not distributed with this file,
// You can obtain one at https://gitee.com/micro-tools/wf/extend/utils.

// https://github.com/open-telemetry/opentelemetry-go-contrib/blob/master/instrumentation/google.golang.org/grpc/otelgrpc/interceptor.go

package grpctracing

// gRPC tracing middleware
// https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/semantic_conventions/rpc.md
import (
	"context"
	"io"
	"net"
	"strings"

	"github.com/golang/protobuf/proto" //nolint:staticcheck

	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/semconv"
	"go.opentelemetry.io/otel/trace"
	"google.golang.org/grpc"
	grpcCodes "google.golang.org/grpc/codes"
	"google.golang.org/grpc/metadata"
	"google.golang.org/grpc/peer"
)

type messageType attribute.KeyValue

// Event adds an event of the messageType to the span associated with the
// passed context with id and size (if message is a proto message).
func (m messageType) Event(ctx context.Context, id int, message interface{}) {
	span := trace.SpanFromContext(ctx)
	if p, ok := message.(proto.Message); ok {
		span.AddEvent("message", trace.WithAttributes(
			attribute.KeyValue(m),
			semconv.RPCMessageIDKey.Int(id),
			semconv.RPCMessageUncompressedSizeKey.Int(proto.Size(p)),
		))
	} else {
		span.AddEvent("message", trace.WithAttributes(
			attribute.KeyValue(m),
			semconv.RPCMessageIDKey.Int(id),
		))
	}
}

var (
	messageSent     = messageType(semconv.RPCMessageTypeSent)
	messageReceived = messageType(semconv.RPCMessageTypeReceived)
)

type streamEventType int

type streamEvent struct {
	Type streamEventType
	Err  error
}

const (
	closeEvent streamEventType = iota
	receiveEndEvent
	errorEvent
)

// clientStream  wraps around the embedded grpc.ClientStream, and intercepts the RecvMsg and
// SendMsg method call.
type clientStream struct {
	grpc.ClientStream

	desc       *grpc.StreamDesc
	events     chan streamEvent
	eventsDone chan struct{}
	finished   chan error

	receivedMessageID int
	sentMessageID     int
}

var _ = proto.Marshal

func (w *clientStream) RecvMsg(m interface{}) error {
	err := w.ClientStream.RecvMsg(m)

	if err == nil && !w.desc.ServerStreams {
		w.sendStreamEvent(receiveEndEvent, nil)
	} else if err == io.EOF {
		w.sendStreamEvent(receiveEndEvent, nil)
	} else if err != nil {
		w.sendStreamEvent(errorEvent, err)
	} else {
		w.receivedMessageID++
		messageReceived.Event(w.Context(), w.receivedMessageID, m)
	}

	return err
}

func (w *clientStream) SendMsg(m interface{}) error {
	err := w.ClientStream.SendMsg(m)
	w.sentMessageID++
	messageSent.Event(w.Context(), w.sentMessageID, m)
	if err != nil {
		w.sendStreamEvent(errorEvent, err)
	}

	return err
}

func (w *clientStream) Header() (metadata.MD, error) {
	md, err := w.ClientStream.Header()

	if err != nil {
		w.sendStreamEvent(errorEvent, err)
	}

	return md, err
}

func (w *clientStream) CloseSend() error {
	err := w.ClientStream.CloseSend()
	if err != nil {
		w.sendStreamEvent(errorEvent, err)
	} else {
		w.sendStreamEvent(closeEvent, nil)
	}

	return err
}

const (
	clientClosedState byte = 1 << iota
	receiveEndedState
)

func wrapClientStream(s grpc.ClientStream, desc *grpc.StreamDesc) *clientStream {
	events := make(chan streamEvent)
	eventsDone := make(chan struct{})
	finished := make(chan error)

	go func() {
		defer close(eventsDone)

		// Both streams have to be closed
		state := byte(0)

		for event := range events {
			switch event.Type {
			case closeEvent:
				state |= clientClosedState
			case receiveEndEvent:
				state |= receiveEndedState
			case errorEvent:
				finished <- event.Err
				return
			}

			if state == clientClosedState|receiveEndedState {
				finished <- nil
				return
			}
		}
	}()

	return &clientStream{
		ClientStream: s,
		desc:         desc,
		events:       events,
		eventsDone:   eventsDone,
		finished:     finished,
	}
}

func (w *clientStream) sendStreamEvent(eventType streamEventType, err error) {
	select {
	case <-w.eventsDone:
	case w.events <- streamEvent{Type: eventType, Err: err}:
	}
}

// serverStream wraps around the embedded grpc.ServerStream, and intercepts the RecvMsg and
// SendMsg method call.
type serverStream struct {
	grpc.ServerStream
	ctx context.Context

	receivedMessageID int
	sentMessageID     int
}

func (w *serverStream) Context() context.Context {
	return w.ctx
}

func (w *serverStream) RecvMsg(m interface{}) error {
	err := w.ServerStream.RecvMsg(m)

	if err == nil {
		w.receivedMessageID++
		messageReceived.Event(w.Context(), w.receivedMessageID, m)
	}

	return err
}

func (w *serverStream) SendMsg(m interface{}) error {
	err := w.ServerStream.SendMsg(m)

	w.sentMessageID++
	messageSent.Event(w.Context(), w.sentMessageID, m)

	return err
}

func wrapServerStream(ctx context.Context, ss grpc.ServerStream) *serverStream {
	return &serverStream{
		ServerStream: ss,
		ctx:          ctx,
	}
}

// spanInfo returns a span name and all appropriate attributes from the gRPC
// method and peer address.
func spanInfo(fullMethod, peerAddress string) (string, []attribute.KeyValue) {
	attrs := []attribute.KeyValue{semconv.RPCSystemGRPC}
	name, mAttrs := parseFullMethod(fullMethod)
	attrs = append(attrs, mAttrs...)
	attrs = append(attrs, peerAttr(peerAddress)...)
	return name, attrs
}

// peerAttr returns attributes about the peer address.
func peerAttr(addr string) []attribute.KeyValue {
	host, port, err := net.SplitHostPort(addr)
	if err != nil {
		return []attribute.KeyValue(nil)
	}

	if host == "" {
		host = "127.0.0.1"
	}

	return []attribute.KeyValue{
		semconv.NetPeerIPKey.String(host),
		semconv.NetPeerPortKey.String(port),
	}
}

// peerFromCtx returns a peer address from a context, if one exists.
func peerFromCtx(ctx context.Context) string {
	p, ok := peer.FromContext(ctx)
	if !ok {
		return ""
	}
	return p.Addr.String()
}

// parseFullMethod returns a span name following the OpenTelemetry semantic
// conventions as well as all applicable span attribute.KeyValue attributes based
// on a gRPC's FullMethod.
func parseFullMethod(fullMethod string) (string, []attribute.KeyValue) {
	name := strings.TrimLeft(fullMethod, "/")
	parts := strings.SplitN(name, "/", 2)
	if len(parts) != 2 {
		// Invalid format, does not follow `/package.service/method`.
		return name, []attribute.KeyValue(nil)
	}

	var attrs []attribute.KeyValue
	if service := parts[0]; service != "" {
		attrs = append(attrs, semconv.RPCServiceKey.String(service))
	}
	if method := parts[1]; method != "" {
		attrs = append(attrs, semconv.RPCMethodKey.String(method))
	}
	return name, attrs
}

// statusCodeAttr returns status code attribute based on given gRPC code.
func statusCodeAttr(c grpcCodes.Code) attribute.KeyValue {
	return GRPCStatusCodeKey.Int64(int64(c))
}