package apm

import (
	"context"
	"github.com/SkyAPM/go2sky/propagation"
	"google.golang.org/grpc/metadata"
)

func GRpcExtractor(ctx context.Context) propagation.Extractor {
	return func() (s string, e error) {
		// https://github.com/googleapis/google-cloud-go/issues/624
		// After some recent changes in grpc-go,
		// metadata.NewContext now assumes you are accessing the outgoing metadata,
		// and metadata.FromContext assumes you are retrieving the incoming credentials.
		md, ok := metadata.FromIncomingContext(ctx)
		if !ok {
			return "", nil
		}
		header, ok := md[propagation.Header]
		if !ok {
			return "", nil
		}
		if len(header) <= 0 {
			return "", nil
		}
		return header[0], nil
	}
}

func GRpcInjector(ctx *context.Context) propagation.Injector {
	return func(header string) error {
		md := metadata.New(map[string]string{propagation.Header: header})
		newCtx := metadata.NewOutgoingContext(*ctx, md)
		*ctx = newCtx
		return nil
	}
}