transport.go

package main

import (
	"context"

	"github.com/go-kit/kit/endpoint"
)

type uppercaseRequest struct {
	S string `json:"s"`
}

type uppercaseResponse struct {
	V   string `json:"v"`
	Err string `json:"err,omitempty"` // errors don't JSON-marshal, so we use a string
}

type countRequest struct {
	S string `json:"s"`
}

type countResponse struct {
	V int `json:"v"`
}

func makeUppercaseEndpoint(svc StringService) endpoint.Endpoint {
	return func(_ context.Context, request interface{}) (interface{}, error) {
		req := request.(uppercaseRequest)
		v, err := svc.Uppercase(req.S)
		if err != nil {
			return uppercaseResponse{v, err.Error()}, nil
		}
		return uppercaseResponse{v, ""}, nil
	}
}

func makeCountEndpoint(svc StringService) endpoint.Endpoint {
	return func(_ context.Context, request interface{}) (interface{}, error) {
		req := request.(countRequest)
		v := svc.Count(req.S)
		return countResponse{v}, nil
	}
}