stefanoj3 / dirstalk

package client

import (

	"errors"

	"fmt"

	"net/http"

	"sync"

)

var (

	// ErrRequestRedundant this error is returned when trying to perform the

	// same request (method, host, path) more than one time.

	ErrRequestRedundant = errors.New("this request has been made already")

)

func decorateTransportWithRequestCacheDecorator(decorated http.RoundTripper) (*requestCacheTransportDecorator, error) {

	if decorated == nil {

		return nil, errors.New("decorated round tripper is nil")

	}

	return &requestCacheTransportDecorator{decorated: decorated}, nil

}

type requestCacheTransportDecorator struct {

	decorated  http.RoundTripper

	requestMap sync.Map

}

func (u *requestCacheTransportDecorator) RoundTrip(r *http.Request) (*http.Response, error) {

	key := u.keyForRequest(r)

	_, found := u.requestMap.Load(key)

	if found {

		return nil, ErrRequestRedundant

	}

	u.requestMap.Store(key, struct{}{})

	return u.decorated.RoundTrip(r)

}

func (u *requestCacheTransportDecorator) keyForRequest(r *http.Request) string {

	return fmt.Sprintf("%s~%s~%s", r.Method, r.Host, r.URL.Path)

}