floww_transport.go

package floww

import (
	"bytes"
	"crypto/hmac"
	"crypto/md5"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"io"
	"net/http"
)

// Transport is a HTTP transport that signs requests.
type Transport struct {
	Base      http.RoundTripper
	PartnerID string
	AccessKey string
	SecretKey []byte
}

// NewTransport returns a new Transport.
func NewTransport(partnerID, accessKey, secretKey string) *Transport {
	return &Transport{
		Base:      http.DefaultTransport,
		PartnerID: partnerID,
		AccessKey: accessKey,
		SecretKey: []byte(secretKey),
	}
}

// RoundTrip implements http.RoundTripper.
func (t *Transport) RoundTrip(req *http.Request) (_ *http.Response, err error) {
	defer req.Body.Close()
	m := md5.New()
	b := &bytes.Buffer{}
	if _, err = io.Copy(b, io.TeeReader(req.Body, m)); err != nil {
		return nil, err
	}
	h := hmac.New(sha256.New, t.SecretKey)
	if _, err = fmt.Fprintf(h, "%x", m.Sum(nil)); err != nil {
		return nil, err
	}
	req.Header.Set("X-Partner-ID", t.PartnerID)
	req.Header.Set("X-Access-Key", t.AccessKey)
	req.Header.Set("X-Signature", hex.EncodeToString(h.Sum(nil)))
	req.Body = io.NopCloser(b)
	return t.Base.RoundTrip(req)
}