[#19] Extract uploading logic into a separate package

Signed-off-by: Pavel Korotkov <pavel@nspcc.ru>

tokens/bearer-token.go

@@ -0,0 +1,93 @@
+package tokens
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+
+	"github.com/nspcc-dev/neofs-api-go/pkg/token"
+	"github.com/pkg/errors"
+	"github.com/valyala/fasthttp"
+)
+
+type fromHandler = func(h *fasthttp.RequestHeader) []byte
+
+const (
+	bearerTokenHdr = "Bearer"
+	bearerTokenKey = "__context_bearer_token_key"
+)
+
+// BearerToken usage:
+//
+// if err = storeBearerToken(ctx); err != nil {
+// 	log.Error("could not fetch bearer token", zap.Error(err))
+// 	c.Error("could not fetch bearer token", fasthttp.StatusBadRequest)
+// 	return
+// }
+
+func BearerTokenFromHeader(h *fasthttp.RequestHeader) []byte {
+	auth := h.Peek(fasthttp.HeaderAuthorization)
+	if auth == nil || !bytes.HasPrefix(auth, []byte(bearerTokenHdr)) {
+		return nil
+	}
+	if auth = bytes.TrimPrefix(auth, []byte(bearerTokenHdr+" ")); len(auth) == 0 {
+		return nil
+	}
+	return auth
+}
+
+func BearerTokenFromCookie(h *fasthttp.RequestHeader) []byte {
+	auth := h.Cookie(bearerTokenHdr)
+	if len(auth) == 0 {
+		return nil
+	}
+
+	return auth
+}
+
+func StoreBearerToken(ctx *fasthttp.RequestCtx) error {
+	tkn, err := fetchBearerToken(ctx)
+	if err != nil {
+		return err
+	}
+	// This is an analog of context.WithValue.
+	ctx.SetUserValue(bearerTokenKey, tkn)
+	return nil
+}
+
+func LoadBearerToken(ctx context.Context) (*token.BearerToken, error) {
+	if tkn, ok := ctx.Value(bearerTokenKey).(*token.BearerToken); ok && tkn != nil {
+		return tkn, nil
+	}
+	return nil, errors.New("found empty bearer token")
+}
+
+func fetchBearerToken(ctx *fasthttp.RequestCtx) (*token.BearerToken, error) {
+	// ignore empty value
+	if ctx == nil {
+		return nil, nil
+	}
+	var (
+		lastErr error
+
+		buf []byte
+		tkn = new(token.BearerToken)
+	)
+	for _, parse := range []fromHandler{BearerTokenFromHeader, BearerTokenFromCookie} {
+		if buf = parse(&ctx.Request.Header); buf == nil {
+			continue
+		} else if data, err := base64.StdEncoding.DecodeString(string(buf)); err != nil {
+			lastErr = errors.Wrap(err, "could not fetch marshaled from base64")
+			continue
+		} else if err = tkn.Unmarshal(data); err != nil {
+			lastErr = errors.Wrap(err, "could not unmarshal bearer token")
+			continue
+		} else if tkn == nil {
+			continue
+		}
+
+		return tkn, nil
+	}
+
+	return nil, lastErr
+}