Added POST method to upload files into NeoFS through HTTP Gate

- Updated README
- Added method to upload files into NeoFS
- HTTP Upload Header Filter loaded from settings
- Added `HeaderFilter` that filters headers (object attributes)

Signed-off-by: Evgeniy Kulikov <kim@nspcc.ru>

upload.go

@@ -0,0 +1,146 @@
+package main
+
+import (
+	"encoding/json"
+	"io"
+	"io/ioutil"
+	"mime/multipart"
+	"os"
+	"strconv"
+	"time"
+
+	sdk "github.com/nspcc-dev/cdn-sdk"
+	"github.com/nspcc-dev/neofs-api-go/pkg/container"
+	"github.com/nspcc-dev/neofs-api-go/pkg/object"
+	"github.com/valyala/fasthttp"
+	"go.uber.org/zap"
+)
+
+type putResponse struct {
+	OID string `json:"object_id"`
+	CID string `json:"container_id"`
+}
+
+func newPutResponse(addr *object.Address) *putResponse {
+	return &putResponse{
+		OID: addr.ObjectID().String(),
+		CID: addr.ContainerID().String(),
+	}
+}
+
+func (pr *putResponse) Encode(w io.Writer) error {
+	enc := json.NewEncoder(w)
+	enc.SetIndent("", "\t")
+	return enc.Encode(pr)
+}
+
+func (a *app) upload(c *fasthttp.RequestCtx) {
+	var (
+		err     error
+		name    string
+		tmp     *os.File
+		addr    *object.Address
+		form    *multipart.Form
+		cid     = container.NewID()
+		sCID, _ = c.UserValue("cid").(string)
+
+		log = a.log.With(zap.String("cid", sCID))
+	)
+
+	if err = cid.Parse(sCID); err != nil {
+		log.Error("wrong container id", zap.Error(err))
+		c.Error("wrong container id", fasthttp.StatusBadRequest)
+		return
+	}
+
+	if tmp, err = ioutil.TempFile("", "http-gate-upload-*"); err != nil {
+		log.Error("could not prepare temporary file", zap.Error(err))
+		c.Error("could not prepare temporary file", fasthttp.StatusBadRequest)
+		return
+	}
+
+	defer func() {
+		tmpName := tmp.Name()
+
+		log.Debug("close temporary file", zap.Error(tmp.Close()))
+		log.Debug("remove temporary file", zap.Error(os.RemoveAll(tmpName)))
+	}()
+
+	if form, err = c.MultipartForm(); err != nil {
+		log.Error("could not receive multipart form", zap.Error(err))
+		c.Error("could not receive multipart form: "+err.Error(), fasthttp.StatusBadRequest)
+
+		return
+	} else if ln := len(form.File); ln != 1 {
+		log.Error("received multipart form with more then one file", zap.Int("count", ln))
+		c.Error("received multipart form with more then one file", fasthttp.StatusBadRequest)
+
+		return
+	}
+
+	for _, file := range form.File {
+		if ln := len(file); ln != 1 {
+			log.Error("received multipart form file should contains one record", zap.Int("count", ln))
+			c.Error("received multipart form file should contains one record", fasthttp.StatusBadRequest)
+
+			return
+		}
+
+		name = file[0].Filename
+
+		if err = fasthttp.SaveMultipartFile(file[0], tmp.Name()); err != nil {
+			log.Error("could not store uploaded file into temporary", zap.Error(err))
+			c.Error("could not store uploaded file into temporary", fasthttp.StatusBadRequest)
+
+			return
+		}
+	}
+
+	filtered := a.hdr.Filter(&c.Request.Header)
+	attributes := make([]*object.Attribute, 0, len(filtered))
+
+	for key, val := range filtered {
+		attribute := object.NewAttribute()
+		attribute.SetKey(key)
+		attribute.SetValue(val)
+
+		attributes = append(attributes, attribute)
+	}
+
+	// Attribute FileName wasn't set from header
+	if _, ok := filtered[object.AttributeFileName]; ok {
+		filename := object.NewAttribute()
+		filename.SetKey(object.AttributeFileName)
+		filename.SetValue(name)
+
+		attributes = append(attributes, filename)
+	}
+
+	// Attribute Timestamp wasn't set from header
+	if _, ok := filtered[object.AttributeTimestamp]; ok {
+		timestamp := object.NewAttribute()
+		timestamp.SetKey(object.AttributeTimestamp)
+		timestamp.SetValue(strconv.FormatInt(time.Now().Unix(), 10))
+
+		attributes = append(attributes, timestamp)
+	}
+
+	raw := object.NewRaw()
+	raw.SetContainerID(cid)
+	raw.SetOwnerID(a.cli.Owner()) // should be various: from sdk / BearerToken
+	raw.SetAttributes(attributes...)
+
+	if addr, err = a.cli.Object().Put(c, raw.Object(), sdk.WithPutReader(tmp)); err != nil {
+		log.Error("could not store file in NeoFS", zap.Error(err))
+		c.Error("could not store file in NeoFS", fasthttp.StatusBadRequest)
+
+		return
+	} else if err = newPutResponse(addr).Encode(c); err != nil {
+		log.Error("could not prepare response", zap.Error(err))
+		c.Error("could not prepare response", fasthttp.StatusBadRequest)
+
+		return
+	}
+
+	c.Response.SetStatusCode(fasthttp.StatusOK)
+}