Feature: detect blob content type

cmd/api/handler/namespace.go

@@ -249,7 +249,12 @@ func (handler *NamespaceHandler) GetBlob(c echo.Context) error {
 		return badRequestError(c, err)
 	}
 
-	return c.JSON(http.StatusOK, blob)
+	response, err := responses.NewBlob(blob)
+	if err != nil {
+		return internalServerError(c, err)
+	}
+
+	return c.JSON(http.StatusOK, response)
 }
 
 type getNamespaceMessages struct {

cmd/api/handler/responses/blob.go

@@ -3,10 +3,33 @@
 
 package responses
 
-// structure is only for documentation
+import (
+	"encoding/base64"
+	"net/http"
+
+	"github.com/celenium-io/celestia-indexer/pkg/node/types"
+)
+
 type Blob struct {
 	Namespace    string `example:"AAAAAAAAAAAAAAAAAAAAAAAAAAAAs2bWWU6FOB0="     format:"base64"  json:"namespace"     swaggertype:"string"`
 	Data         string `example:"b2sgZGVtbyBkYQ=="                             format:"base64"  json:"data"          swaggertype:"string"`
 	ShareVersion int    `example:"0"                                            format:"integer" json:"share_version" swaggertype:"integer"`
 	Commitment   string `example:"vbGakK59+Non81TE3ULg5Ve5ufT9SFm/bCyY+WLR3gg=" format:"base64"  json:"commitment"    swaggertype:"string"`
+	ContentType  string `example:"image/png"                                    format:"string"  json:"content_type"  swaggertype:"string"`
+}
+
+func NewBlob(blob types.Blob) (Blob, error) {
+	b := Blob{
+		Namespace:    blob.Namespace,
+		Data:         blob.Data,
+		Commitment:   blob.Commitment,
+		ShareVersion: blob.ShareVersion,
+	}
+
+	data, err := base64.StdEncoding.DecodeString(blob.Data)
+	if err != nil {
+		return b, err
+	}
+	b.ContentType = http.DetectContentType(data)
+	return b, nil
 }