Guess content type for binary params by filename extension

const.go

@@ -26,6 +26,7 @@ const (
 	ERROR_CODE_UNKNOWN = -1 // unknown facebook graph api error code.
 
 	_MIME_FORM_URLENCODED = "application/x-www-form-urlencoded"
+	_MIME_FORM_DATA = "multipart/form-data"
 )
 
 // Graph API debug mode values.

facebook_test.go

@@ -14,6 +14,7 @@ import (
 	"fmt"
 	"testing"
 	"time"
+	"strings"
 )
 
 const (
@@ -890,6 +891,27 @@ func TestParamsEncode(t *testing.T) {
 	t.Logf("complex encode result is '%v'. [e:%v] [mime:%v]", buf.String(), err, mime)
 }
 
+func TestBinaryParamsEncode(t *testing.T) {
+
+	buf := &bytes.Buffer{}
+	params := Params{}
+	params["attachment"] = FileAlias("image.jpg", "LICENSE")
+
+	contentTypeImage := "Content-Type: image/jpeg"
+	if mime, err := params.Encode(buf); err != nil || !strings.Contains(mime, _MIME_FORM_DATA) || !strings.Contains(buf.String(), contentTypeImage) {
+		t.Fatalf("wrong binary params encode result. expected content type is '%v'. actual is '%v'. [e:%v] [mime:%v]", contentTypeImage, buf.String(), err, mime)
+	}
+
+	// Fallback for unknown content types
+	// should be application/octet-stream
+	buf.Reset()
+	params = Params{"attachment": FileAlias("image.unknown", "LICENSE")}
+	contentTypeOctet := "Content-Type: application/octet-stream"
+	if mime, err := params.Encode(buf); err != nil || !strings.Contains(mime, _MIME_FORM_DATA) || !strings.Contains(buf.String(), contentTypeOctet) {
+		t.Fatalf("wrong binary params encode result. expected content type is '%v'. actual is '%v'. [e:%v] [mime:%v]", contentTypeOctet, buf.String(), err, mime)
+	}
+}
+
 func TestStructFieldTag(t *testing.T) {
 	strNormalField := `{
         "field2": "hey",

params.go

@@ -9,12 +9,17 @@ package facebook
 
 import (
 	"encoding/json"
+	"fmt"
 	"io"
+	"mime"
 	"mime/multipart"
+	"net/textproto"
 	"net/url"
 	"os"
+	"path"
 	"reflect"
 	"runtime"
+	"strings"
 )
 
 // Makes a new Params instance by given data.
@@ -158,7 +163,8 @@ func (params Params) encodeMultipartForm(writer io.Writer) (mime string, err err
 		switch value := v.(type) {
 		case *binaryData:
 			var dst io.Writer
-			dst, err = w.CreateFormFile(k, value.Filename)
+			filePart := createFormFile(k, value.Filename)
+			dst, err = w.CreatePart(filePart)
 
 			if err != nil {
 				return
@@ -175,7 +181,8 @@ func (params Params) encodeMultipartForm(writer io.Writer) (mime string, err err
 			var file *os.File
 			var path string
 
-			dst, err = w.CreateFormFile(k, value.Filename)
+			filePart := createFormFile(k, value.Filename)
+			dst, err = w.CreatePart(filePart)
 
 			if err != nil {
 				return
@@ -225,3 +232,20 @@ func (params Params) encodeMultipartForm(writer io.Writer) (mime string, err err
 
 	return
 }
+
+var quoteEscaper = strings.NewReplacer("\\", "\\\\", `"`, "\\\"")
+
+func createFormFile(fieldName, fileName string) textproto.MIMEHeader {
+	h := make(textproto.MIMEHeader)
+	h.Set("Content-Disposition",
+		fmt.Sprintf(`form-data; name="%s"; filename="%s"`,
+			quoteEscaper.Replace(fieldName), quoteEscaper.Replace(fileName)))
+
+	contentType := mime.TypeByExtension(path.Ext(fileName))
+	if contentType == "" {
+		contentType = "application/octet-stream"
+	}
+
+	h.Set("Content-Type", contentType)
+	return h
+}