Intelligently set multipart file content-type

integration/integration_test.go

@@ -365,7 +365,13 @@ func TestMain(t *testing.T) {
 				io.WriteString(w, fmt.Sprintf("invalid form files: %+v", form.File))
 				return
 			}
-			file, err := form.File["file1"][0].Open()
+			header := form.File["file1"][0]
+			if ct := header.Header.Get("Content-Type"); ct != "image/jpeg" {
+				w.WriteHeader(400)
+				io.WriteString(w, fmt.Sprintf("invalid content-type: %q", ct))
+				return
+			}
+			file, err := header.Open()
 			if err != nil {
 				w.WriteHeader(400)
 				io.WriteString(w, "cannot open form file: "+err.Error())
@@ -374,15 +380,15 @@ func TestMain(t *testing.T) {
 
 			var buf bytes.Buffer
 			buf.ReadFrom(file)
-			if buf.String() != "file content" {
+			if buf.String() != "\xFF\xD8\xFF" {
 				w.WriteHeader(400)
 				io.WriteString(w, "invalid file content: "+buf.String())
 				return
 			}
 		})
 		defer server.Close()
 
-		tempFile := createTempFile(t, "file content")
+		tempFile := createTempFile(t, "\xFF\xD8\xFF") // JPEG signature.
 		defer os.Remove(tempFile)
 		res := runFetch(t, fetchPath, server.URL, "-F", "key1=val1", "-F", "file1=@"+tempFile)
 		assertExitCode(t, 0, res)

internal/multipart/multipart.go

@@ -1,9 +1,13 @@
 package multipart
 
 import (
+	"bytes"
 	"io"
 	"mime/multipart"
+	"net/http"
+	"net/textproto"
 	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/ryanfowler/fetch/internal/core"
@@ -41,20 +45,7 @@ func NewMultipart(kvs []core.KeyVal) *Multipart {
 			}
 
 			// Form part is a file.
-			w, err := mpw.CreateFormFile(kv.Key, kv.Val[1:])
-			if err != nil {
-				writer.CloseWithError(err)
-				return
-			}
-
-			f, err := os.Open(kv.Val[1:])
-			if err != nil {
-				writer.CloseWithError(err)
-				return
-			}
-
-			_, err = io.Copy(w, f)
-			f.Close()
+			err := writeFilePart(mpw, kv.Key, kv.Val[1:])
 			if err != nil {
 				writer.CloseWithError(err)
 				return
@@ -72,3 +63,212 @@ func NewMultipart(kvs []core.KeyVal) *Multipart {
 func (m *Multipart) ContentType() string {
 	return m.contentType
 }
+
+// writes the multipart file part and returns any error encountered.
+func writeFilePart(mpw *multipart.Writer, key, filename string) error {
+	f, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	var r io.Reader = f
+	ct := detectTypeByExtension(filename)
+	if ct == "" {
+		// Unable to detect MIME type by extension, try from raw bytes.
+		sniff := make([]byte, 512)
+		n, err := f.Read(sniff)
+		if err != nil && err != io.EOF {
+			return err
+		}
+
+		ct = http.DetectContentType(sniff[:n])
+		r = io.MultiReader(bytes.NewReader(sniff[:n]), f)
+	}
+
+	headers := textproto.MIMEHeader{}
+	headers.Set("Content-Disposition", multipart.FileContentDisposition(key, filename))
+	headers.Set("Content-Type", ct)
+
+	w, err := mpw.CreatePart(headers)
+	if err != nil {
+		return err
+	}
+
+	_, err = io.Copy(w, r)
+	return err
+}
+
+func detectTypeByExtension(filename string) string {
+	ext := strings.ToLower(filepath.Ext(filename))
+	if ext == "" {
+		return ""
+	}
+
+	switch ext {
+	// Images
+	case ".jpg", ".jpeg":
+		return "image/jpeg"
+	case ".png":
+		return "image/png"
+	case ".gif":
+		return "image/gif"
+	case ".webp":
+		return "image/webp"
+	case ".avif":
+		return "image/avif"
+	case ".heic", ".heif":
+		return "image/heif"
+	case ".jxl":
+		return "image/jxl"
+	case ".tif", ".tiff":
+		return "image/tiff"
+	case ".bmp":
+		return "image/bmp"
+	case ".ico":
+		return "image/x-icon"
+	case ".svg":
+		return "image/svg+xml"
+	case ".psd":
+		return "image/vnd.adobe.photoshop"
+	case ".raw", ".dng", ".nef", ".cr2", ".arw":
+		return "image/x-raw"
+
+	// Video
+	case ".mp4":
+		return "video/mp4"
+	case ".m4v":
+		return "video/x-m4v"
+	case ".webm":
+		return "video/webm"
+	case ".mov":
+		return "video/quicktime"
+	case ".mkv":
+		return "video/x-matroska"
+	case ".avi":
+		return "video/x-msvideo"
+	case ".wmv":
+		return "video/x-ms-wmv"
+	case ".flv":
+		return "video/x-flv"
+	case ".mpeg", ".mpg":
+		return "video/mpeg"
+	case ".ogv":
+		return "video/ogg"
+
+	// Audio
+	case ".mp3":
+		return "audio/mpeg"
+	case ".m4a":
+		return "audio/mp4"
+	case ".aac":
+		return "audio/aac"
+	case ".wav":
+		return "audio/wav"
+	case ".flac":
+		return "audio/flac"
+	case ".ogg":
+		return "audio/ogg"
+	case ".opus":
+		return "audio/opus"
+	case ".aiff", ".aif":
+		return "audio/aiff"
+	case ".mid", ".midi":
+		return "audio/midi"
+
+	// Documents
+	case ".pdf":
+		return "application/pdf"
+	case ".txt":
+		return "text/plain; charset=utf-8"
+	case ".html", ".htm":
+		return "text/html; charset=utf-8"
+	case ".css":
+		return "text/css; charset=utf-8"
+	case ".csv":
+		return "text/csv; charset=utf-8"
+	case ".json":
+		return "application/json"
+	case ".xml":
+		return "application/xml"
+	case ".yaml", ".yml":
+		return "application/yaml"
+	case ".md":
+		return "text/markdown; charset=utf-8"
+	case ".rtf":
+		return "application/rtf"
+
+	// Office formats
+	case ".doc":
+		return "application/msword"
+	case ".docx":
+		return "application/vnd.openxmlformats-officedocument.wordprocessingml.document"
+	case ".xls":
+		return "application/vnd.ms-excel"
+	case ".xlsx":
+		return "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
+	case ".ppt":
+		return "application/vnd.ms-powerpoint"
+	case ".pptx":
+		return "application/vnd.openxmlformats-officedocument.presentationml.presentation"
+
+	// Fonts
+	case ".woff":
+		return "font/woff"
+	case ".woff2":
+		return "font/woff2"
+	case ".ttf":
+		return "font/ttf"
+	case ".otf":
+		return "font/otf"
+	case ".eot":
+		return "application/vnd.ms-fontobject"
+
+	// Archives
+	case ".zip":
+		return "application/zip"
+	case ".tar":
+		return "application/x-tar"
+	case ".gz":
+		return "application/gzip"
+	case ".tgz":
+		return "application/gzip"
+	case ".bz2":
+		return "application/x-bzip2"
+	case ".xz":
+		return "application/x-xz"
+	case ".7z":
+		return "application/x-7z-compressed"
+	case ".rar":
+		return "application/vnd.rar"
+
+	// Executables / binaries
+	case ".exe":
+		return "application/vnd.microsoft.portable-executable"
+	case ".msi":
+		return "application/x-msi"
+	case ".deb":
+		return "application/vnd.debian.binary-package"
+	case ".rpm":
+		return "application/x-rpm"
+
+	// Scripts / code
+	case ".js":
+		return "application/javascript"
+	case ".mjs":
+		return "application/javascript"
+	case ".ts":
+		return "application/typescript"
+	case ".go":
+		return "text/x-go; charset=utf-8"
+	case ".rs":
+		return "text/x-rust; charset=utf-8"
+	case ".py":
+		return "text/x-python; charset=utf-8"
+	case ".sh":
+		return "application/x-sh"
+
+	default:
+		return ""
+	}
+}