Function DetectMimeType

pkg/chat/chat.go:187–199

DetectMimeType returns the MIME type for a file by reading its first 512 bytes and inspecting the content (magic bytes). For text-based files that http.DetectContentType cannot distinguish (e.g. source code vs plain text), it falls back to extension matching. This is the canonical implementation use

(filePath string)

// it falls back to extension matching. This is the canonical implementation
// used across all packages for consistency.
func DetectMimeType(filePath string) string {
	// Content sniffing — reliably detects images, PDF, etc.
	if ct := detectMimeTypeFromFile(filePath); ct != "application/octet-stream" {
		return ct
	}

	// http.DetectContentType returns "application/octet-stream" for text
	// files it can't classify, so fall back to extension for those.
	if isTextExtension(strings.ToLower(filepath.Ext(filePath))) {
		return "text/plain"
	}
	return "application/octet-stream"
}

// detectMimeTypeFromFile reads the first 512 bytes of a file and uses
// content-based detection (magic bytes) to determine the MIME type.