From 13547ec63efc7d1b2beaf94dfb5e595e8dba55fc Mon Sep 17 00:00:00 2001
From: xfy <i@rua.plus>
Date: Wed, 3 Jun 2026 17:44:16 +0800
Subject: [PATCH] fix: use defaultMIME fallback in DetectContentType

---
 internal/mimeutil/detect.go      | 8 +++++++-
 internal/mimeutil/detect_test.go | 4 ++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/internal/mimeutil/detect.go b/internal/mimeutil/detect.go
index fb77457..e4f6256 100644
--- a/internal/mimeutil/detect.go
+++ b/internal/mimeutil/detect.go
@@ -102,7 +102,7 @@ func SetDefaultType(defaultType string) {
 //   - filePath: 文件路径
 //
 // 返回值:
-//   - string: MIME 类型，未知类型返回空字符串
+//	- string: MIME 类型，未知类型返回 defaultMIME（默认为 application/octet-stream）
 func DetectContentType(filePath string) string {
 	ext := strings.ToLower(filepath.Ext(filePath))
 
@@ -151,5 +151,11 @@ func DetectContentType(filePath string) string {
 	entry.element = mimeLRU.PushFront(entry)
 	mimeCache[ext] = entry
 
+	if mimeType == "" {
+		defaultMutex.RLock()
+		mimeType = defaultMIME
+		defaultMutex.RUnlock()
+	}
+
 	return mimeType
 }
diff --git a/internal/mimeutil/detect_test.go b/internal/mimeutil/detect_test.go
index 9daa82e..ba0bf88 100644
--- a/internal/mimeutil/detect_test.go
+++ b/internal/mimeutil/detect_test.go
@@ -31,8 +31,8 @@ func TestDetectContentType(t *testing.T) {
 		{"test.WEBMANIFEST", "application/manifest+json"},
 		{"test.JPG", "image/jpeg"}, // Go 已知，也处理大小写
 
-		// 未知类型
-		{"test.unknown", ""},
+		// 未知类型 - 回退到 defaultMIME
+		{"test.unknown", "application/octet-stream"},
 	}
 
 	for _, tt := range tests {