Fix Mac Roman decoding incorrectly applied to filesystem root paths

ReadPath() and HandleNewFolder decoded the entire joined path from Mac
Roman, including the fileRoot prefix which is already UTF-8. This caused
file listing failures when config paths or FileRoot values contained
non-ASCII characters. Now only client-provided path components (subPath,
fileName/folderName) are decoded before joining with fileRoot.

3 files changed, 46 insertions, 7 deletions

diff --git a/hotline/file_path.go b/hotline/file_path.go
index a3a13f1..c97faea 100644
--- a/hotline/file_path.go
+++ b/hotline/file_path.go
@@ -115,14 +115,22 @@ func ReadPath(fileRoot string, filePath, fileName []byte) (fullPath string, err
 		subPath = path.Join("/", subPath, string(pathItem.Name))
 	}
 
+	// Decode only client-provided path components from Mac Roman to UTF-8.
+	// The fileRoot is already a UTF-8 filesystem path and must not be decoded.
+	subPath, err = txtDecoder.String(subPath)
+	if err != nil {
+		return "", fmt.Errorf("invalid filepath encoding: %w", err)
+	}
+
+	decodedFileName, err := txtDecoder.String(string(fileName))
+	if err != nil {
+		return "", fmt.Errorf("invalid filename encoding: %w", err)
+	}
+
 	fullPath = path.Join(
 		fileRoot,
 		subPath,
-		path.Join("/", string(fileName)),
+		path.Join("/", decodedFileName),
 	)
-	fullPath, err = txtDecoder.String(fullPath)
-	if err != nil {
-		return "", fmt.Errorf("invalid filepath encoding: %w", err)
-	}
 	return fullPath, nil
 }
diff --git a/hotline/file_path_test.go b/hotline/file_path_test.go
index ee0cbac..c86a8d9 100644
--- a/hotline/file_path_test.go
+++ b/hotline/file_path_test.go
@@ -152,6 +152,29 @@ func Test_readPath(t *testing.T) {
 			},
 			want: "/usr/local/var/mobius/Files",
 		},
+		{
+			name: "when fileRoot contains non-ASCII UTF-8 characters",
+			args: args{
+				fileRoot: "/files/español",
+				filePath: nil,
+				fileName: []byte("foo"),
+			},
+			want: "/files/español/foo",
+		},
+		{
+			name: "when fileRoot contains non-ASCII and filePath has Mac Roman bytes",
+			args: args{
+				fileRoot: "/files/español",
+				filePath: []byte{
+					0x00, 0x01,
+					0x00, 0x00,
+					0x06,
+					0x63, 0x61, 0x66, 0x8e, 0x73, 0x21, // "caf\x8es!" where 0x8e is Mac Roman é
+				},
+				fileName: []byte("foo"),
+			},
+			want: "/files/español/cafés!/foo",
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
diff --git a/internal/mobius/transaction_handlers.go b/internal/mobius/transaction_handlers.go
index 259ac02..33af941 100644
--- a/internal/mobius/transaction_handlers.go
+++ b/internal/mobius/transaction_handlers.go
@@ -568,11 +568,19 @@ func HandleNewFolder(cc *hotline.ClientConn, t *hotline.Transaction) (res []hotl
 			subPath = path.Join("/", subPath, string(pathItem.Name))
 		}
 	}
-	newFolderPath := path.Join(cc.FileRoot(), subPath, folderName)
-	newFolderPath, err := txtDecoder.String(newFolderPath)
+
+	// Decode only client-provided path components from Mac Roman to UTF-8.
+	// The FileRoot is already a UTF-8 filesystem path and must not be decoded.
+	subPath, err := txtDecoder.String(subPath)
 	if err != nil {
 		return res
 	}
+	folderName, err = txtDecoder.String(folderName)
+	if err != nil {
+		return res
+	}
+
+	newFolderPath := path.Join(cc.FileRoot(), subPath, folderName)
 
 	// TODO: check path and folder Name lengths