Add configurable text encoding for file and folder names

Replace hardcoded Mac Roman encoding globals with a configurable Encoding
field in config.yaml. Servers that exclusively serve modern UTF-8 clients
can now set Encoding: utf8 to disable Mac Roman conversion. The default
remains "macintosh" for backward compatibility.

- Add Encoding field to Config struct (macintosh|utf8)
- Store TextDecoder/TextEncoder on Server, initialized from config
- Add TextDecoder()/TextEncoder() accessors on ClientConn
- Pass decoder/encoder explicitly to ReadPath and GetFileNameList
- Remove package-level txtEncoder/txtDecoder globals
- Add warning log when files are skipped due to encoding errors
- Log and return error replies in HandleGetFileNameList on failure
- Document the new config option in docs/text-encoding.md

1 files changed, 15 insertions, 7 deletions

diff --git a/hotline/server.go b/hotline/server.go
index 545e84c..dcb90e7 100644
--- a/hotline/server.go
+++ b/hotline/server.go
@@ -18,6 +18,7 @@ import (
 	"time"
 
 	"github.com/redis/go-redis/v9"
+	"golang.org/x/text/encoding"
 	"golang.org/x/text/encoding/charmap"
 	"golang.org/x/time/rate"
 )
@@ -30,12 +31,6 @@ type requestCtx struct {
 	remoteAddr string
 }
 
-// Converts bytes from Mac Roman encoding to UTF-8
-var txtDecoder = charmap.Macintosh.NewDecoder()
-
-// Converts bytes from UTF-8 to Mac Roman encoding
-var txtEncoder = charmap.Macintosh.NewEncoder()
-
 type Server struct {
 	NetInterface string
 	Port         int
@@ -73,6 +68,9 @@ type Server struct {
 	// TrackerRegistrar handles tracker registration (injectable for testing)
 	TrackerRegistrar TrackerRegistrar
 
+	TextDecoder *encoding.Decoder
+	TextEncoder *encoding.Encoder
+
 	TLSConfig *tls.Config
 	TLSPort   int
 }
@@ -140,6 +138,16 @@ func NewServer(options ...Option) (*Server, error) {
 		opt(&server)
 	}
 
+	// Initialize text encoding based on config.
+	switch server.Config.Encoding {
+	case "utf8":
+		server.TextDecoder = encoding.Nop.NewDecoder()
+		server.TextEncoder = encoding.Nop.NewEncoder()
+	default:
+		server.TextDecoder = charmap.Macintosh.NewDecoder()
+		server.TextEncoder = charmap.Macintosh.NewEncoder()
+	}
+
 	// generate a new random passID for tracker registration
 	_, err := rand.Read(server.TrackerPassID[:])
 	if err != nil {
@@ -690,7 +698,7 @@ func (s *Server) handleFileTransfer(ctx context.Context, rwc io.ReadWriter) erro
 		"Name", string(fileTransfer.ClientConn.UserName),
 	)
 
-	fullPath, err := ReadPath(fileTransfer.FileRoot, fileTransfer.FilePath, fileTransfer.FileName)
+	fullPath, err := ReadPath(fileTransfer.FileRoot, fileTransfer.FilePath, fileTransfer.FileName, s.TextDecoder)
 	if err != nil {
 		return err
 	}