fix: make --events-stream-to work with chat

pkg/monitor/fd.go

@@ -7,7 +7,6 @@ import (
 	"strconv"
 	"strings"
 	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/gptscript-ai/gptscript/pkg/runner"
@@ -23,8 +22,10 @@ type Event struct {
 }
 
 type fileFactory struct {
+	fileName     string
 	file         *os.File
-	runningCount atomic.Int32
+	lock         sync.Mutex
+	runningCount int
 }
 
 // NewFileFactory creates a new monitor factory that writes events to the location specified.
@@ -33,33 +34,23 @@ type fileFactory struct {
 // 2. a file name
 // 3. a named pipe in the form "\\.\pipe\my-pipe"
 func NewFileFactory(loc string) (runner.MonitorFactory, error) {
-	var (
-		file *os.File
-		err  error
-	)
-
-	if strings.HasPrefix(loc, "fd://") {
-		fd, err := strconv.Atoi(strings.TrimPrefix(loc, "fd://"))
-		if err != nil {
-			return nil, err
-		}
-
-		file = os.NewFile(uintptr(fd), "events")
-	} else {
-		file, err = os.OpenFile(loc, os.O_WRONLY|os.O_CREATE, 0644)
-		if err != nil {
-			return nil, err
-		}
-	}
-
 	return &fileFactory{
-		file:         file,
-		runningCount: atomic.Int32{},
+		fileName: loc,
 	}, nil
 }
 
 func (s *fileFactory) Start(_ context.Context, prg *types.Program, env []string, input string) (runner.Monitor, error) {
-	s.runningCount.Add(1)
+	s.lock.Lock()
+	s.runningCount++
+	if s.runningCount == 1 {
+		if err := s.openFile(); err != nil {
+			s.runningCount--
+			s.lock.Unlock()
+			return nil, err
+		}
+	}
+	s.lock.Unlock()
+
 	fd := &fd{
 		prj:     prg,
 		env:     env,
@@ -80,13 +71,40 @@ func (s *fileFactory) Start(_ context.Context, prg *types.Program, env []string,
 }
 
 func (s *fileFactory) close() {
-	if count := s.runningCount.Add(-1); count == 0 {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+
+	s.runningCount--
+	if s.runningCount == 0 {
 		if err := s.file.Close(); err != nil {
 			log.Errorf("error closing monitor file: %v", err)
 		}
 	}
 }
 
+func (s *fileFactory) openFile() error {
+	var (
+		err  error
+		file *os.File
+	)
+	if strings.HasPrefix(s.fileName, "fd://") {
+		fd, err := strconv.Atoi(strings.TrimPrefix(s.fileName, "fd://"))
+		if err != nil {
+			return err
+		}
+
+		file = os.NewFile(uintptr(fd), "events")
+	} else {
+		file, err = os.OpenFile(s.fileName, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0644)
+		if err != nil {
+			return err
+		}
+	}
+
+	s.file = file
+	return nil
+}
+
 type fd struct {
 	prj     *types.Program
 	env     []string