Fixing updates

core/run_manager/run_file_manager.go

@@ -0,0 +1,95 @@
+package run_manager
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"syscall"
+	"time"
+)
+
+func File(index string) RunFileManagerContract {
+	value, ok := indexedPaths[index]
+	if !ok {
+		err := indexPaths()
+		if err != nil {
+			return &RunFileManager{
+				err: err,
+			}
+		}
+		value, ok = indexedPaths[index]
+		if !ok {
+			return &RunFileManager{
+				err: fmt.Errorf("cannot detect file under index %s", index),
+			}
+		}
+	}
+	return &RunFileManager{
+		indexedPath: value,
+	}
+}
+
+func (r *RunFileManager) Open() (*os.File, error) {
+	if r.err != nil {
+		return nil, r.err
+	}
+	file, err := os.OpenFile(r.indexedPath, os.O_RDWR, 0)
+	if err != nil {
+		return nil, err
+	}
+	r.file = file
+	return file, nil
+}
+
+func (r *RunFileManager) Close() error {
+	return r.file.Close()
+}
+
+func (r *RunFileManager) Watch(parentCtx context.Context, callback func()) (context.CancelFunc, error) {
+	if r.err != nil {
+		return nil, r.err
+	}
+	if r.file == nil {
+		return nil, fmt.Errorf("file is not opened")
+	}
+
+	info, err := r.file.Stat()
+	if err != nil {
+		return nil, err
+	}
+	origStat := info.Sys().(*syscall.Stat_t)
+	origIno := origStat.Ino
+	origModTime := info.ModTime()
+
+	ctx, cancel := context.WithCancel(parentCtx)
+
+	go func() {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			default:
+				newInfo, err := os.Stat(r.indexedPath)
+				if err != nil {
+					if os.IsNotExist(err) {
+						callback()
+						return
+					}
+				} else {
+					newStat := newInfo.Sys().(*syscall.Stat_t)
+					if newStat.Ino != origIno {
+						callback()
+						return
+					}
+					if !newInfo.ModTime().Equal(origModTime) {
+						callback()
+						return
+					}
+				}
+				time.Sleep(1 * time.Second)
+			}
+		}
+	}()
+
+	return cancel, nil
+}