add save edit to cli via -e

cmd/cli.go

@@ -8,6 +8,8 @@ import (
 	"io/ioutil"
 	"local/pt-todo-server/pttodo"
 	"os"
+	"path"
+	"syscall"
 
 	"gopkg.in/yaml.v2"
 )
@@ -20,13 +22,88 @@ func main() {
 
 func _main() error {
 	filepath := flag.String("f", "-", "path to yaml file")
+	e := flag.Bool("e", false, "edit file")
 	flag.Parse()
+	if *e {
+		if err := edit(*filepath); err != nil {
+			return err
+		}
+	}
+	return dump(os.Stdout, *filepath)
+}
 
+func edit(filepath string) error {
+	var tempFile string
+	cp := func() error {
+		f, err := ioutil.TempFile(os.TempDir(), path.Base(filepath))
+		if err != nil {
+			return err
+		}
+		g, err := os.Open(filepath)
+		if err != nil {
+			return err
+		}
+		if _, err := io.Copy(f, g); err != nil {
+			return err
+		}
+		g.Close()
+		f.Close()
+		tempFile = f.Name()
+		return nil
+	}
+	vi := func() error {
+		vibin := "/usr/bin/vi"
+		cpid, err := syscall.ForkExec(
+			vibin,
+			[]string{vibin, tempFile},
+			&syscall.ProcAttr{
+				Dir:   "",
+				Env:   os.Environ(),
+				Files: []uintptr{os.Stdin.Fd(), os.Stdout.Fd(), os.Stderr.Fd()},
+				Sys:   nil,
+			},
+		)
+		if err != nil {
+			return err
+		}
+		proc, err := os.FindProcess(cpid)
+		if err != nil {
+			return err
+		}
+		state, err := proc.Wait()
+		if err != nil {
+			return err
+		}
+		if exitCode := state.ExitCode(); exitCode != 0 {
+			return fmt.Errorf("bad exit code on vim: %d, state: %+v", exitCode, state)
+		}
+		return nil
+	}
+	verify := func() error {
+		return dump(io.Discard, tempFile)
+	}
+	save := func() error {
+		return os.Rename(tempFile, filepath)
+	}
+
+	for _, foo := range []func() error{cp, vi, verify, save} {
+		if err := foo(); err != nil {
+			if tempFile != "" {
+				os.Remove(tempFile)
+			}
+			return err
+		}
+	}
+
+	return nil
+}
+
+func dump(writer io.Writer, filepath string) error {
 	var reader io.Reader
-	if *filepath == "-" {
+	if filepath == "-" {
 		reader = os.Stdin
 	} else {
-		b, err := ioutil.ReadFile(*filepath)
+		b, err := ioutil.ReadFile(filepath)
 		if err != nil {
 			return err
 		}
@@ -48,6 +125,6 @@ func _main() error {
 	if err != nil {
 		return err
 	}
-	fmt.Printf("%s\n", b2)
+	fmt.Fprintf(writer, "%s\n", b2)
 	return nil
 }