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editstash.go
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editstash.go
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package anystore
import (
"bufio"
"context"
"encoding/json"
"errors"
"fmt"
"os"
"os/exec"
"os/signal"
"strings"
"syscall"
"unsafe"
)
var (
DefaultEditors = []string{"/bin/vim", "/usr/bin/vim", "/bin/vi", "/usr/bin/nano"}
)
var (
ErrNoEditorFound error = errors.New("no editor found")
ErrNotATerminal error = errors.New("os.Stdin is not a terminal")
)
// EditThing is an interactive variant of Stash, editing the Thing
// before Stashing it. EditThing does not Unstash before editing, it
// uses the actual Thing. If you need to load Thing from persistence
// before editing, call Unstash prior to EditThing (make sure Thing is
// zero/new/empty before Unstash). EditThing uses encoding/json for
// editing, beware if a user enters "null" on a non-pointer field and
// saves, encoding/json will ignore it effectively using the original
// value without producing an error. Similarily, if a user removes a
// field while editing, the original value will be retained.
//
// Environment variable EDITOR is used as a json editor falling back
// to conf.Editor and finally one of the DefaultEditors.
func EditThing(conf *StashConfig) error {
if !IsUnixTerminal(os.Stdin) {
return ErrNotATerminal
}
executables := []string{}
envEditor := os.Getenv("EDITOR")
switch {
case envEditor != "" && fileExists(envEditor):
// Use editor in the EDITOR environment variable
executables = append(executables, envEditor)
case conf.Editor == "":
// Use one of DefaultEditors
executables = append(executables, DefaultEditors...)
default:
// Use conf.Editor
if !fileExists(conf.Editor) {
return fmt.Errorf("%q not found", conf.Editor)
}
executables = append(executables, conf.Editor)
}
if len(executables) == 0 {
return ErrNoEditorFound
}
tempfile, err := dumpThingInTemp(conf.Key, conf.Thing)
if err != nil {
return err
}
ctx, cancel := context.WithCancel(context.Background())
ch := make(chan os.Signal, 1)
signal.Notify(ch, syscall.SIGINT, syscall.SIGTERM)
go func() {
<-ch
cancel()
}()
defer func() {
os.Remove(tempfile)
signal.Stop(ch)
close(ch)
}()
for {
err = tryExec(ctx, executables, tempfile)
if err != nil {
return err
}
if ctx.Err() != nil {
// Probably unnecessary as tryExec will return error on *exec.ExitError. If
// terminated by cancel() above, do not read, unmarshal or Stash the
// tempfile (require clean exit).
break
}
marshalledThing, err := os.ReadFile(tempfile)
if err != nil {
return err
}
if err := json.Unmarshal(marshalledThing, conf.Thing); err != nil {
fmt.Printf("Error encoding json: %v\n", err)
fmt.Printf("Edit file again? [Y/n] ")
retryQuestion:
s := bufio.NewScanner(os.Stdin)
s.Scan()
if ctx.Err() != nil {
break
}
switch {
case s.Text() == "", strings.EqualFold(s.Text(), "y"), strings.EqualFold(s.Text(), "yes"):
continue
case strings.EqualFold(s.Text(), "n"), strings.EqualFold(s.Text(), "no"):
return err
default:
fmt.Printf("Sorry, please answer yes or no. Edit file again? [Y/n] ")
goto retryQuestion
}
}
if err := Stash(conf); err != nil {
return err
}
break
}
return nil
}
func fileExists(file string) bool {
fs, err := os.Stat(file)
if err != nil {
return false
}
if fs.Mode().IsRegular() {
return true
}
return false
}
func dumpThingInTemp(name string, thing any) (string, error) {
j, err := json.MarshalIndent(thing, "", " ")
if err != nil {
return "", err
}
var tempfileTemplate string
runes := []rune{}
for _, r := range name {
if (r >= 'A' && r <= 'Z') || (r >= 'a' && r <= 'z') || r == '-' || r == '_' {
runes = append(runes, r)
}
}
tempfileTemplate = string(runes) + "-" + rndstr(8) + "-*.json"
fl, err := os.CreateTemp("", tempfileTemplate)
if err != nil {
return "", err
}
tempfile := fl.Name()
remove := true
defer func() {
defer fl.Close()
if remove {
os.Remove(tempfile)
}
}()
if n, err := fl.Write(j); err != nil {
return "", err
} else if n != len(j) {
return "", ErrWroteTooLittle
}
remove = false
return tempfile, nil
}
func tryExec(ctx context.Context, executables []string, arg ...string) error {
for _, executable := range executables {
cmd := exec.CommandContext(ctx, executable, arg...)
cmd.Stdin = os.Stdin
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
err := cmd.Run()
if err != nil {
if _, found := err.(*exec.ExitError); found {
return err
}
continue
}
return nil
}
return ErrNoEditorFound
}
// IsUnixTerminal is constructed from terminal.IsTerminal() and is only
// reproduced here in order not to import an external dependency.
func IsUnixTerminal(f *os.File) bool {
type UnixTermios struct {
Iflag uint32
Oflag uint32
Cflag uint32
Lflag uint32
Line uint8
Cc [19]uint8
Ispeed uint32
Ospeed uint32
}
const TCGETS = 0x5401
const SYS_IOCTL = 16
fd := f.Fd()
var value UnixTermios
req := TCGETS
_, _, e1 := syscall.Syscall(SYS_IOCTL, uintptr(fd), uintptr(req), uintptr(unsafe.Pointer(&value)))
return e1 == 0
}