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// Package repl implements a REPL (read-eval-print loop) for otto.
package repl
import (
"fmt"
"io"
"strings"
"sync/atomic"
"github.com/robertkrimen/otto"
"gopkg.in/readline.v1"
)
var counter uint32
// DebuggerHandler implements otto's debugger handler signature, providing a
// simple drop-in debugger implementation.
func DebuggerHandler(vm *otto.Otto) {
i := atomic.AddUint32(&counter, 1)
// purposefully ignoring the error here - we can't do anything useful with
// it except panicking, and that'd be pretty rude. it'd be easy enough for a
// consumer to define an equivalent function that _does_ panic if desired.
_ = RunWithPrompt(vm, fmt.Sprintf("DEBUGGER[%d]>", i))
}
// Run creates a REPL with the default prompt and no prelude.
func Run(vm *otto.Otto) error {
return RunWithPromptAndPrelude(vm, "", "")
}
// RunWithPrompt runs a REPL with the given prompt and no prelude.
func RunWithPrompt(vm *otto.Otto, prompt string) error {
return RunWithPromptAndPrelude(vm, prompt, "")
}
// RunWithPrelude runs a REPL with the default prompt and the given prelude.
func RunWithPrelude(vm *otto.Otto, prelude string) error {
return RunWithPromptAndPrelude(vm, "", prelude)
}
// RunWithPromptAndPrelude runs a REPL with the given prompt and prelude.
func RunWithPromptAndPrelude(vm *otto.Otto, prompt, prelude string) error {
if prompt == "" {
prompt = ">"
}
prompt = strings.Trim(prompt, " ")
prompt += " "
rl, err := readline.New(prompt)
if err != nil {
return err
}
if prelude != "" {
if _, err := io.Copy(rl.Stderr(), strings.NewReader(prelude+"\n")); err != nil {
return err
}
rl.Refresh()
}
var d []string
for {
l, err := rl.Readline()
if err != nil {
if err == readline.ErrInterrupt {
if d != nil {
d = nil
rl.SetPrompt(prompt)
rl.Refresh()
continue
}
break
}
return err
}
if l == "" {
continue
}
d = append(d, l)
s, err := vm.Compile("repl", strings.Join(d, "\n"))
if err != nil {
rl.SetPrompt(strings.Repeat(" ", len(prompt)))
} else {
rl.SetPrompt(prompt)
d = nil
v, err := vm.Eval(s)
if err != nil {
if oerr, ok := err.(*otto.Error); ok {
io.Copy(rl.Stdout(), strings.NewReader(oerr.String()))
} else {
io.Copy(rl.Stdout(), strings.NewReader(err.Error()))
}
} else {
rl.Stdout().Write([]byte(v.String() + "\n"))
}
}
rl.Refresh()
}
return rl.Close()
}
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