path: root/console/prompter.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package console

import (
    "fmt"
    "strings"

    "github.com/peterh/liner"
)

// TerminalPrompter holds the stdin line reader (also using stdout for printing
// prompts). Only this reader may be used for input because it keeps an internal
// buffer.
var TerminalPrompter = newTerminalPrompter()

// UserPrompter defines the methods needed by the console to promt the user for
// various types of inputs.
type UserPrompter interface {
    // PromptInput displays the given prompt to the user and requests some textual
    // data to be entered, returning the input of the user.
    PromptInput(prompt string) (string, error)

    // PromptPassword displays the given prompt to the user and requests some textual
    // data to be entered, but one which must not be echoed out into the terminal.
    // The method returns the input provided by the user.
    PromptPassword(prompt string) (string, error)

    // PromptConfirm displays the given prompt to the user and requests a boolean
    // choice to be made, returning that choice.
    PromptConfirm(prompt string) (bool, error)

    // SetScrollHistory sets the the input scrollback history that the prompter will
    // allow the user to scoll back to.
    SetScrollHistory(history []string)

    // SetWordCompleter sets the completion function that the prompter will call to
    // fetch completion candidates when the user presses tab.
    SetWordCompleter(completer WordCompleter)
}

// WordCompleter takes the currently edited line with the cursor position and
// returns the completion candidates for the partial word to be completed. If
// the line is "Hello, wo!!!" and the cursor is before the first '!', ("Hello,
// wo!!!", 9) is passed to the completer which may returns ("Hello, ", {"world",
// "Word"}, "!!!") to have "Hello, world!!!".
type WordCompleter func(line string, pos int) (string, []string, string)

// terminalPrompter is a UserPrompter backed by the liner package. It supports
// prompting the user for various input, among others for non-echoing password
// input.
type terminalPrompter struct {
    *liner.State
    warned     bool
    supported  bool
    normalMode liner.ModeApplier
    rawMode    liner.ModeApplier
}

// newTerminalPrompter creates a liner based user input prompter working off the
// standard input and output streams.
func newTerminalPrompter() *terminalPrompter {
    r := new(terminalPrompter)
    // Get the original mode before calling NewLiner.
    // This is usually regular "cooked" mode where characters echo.
    normalMode, _ := liner.TerminalMode()
    // Turn on liner. It switches to raw mode.
    r.State = liner.NewLiner()
    rawMode, err := liner.TerminalMode()
    if err != nil || !liner.TerminalSupported() {
        r.supported = false
    } else {
        r.supported = true
        r.normalMode = normalMode
        r.rawMode = rawMode
        // Switch back to normal mode while we're not prompting.
        normalMode.ApplyMode()
    }
    r.SetCtrlCAborts(true)
    r.SetTabCompletionStyle(liner.TabPrints)

    return r
}

// PromptInput displays the given prompt to the user and requests some textual
// data to be entered, returning the input of the user.
func (r *terminalPrompter) PromptInput(prompt string) (string, error) {
    if r.supported {
        r.rawMode.ApplyMode()
        defer r.normalMode.ApplyMode()
    } else {
        // liner tries to be smart about printing the prompt
        // and doesn't print anything if input is redirected.
        // Un-smart it by printing the prompt always.
        fmt.Print(prompt)
        prompt = ""
        defer fmt.Println()
    }
    return r.State.Prompt(prompt)
}

// PromptPassword displays the given prompt to the user and requests some textual
// data to be entered, but one which must not be echoed out into the terminal.
// The method returns the input provided by the user.
func (r *terminalPrompter) PromptPassword(prompt string) (passwd string, err error) {
    if r.supported {
        r.rawMode.ApplyMode()
        defer r.normalMode.ApplyMode()
        return r.State.PasswordPrompt(prompt)
    }
    if !r.warned {
        fmt.Println("!! Unsupported terminal, password will be echoed.")
        r.warned = true
    }
    // Just as in Prompt, handle printing the prompt here instead of relying on liner.
    fmt.Print(prompt)
    passwd, err = r.State.Prompt("")
    fmt.Println()
    return passwd, err
}

// PromptConfirm displays the given prompt to the user and requests a boolean
// choice to be made, returning that choice.
func (r *terminalPrompter) PromptConfirm(prompt string) (bool, error) {
    input, err := r.Prompt(prompt + " [y/N] ")
    if len(input) > 0 && strings.ToUpper(input[:1]) == "Y" {
        return true, nil
    }
    return false, err
}

// SetScrollHistory sets the the input scrollback history that the prompter will
// allow the user to scoll back to.
func (r *terminalPrompter) SetScrollHistory(history []string) {
    r.State.ReadHistory(strings.NewReader(strings.Join(history, "\n")))
}

// SetWordCompleter sets the completion function that the prompter will call to
// fetch completion candidates when the user presses tab.
func (r *terminalPrompter) SetWordCompleter(completer WordCompleter) {
    r.State.SetWordCompleter(liner.WordCompleter(completer))
}