promptSync.js

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @format
 */

// Simplified version of:
// https://github.com/0x00A/prompt-sync/blob/master/index.js

'use strict';

var fs = require('fs');
var term = 13; // carriage return

function create() {
  return prompt;

  function prompt(ask, value, opts) {
    var insert = 0;
    opts = opts || {};

    if (Object(ask) === ask) {
      opts = ask;
      ask = opts.ask;
    } else if (Object(value) === value) {
      opts = value;
      value = opts.value;
    }
    ask = ask || '';
    var echo = opts.echo;
    var masked = 'echo' in opts;

    var fd =
      process.platform === 'win32'
        ? process.stdin.fd
        : fs.openSync('/dev/tty', 'rs');

    var wasRaw = process.stdin.isRaw;
    if (!wasRaw) {
      process.stdin.setRawMode(true);
    }

    var buf = Buffer.alloc(3);
    var str = '',
      character,
      read;

    if (ask) {
      process.stdout.write(ask);
    }

    while (true) {
      read = fs.readSync(fd, buf, 0, 3);
      if (read > 1) {
        // received a control sequence
        if (buf.toString()) {
          str = str + buf.toString();
          str = str.replace(/\0/g, '');
          insert = str.length;
          process.stdout.write('\u001b[2K\u001b[0G' + ask + str);
          process.stdout.write('\u001b[' + (insert + ask.length + 1) + 'G');
          buf = Buffer.alloc(3);
        }
        continue; // any other 3 character sequence is ignored
      }

      // if it is not a control character seq, assume only one character is read
      character = buf[read - 1];

      // catch a ^C and return null
      if (character === 3) {
        process.stdout.write('^C\n');
        fs.closeSync(fd);
        process.exit(130);
        process.stdin.setRawMode(wasRaw);
        return null;
      }

      // catch the terminating character
      if (character === term) {
        fs.closeSync(fd);
        break;
      }

      if (
        character === 127 ||
        (process.platform === 'win32' && character === 8)
      ) {
        //backspace
        if (!insert) {
          continue;
        }
        str = str.slice(0, insert - 1) + str.slice(insert);
        insert--;
        process.stdout.write('\u001b[2D');
      } else {
        if (character < 32 || character > 126) {
          continue;
        }
        str =
          str.slice(0, insert) +
          String.fromCharCode(character) +
          str.slice(insert);
        insert++;
      }

      if (masked) {
        process.stdout.write(
          '\u001b[2K\u001b[0G' + ask + Array(str.length + 1).join(echo),
        );
      } else {
        process.stdout.write('\u001b[s');
        if (insert === str.length) {
          process.stdout.write('\u001b[2K\u001b[0G' + ask + str);
        } else {
          if (ask) {
            process.stdout.write('\u001b[2K\u001b[0G' + ask + str);
          } else {
            process.stdout.write(
              '\u001b[2K\u001b[0G' +
                str +
                '\u001b[' +
                (str.length - insert) +
                'D',
            );
          }
        }
        process.stdout.write('\u001b[u');
        process.stdout.write('\u001b[1C');
      }
    }

    process.stdout.write('\n');

    process.stdin.setRawMode(wasRaw);

    return str || value || '';
  }
}

module.exports = create;