denoland-deno/runtime/js/41_prompt.js

// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
import { core, primordials } from "ext:core/mod.js";
import { isatty } from "ext:runtime/40_tty.js";
import { stdin } from "ext:deno_io/12_io.js";
const { ArrayPrototypePush, StringPrototypeCharCodeAt, Uint8Array } =
  primordials;
const LF = StringPrototypeCharCodeAt("\n", 0);
const CR = StringPrototypeCharCodeAt("\r", 0);

function alert(message = "Alert") {
  if (!isatty(stdin.rid)) {
    return;
  }

  core.print(`${message} [Enter] `, false);

  readLineFromStdinSync();
}

function confirm(message = "Confirm") {
  if (!isatty(stdin.rid)) {
    return false;
  }

  core.print(`${message} [y/N] `, false);

  const answer = readLineFromStdinSync();

  return answer === "Y" || answer === "y";
}

function prompt(message = "Prompt", defaultValue) {
  defaultValue ??= null;

  if (!isatty(stdin.rid)) {
    return null;
  }

  if (defaultValue) {
    message += ` [${defaultValue}]`;
  }

  message += " ";

  // output in one shot to make the tests more reliable
  core.print(message, false);

  return readLineFromStdinSync() || defaultValue;
}

function readLineFromStdinSync() {
  const c = new Uint8Array(1);
  const buf = [];

  while (true) {
    const n = stdin.readSync(c);
    if (n === null || n === 0) {
      break;
    }
    if (c[0] === CR) {
      const n = stdin.readSync(c);
      if (c[0] === LF) {
        break;
      }
      ArrayPrototypePush(buf, CR);
      if (n === null || n === 0) {
        break;
      }
    }
    if (c[0] === LF) {
      break;
    }
    ArrayPrototypePush(buf, c[0]);
  }
  return core.decode(new Uint8Array(buf));
}

export { alert, confirm, prompt };