hongaar/bandersnatch

import Enquirer from "enquirer";
import { Argument } from "./argument.js";
import { Option } from "./option.js";

/**
 * Workaround for "The requested module 'enquirer' is a CommonJS module, which
 * may not support all module.exports as named exports."
 */
const prompt = Enquirer.prompt;

/**
 * Extract PromptOptions from exported Enquirer types, since types are not
 * exported natively.
 * @todo Wait for upstream change to import types from enquirer
 * @link https://github.com/enquirer/enquirer/pull/258
 */
type EnquirerQuestion = Extract<
  Parameters<typeof prompt>[0],
  { initial?: any }
>;

// Another workaround: we need to add the `limit` option to ArrayPromptOptions.
type ArrayPromptOptions = Extract<EnquirerQuestion, { maxChoices?: number }> & {
  limit?: number;
};

type Question = EnquirerQuestion | ArrayPromptOptions;

/**
 * Creates a new prompter instance
 */
export function prompter<T = {}>(baseArgs: Array<Argument | Option>, args: T) {
  return new Prompter(baseArgs, args);
}

export class Prompter<T = {}> {
  constructor(
    private baseArgs: Array<Argument | Option>,
    private args: T,
  ) {}

  public async prompt() {
    const questions = this.getQuestions(this.args);

    // Short circuit if there are no questions to ask.
    if (!questions.length) {
      return this.args;
    }

    // Ask questions and merge with passed in args.
    const answers = await prompt(questions);

    return {
      ...this.args,
      ...answers,
    };
  }

  private getSelectLimit() {
    // Never more than what fits on the screen (+ some padding) or 20
    return Math.min(process.stdout.rows - 3, 20);
  }

  /**
   * Returns an array of arguments and options which should be prompted, because
   * they are promptable (`isPromptable()` returned true) and they are not
   * provided in the args passed in to this function.
   */
  private getQuestions(args: T) {
    // If we need to prompt for things, fill questions array
    return this.baseArgs.reduce((questions, arg) => {
      const name = arg.getName();
      const defaultValue = arg.getDefault();
      const isPromptable = arg.isPromptable();
      const presentInArgs = Object.constructor.hasOwnProperty.call(args, name);
      const isDefault =
        presentInArgs &&
        typeof defaultValue !== "undefined" &&
        defaultValue == (args as any)[name];

      // We're going to assume that if an argument/option still has its default
      // value and it is promptable, it should get a prompt.
      if (isPromptable && (!presentInArgs || isDefault)) {
        // Detect the type of question we need to ask
        switch (true) {
          case typeof arg.getChoices() !== "undefined" &&
            (arg.getType() === "array" || Array.isArray(defaultValue)):
            // Use checkbox question type
            questions.push({
              name,
              type: "multiselect",
              message: arg.getPrompt(),
              initial: defaultValue,
              choices: arg.getChoices() as string[],
              limit: this.getSelectLimit(),
            });
            break;

          case typeof arg.getChoices() !== "undefined":
            // Use list question type
            questions.push({
              name,
              type: "autocomplete",
              message: arg.getPrompt(),
              initial: defaultValue,
              choices: arg.getChoices() as string[],
              limit: this.getSelectLimit(),
            });
            break;

          case arg.getType() === "boolean" || typeof defaultValue === "boolean":
            // Use confirm question type
            questions.push({
              name,
              type: "confirm",
              message: arg.getPrompt(),
              initial: defaultValue,
            });
            break;

          default:
            // Use input question type as default
            questions.push({
              name,
              type: "input",
              message: arg.getPrompt(),
              initial: defaultValue,
            });
        }
      }

      return questions;
    }, [] as Question[]);
  }
}