prompt.ts

import prompts from 'prompts';

type Choice = {
  title: string;
  value: string;
  description?: string;
};

export type Question<T extends string> = Omit<
  prompts.PromptObject<T>,
  'validate' | 'name' | 'choices'
> & {
  name: T;
  validate?: (value: string) => boolean | string;
  choices?:
    | Choice[]
    | ((prev: unknown, values: Partial<prompts.Answers<T>>) => Choice[]);
};

/**
 * Wrapper around `prompts` with additional features:
 *
 * - Improved type-safety
 * - Read answers from passed arguments
 * - Skip questions with a single choice
 * - Exit on canceling the prompt
 */
export async function prompt<T extends string>(
  questions: Question<T>[] | Question<T>,
  argv?: Record<T, string>,
  options?: prompts.Options
) {
  const singleChoiceAnswers = {};
  const promptQuestions = [];

  if (Array.isArray(questions)) {
    for (const question of questions) {
      // Skip questions which are passed as parameter and pass validation
      const argValue = argv?.[question.name];

      if (argValue && question.validate?.(argValue) !== false) {
        continue;
      }

      // Don't prompt questions with a single choice
      if (Array.isArray(question.choices) && question.choices.length === 1) {
        const onlyChoice = question.choices[0];

        if (onlyChoice?.value) {
          // @ts-expect-error assume the passed value is correct
          singleChoiceAnswers[question.name] = onlyChoice.value;
        }

        continue;
      }

      const { type, choices } = question;

      // Don't prompt dynamic questions with a single choice
      if (type === 'select' && typeof choices === 'function') {
        question.type = (prev, values) => {
          const dynamicChoices = choices(prev, { ...argv, ...values });

          if (dynamicChoices && dynamicChoices.length === 1) {
            const onlyChoice = dynamicChoices[0];

            if (onlyChoice?.value) {
              // @ts-expect-error assume the passed value is correct
              singleChoiceAnswers[question.name] = onlyChoice.value;
            }

            return null;
          }

          return type;
        };
      }

      promptQuestions.push(question);
    }
  } else {
    promptQuestions.push(questions);
  }

  const promptAnswers = await prompts(promptQuestions, {
    onCancel() {
      // Exit the CLI on cancel
      process.exit(1);
    },
    ...options,
  });

  return {
    ...argv,
    ...singleChoiceAnswers,
    ...promptAnswers,
  };
}