message handler example

import { Handler, MessageFilterCallback } from './handler';

// Structure for all questions
// `description` is the actual "question" that the user responds to
// `property` is the object key that will be set
// `fn` is the filter function that's called to check whether a given message is valid
// `errorMessage` is the error message that is sent if the given message does not match filter
// `toPropertyValue` is an optional function that returns the value that will be assigned to data[property]
interface Question {
  description: string;
  property: string;
  fn: MessageFilterCallback;
  errorMessage: string;
  toPropertyValue?: (p: string) => string | number;
}

// Command group for the command
const commands = new discord.command.CommandGroup({
  defaultPrefix: '..'
});

const handler = new Handler();

// Regular expression for checking if input is a "color code" (e.g. #ff0000, #fff, ...)
const COLOR_REGEX = new RegExp('^\\d+|#([A-F\\d]{3}|[A-F\\d]{6})$', 'i');

function isColorCode(str: string) {
  return COLOR_REGEX.test(str);
}

// Turns a "color code" into a number ("#ff0000" -> 16711680)
function formatColor(str: string) {
  return str.startsWith('#') ? parseInt(str.substr(1), 16) : Number(str);
}

// This array includes all "questions"
// See comments above `Question` interface to see what each field is for
const questions: ReadonlyArray<Question> = [
  // Question 1: embed title
  // `fn` makes sure that the title won't exceed 256 characters
  {
    description: 'Embed title (max 256 characters)',
    property: 'title',
    fn: (handler, msg) => msg.content.length < 256,
    errorMessage: 'Embed title must not be longer than 256 characters'
  },

  // Question 2: embed description
  // `fn` makes sure that the description won't exceed 1024 characters
  {
    description: 'Embed description (max 1024 characters)',
    property: 'description',
    fn: (handler, msg) => msg.content.length < 1024,
    errorMessage: 'Embed description must not be longer than 1024 character'
  },

  // Question 3: embed color
  // `fn` makes sure that the color is a valid color code:
  // #fff, #ffffff, 16777215
  {
    description: 'Embed color',
    property: 'color',
    fn: (handler, msg) => isColorCode(msg.content),
    toPropertyValue: formatColor,
    errorMessage:
      "That doesn't look like a valid color code. Examples: #ff0000, #fff, #ffff00, 16777215"
  }
];

commands.raw('embed', async (message) => {
  // `question` will be the index used to get the current question
  let question = 0;

  // `data` is the embed data that is sent after the user has answered all questions
  // Using a null prototype object to keep it simple (won't inherit Object)
  const data = Object.create(null);

  // Initial message
  await message.reply(questions[question].description);

  await handler.createMessageHandler({
    message,
    async filter(handler, message) {
      const currentQuestion = questions[question];

      // Forward all parameters to the current filter function
      const result = await currentQuestion.fn(handler, message);

      // If the filter function returned false, respond with an error
      if (!result) {
        await message.reply(currentQuestion.errorMessage);
        return false;
      }

      // If everything is good, return true
      return true;
    },
    async onMatch(handler, msg) {
      // `onMatch` is called if the filter function returned true, which means that we can be sure that the given message is valid

      const currentQuestion = questions[question];

      // Assigns the formatted value to `property`, e.g. `data['title'] = msg.content` for the first question
      // If `toPropertyValue` does not exist for this question, it defaults to the message content
      data[currentQuestion.property] =
        currentQuestion.toPropertyValue?.(msg.content) ?? msg.content;

      // Check if this was the last question
      if (question >= questions.length - 1) {
        // End handler by calling `done` on it
        handler.done();

        // Finally respond with embed data
        // `data` is an object that has all properties that were assigned previously (see line 103-104)
        message.reply({ embed: data });
        return;
      }

      // Increment index (question) and send next question
      question++;
      await message.reply(questions[question].description);
    }
  });
});