discordeno/plugins/helpers/src/sendDirectMessage.ts

import { Bot, Collection, CreateMessage } from "../deps.ts";

/** Maps the <userId, channelId> for dm channels */
export const dmChannelIds = new Collection<bigint, bigint>();

/** Sends a direct message to a user. This can take two API calls. The first call is to create a dm channel. Then sending the message to that channel. Channel ids are cached as needed to prevent duplicate requests. */
export async function sendDirectMessage(
  bot: Bot,
  userId: bigint,
  content: string | CreateMessage,
) {
  if (typeof content === "string") content = { content };
  
  // GET CHANNEL ID FROM CACHE OR CREATE THE CHANNEL FOR THIS USER
  const cachedChannelId = dmChannelIds.get(userId);
  // IF ID IS CACHED SEND MESSAGE DIRECTLY
  if (cachedChannelId) return bot.helpers.sendMessage(cachedChannelId, content);

  // CREATE A NEW DM CHANNEL AND PULCK ITS ID
  const channel = (await bot.helpers.getDmChannel(userId));

  // CACHE IT FOR FUTURE REQUESTS
  dmChannelIds.set(userId, channel.id);

  // CACHE CHANNEL IF NEEDED
  return bot.helpers.sendMessage(channel.id, content);
}