hikari/server/src/modules/announceOnMastodon.ts

/**
 * @copyright nhcarrigan
 * @license Naomi's Public License
 * @author Naomi Carrigan
 */

import { isValidString } from "../utils/typeguards.js";

/**
 * Forwards an announcement to our Mastodon account.
 * @param content - The main body of the announcement.
 * @returns A message indicating the success or failure of the operation.
 */
// eslint-disable-next-line max-lines-per-function, max-statements, complexity -- This is a big function.
export const announceOnMastodon = async(
  content: Array<string>,
): Promise<string> => {
  if (
    process.env.MASTODON_INSTANCE_URL === undefined
    || process.env.MASTODON_ACCESS_TOKEN === undefined
  ) {
    return "Mastodon credentials are not set.";
  }
  const [ firstPost, ...restOfPosts ] = content;
  const failedReplies: Array<string> = [];
  if (firstPost === undefined) {
    return "No posts to send to Mastodon.";
  }
  const instanceUrl = process.env.MASTODON_INSTANCE_URL.replace(/\/$/, "");
  const accessToken = process.env.MASTODON_ACCESS_TOKEN;
  const apiUrl = `${instanceUrl}/api/v1/statuses`;
  const headers = {
    // eslint-disable-next-line @typescript-eslint/naming-convention -- HTTP header name.
    "Authorization": `Bearer ${accessToken}`,
    // eslint-disable-next-line @typescript-eslint/naming-convention -- HTTP header name.
    "Content-Type":  "application/json",
  };
  const firstPostResponse = await fetch(apiUrl, {
    body:    JSON.stringify({ status: firstPost }),
    headers: headers,
    method:  "POST",
  }).catch((error: unknown) => {
    return error instanceof Error
      ? error.message
      : String(error);
  });
  if (typeof firstPostResponse === "string") {
    return `Failed to send initial post to Mastodon. ${firstPostResponse}`;
  }
  if (!firstPostResponse.ok) {
    const errorText = await firstPostResponse.text().catch(() => {
      return firstPostResponse.statusText;
    });
    return `Failed to send initial post to Mastodon. Status: ${firstPostResponse.status.toString()} ${errorText}`;
  }
  // eslint-disable-next-line @typescript-eslint/consistent-type-assertions -- Fetch does not accept generics.
  const firstPostData = await firstPostResponse.json() as { id?: string };
  if (firstPostData.id === undefined) {
    return `Failed to parse initial post ID from Mastodon. ${JSON.stringify(firstPostData)}`;
  }
  let inReplyToId = firstPostData.id;
  for (const post of restOfPosts) {
    // eslint-disable-next-line no-await-in-loop -- We need to do this sequentially.
    const replyResponse = await fetch(apiUrl, {
      body: JSON.stringify({
        // eslint-disable-next-line @typescript-eslint/naming-convention -- API requirement.
        in_reply_to_id: inReplyToId,
        status:         post,
      }),
      headers: headers,
      method:  "POST",
    }).catch((error: unknown) => {
      return error instanceof Error
        ? error.message
        : String(error);
    });
    if (typeof replyResponse === "string") {
      failedReplies.push(post);
      continue;
    }
    if (!replyResponse.ok) {
      failedReplies.push(post);
      continue;
    }
    // eslint-disable-next-line @typescript-eslint/consistent-type-assertions, no-await-in-loop -- Fetch does not accept generics.
    const replyData = await replyResponse.json() as { id?: string };
    if (isValidString(replyData.id)) {
      inReplyToId = replyData.id;
      continue;
    }
    failedReplies.push(post);
  }
  return `Successfully sent initial post to Mastodon. ${failedReplies.length > 0
    ? `Failed to send ${failedReplies.length.toString()} replies: ${failedReplies.join(", ")}`
    : `All ${(content.length - 1).toString()} replies were sent successfully.`}`;
};