import {
  parseReleasePost,
  RELEASE_NEWS_CHANNEL,
  RELEASE_WEBHOOK_ID,
  type ReleasePost,
} from "../shared/changelog";

export async function readChangelogFeed({
  token,
  channel = RELEASE_NEWS_CHANNEL,
  webhookId = RELEASE_WEBHOOK_ID,
  before,
  request = fetch,
}: {
  token: string;
  channel?: string;
  webhookId?: string;
  before?: string;
  request?: typeof fetch;
}) {
  if (!/^\d{17,20}$/.test(channel) || (before && !/^\d{17,20}$/.test(before)))
    throw new Error("Invalid news channel or cursor");
  const url = new URL(
    `https://discord.com/api/v10/channels/${channel}/messages`,
  );
  url.searchParams.set("limit", "100");
  if (before) url.searchParams.set("before", before);
  // Reading history only. No Discord write endpoint is used by this feature.
  const response = await request(url.toString(), {
    method: "GET",
    headers: { Authorization: `Bot ${token}` },
    next: { revalidate: 60 },
    signal: AbortSignal.timeout(10_000),
    redirect: "error",
  });
  if (!response.ok)
    throw new Error(`News feed unavailable (${response.status})`);
  const posts: ReleasePost[] = await response.json();
  if (
    !Array.isArray(posts) ||
    posts.some(
      (post) =>
        typeof post.content !== "string" ||
        post.channel_id !== channel ||
        !/^\d{17,20}$/.test(post.id),
    )
  )
    throw new Error("Invalid news response");
  if (
    posts.some((post) => post.webhook_id === webhookId) &&
    posts
      .filter((post) => post.webhook_id === webhookId)
      .every((post) => !post.content.trim())
  )
    throw new Error(
      "Release text is unavailable; check Discord Message Content access",
    );
  const entries = posts
    .flatMap((post) => {
      const entry = parseReleasePost(post, webhookId);
      return entry ? [entry] : [];
    })
    .sort(
      (a, b) =>
        b.publishedAt.localeCompare(a.publishedAt) ||
        (BigInt(a.id) > BigInt(b.id) ? -1 : 1),
    );
  const oldest = posts.reduce<string | undefined>(
    (id, post) => (!id || BigInt(post.id) < BigInt(id) ? post.id : id),
    undefined,
  );
  return {
    entries,
    before: posts.length === 100 && oldest !== before ? oldest : undefined,
  };
}