/**
 * The site's copy of the published notes.
 *
 * The site reads only the content service, with a reader token, and only
 * published notes. It keeps every note in memory and refreshes in the
 * background, so a saved note shows within a minute and a slow or restarting
 * content service never takes a page down: the last good copy keeps serving.
 */
import { env } from "./env.ts";
import type { NoteData, NoteType } from "@gk/schema";
import { SiteIndex } from "./site.ts";

export interface Note<T extends NoteType = NoteType> {
  path: string;
  type: T;
  /** The file name without `.md`: what wikilinks point at. */
  name: string;
  slug: string;
  title: string;
  data: NoteData<T>;
  body: string;
  acceptedAt: string;
}

export interface Redirect {
  type: string;
  fromSlug: string;
  toPath: string;
}

const baseUrl = () => (env("CONTENT_URL", "http://localhost:4310") as string).replace(/\/$/, "");
const token = () => env("CONTENT_TOKEN", "") as string;
/** Preview only: include unpublished notes. Needs an editor or admin token; never set in production. */
const includeDrafts = () => env("CONTENT_INCLUDE_DRAFTS", "") === "true";
const refreshMs = () => Number(env("CONTENT_REFRESH_SECONDS", "30")) * 1000;

async function api<T>(path: string): Promise<T> {
  const res = await fetch(`${baseUrl()}${path}`, {
    headers: { authorization: `Bearer ${token()}` },
    signal: AbortSignal.timeout(10_000),
  });
  if (!res.ok) throw new Error(`Content service answered ${res.status} for ${path}`);
  return (await res.json()) as T;
}

async function loadAll(): Promise<SiteIndex> {
  const notes: Note[] = [];
  for (let offset = 0; ; offset += 1000) {
    const published = includeDrafts() ? "" : "&published=true";
    const page = await api<(Note & { publish?: boolean })[]>(`/api/notes?full=true${published}&limit=1000&offset=${offset}`);
    notes.push(...page);
    if (page.length < 1000) break;
  }
  const redirects = await api<Redirect[]>("/api/redirects").catch(() => []);
  return new SiteIndex(notes, redirects);
}

let current: SiteIndex | null = null;
let loadedAt = 0;
let inflight: Promise<SiteIndex> | null = null;

function refresh(): Promise<SiteIndex> {
  inflight ??= loadAll()
    .then((index) => {
      current = index;
      loadedAt = Date.now();
      return index;
    })
    .finally(() => {
      inflight = null;
    });
  return inflight;
}

/** The current index. Waits only on the very first load. */
export async function site(): Promise<SiteIndex> {
  if (!current) return refresh();
  if (Date.now() - loadedAt > refreshMs()) {
    refresh().catch((err) => console.error("Content refresh failed; serving the last copy.", err));
  }
  return current;
}

/** Fetch a vault image from the content service, for the /media route. */
export async function attachment(file: string): Promise<Response> {
  return fetch(`${baseUrl()}/attachments/${encodeURIComponent(file)}`, {
    headers: { authorization: `Bearer ${token()}` },
    signal: AbortSignal.timeout(15_000),
  });
}

/** Use a fixed set of notes instead of the content service, for tests. */
export function useIndex(index: SiteIndex) {
  current = index;
  loadedAt = Number.POSITIVE_INFINITY;
}