import { FEED_BASE_URL } from "./env";
import { ensureFreshSession, refreshSession } from "./session-refresh";

// Home-feed proxy logic. Reads one page of the person's home feed from Minnect
// with their server-held feed token. Tokens never leave the server and are
// never logged. Card-field extraction is a later task; items pass through raw.

export const DEFAULT_LIMIT = 20;
export const MAX_LIMIT = 50;

export type FeedPageResult =
  | { ok: true; items: unknown[]; nextCursor: string | null }
  | { ok: false; status: 401 | 502; error: "sign_in" | "feed_unavailable" };

interface FeedOptions {
  fetchImpl?: typeof fetch;
  now?: number;
}

/** Clamp a requested page size to 1..50, defaulting to 20. */
export function clampLimit(raw: string | number | null | undefined): number {
  const n = typeof raw === "number" ? raw : Number.parseInt(raw ?? "", 10);
  if (!Number.isFinite(n) || n < 1) return DEFAULT_LIMIT;
  return Math.min(Math.floor(n), MAX_LIMIT);
}

function buildUrl(cursor: string | null, limit: number): string {
  const params = new URLSearchParams({ limit: String(limit) });
  if (cursor) params.set("cursor", cursor);
  return `${FEED_BASE_URL}/api/v1/feeds/home/items?${params.toString()}`;
}

async function callFeed(
  token: string,
  cursor: string | null,
  limit: number,
  doFetch: typeof fetch,
): Promise<Response> {
  return doFetch(buildUrl(cursor, limit), {
    method: "GET",
    headers: { Accept: "application/json", Authorization: `Bearer ${token}` },
  });
}

export async function getHomeFeedPage(
  sessionId: string | undefined,
  cursor: string | null,
  limit: number,
  options: FeedOptions = {},
): Promise<FeedPageResult> {
  const signIn = { ok: false, status: 401, error: "sign_in" } as const;
  const doFetch = options.fetchImpl ?? fetch;

  let session = await ensureFreshSession(sessionId, options);
  if (!session || !sessionId) return signIn;

  let res: Response;
  try {
    res = await callFeed(session.feedAccessToken, cursor, limit, doFetch);
    if (res.status === 401) {
      // One refresh, then one retry. A second 401 means sign in again.
      session = await refreshSession(sessionId, options);
      if (!session) return signIn;
      res = await callFeed(session.feedAccessToken, cursor, limit, doFetch);
      if (res.status === 401) return signIn;
    }
  } catch {
    return { ok: false, status: 502, error: "feed_unavailable" };
  }
  if (res.status !== 200) {
    return { ok: false, status: 502, error: "feed_unavailable" };
  }

  let body: unknown;
  try {
    body = await res.json();
  } catch {
    return { ok: false, status: 502, error: "feed_unavailable" };
  }
  const root = body && typeof body === "object" ? (body as Record<string, unknown>) : {};
  const meta =
    root.metadata && typeof root.metadata === "object"
      ? (root.metadata as Record<string, unknown>)
      : {};
  return {
    ok: true,
    items: Array.isArray(root.data) ? root.data : [],
    nextCursor: typeof meta.nextCursor === "string" && meta.nextCursor ? meta.nextCursor : null,
  };
}