// Browser-side calls to this app's own /api/session. No token, password or
// session id is stored or logged here; the session lives in an httpOnly cookie.

export type Person = { name: string; email: string; pictureUrl: string | null; feedUserId?: string };

export const WRONG_CREDENTIALS = "Email or password is incorrect.";
export const GENERIC_FAILURE = "Could not sign you in. Try again.";

type Fetch = typeof fetch;

function toPerson(body: unknown): Person | null {
  if (!body || typeof body !== "object") return null;
  const r = body as Record<string, unknown>;
  if (typeof r.email !== "string") return null;
  return {
    name: typeof r.name === "string" ? r.name : "",
    email: r.email,
    pictureUrl: typeof r.pictureUrl === "string" ? r.pictureUrl : null,
    ...(typeof r.feedUserId === "string" && r.feedUserId ? { feedUserId: r.feedUserId } : {}),
  };
}

/** GET /api/session: the person, or null when signed out or unreachable. */
export async function loadSession(f: Fetch = fetch): Promise<Person | null> {
  try {
    const res = await f("/api/session", { credentials: "same-origin", cache: "no-store" });
    if (!res.ok) return null;
    return toPerson(await res.json());
  } catch {
    return null;
  }
}

export type SignInResult = { ok: true; person: Person } | { ok: false; message: string };

/** POST /api/session. A 401 is always the one wrong-credentials message. */
export async function signIn(email: string, password: string, f: Fetch = fetch): Promise<SignInResult> {
  try {
    const res = await f("/api/session", {
      method: "POST",
      credentials: "same-origin",
      headers: { "content-type": "application/json" },
      body: JSON.stringify({ email, password }),
    });
    if (res.status === 401) return { ok: false, message: WRONG_CREDENTIALS };
    if (!res.ok) return { ok: false, message: GENERIC_FAILURE };
    const person = toPerson(await res.json());
    return person ? { ok: true, person } : { ok: false, message: GENERIC_FAILURE };
  } catch {
    return { ok: false, message: GENERIC_FAILURE };
  }
}