// Pure OIDC-login state helpers (no imports) so they're unit-testable under the
// tsx + node:test harness. The SDK-driven flow lives in oidcLoginUtil.ts.

/**
 * Dynamic-registration cache. MAS issues a `client_id` per dynamic registration;
 * caching by issuer (scoped to the current redirectUri) avoids re-registering on
 * every login. Invalidated when the redirectUri changes or the provider later
 * rejects the cached id (`invalid_client`).
 */
const REG_CACHE_KEY = 'cinny_oidc_dynamic_clients';
type RegEntry = { clientId: string; redirectUri: string };
type RegCache = Record<string, RegEntry>;

const readRegCache = (): RegCache => {
  try {
    const raw = localStorage.getItem(REG_CACHE_KEY);
    return raw ? (JSON.parse(raw) as RegCache) : {};
  } catch {
    return {};
  }
};
const writeRegCache = (cache: RegCache): void => {
  localStorage.setItem(REG_CACHE_KEY, JSON.stringify(cache));
};

export const getCachedClientId = (issuer: string, redirectUri: string): string | undefined => {
  const entry = readRegCache()[issuer];
  return entry && entry.redirectUri === redirectUri ? entry.clientId : undefined;
};
export const cacheClientId = (issuer: string, clientId: string, redirectUri: string): void => {
  const cache = readRegCache();
  cache[issuer] = { clientId, redirectUri };
  writeRegCache(cache);
};
export const invalidateCachedClient = (issuer: string): void => {
  const cache = readRegCache();
  if (cache[issuer]) {
    delete cache[issuer];
    writeRegCache(cache);
  }
};

// OAuth error codes that mean the provider no longer recognises our client id
// (deleted/expired dynamic registration, or one issued by a different deployment).
const STALE_CLIENT_ERROR_CODES = new Set(['invalid_client', 'unauthorized_client']);

/**
 * #67 / #102 — pure: does an OIDC failure indicate the CACHED client id is
 * bad? Only then is dropping the registration cache justified; a transient
 * network error, an offline discovery fetch, or a local (`crypto.randomUUID`)
 * failure must leave it alone, otherwise every retry performs a fresh dynamic
 * registration and piles throwaway clients onto the provider. Recognised
 * shapes: an OAuth error response (`{ error: 'invalid_client' }`, as thrown by
 * oidc-client-ts `ErrorResponse`, OR as echoed back on the callback redirect's
 * `?error=` query param via {@link OidcCallbackParams}), or an HTTP 400/401
 * carried as `httpStatus`/`status` (MatrixError-style) from the
 * registration/authorize step.
 */
export const isStaleClientError = (e: unknown): boolean => {
  if (!e || typeof e !== 'object') return false;
  const { error, httpStatus, status } = e as {
    error?: unknown;
    httpStatus?: unknown;
    status?: unknown;
  };
  if (typeof error === 'string' && STALE_CLIENT_ERROR_CODES.has(error)) return true;
  const code = typeof httpStatus === 'number' ? httpStatus : status;
  return code === 400 || code === 401;
};

/** Parsed shape of the provider's redirect back to our callback URL. */
export type OidcCallbackParams =
  | { kind: 'success'; code: string; state: string }
  | { kind: 'error'; error: string; errorDescription?: string; state?: string }
  | { kind: 'invalid' };

/** Pure: classify the callback query string into success / error / invalid. */
export const parseOidcCallbackParams = (search: string): OidcCallbackParams => {
  const params = new URLSearchParams(search);
  const error = params.get('error');
  if (error) {
    return {
      kind: 'error',
      error,
      errorDescription: params.get('error_description') ?? undefined,
      // OAuth error redirects echo back the `state` we sent, same as a
      // success redirect would — needed to look up the pending sign-in's
      // issuer (see readStoredOidcIssuer) when the client id itself was
      // rejected.
      state: params.get('state') ?? undefined,
    };
  }
  const code = params.get('code');
  const state = params.get('state');
  if (code && state) return { kind: 'success', code, state };
  return { kind: 'invalid' };
};

/**
 * [Gitea #201, SDK 44] The app keeps a pending OAuth sign-in itself (the SDK's
 * OAuth2 class no longer persists anything). Saved in sessionStorage right
 * before the redirect, keyed by the `state` we send, which the provider echoes
 * back: a callback whose state has no entry is rejected (CSRF), and an entry is
 * used once. Holds the PKCE code verifier, so it never goes to localStorage.
 */
export type PendingOidcLogin = {
  issuer: string;
  clientId: string;
  deviceId: string;
  codeVerifier: string;
  homeserverUrl: string;
  redirectUri: string;
};
const PENDING_PREFIX = 'lotus_oidc_pending_';

const isPending = (v: unknown): v is PendingOidcLogin => {
  if (!v || typeof v !== 'object') return false;
  const p = v as Record<string, unknown>;
  return ['issuer', 'clientId', 'deviceId', 'codeVerifier', 'homeserverUrl', 'redirectUri'].every(
    (k) => typeof p[k] === 'string' && (p[k] as string).length > 0,
  );
};

export const savePendingOidcLogin = (state: string, pending: PendingOidcLogin): void => {
  sessionStorage.setItem(`${PENDING_PREFIX}${state}`, JSON.stringify(pending));
};

/** Read the pending sign-in for `state` without consuming it. */
export const readPendingOidcLogin = (state: string): PendingOidcLogin | undefined => {
  try {
    const raw = sessionStorage.getItem(`${PENDING_PREFIX}${state}`);
    if (!raw) return undefined;
    const parsed: unknown = JSON.parse(raw);
    return isPending(parsed) ? parsed : undefined;
  } catch {
    return undefined;
  }
};

/** Read and remove: an authorization code can only be redeemed once anyway. */
export const takePendingOidcLogin = (state: string): PendingOidcLogin | undefined => {
  const pending = readPendingOidcLogin(state);
  try {
    sessionStorage.removeItem(`${PENDING_PREFIX}${state}`);
  } catch {
    // storage unavailable — nothing to clean up
  }
  return pending;
};

/**
 * #102 — on the callback's error branch, the pending sign-in's issuer tells
 * us whose cached client id to evict when the provider rejected it.
 */
export const readStoredOidcIssuer = (state: string): string | undefined =>
  readPendingOidcLogin(state)?.issuer;