/**
 * A client for Nginx Proxy Manager's admin API (verified against 2.15.1).
 *
 * ── The quirk worth knowing before you debug anything here ──
 *
 * NPM answers an unauthenticated read with **404, not 401**:
 *
 *     GET /api/nginx/proxy-hosts  ->  {"error":{"code":404,"message":"Not Found - /nginx/proxy-hosts"}}
 *
 * Its router only registers a resource once the request carries a token, so "not signed in" and "no such
 * endpoint" are the same response. Left alone that produces the worst kind of bug report — a feature that
 * reads as missing when the credential is simply wrong. So a 404 on a path we know exists is reported as
 * an authentication failure, and `NpmError.likelyAuth` carries that judgement rather than hiding it.
 *
 * ── Tokens ──
 *
 * `POST /api/tokens {identity, secret}` returns `{token, expires}`. Tokens are cached in memory only,
 * never persisted: the credential is already stored encrypted, and a second copy of a derived token on
 * disk would be a second thing to protect for no benefit.
 */

export type NpmCredentials = { url: string; identity: string; secret: string };

export class NpmError extends Error {
  constructor(
    message: string,
    readonly status: number,
    /** NPM cannot distinguish "unauthenticated" from "no such route" — see the note above. */
    readonly likelyAuth: boolean = false,
  ) {
    super(message);
    this.name = 'NpmError';
  }
}

type TokenCacheEntry = { token: string; expiresAt: number };

/** Keyed by url+identity, so changing the credential cannot serve a token minted for the old one. */
const tokenCache = new Map<string, TokenCacheEntry>();

const cacheKey = (c: NpmCredentials) => `${c.url} ${c.identity}`;

export const forgetToken = (c: NpmCredentials): void => {
  tokenCache.delete(cacheKey(c));
};

export const normaliseUrl = (url: string): string => url.trim().replace(/\/+$/, '');

async function readError(response: Response): Promise<string> {
  try {
    const body = (await response.json()) as { error?: { message?: string } };
    return body.error?.message ?? `${response.status} ${response.statusText}`;
  } catch {
    return `${response.status} ${response.statusText}`;
  }
}

async function mintToken(credentials: NpmCredentials, timeoutMs: number): Promise<string> {
  const response = await fetch(`${normaliseUrl(credentials.url)}/api/tokens`, {
    method: 'POST',
    headers: { 'content-type': 'application/json' },
    body: JSON.stringify({ identity: credentials.identity, secret: credentials.secret }),
    signal: AbortSignal.timeout(timeoutMs),
  }).catch((error: Error) => {
    throw new NpmError(`Cannot reach Nginx Proxy Manager at ${credentials.url}: ${error.message}`, 0);
  });

  if (!response.ok) {
    // NPM returns 400 "Invalid email or password" for a bad credential, not 401.
    const message = await readError(response);
    throw new NpmError(message, response.status, /invalid email or password/i.test(message));
  }

  const body = (await response.json()) as { token?: string; expires?: string };
  if (!body.token) throw new NpmError('Nginx Proxy Manager returned no token', 500);

  const expiresAt = body.expires ? Date.parse(body.expires) : Date.now() + 60 * 60 * 1000;
  // A minute of headroom: a token that expires mid-flight fails as a 404, which reads as a missing route.
  tokenCache.set(cacheKey(credentials), { token: body.token, expiresAt: expiresAt - 60_000 });
  return body.token;
}

async function tokenFor(credentials: NpmCredentials, timeoutMs: number): Promise<string> {
  const cached = tokenCache.get(cacheKey(credentials));
  if (cached && cached.expiresAt > Date.now()) return cached.token;
  return mintToken(credentials, timeoutMs);
}

export type NpmRequest = { path: string; method?: string; body?: unknown; timeoutMs?: number };

export async function npmRequest<T>(credentials: NpmCredentials, request: NpmRequest): Promise<T> {
  const timeoutMs = request.timeoutMs ?? 8_000;
  const base = normaliseUrl(credentials.url);

  const send = async (token: string): Promise<Response> =>
    fetch(`${base}/api${request.path}`, {
      method: request.method ?? 'GET',
      headers: {
        authorization: `Bearer ${token}`,
        ...(request.body === undefined ? {} : { 'content-type': 'application/json' }),
      },
      body: request.body === undefined ? undefined : JSON.stringify(request.body),
      signal: AbortSignal.timeout(timeoutMs),
    }).catch((error: Error) => {
      throw new NpmError(`Cannot reach Nginx Proxy Manager at ${base}: ${error.message}`, 0);
    });

  let response = await send(await tokenFor(credentials, timeoutMs));

  // A cached token NPM has already forgotten looks like a missing route. Mint once and retry before
  // concluding anything — without this, a restarted NPM makes every panel look broken until a reload.
  if (response.status === 404 || response.status === 401) {
    forgetToken(credentials);
    response = await send(await mintToken(credentials, timeoutMs));
  }

  if (!response.ok) {
    const message = await readError(response);
    throw new NpmError(
      response.status === 404
        ? `Nginx Proxy Manager refused "${request.path}". Its API answers 404 when unauthenticated, so this is most likely the credential rather than a missing endpoint.`
        : message,
      response.status,
      response.status === 404 || response.status === 401,
    );
  }

  if (response.status === 204) return undefined as T;
  return (await response.json()) as T;
}

/** `GET /api/` needs no token — the cheapest proof that a URL is an NPM at all. */
export async function probe(url: string, timeoutMs = 5_000): Promise<{ version: string; setup: boolean }> {
  const response = await fetch(`${normaliseUrl(url)}/api/`, { signal: AbortSignal.timeout(timeoutMs) }).catch(
    (error: Error) => {
      throw new NpmError(`Cannot reach ${url}: ${error.message}`, 0);
    },
  );
  if (!response.ok) {
    throw new NpmError(`${url} answered ${response.status} — is that an Nginx Proxy Manager?`, response.status);
  }

  const body = (await response.json()) as {
    status?: string;
    setup?: boolean;
    version?: { major: number; minor: number; revision: number };
  };
  if (!body.version) throw new NpmError(`${url} answered, but not like an Nginx Proxy Manager`, response.status);

  return {
    version: `${body.version.major}.${body.version.minor}.${body.version.revision}`,
    setup: body.setup ?? false,
  };
}