import { t } from './i18n.js';
const BASE = '/api';

// Paths where a 401 is a normal answer rather than an expired session, so the
// auto-logout reload must not fire (it would loop on a failed SSO handoff).
const NO_RELOAD_ON_401 = ['/auth/login', '/auth/oidc/complete', '/auth/oidc/exchange',
                          '/auth/oidc/link-pending'];

async function request(method, path, body = null, formEncoded = false) {
  const token = localStorage.getItem('token');
  const headers = {};

  if (token) headers['Authorization'] = `Bearer ${token}`;

  let bodyStr = null;
  if (body !== null) {
    if (formEncoded) {
      headers['Content-Type'] = 'application/x-www-form-urlencoded';
      bodyStr = new URLSearchParams(body).toString();
    } else {
      headers['Content-Type'] = 'application/json';
      bodyStr = JSON.stringify(body);
    }
  }

  const res = await fetch(`${BASE}${path}`, { method, headers, body: bodyStr });

  if (res.status === 401 && !NO_RELOAD_ON_401.some(p => path.startsWith(p))) {
    localStorage.removeItem('token');
    localStorage.removeItem('user');
    window.location.reload();
    return null;
  }

  if (!res.ok) {
    const err = await res.json().catch(() => ({ detail: t('unknown_error') }));
    const e = new Error(err.detail || `HTTP ${res.status}`);
    // Keep the status so callers can map it to a translated message instead of
    // showing the backend's German detail to someone running the app in Finnish.
    e.status = res.status;
    throw e;
  }

  if (res.status === 204) return null;
  return res.json();
}

async function uploadRequest(path, formData) {
  const token = localStorage.getItem('token');
  const headers = {};
  if (token) headers['Authorization'] = `Bearer ${token}`;

  const res = await fetch(`${BASE}${path}`, { method: 'POST', headers, body: formData });

  if (res.status === 401) {
    localStorage.removeItem('token');
    localStorage.removeItem('user');
    window.location.reload();
    return null;
  }
  if (!res.ok) {
    // Upload errors may be non-JSON (e.g. an nginx 413/502 HTML page); fall back
    // to the HTTP status so the message is diagnostic, not "unknown error".
    const err = await res.json().catch(() => null);
    const detail = (err && err.detail)
      ? err.detail
      : (res.status === 413 ? t('upload_too_large') : `HTTP ${res.status} ${res.statusText || ''}`.trim());
    const e = new Error(detail);
    e.status = res.status;
    throw e;
  }
  if (res.status === 204) return null;
  return res.json();
}

async function downloadRequest(path, fallbackName) {
  const token = localStorage.getItem('token');
  const headers = {};
  if (token) headers['Authorization'] = `Bearer ${token}`;

  const res = await fetch(`${BASE}${path}`, { method: 'GET', headers });
  if (res.status === 401) {
    localStorage.removeItem('token');
    localStorage.removeItem('user');
    window.location.reload();
    return null;
  }
  if (!res.ok) {
    const err = await res.json().catch(() => ({ detail: t('unknown_error') }));
    const e = new Error(err.detail || `HTTP ${res.status}`);
    // Keep the status so callers can map it to a translated message instead of
    // showing the backend's German detail to someone running the app in Finnish.
    e.status = res.status;
    throw e;
  }
  // Derive filename from Content-Disposition if present.
  let filename = fallbackName || 'calendar.ics';
  const cd = res.headers.get('Content-Disposition') || '';
  const m = cd.match(/filename="?([^"]+)"?/);
  if (m) filename = m[1];

  const blob = await res.blob();
  const url = URL.createObjectURL(blob);
  const a = document.createElement('a');
  a.href = url;
  a.download = filename;
  document.body.appendChild(a);
  a.click();
  a.remove();
  URL.revokeObjectURL(url);
}

export const api = {
  get:    (path)        => request('GET',    path),
  post:   (path, body)  => request('POST',   path, body),
  put:    (path, body)  => request('PUT',    path, body),
  delete: (path)        => request('DELETE', path),
  upload: (path, form)  => uploadRequest(path, form),
  download: (path, name) => downloadRequest(path, name),

  login: (username, password, totp_code = null, remember_me = false) =>
    request('POST', '/auth/login', { username, password, totp_code, remember_me }),

  setupRequired: () => request('GET', '/auth/setup-required'),
  setup: (data)      => request('POST', '/auth/setup', data),

  // Single sign-on. oidcComplete() trades the one-time HttpOnly handoff cookie
  // set by the OIDC callback for the access token.
  oidcProviders: () => request('GET',  '/auth/oidc/providers'),
  oidcComplete:  () => request('POST', '/auth/oidc/complete', {}),
  oidcIdentities: () => request('GET', '/auth/oidc/identities'),
  oidcLinkPending: () => request('POST', '/auth/oidc/link-pending', {}),
  oidcUnlink: (id)   => request('DELETE', `/auth/oidc/identities/${id}`),
};