const BASE = import.meta.env.VITE_API_BASE_URL || '';

// Where the access token lives. sessionStorage, not localStorage: the token is
// a bearer credential, and a tab-scoped store means closing the tab ends the
// session rather than leaving a working credential on disk.
export const TOKEN_STORAGE_KEY = 'app_access_token';

// Read at module load so a page refresh is already authenticated before
// AuthContext mounts and the first request goes out.
let authToken = (() => {
  try {
    return sessionStorage.getItem(TOKEN_STORAGE_KEY);
  } catch {
    return null;
  }
})();

let onUnauthorized = null;

/** Called by AuthContext on login/logout. Pass null to clear. */
export function setAuthToken(token) {
  authToken = token || null;
  try {
    if (token) sessionStorage.setItem(TOKEN_STORAGE_KEY, token);
    else sessionStorage.removeItem(TOKEN_STORAGE_KEY);
  } catch {
    /* private browsing with storage disabled - the in-memory copy still works */
  }
}

export function getAuthToken() {
  return authToken;
}

/**
 * Registered by AuthContext so an expired token anywhere in the app drops the
 * session once, rather than leaving every panel to render its own 401 error.
 */
export function setUnauthorizedHandler(fn) {
  onUnauthorized = fn;
}

function authHeaders() {
  return authToken ? { Authorization: `Bearer ${authToken}` } : {};
}

class ApiError extends Error {
  constructor(message, status) {
    super(message);
    this.status = status;
  }
}

async function request(path, options = {}) {
  let res;
  try {
    res = await fetch(`${BASE}${path}`, {
      headers: {
        'Content-Type': 'application/json',
        ...authHeaders(),
        ...(options.headers || {}),
      },
      ...options,
    });
  } catch {
    throw new ApiError(
      `Could not reach the API at ${BASE || '(same origin)'}${path}. Is the backend running ` +
      `(uvicorn app.main:app) and reachable?`,
      0
    );
  }

  if (!res.ok) {
    let detail = `Request failed (${res.status})`;
    try {
      const body = await res.json();
      detail = body.detail || JSON.stringify(body);
    } catch {
      /* ignore parse errors, keep generic message */
    }
    // 401 means the token is missing, expired or invalid - the session is over.
    // 403 is a live session lacking a permission, so it must NOT log you out.
    if (res.status === 401 && onUnauthorized) onUnauthorized(detail);
    throw new ApiError(detail, res.status);
  }

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

function qs(params = {}) {
  const usp = new URLSearchParams();
  Object.entries(params).forEach(([k, v]) => {
    if (v !== undefined && v !== null && v !== '' && v !== false) usp.set(k, v);
  });
  const s = usp.toString();
  return s ? `?${s}` : '';
}

export const api = {
  getHealth: () => request('/api/health'),

  // --- Auth ---
  login: (username, password) =>
    request('/api/auth/login', {
      method: 'POST',
      body: JSON.stringify({ username, password }),
    }),
  getMe: () => request('/api/auth/me'),
  getRoles: () => request('/api/auth/roles'),

  // --- Electronics catalogue (verified products only) ---
  getCategories: () => request('/api/elec/categories'),
  getBrands: (category) => request(`/api/elec/brands${qs({ category })}`),
  getProducts: (params) => request(`/api/elec/products${qs(params)}`),
  getProduct: (id) => request(`/api/elec/products/${id}`),
  getPriceHistory: (id) => request(`/api/elec/products/${id}/price-history`),
  getSites: () => request('/api/elec/sites'),

  // --- Admin ---
  startRun: (body) => request('/api/elec/admin/runs', { method: 'POST', body: JSON.stringify(body) }),
  getRunJob: (jobId) => request(`/api/elec/admin/runs/${jobId}`),
  getRuns: () => request('/api/elec/admin/runs'),
  probeSite: (domain) => request(`/api/elec/admin/sites/${encodeURIComponent(domain)}/probe`, { method: 'POST' }),
  getReviewQueue: () => request('/api/elec/admin/review'),
  reviewMatch: (listingId, approve) =>
    request(`/api/elec/admin/review/${listingId}`, { method: 'POST', body: JSON.stringify({ approve }) }),
};

export { ApiError };