/**
 * @file warehouseAutomat.js
 * @description Manages cached warehouse locations (`GET /api/warehouse`) for the active company.
 *
 * Upstream Triggers:
 * - `authAutomat`: Subscribes to auth state changes (`syncWithAuth`) — triggers
 *   `actions.load()` on `'authed'` with a `selectedCompanyId`, and `actions.clear()` on `'anon'`.
 * - `sseAutomat`: Calls `actions.reload()` upon receiving a `'warehouse'` SSE event.
 * - UI / Routes: Calls to `actions.load()`, `actions.reload()`, or `actions.setWarehouses()`.
 */

import { Automat } from 'react-automat';
import { warehouse as warehouseApi } from '../api';
import { requireArray, requireDefined, requireObject } from '../utils/apiShape';
import authAutomat from './authAutomat';

/**
 * @typedef {Object} Warehouse
 * @property {string|number} id Warehouse identifier.
 * @property {string} name Warehouse name.
 */

/**
 * @typedef {Object} WarehouseState
 * @property {Array<Warehouse>} warehouses Company-scoped warehouses.
 * @property {Array<Warehouse>} filteredWarehouses Filtered warehouses according to active filter query.
 * @property {string} filter Active search/filter string.
 * @property {'idle'|'loading'|'ready'|'failed'} status Load lifecycle state.
 * @property {Error|null} error Last load error.
 */

/** @type {WarehouseState} */
const initialState = {
  warehouses: [],
  filteredWarehouses: [],
  filter: '',
  status: 'idle',
  error: null,
};

let warehouseAutomat;

const applyFilter = (warehouses, filter) => {
  const query = String(filter ?? '').trim().toLowerCase();
  return query ? warehouses.filter((w) => String(w.name ?? '').toLowerCase().includes(query)) : warehouses;
};

const updateStateWithWarehouses = (warehouses, extra = {}) => {
  const list = Array.isArray(warehouses) ? warehouses : [];
  const filteredWarehouses = applyFilter(list, warehouseAutomat.state.filter);
  warehouseAutomat.setState({ warehouses: list, filteredWarehouses, ...extra });
  return list;
};

/**
 * Fetches the company-scoped warehouse list.
 *
 * @returns {Promise<Array<Warehouse>>} Warehouse list.
 */
async function fetchWarehouses() {
  const data = await warehouseApi.list();
  requireObject(data, 'GET /api/warehouse');
  return requireArray(data.warehouses, 'warehouses');
}

/** In-flight `load()` promise so concurrent callers share one request. */
let inflightLoad = null;

/**
 * Loads the warehouse list once, deduplicating concurrent callers.
 *
 * @returns {Promise<Array<Warehouse>>} Loaded warehouses.
 */
function loadWarehouses() {
  if (inflightLoad) return inflightLoad;
  inflightLoad = (async () => {
    warehouseAutomat.setState({ status: 'loading', error: null });
    try {
      const warehouses = await fetchWarehouses();
      updateStateWithWarehouses(warehouses, { status: 'ready', error: null });
      return warehouses;
    } catch (error) {
      warehouseAutomat.setState({ status: 'failed', error });
      throw error;
    } finally {
      inflightLoad = null;
    }
  })();
  return inflightLoad;
}

const actions = {
  /** Sets the active warehouse search filter and updates filteredWarehouses. */
  filter(query) {
    const filter = String(query ?? '');
    warehouseAutomat.setState({
      filter,
      filteredWarehouses: applyFilter(warehouseAutomat.state.warehouses, filter),
    });
  },

  /**
   * Loads the warehouse list, exposing a loading/failed lifecycle.
   *
   * @returns {Promise<Array<Warehouse>>} Loaded warehouses.
   */
  load() {
    return loadWarehouses();
  },

  /**
   * Silently re-fetches the warehouse list while keeping the current state.
   *
   * @returns {Promise<Array<Warehouse>>} Fresh warehouses.
   */
  async reload() {
    try {
      const warehouses = await fetchWarehouses();
      updateStateWithWarehouses(warehouses, { status: 'ready', error: null });
      return warehouses;
    } catch (error) {
      warehouseAutomat.setState({ error });
      throw error;
    }
  },

  /**
   * Creates a warehouse and refreshes the cached list.
   *
   * @param {{name: string}} body Creation payload.
   * @returns {Promise<Warehouse>} Created warehouse.
   */
  async create(body) {
    const data = await warehouseApi.create(body);
    requireObject(data, 'POST /api/warehouse');
    requireObject(data.warehouse, 'warehouse');
    requireDefined(data.warehouse.id, 'warehouse.id');
    await warehouseAutomat.actions.reload();
    return data.warehouse;
  },

  /**
   * Renames a warehouse and refreshes the cached list.
   *
   * @param {string|number} id Warehouse identifier.
   * @param {{name: string}} body Update payload.
   * @returns {Promise<Warehouse>} Updated warehouse.
   */
  async update(id, body) {
    const data = await warehouseApi.update(id, body);
    requireObject(data, 'PATCH /api/warehouse/:id');
    requireObject(data.warehouse, 'warehouse');
    requireDefined(data.warehouse.id, 'warehouse.id');
    await warehouseAutomat.actions.reload();
    return data.warehouse;
  },

  rename(id, body) {
    return actions.update(id, body);
  },

  /**
   * Deletes a warehouse and refreshes the cached list.
   *
   * @param {string|number} id Warehouse identifier.
   * @returns {Promise<void>}
   */
  async remove(id) {
    await warehouseApi.delete(id);
    await warehouseAutomat.actions.reload();
  },

  /**
   * Persists a new sort order for all warehouses.
   *
   * @param {Array<string|number>} warehouseIds IDs in the desired order.
   * @returns {Promise<void>}
   */
  async reorder(warehouseIds) {
    const byId = new Map(warehouseAutomat.state.warehouses.map((w) => [w.id, w]));
    const reordered = warehouseIds.map((id) => byId.get(id)).filter(Boolean);
    if (reordered.length === warehouseAutomat.state.warehouses.length) {
      updateStateWithWarehouses(reordered);
    }
    await warehouseApi.order({ warehouseIds });
    await warehouseAutomat.actions.reload();
  },

  /**
   * Replaces the cached list without a round-trip.
   *
   * @param {Array<Warehouse>} warehouses Warehouses to cache.
   * @returns {void}
   */
  setWarehouses(warehouses) {
    updateStateWithWarehouses(warehouses, {
      status: 'ready',
      error: null,
    });
  },

  /**
   * Forgets the cached list and returns to the initial state.
   *
   * @returns {void}
   */
  clear() {
    warehouseAutomat.setState({ ...initialState });
  },
};

/**
 * Company-scoped warehouse cache. Loads automatically once an authenticated
 * session with a selected company exists and is cleared when auth is gone.
 *
 * @type {Automat<WarehouseState>}
 */
warehouseAutomat = new Automat(initialState, actions, { name: 'warehouse' });

/**
 * Derives the cache key from the auth state: the selected company while
 * authenticated, otherwise `null`.
 *
 * @param {import('./authAutomat').AuthState} authState Auth automat state.
 * @returns {string|null} Cache key.
 */
function authKey(authState) {
  if (authState?.status !== 'authed' || !authState.user) return null;
  const companyId = authState.user.selectedCompanyId;
  return companyId == null ? null : String(companyId);
}

let lastAuthKey;

/**
 * Loads the warehouse list when auth/company becomes available and forgets it
 * when the session ends.
 *
 * @param {import('./authAutomat').AuthState} authState Auth automat state.
 * @returns {void}
 */
function syncWithAuth(authState) {
  const key = authKey(authState);
  if (key === lastAuthKey) return;
  lastAuthKey = key;
  if (key == null) {
    warehouseAutomat.actions.clear();
  } else {
    void warehouseAutomat.actions.load().catch(() => {});
  }
}

authAutomat.subscribe(syncWithAuth);
syncWithAuth(authAutomat.state);

export default warehouseAutomat;