/**
 * Module-level houseplan config cache shared by every embedded card on a board,
 * so N cards do NOT issue N identical `houseplan/config/get` requests. The cache
 * is invalidated when the integration emits `houseplan_config_updated`
 * (fired on config/set); subscribers are then notified to reload.
 *
 * The full `houseplan-card` already persists a `{config, rev, layout}` snapshot in
 * localStorage (`houseplan_card_cfg_v1`) for its own instant start — we seed from it
 * so embedded cards paint immediately, then refresh from the server in the background.
 */
import { contentFingerprint } from './visual-continuity';
import {
  adoptVirtualLightServerSnapshot,
  applyVirtualLightEvent,
  virtualLightSnapshot,
  type VirtualLightSnapshot,
} from './virtual-light-state';

const LS_CFG = 'houseplan_card_cfg_v1';

export interface HpConfigSnapshot {
  config: any | null;
  rev: number;
  /** Runtime-only: absent until a fresh config/get advertises exact v1. */
  decorAssetsApi: number | null;
  summaryPanelApi: number | null;
  configFingerprint: string;
  layout: Record<string, any>;
  layoutRev: number;
  layoutFingerprint: string;
  virtualLights: VirtualLightSnapshot;
}

let cache: HpConfigSnapshot | null = null;
let inflight: Promise<HpConfigSnapshot> | null = null;
let fetchGeneration = 0;
let inflightGeneration = -1;
let subscribedConnection: any = null;
let subscriptionUnsubscribers: Array<() => void> = [];
const listeners = new Set<() => void>();

const keepUnsubscriber = (value: unknown, target: Array<() => void>): void => {
  if (typeof value === 'function') target.push(value as () => void);
};

/** Instant, synchronous best-effort snapshot from the full card's localStorage cache. */
export function cachedSnapshot(): HpConfigSnapshot | null {
  if (cache) return cache;
  try {
    const c = JSON.parse(localStorage.getItem(LS_CFG) || 'null');
    if (c && c.config && Array.isArray(c.config.spaces)) {
      const layout = c.layout || {};
      return {
        config: c.config,
        rev: c.rev || 0,
        decorAssetsApi: null,
        summaryPanelApi: null,
        configFingerprint: c.config_fingerprint || contentFingerprint(c.config),
        layout,
        layoutRev: c.layout_rev || 0,
        layoutFingerprint: c.layout_fingerprint || contentFingerprint(layout),
        virtualLights: virtualLightSnapshot(c.virtual_lights, c.rev || 0),
      };
    }
  } catch {
    /* ignore */
  }
  return null;
}

async function fetchFresh(hass: any, generation: number): Promise<HpConfigSnapshot> {
  const [cfgResp, layResp] = await Promise.all([
    hass.callWS({ type: 'houseplan/config/get' }),
    hass.callWS({ type: 'houseplan/layout/get' }),
  ]);
  const configRev = cfgResp?.rev ?? 0;
  const virtualLights = cache
    ? adoptVirtualLightServerSnapshot(
      cache.virtualLights,
      cfgResp?.virtual_lights,
      configRev,
      !!cfgResp && 'virtual_lights' in cfgResp,
    )
    : virtualLightSnapshot(cfgResp?.virtual_lights, configRev);
  const snapshot: HpConfigSnapshot = {
    config: cfgResp?.config ?? null,
    rev: configRev,
    decorAssetsApi: cfgResp?.decor_assets_api === 1 ? 1 : null,
    summaryPanelApi: cfgResp?.summary_panel_api === 1 ? 1 : null,
    configFingerprint: contentFingerprint(cfgResp?.config ?? null),
    layout: layResp?.layout ?? {},
    layoutRev: layResp?.rev ?? 0,
    layoutFingerprint: contentFingerprint(layResp?.layout ?? {}),
    virtualLights,
  };
  // A force request may arrive while this fetch is in flight. Its older
  // response remains useful to its original caller, but must not repopulate
  // the shared cache after the newer generation invalidated it.
  if (generation === fetchGeneration) cache = snapshot;
  const connection = hass.connection;
  if (connection?.subscribeEvents && subscribedConnection !== connection) {
    for (const unsubscribe of subscriptionUnsubscribers) unsubscribe();
    subscriptionUnsubscribers = [];
    subscribedConnection = connection;
    const invalidate = () => {
      cache = null; // invalidate; listeners reload
      fetchGeneration++;
      listeners.forEach((l) => l());
    };
    const pendingUnsubscribers: Array<() => void> = [];
    try {
      keepUnsubscriber(
        await connection.subscribeEvents(invalidate, 'houseplan_config_updated'),
        pendingUnsubscribers,
      );
      // Layout is separate state: dragging an icon on the full card writes only
      // the layout, so a static card on the same dashboard kept showing the old
      // position until the config changed or the page was reloaded — possibly
      // forever on a wall tablet (HP-1454-08).
      keepUnsubscriber(
        await connection.subscribeEvents(invalidate, 'houseplan_layout_updated'),
        pendingUnsubscribers,
      );
      keepUnsubscriber(await connection.subscribeEvents((event: any) => {
        if (cache) {
          const next = applyVirtualLightEvent(cache.virtualLights, event?.data);
          if (next === cache.virtualLights) return;
          cache = { ...cache, virtualLights: next };
        } else {
          fetchGeneration++;
        }
        listeners.forEach((listener) => listener());
      }, 'houseplan_virtual_light_updated'), pendingUnsubscribers);
      if (subscribedConnection === connection) {
        subscriptionUnsubscribers = pendingUnsubscribers;
      } else {
        for (const unsubscribe of pendingUnsubscribers) unsubscribe();
      }
    } catch {
      for (const unsubscribe of pendingUnsubscribers) unsubscribe();
      if (subscribedConnection === connection) subscribedConnection = null;
    }
  }
  return snapshot;
}

/** Get the shared config snapshot (cached, deduped across cards). */
export function getConfig(hass: any, force = false): Promise<HpConfigSnapshot> {
  if (force) {
    cache = null;
    fetchGeneration++;
    if (inflight) {
      // Do not let `force` silently join the stale request it was meant to
      // supersede. Wait for that transport slot, then issue a fresh generation.
      return inflight.catch(() => null).then(() => getConfig(hass, false));
    }
  }
  if (cache) return Promise.resolve(cache);
  if (inflight) {
    if (inflightGeneration !== fetchGeneration) {
      return inflight.catch(() => null).then(() => getConfig(hass, false));
    }
    return inflight;
  }
  const generation = fetchGeneration;
  inflightGeneration = generation;
  inflight = fetchFresh(hass, generation).finally(() => {
    inflight = null;
    inflightGeneration = -1;
  });
  return inflight;
}

/** Subscribe to config-changed notifications; returns an unsubscribe function. */
export function onConfigChange(cb: () => void): () => void {
  listeners.add(cb);
  return () => listeners.delete(cb);
}