parking_solution/apps/web/src/lib/use-live-feed.ts

import { useEffect, useRef } from "react";
import { useQueryClient } from "@tanstack/react-query";
import type { DeviceStatus, LedgerEvent, Occupancy } from "../api.js";
import { qk } from "./query.js";
import { useLiveStore, type LaneStatus, type LanePresence } from "./live-store.js";
import { wsUrl } from "./origin.js";
import { createPlatformSocket, type PlatformSocket } from "./platform-ws.js";

// Booth WebSocket client. Opens ONE socket to /api/ws and turns server pushes into
// (a) live-store updates for the ticker/occupancy and (b) Query cache invalidations
// so TanStack Query remains the source of truth for durable server data. The browser
// attaches the auth cookie automatically; the backend gates by cookie + Origin
// (see routes/ws.ts). Auto-reconnects with capped backoff so a booth left running
// recovers from a server restart without a manual refresh.

/** Server → client message shapes (mirror routes/ws.ts OutMsg). */
type WsMessage =
  | { kind: "hello"; occupancy: Occupancy; devices: DeviceStatus[]; lanes: LaneStatus; radar: LanePresence }
  | { kind: "ledger"; event: LedgerEvent; occupancy: Occupancy }
  | { kind: "printer-status"; event: unknown }
  | { kind: "device-status"; event: DeviceStatus }
  | { kind: "lane-status"; lanes: LaneStatus }
  | { kind: "lane-presence"; radar: LanePresence }
  | { kind: "plate-recognized"; plate: { identity: string; plate: string; direction: "entry" | "exit" } };


/**
 * @param enabled Gate on the WATCHER permission (`report:read` — mirrors the server's
 *   WS guard in routes/ws.ts). A user whose role lacks it (e.g. a merchant validator
 *   with only `validation:create`) must not attempt the socket at all: the server
 *   403s the upgrade and the capped-backoff reconnect would otherwise hammer it
 *   forever, filling the server log with a 403 every few seconds.
 */
export function useLiveFeed(enabled: boolean = true): void {
  const qc = useQueryClient();
  const { setStatus, setOccupancy, pushEvent, setDevices, upsertDevice, setLanes, setRadar, patchPlate } =
    useLiveStore();
  // Hold the socket + reconnect timer across renders; guard against StrictMode
  // double-invoke and unmount.
  const sockRef = useRef<PlatformSocket | null>(null);
  const retryRef = useRef(0);
  const closedRef = useRef(false);

  useEffect(() => {
    if (!enabled) {
      setStatus("closed");
      return;
    }
    closedRef.current = false;

    const connect = () => {
      if (closedRef.current) return;
      setStatus(retryRef.current === 0 ? "connecting" : "connecting");
      const sock = createPlatformSocket(wsUrl("/api/ws"));
      sockRef.current = sock;

      sock.onopen = () => {
        retryRef.current = 0;
        setStatus("open");
      };

      sock.onmessage = (ev) => {
        let msg: WsMessage;
        try {
          msg = JSON.parse(ev.data as string) as WsMessage;
        } catch {
          return; // ignore malformed frames
        }
        if (msg.kind === "hello") {
          setOccupancy(msg.occupancy);
          // Initial device-status snapshot for the footer.
          if (Array.isArray(msg.devices)) setDevices(msg.devices);
          if (msg.lanes) setLanes(msg.lanes);
          if (msg.radar) setRadar(msg.radar);
        } else if (msg.kind === "device-status") {
          upsertDevice(msg.event);
        } else if (msg.kind === "lane-status") {
          setLanes(msg.lanes);
        } else if (msg.kind === "lane-presence") {
          setRadar(msg.radar);
        } else if (msg.kind === "plate-recognized") {
          // Backfill the badge on the already-rendered feed row, and refetch the
          // Query-owned active-sessions list (re-runs enrichEvents → the now-written plate).
          patchPlate(msg.plate.identity, msg.plate.plate);
          void qc.invalidateQueries({ queryKey: qk.activeSessions });
        } else if (msg.kind === "ledger") {
          setOccupancy(msg.occupancy);
          pushEvent(msg.event);
          // Keep Query authoritative: the durable event list, occupancy totals,
          // and active-sessions list refetch on the next read instead of trusting
          // the pushed copy alone.
          void qc.invalidateQueries({ queryKey: qk.events });
          void qc.invalidateQueries({ queryKey: qk.occupancy });
          void qc.invalidateQueries({ queryKey: qk.activeSessions });
          // A shift open/close (or a drawer movement) changes the header control
          // state and the per-shift log window — refresh the shift status too.
          if (
            msg.event.type === "shift_open" ||
            msg.event.type === "shift_z_report" ||
            msg.event.type === "cash_movement" ||
            msg.event.type === "cash_in" ||
            msg.event.type === "cash_out"
          ) {
            void qc.invalidateQueries({ queryKey: qk.shift });
          }
        } else if (msg.kind === "printer-status") {
          void qc.invalidateQueries({ queryKey: ["printers"] });
        }
      };

      const scheduleReconnect = () => {
        if (closedRef.current) return;
        setStatus("closed");
        // Capped exponential backoff: 0.5s, 1s, 2s, … up to 10s.
        const delay = Math.min(500 * 2 ** retryRef.current, 10_000);
        retryRef.current += 1;
        window.setTimeout(connect, delay);
      };

      sock.onclose = scheduleReconnect;
      // onerror fires before onclose; let onclose own the reconnect to avoid double.
      sock.onerror = () => sock.close();
    };

    connect();

    return () => {
      closedRef.current = true;
      sockRef.current?.close();
      sockRef.current = null;
    };
    // qc / store setters are stable; re-run only if the permission gate flips
    // (login as a different role without a full reload).
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [enabled]);
}