flxn-app/src/hooks/use-server-events.ts

import { useEffect } from "react";
import { useQueryClient } from "@tanstack/react-query";
import { Logger } from "@/lib/logger";
import { useAuth } from "@/contexts/auth-context";
import { tournamentKeys } from "@/features/tournaments/queries";
import { reactionKeys } from "@/features/reactions/queries";
import { predictionKeys } from "@/features/predictions/queries";

const logger = new Logger('ServerEvents');

type SSEEvent = {
  type: string;
  [key: string]: any;
};

type EventHandler = (event: SSEEvent, queryClient: ReturnType<typeof useQueryClient>) => void;

const INVALIDATE_DEBOUNCE_MS = 1000;
const INVALIDATE_JITTER_MS = 1500;
const invalidateTimers = new Map<string, ReturnType<typeof setTimeout>>();

const WATCHDOG_MS = 45_000;

function debouncedInvalidate(
  queryClient: ReturnType<typeof useQueryClient>,
  filters: { queryKey: readonly unknown[] }
) {
  const key = JSON.stringify(filters.queryKey);
  const existing = invalidateTimers.get(key);
  if (existing) clearTimeout(existing);

  const delay = INVALIDATE_DEBOUNCE_MS + Math.random() * INVALIDATE_JITTER_MS;
  invalidateTimers.set(key, setTimeout(() => {
    invalidateTimers.delete(key);
    queryClient.invalidateQueries(filters);
  }, delay));
}

function clearPendingInvalidations() {
  for (const timer of invalidateTimers.values()) {
    clearTimeout(timer);
  }
  invalidateTimers.clear();
}

const eventHandlers: Record<string, EventHandler> = {
  "ping": () => {},
  "test": (event) => {
    logger.info("Test event", event);
  },
  "tournament": (event, queryClient) => {
    debouncedInvalidate(queryClient, { queryKey: ['tournaments'] });
    debouncedInvalidate(queryClient, { queryKey: ['players', 'unenrolled'] });
  },
  "match": (event, queryClient) => {
    debouncedInvalidate(queryClient, { queryKey: tournamentKeys.details(event.tournamentId) });
    debouncedInvalidate(queryClient, { queryKey: tournamentKeys.current });
    debouncedInvalidate(queryClient, { queryKey: predictionKeys.tournament(event.tournamentId) });
    debouncedInvalidate(queryClient, { queryKey: ['players', 'stats'] });
    debouncedInvalidate(queryClient, { queryKey: ['players', 'matches'] });
    debouncedInvalidate(queryClient, { queryKey: ['players', 'activity'] });
    debouncedInvalidate(queryClient, { queryKey: ['teams', 'stats'] });
    debouncedInvalidate(queryClient, { queryKey: ['teams', 'matches'] });
    debouncedInvalidate(queryClient, { queryKey: ['matches'] });
  },
  "reaction": (event, queryClient) => {
    queryClient.setQueryData(reactionKeys.match(event.matchId), () => event.reactions);
  },
  "team": (event, queryClient) => {
    debouncedInvalidate(queryClient, { queryKey: ['teams'] });
    debouncedInvalidate(queryClient, { queryKey: ['tournaments'] });
  },
  "player": (event, queryClient) => {
    debouncedInvalidate(queryClient, { queryKey: ['players'] });
  },
  "badge": (event, queryClient) => {
    debouncedInvalidate(queryClient, { queryKey: ['badges'] });
  },
};

export function useServerEvents() {
  const queryClient = useQueryClient();
  const { user } = useAuth();

  useEffect(() => {
    if (typeof window === 'undefined') return;
    if (!user?.id) return;

    let disposed = false;
    let eventSource: EventSource | null = null;
    let reconnectTimer: ReturnType<typeof setTimeout> | null = null;
    let watchdogTimer: ReturnType<typeof setTimeout> | null = null;
    let retryCount = 0;
    let hasConnectedOnce = false;

    const disconnect = () => {
      if (watchdogTimer) { clearTimeout(watchdogTimer); watchdogTimer = null; }
      if (reconnectTimer) { clearTimeout(reconnectTimer); reconnectTimer = null; }
      eventSource?.close();
      eventSource = null;
    };

    const reconnect = (delay: number) => {
      if (disposed) return;
      disconnect();
      reconnectTimer = setTimeout(connect, delay);
    };

    const armWatchdog = () => {
      if (watchdogTimer) clearTimeout(watchdogTimer);
      watchdogTimer = setTimeout(() => {
        logger.warn(`SSE watchdog: no messages in ${WATCHDOG_MS}ms, reconnecting`);
        retryCount = 0;
        reconnect(0);
      }, WATCHDOG_MS);
    };

    const connect = () => {
      if (disposed || eventSource) return;

      eventSource = new EventSource(`/api/events/$`);
      armWatchdog();

      eventSource.onopen = () => {
        retryCount = 0;
      };

      eventSource.onmessage = (event) => {
        armWatchdog();
        try {
          const data: SSEEvent = JSON.parse(event.data);
          if (data.type !== "ping") {
            logger.info("Event received", data);
          }

          if (data.type === "connected") {
            if (hasConnectedOnce) {
              setTimeout(() => {
                if (!disposed) queryClient.invalidateQueries();
              }, Math.random() * 2000);
            }
            hasConnectedOnce = true;
            return;
          }

          const handler = eventHandlers[data.type];
          if (handler) {
            handler(data, queryClient);
          } else {
            logger.warn(`Unhandled SSE event type: ${data.type}`);
          }
        } catch (error) {
          logger.error("Error parsing SSE message", error);
        }
      };

      eventSource.onerror = async (error) => {
        if (disposed) return;
        logger.error("SSE connection error", error);
        disconnect();

        // The stream is auth-guarded, so an error is often the server rejecting
        // an expired session rather than a network blip. Try to refresh; if the
        // session is genuinely gone, stop retrying so we don't hammer the
        // endpoint forever — a real re-login (or a wake event) will reconnect.
        let sessionValid = true;
        try {
          const { attemptRefreshingSession } = await import('supertokens-web-js/recipe/session');
          sessionValid = await attemptRefreshingSession();
        } catch {
          // Refresh call itself failed (likely offline) — treat as transient.
        }

        if (disposed) return;

        if (!sessionValid) {
          logger.warn("SSE stopped: session is no longer valid");
          return;
        }

        retryCount += 1;
        const delay = Math.min(1000 * Math.pow(1.5, retryCount - 1), 15000);
        logger.info(`SSE reconnection attempt ${retryCount} in ${Math.round(delay)}ms`);

        reconnect(delay);
      };
    };

    const wake = () => {
      if (disposed) return;
      if (!eventSource || eventSource.readyState === EventSource.CLOSED) {
        retryCount = 0;
        reconnect(0);
      }
    };
    const handleVisibility = () => {
      if (document.visibilityState === 'visible') wake();
    };

    window.addEventListener('online', wake);
    document.addEventListener('visibilitychange', handleVisibility);

    connect();

    return () => {
      logger.info("Closing SSE connection");
      disposed = true;

      clearPendingInvalidations();

      window.removeEventListener('online', wake);
      document.removeEventListener('visibilitychange', handleVisibility);

      disconnect();
    };
  }, [user?.id, queryClient]);
}