"use client";

import { SSE_EVENT_TYPES } from "@capakraken/shared";
import { useQueryClient } from "@tanstack/react-query";
import { useEffect, useRef } from "react";
import { getTimelineSseInvalidationKeys, parseTimelineSseEvent } from "./timelineSsePolicy.js";

/**
 * Connects to the SSE timeline endpoint and invalidates React Query caches
 * when allocation/project change events arrive.
 */
export function useTimelineSSE() {
  const queryClient = useQueryClient();
  const reconnectTimeout = useRef<ReturnType<typeof setTimeout> | null>(null);

  useEffect(() => {
    let es: EventSource | null = null;
    let reconnectAttempts = 0;
    let isDisposed = false;

    function scheduleReconnect() {
      if (isDisposed || reconnectTimeout.current) return;
      reconnectAttempts++;
      const delay = Math.min(1000 * Math.pow(2, reconnectAttempts), 30000);
      reconnectTimeout.current = setTimeout(() => {
        reconnectTimeout.current = null;
        if (isDisposed) return;
        connect();
      }, delay);
    }

    function connect() {
      if (isDisposed) return;
      es = new EventSource("/api/sse/timeline");

      es.onopen = () => {
        reconnectAttempts = 0;
      };

      es.onmessage = (event) => {
        const eventType = parseTimelineSseEvent(String(event.data));
        if (!eventType) {
          return;
        }

        if (eventType === SSE_EVENT_TYPES.PING) {
          reconnectAttempts = 0;
          return;
        }

        for (const queryKey of getTimelineSseInvalidationKeys(eventType)) {
          void queryClient.invalidateQueries({ queryKey });
        }
      };

      es.onerror = () => {
        es?.close();
        scheduleReconnect();
      };
    }

    connect();

    return () => {
      isDisposed = true;
      es?.close();
      if (reconnectTimeout.current) {
        clearTimeout(reconnectTimeout.current);
        reconnectTimeout.current = null;
      }
    };
  }, [queryClient]);
}