Mav-Mobile-UI/src/hooks/useSightingFeed.ts

import { useEffect, useMemo, useRef, useState } from "react";
import type { SightingWidgetType } from "../types/types";
import { useQuery } from "@tanstack/react-query";

// const url = `http://100.82.205.44/SightingListFront/sightingSummary?mostRecentRef=-1`;

async function fetchSighting(url: string, ref: number, signal?: AbortSignal) {
  const dynamicUrl = `${url}${ref}`;
  const res = await fetch(dynamicUrl, { signal });
  if (!res.ok) throw new Error(String(res.status));
  return (await res.json()) as SightingWidgetType;
}

export function useSightingFeed(url: string) {
  const [sightings, setSightings] = useState<SightingWidgetType[]>(
    () => Array(7).fill(null) as unknown as SightingWidgetType[]
  );
  const [noSighting, setNoSighting] = useState(false);
  const [selectedRef, setSelectedRef] = useState<number | null>(null);
  const [mostRecent, setMostRecent] = useState<SightingWidgetType | null>(null);

  const mostRecentRef = useRef<number>(-1);
  const lastSeenRef = useRef<number | null>(null);

  const { data, isPending } = useQuery({
    queryKey: ["sighting"],
    queryFn: ({ signal }) => fetchSighting(url, mostRecentRef.current, signal),
    refetchInterval: 200,
    refetchIntervalInBackground: true,
    refetchOnWindowFocus: false,
    staleTime: 0,
    notifyOnChangeProps: ["data"],
  });

  useEffect(() => {
    if (!data) return;

    if (data.ref === -1) {
      setNoSighting(true);
    } else {
      setNoSighting(false);
    }
    if (data.ref === lastSeenRef.current) return; // duplicate payload → do nothing
    lastSeenRef.current = data.ref;

    setSightings((prev) => {
      const existing = prev.find((p) => p?.ref === data.ref);
      const next = existing
        ? prev
        : [data, ...prev.filter(Boolean)].slice(0, 7);

      const stillHasSelection =
        selectedRef != null && next.some((s) => s?.ref === selectedRef);
      if (!stillHasSelection) {
        setSelectedRef(data.ref);
      }

      return next;
    });
    setMostRecent(sightings[0]);
    mostRecentRef.current = data.ref ?? -1;
  }, [data, selectedRef, sightings]);

  const selected = useMemo(
    () =>
      selectedRef == null
        ? null
        : sightings.find((s) => s?.ref === selectedRef) ?? null,
    [sightings, selectedRef]
  );

  const effectiveSelected = selected ?? mostRecent ?? null;

  return {
    sightings,
    selectedRef,
    setSelectedRef,
    mostRecent,
    effectiveSelected,
    mostRecentRef,
    isPending,
    noSighting,
  };
}