// composables/useInfiniteScroll.ts
import { ref, onMounted, onBeforeUnmount } from "vue";

export default function useInfiniteScroll(
  callback: () => Promise<void>,
  elementId?: string
) {
  const route = useRoute();
  const isFetching = ref(false);
  const infiniteScroll = ref<HTMLElement | Window | null>(null);

  // Throttle function to limit scroll event frequency
  const throttle = (func: (...args: any[]) => void, limit: number) => {
    let lastFunc: ReturnType<typeof setTimeout>;
    let lastRan: number;
    return function (this: any, ...args: any[]) {
      const context = this;
      if (!lastRan) {
        func.apply(context, args);
        lastRan = Date.now();
      } else {
        clearTimeout(lastFunc);
        lastFunc = setTimeout(() => {
          if (Date.now() - lastRan >= limit) {
            func.apply(context, args);
            lastRan = Date.now();
          }
        }, limit - (Date.now() - lastRan));
      }
    };
  };

  const checkScrollPosition = () => {
    if (isFetching.value || !infiniteScroll.value) return;

    let scrollPosition: number;
    let threshold: number;
    let clientHeight: number;
    let scrollHeight: number;

    if (infiniteScroll.value === window) {
      scrollPosition = window.scrollY || window.pageYOffset;
      clientHeight = document.documentElement.clientHeight;
      scrollHeight = document.documentElement.scrollHeight;
    } else {
      const el = infiniteScroll.value as HTMLElement;
      scrollPosition = el.scrollTop;
      clientHeight = el.clientHeight;
      scrollHeight = el.scrollHeight;
    }

    threshold = scrollHeight - 100;
    const currentPosition = scrollPosition + clientHeight;

    if (currentPosition >= threshold) {
      isFetching.value = true;
      callback().finally(() => {
        isFetching.value = false;
      });
    }
  };

  // Throttled version of scroll handler
  const throttledScrollHandler = throttle(checkScrollPosition, 200);

  const handleTouchEnd = () => {
    setTimeout(throttledScrollHandler, 100);
  };

  onMounted(() => {
    console.info(route.name)
    
    if (route.name == "hadithaSearch" || route.name == "hadithaLibrary") {
      const targetElement = elementId
        ? document.getElementById(elementId)
        : window;

      if (!targetElement) {
        console.warn(
          `Element ${elementId || "window"} not found for infinite scroll`
        );
        return;
      }

      infiniteScroll.value = targetElement;

      if (targetElement === window) {
        window.addEventListener("scroll", throttledScrollHandler);
        window.addEventListener("touchend", handleTouchEnd);
      } else {
        targetElement.addEventListener("scroll", throttledScrollHandler);
        targetElement.addEventListener("touchend", handleTouchEnd);
      }
    }
  });

  onBeforeUnmount(() => {
    if (route.name == "hadithaSearch" || route.name == "hadithaLibrary") {
      if (!infiniteScroll.value) return;

      if (infiniteScroll.value === window) {
        window.removeEventListener("scroll", throttledScrollHandler);
        window.removeEventListener("touchend", handleTouchEnd);
      } else {
        (infiniteScroll.value as HTMLElement).removeEventListener(
          "scroll",
          throttledScrollHandler
        );
        (infiniteScroll.value as HTMLElement).removeEventListener(
          "touchend",
          handleTouchEnd
        );
      }
    }
  });

  return { isFetching };
}