"use client";

import { useCallback, useEffect, useRef } from "react";
import { useHardwareBackHandler } from "@/hooks/use-hardware-back-handler";

let activeSheetCount = 0;
let bodyHadDropdownClass = false;
let initialBodyOverflow = "";
let initialHtmlOverflow = "";
let initialAppShellOverflow = "";
let initialAppShellTouchAction = "";
let lockedAppShell: HTMLElement | null = null;

type SheetScrollLockOptions = {
  onBack?: () => void;
};

export function useSheetScrollLock(
  isOpen: boolean,
  options: SheetScrollLockOptions = {},
) {
  const { onBack } = options;
  const onBackRef = useRef(onBack);
  onBackRef.current = onBack;

  // Register in the hardware-back handler stack so that Flutter's
  // __habibHandleHardwareBackSync() closes the sheet instead of exiting the screen.
  const handleHardwareBack = useCallback(() => {
    if (onBackRef.current) {
      onBackRef.current();
      return true; // handled — sheet closed
    }
    return false;
  }, []);

  useHardwareBackHandler(handleHardwareBack, isOpen);

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

    if (activeSheetCount === 0) {
      bodyHadDropdownClass = document.body.classList.contains("dropdown-open");
      initialBodyOverflow = document.body.style.overflow;
      initialHtmlOverflow = document.documentElement.style.overflow;
      lockedAppShell = document.querySelector<HTMLElement>(".app-shell");
      initialAppShellOverflow = lockedAppShell?.style.overflowY ?? "";
      initialAppShellTouchAction = lockedAppShell?.style.touchAction ?? "";
    }
    activeSheetCount += 1;

    document.body.classList.add("dropdown-open");
    document.body.classList.add("question-sheet-open");
    document.body.style.overflow = "hidden";
    document.documentElement.style.overflow = "hidden";
    if (lockedAppShell) {
      lockedAppShell.style.overflowY = "hidden";
      lockedAppShell.style.touchAction = "none";
    }

    return () => {
      activeSheetCount = Math.max(0, activeSheetCount - 1);
      if (activeSheetCount === 0) {
        document.body.style.overflow = initialBodyOverflow;
        document.documentElement.style.overflow = initialHtmlOverflow;
        if (lockedAppShell) {
          lockedAppShell.style.overflowY = initialAppShellOverflow;
          lockedAppShell.style.touchAction = initialAppShellTouchAction;
          lockedAppShell = null;
        }
        if (!bodyHadDropdownClass) {
          document.body.classList.remove("dropdown-open");
        }
        document.body.classList.remove("question-sheet-open");
      }
    };
  }, [isOpen]);
}