"use client";

import { useEffect } from "react";
import { viewPaddingsBridge } from "@/lib/view-paddings";

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

export function useSheetScrollLock(isOpen: boolean) {
  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]);
}

const NON_KEYBOARD_INPUT_TYPES = new Set([
  "button",
  "checkbox",
  "color",
  "file",
  "hidden",
  "image",
  "radio",
  "range",
  "reset",
  "submit",
]);

function isKeyboardInputTarget(target: EventTarget | null): boolean {
  if (target instanceof HTMLTextAreaElement) {
    return !target.disabled && !target.readOnly;
  }
  if (target instanceof HTMLInputElement) {
    const type = (target.getAttribute("type") ?? "text").toLowerCase();
    return (
      !NON_KEYBOARD_INPUT_TYPES.has(type) &&
      !target.disabled &&
      !target.readOnly
    );
  }
  if (target instanceof HTMLElement) {
    return target.isContentEditable;
  }
  return false;
}

function syncQuestionInputOpenClass() {
  if (hasFocusedKeyboardInput) {
    document.body.classList.add("question-keyboard-open");
  } else {
    document.body.classList.remove("question-keyboard-open");
  }
}

/**
 * Moves the active question up (same animation the dropdown sheet uses) while
 * a keyboard input is focused, so the mobile keyboard cannot cover it.
 */
export function useQuestionInputFocusSync() {
  useEffect(() => {
    const handleFocusIn = (event: FocusEvent) => {
      if (!isKeyboardInputTarget(event.target)) return;
      hasFocusedKeyboardInput = true;
      syncQuestionInputOpenClass();
    };
    const handleFocusOut = (event: FocusEvent) => {
      if (!isKeyboardInputTarget(event.target)) return;
      window.setTimeout(() => {
        hasFocusedKeyboardInput = isKeyboardInputTarget(document.activeElement);
        syncQuestionInputOpenClass();
      }, 0);
    };

    const unsubscribeConfig = viewPaddingsBridge.subscribeConfig((config) => {
      if (config.keyboardHeight > 0) {
        hasFocusedKeyboardInput = isKeyboardInputTarget(document.activeElement);
      } else {
        // Android Back can hide Flutter's keyboard without dispatching blur.
        hasFocusedKeyboardInput = false;
      }
      syncQuestionInputOpenClass();
    });

    const initialViewportHeight = window.visualViewport?.height ?? 0;
    const handleViewportResize = () => {
      const viewportHeight = window.visualViewport?.height ?? 0;
      if (
        initialViewportHeight > 0 &&
        viewportHeight >= initialViewportHeight - 40
      ) {
        hasFocusedKeyboardInput = false;
        syncQuestionInputOpenClass();
      }
    };

    document.addEventListener("focusin", handleFocusIn);
    document.addEventListener("focusout", handleFocusOut);
    window.visualViewport?.addEventListener("resize", handleViewportResize);
    return () => {
      document.removeEventListener("focusin", handleFocusIn);
      document.removeEventListener("focusout", handleFocusOut);
      window.visualViewport?.removeEventListener(
        "resize",
        handleViewportResize,
      );
      unsubscribeConfig();
      hasFocusedKeyboardInput = false;
      document.body.classList.remove("question-keyboard-open");
    };
  }, []);
}