import { useEffect, useRef } from "react";

const FOCUSABLE = [
  "a[href]",
  "button:not([disabled])",
  "input:not([disabled])",
  "textarea:not([disabled])",
  "select:not([disabled])",
  "[tabindex]:not([tabindex='-1'])",
].join(",");

let titleSequence = 0;

/** Adds the small amount of focus management TDesign Drawer does not expose. */
export function useDrawerFocus(active: boolean, selector: string) {
  const returnFocusRef = useRef<HTMLElement | null>(null);

  useEffect(() => {
    if (!active) return;
    const previous = document.activeElement;
    if (previous instanceof HTMLElement && !previous.closest(".t-drawer")) {
      returnFocusRef.current = previous;
    }

    let disposed = false;
    let root: HTMLElement | null = null;
    let cleanupRoot: (() => void) | undefined;
    let frame = 0;
    let timer: number | undefined;
    let focusTimer: number | undefined;
    let initialized = false;
    const restoreTimers: number[] = [];

    const focusFirst = () => {
      if (disposed || !root) return;
      const current = document.activeElement;
      if (current && root.contains(current) && current !== root) return;
      const first = Array.from(root.querySelectorAll<HTMLElement>(FOCUSABLE)).find(node => {
        const rect = node.getBoundingClientRect();
        const style = window.getComputedStyle(node);
        return rect.width > 0 && rect.height > 0 && style.visibility !== "hidden" && style.display !== "none";
      });
      (first || root).focus();
    };

    const setup = () => {
      if (disposed) return;
      root = document.querySelector<HTMLElement>(`${selector}.t-drawer--open`) || document.querySelector<HTMLElement>(selector);
      if (!root) {
        timer = window.setTimeout(setup, 40);
        return;
      }

      if (!root.hasAttribute("tabindex")) root.setAttribute("tabindex", "-1");
      if (initialized) {
        // Lazy Drawer content can be inserted after the first animation frame.
        // Re-run only the initial focus lookup without duplicating listeners.
        focusTimer = window.setTimeout(focusFirst, 80);
        return;
      }
      initialized = true;
      root.setAttribute("role", "dialog");
      root.setAttribute("aria-modal", "true");
      const header = root.querySelector<HTMLElement>(".t-drawer__header");
      if (header) {
        if (!header.id) {
          titleSequence += 1;
          header.id = `tn-drawer-title-${titleSequence}`;
        }
        root.setAttribute("aria-labelledby", header.id);
      } else if (!root.getAttribute("aria-label")) {
        root.setAttribute("aria-label", "抽屉");
      }

      const closeButton = root.querySelector<HTMLElement>(".t-drawer__close-btn");
      const onCloseKeyDown = (event: KeyboardEvent) => {
        if (event.key !== "Enter" && event.key !== " ") return;
        event.preventDefault();
        closeButton?.click();
      };
      if (closeButton) {
        closeButton.setAttribute("role", "button");
        closeButton.setAttribute("tabindex", "0");
        closeButton.setAttribute("aria-label", "关闭");
        closeButton.addEventListener("keydown", onCloseKeyDown);
      }

      const isNestedDialogOpen = () => Array.from(document.querySelectorAll<HTMLElement>(".t-dialog, .t-dialog__wrapper")).some(dialog => {
        if (dialog === root || root?.contains(dialog)) return false;
        const style = window.getComputedStyle(dialog);
        const rect = dialog.getBoundingClientRect();
        return style.display !== "none" && style.visibility !== "hidden" && rect.width > 0 && rect.height > 0;
      });
      const onKeyDown = (event: KeyboardEvent) => {
        if (event.key !== "Tab" || !root || isNestedDialogOpen()) return;
        const items = Array.from(root.querySelectorAll<HTMLElement>(FOCUSABLE)).filter(node => {
          const rect = node.getBoundingClientRect();
          const style = window.getComputedStyle(node);
          return (rect.width > 0 && rect.height > 0 && style.visibility !== "hidden" && style.display !== "none") || node === document.activeElement;
        });
        if (!items.length) {
          event.preventDefault();
          event.stopPropagation();
          root.focus();
          return;
        }
        event.preventDefault();
        event.stopPropagation();
        const activeIndex = items.indexOf(document.activeElement as HTMLElement);
        const nextIndex = event.shiftKey
          ? activeIndex <= 0 ? items.length - 1 : activeIndex - 1
          : activeIndex < 0 || activeIndex === items.length - 1 ? 0 : activeIndex + 1;
        items[nextIndex]!.focus();
      };
      root.addEventListener("keydown", onKeyDown, true);
      cleanupRoot = () => {
        root?.removeEventListener("keydown", onKeyDown, true);
        closeButton?.removeEventListener("keydown", onCloseKeyDown);
      };

      frame = window.requestAnimationFrame(() => {
        focusFirst();
        focusTimer = window.setTimeout(focusFirst, 90);
      });
    };

    frame = window.requestAnimationFrame(setup);
    timer = window.setTimeout(setup, 180);
    return () => {
      disposed = true;
      window.cancelAnimationFrame(frame);
      if (timer !== undefined) window.clearTimeout(timer);
      if (focusTimer !== undefined) window.clearTimeout(focusTimer);
      cleanupRoot?.();
      const restore = () => {
        if (!disposed) return;
        if (document.querySelector(`${selector}.t-drawer--open`)) return;
        const target = returnFocusRef.current;
        const current = document.activeElement;
        if (!target?.isConnected) return;
        // Do not steal focus if the user has already moved to another page
        // control while the close animation was running.
        if (current && current !== document.body && !current.closest(".t-drawer")) return;
        target.focus();
      };
      [0, 180, 380].forEach(delay => {
        restoreTimers.push(window.setTimeout(restore, delay));
      });
      restore();
    };
  }, [active, selector]);
}