import { useEffect } from "react";

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

let dialogTitleSequence = 0;

function isVisible(node: HTMLElement): boolean {
  const rect = node.getBoundingClientRect();
  const style = window.getComputedStyle(node);
  return rect.width > 0 && rect.height > 0 && style.display !== "none" && style.visibility !== "hidden";
}

/** Normalizes the semantics and keyboard behavior missing from TDesign Dialog. */
export function useDialogAccessibility() {
  useEffect(() => {
    let lastFocusOutside: HTMLElement | null = document.activeElement instanceof HTMLElement ? document.activeElement : null;
    let scheduledFrame = 0;
    const enhanced = new Map<HTMLElement, () => void>();

    const onFocusIn = (event: FocusEvent) => {
      const target = event.target;
      if (!(target instanceof HTMLElement) || target.closest(".t-dialog__ctx")) return;
      lastFocusOutside = target;
    };

    const focusableItems = (dialog: HTMLElement) => Array.from(dialog.querySelectorAll<HTMLElement>(FOCUSABLE)).filter(isVisible);

    const enhance = (dialog: HTMLElement) => {
      if (enhanced.has(dialog)) return;
      const context = dialog.closest<HTMLElement>(".t-dialog__ctx") ?? dialog;
      const returnFocus = lastFocusOutside;
      dialogTitleSequence += 1;
      const dialogSequence = dialogTitleSequence;
      dialog.setAttribute("role", "dialog");
      dialog.setAttribute("aria-modal", "true");
      if (!dialog.hasAttribute("tabindex")) dialog.setAttribute("tabindex", "-1");

      const header = dialog.querySelector<HTMLElement>(".t-dialog__header-content, .t-dialog__header");
      if (header) {
        if (!header.id) {
          header.id = `tn-dialog-title-${dialogSequence}`;
        }
        dialog.setAttribute("aria-labelledby", header.id);
      } else {
        dialog.setAttribute("aria-label", "确认操作");
      }

      const body = dialog.querySelector<HTMLElement>(".t-dialog__body");
      if (body?.textContent?.trim()) {
        if (!body.id) body.id = `tn-dialog-description-${dialogSequence}`;
        dialog.setAttribute("aria-describedby", body.id);
      }

      const closeButton = dialog.querySelector<HTMLElement>(".t-dialog__close");
      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", "关闭弹窗");
        closeButton.addEventListener("keydown", onCloseKeyDown);
      }

      const onKeyDown = (event: KeyboardEvent) => {
        if (event.key !== "Tab") return;
        const items = focusableItems(dialog);
        if (!items.length) {
          event.preventDefault();
          event.stopPropagation();
          dialog.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();
      };
      context.addEventListener("keydown", onKeyDown, true);

      const focusInitial = () => {
        if (!isVisible(dialog) || dialog.contains(document.activeElement)) return;
        const preferred = dialog.querySelector<HTMLElement>(".t-dialog__cancel:not([disabled])")
          ?? dialog.querySelector<HTMLElement>(".t-dialog__close[tabindex='0']");
        (preferred && isVisible(preferred) ? preferred : focusableItems(dialog)[0] ?? dialog).focus();
      };
      const frame = window.requestAnimationFrame(focusInitial);
      const timer = window.setTimeout(focusInitial, 80);

      enhanced.set(dialog, () => {
        window.cancelAnimationFrame(frame);
        window.clearTimeout(timer);
        context.removeEventListener("keydown", onKeyDown, true);
        closeButton?.removeEventListener("keydown", onCloseKeyDown);
        window.setTimeout(() => {
          const anotherDialogOpen = Array.from(document.querySelectorAll<HTMLElement>(".t-dialog")).some(candidate => candidate !== dialog && isVisible(candidate));
          const active = document.activeElement;
          if (!anotherDialogOpen && returnFocus?.isConnected && (!active || active === document.body || context.contains(active))) returnFocus.focus();
        }, 0);
      });
    };

    const sync = () => {
      scheduledFrame = 0;
      const visibleDialogs = new Set(Array.from(document.querySelectorAll<HTMLElement>(".t-dialog")).filter(isVisible));
      visibleDialogs.forEach(enhance);
      enhanced.forEach((cleanup, dialog) => {
        if (visibleDialogs.has(dialog)) return;
        cleanup();
        enhanced.delete(dialog);
      });
    };
    const scheduleSync = () => {
      if (scheduledFrame) return;
      scheduledFrame = window.requestAnimationFrame(sync);
    };

    document.addEventListener("focusin", onFocusIn);
    const observer = new MutationObserver(scheduleSync);
    observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ["class", "style"] });
    scheduleSync();
    return () => {
      document.removeEventListener("focusin", onFocusIn);
      observer.disconnect();
      window.cancelAnimationFrame(scheduledFrame);
      enhanced.forEach(cleanup => cleanup());
      enhanced.clear();
    };
  }, []);
}