"use client";

import { useEffect, useRef, type RefObject } from "react";
import { useTabStore } from "@/stores/tabStore";

const ERROR_ATTR = "data-auto-validation-error";
const DISABLED_ATTR = "data-validation-disabled";
const ACTION_BTN_SELECTOR = '[data-variant="default"]';

/**
 * 모달 자동 폼 검증 훅
 *
 * 활성화 조건:
 *   - useTabStore.mode === "user" (사용자 모드)
 *   - 필수 필드(label 내 <span>*</span>)가 1개 이상 존재
 *
 * 동작:
 *   - Label 내부 <span> 안의 * 문자로 필수 필드 자동 탐지
 *   - 빈 필수 필드에 빨간 테두리 + 에러 메시지 주입
 *   - data-variant="default" 버튼 비활성화 (저장/등록/수정/확인)
 */
export function useDialogAutoValidation(
  contentRef: RefObject<HTMLElement | null>,
) {
  const mode = useTabStore((s) => s.mode);
  const activeRef = useRef(false);

  useEffect(() => {
    if (mode !== "user") return;

    const el = contentRef.current;
    if (!el) return;

    activeRef.current = true;
    const injected = new Set<HTMLElement>();
    let isValidating = false;

    type InputEl = HTMLInputElement | HTMLTextAreaElement | HTMLSelectElement;

    function findRequiredFields(): Map<InputEl, string> {
      const fields = new Map<InputEl, string>();
      if (!el) return fields;

      el.querySelectorAll("label").forEach((label) => {
        const hasRequiredMark = Array.from(label.querySelectorAll("span")).some(
          (span) => span.textContent?.trim() === "*",
        );
        if (!hasRequiredMark) return;

        const forId =
          label.getAttribute("for") || (label as HTMLLabelElement).htmlFor;
        let input: Element | null = null;

        if (forId) {
          try {
            input = el!.querySelector(`#${CSS.escape(forId)}`);
          } catch {
            /* invalid id */
          }
        }

        if (!input) {
          const parent =
            label.closest('[class*="space-y"]') || label.parentElement;
          input = parent?.querySelector("input, textarea, select") || null;
        }

        if (
          input instanceof HTMLInputElement ||
          input instanceof HTMLTextAreaElement ||
          input instanceof HTMLSelectElement
        ) {
          const labelText =
            label.textContent?.replace(/\*/g, "").trim() || "";
          fields.set(input, labelText);
        }
      });

      return fields;
    }

    function isEmpty(input: InputEl): boolean {
      return input.value.trim() === "";
    }

    function validate() {
      if (isValidating) return;
      isValidating = true;

      try {
        const fields = findRequiredFields();
        if (fields.size === 0) return;

        let hasEmpty = false;

        fields.forEach((_label, input) => {
          if (isEmpty(input)) {
            hasEmpty = true;
            input.classList.add("border-destructive");

            const parent = input.parentElement;
            if (parent && !parent.querySelector(`[${ERROR_ATTR}]`)) {
              const p = document.createElement("p");
              p.className = "text-xs text-destructive mt-1";
              p.textContent = "필수 입력 항목입니다";
              p.setAttribute(ERROR_ATTR, "true");
              input.insertAdjacentElement("afterend", p);
              injected.add(p);
            }
          } else {
            input.classList.remove("border-destructive");

            const errorEl = input.parentElement?.querySelector(
              `[${ERROR_ATTR}]`,
            );
            if (errorEl) {
              injected.delete(errorEl as HTMLElement);
              errorEl.remove();
            }
          }
        });

        updateButtons(hasEmpty);
      } finally {
        requestAnimationFrame(() => {
          isValidating = false;
        });
      }
    }

    function updateButtons(hasErrors: boolean) {
      el!.querySelectorAll<HTMLButtonElement>(ACTION_BTN_SELECTOR).forEach(
        (btn) => {
          if (hasErrors) {
            btn.setAttribute(DISABLED_ATTR, "true");
            btn.style.opacity = "0.5";
            btn.style.cursor = "not-allowed";
            btn.title = "필수 입력 항목을 모두 채워주세요";
          } else if (btn.hasAttribute(DISABLED_ATTR)) {
            btn.removeAttribute(DISABLED_ATTR);
            btn.style.opacity = "";
            btn.style.cursor = "";
            btn.title = "";
          }
        },
      );
    }

    function blockClick(e: Event) {
      const btn = (e.target as HTMLElement).closest(`[${DISABLED_ATTR}]`);
      if (btn) {
        e.stopPropagation();
        e.preventDefault();
      }
    }

    el.addEventListener("input", validate);
    el.addEventListener("change", validate);
    el.addEventListener("click", blockClick, true);

    const initTimer = setTimeout(validate, 50);

    const observer = new MutationObserver(() => {
      if (!isValidating) validate();
    });
    observer.observe(el, { childList: true, subtree: true });

    return () => {
      activeRef.current = false;
      el.removeEventListener("input", validate);
      el.removeEventListener("change", validate);
      el.removeEventListener("click", blockClick, true);
      clearTimeout(initTimer);
      observer.disconnect();

      injected.forEach((p) => p.remove());
      injected.clear();

      el.querySelectorAll(`[${DISABLED_ATTR}]`).forEach((btn) => {
        btn.removeAttribute(DISABLED_ATTR);
        (btn as HTMLElement).style.opacity = "";
        (btn as HTMLElement).style.cursor = "";
        (btn as HTMLElement).title = "";
      });

      el.querySelectorAll(".border-destructive").forEach((input) => {
        input.classList.remove("border-destructive");
      });
    };
  }, [mode]);
}