/* =============================================================================
 * A08_Support_UI_Page.ts
 * 로그인 전 08: 기술지원 요청 (이름 + 이메일 + 제목 + 문의내용 폼)
 *
 * 제약 준수:
 *   - 모든 문구는 ui_template_locale.ts 참조 (하드코딩 금지).
 *   - 색상/간격은 A08_Support_UI_Style.css + theme.css 변수만 사용.
 *   - 공통 컴포넌트(createButton/createInputField) 우선 사용.
 *   - 이벤트 핸들러는 on[페이지]_[기능]_[액션] 명명.
 *   - 백엔드 전송 전 1차 유효성 검사 (frontend.md §4).
 * ========================================================================== */

import { ui_locales, currentLanguageIndex } from "@ui/ui_template_locale";
import { createButton, createInputField } from "@ui/ui_template_elements";
import { isBlank, isValidEmail } from "@util/common_util_validate";
import { fetchSessionUser } from "../A06_Login/A06_Login_Api_Fetch";
import "./A08_Support_UI_Style.css";

/** locale 헬퍼 */
function L(key: keyof typeof ui_locales): string {
  return ui_locales[key][currentLanguageIndex];
}

/** 문의내용 textarea 핸들 (createInputField와 유사한 형태로 에러 슬롯 포함) */
interface TextAreaHandle {
  root: HTMLDivElement;
  textarea: HTMLTextAreaElement;
  setError: (msg?: string) => void;
}

/** 여러 줄 입력용 textarea 필드 생성 (공통 .ui-field/.ui-input 스타일 상속). */
function createTextAreaField(label: string, placeholder: string): TextAreaHandle {
  const root = document.createElement("div");
  root.className = "ui-field";

  const labelEl = document.createElement("label");
  labelEl.className = "ui-field__label";
  labelEl.textContent = label;

  const textarea = document.createElement("textarea");
  textarea.className = "ui-input a08-support__textarea";
  textarea.placeholder = placeholder;
  textarea.rows = 6;

  const errorSlot = document.createElement("span");
  errorSlot.className = "ui-field__error";
  errorSlot.setAttribute("role", "alert");

  root.append(labelEl, textarea, errorSlot);

  const setError = (msg?: string): void => {
    if (msg) {
      textarea.classList.add("ui-input--error");
      errorSlot.textContent = msg;
      errorSlot.classList.add("is-visible");
    } else {
      textarea.classList.remove("ui-input--error");
      errorSlot.textContent = "";
      errorSlot.classList.remove("is-visible");
    }
  };

  return { root, textarea, setError };
}

/* -----------------------------------------------------------------------------
 * 페이지 진입점
 * -------------------------------------------------------------------------- */
export function renderA08Support(root: HTMLElement): void {
  const page = document.createElement("div");
  page.className = "a08-support";

  const card = document.createElement("div");
  card.className = "a08-support__card";

  const title = document.createElement("h1");
  title.className = "a08-support__title";
  title.textContent = L("A08_Support_Title");

  const subtitle = document.createElement("p");
  subtitle.className = "a08-support__subtitle";
  subtitle.textContent = L("A08_Support_Subtitle");

  // 성공 메시지 슬롯 (제출 성공 시 표시)
  const successMsg = document.createElement("p");
  successMsg.className = "a08-support__success";
  successMsg.textContent = L("A08_Support_Success");
  successMsg.hidden = true;

  // 입력 필드
  const nameField = createInputField({
    label: L("A08_Support_Field_Name"),
    placeholder: L("A08_Support_Field_Name_Placeholder"),
    type: "text",
    required: true,
  });

  const emailField = createInputField({
    label: L("A08_Support_Field_Email"),
    placeholder: L("A08_Support_Field_Email_Placeholder"),
    type: "email",
    required: true,
  });
  const phoneField = createInputField({
    label: L("A08_Support_Field_Phone"),
    placeholder: L("A08_Support_Field_Phone_Placeholder"),
    type: "tel",
    required: false,
  });
  const subjectField = createInputField({
    label: L("A08_Support_Field_Subject"),
    placeholder: L("A08_Support_Field_Subject_Placeholder"),
    type: "text",
    required: true,
  });
  const messageField = createTextAreaField(
    L("A08_Support_Field_Message"),
    L("A08_Support_Field_Message_Placeholder"),
  );

  const form = document.createElement("form");
  form.className = "a08-support__form";
  form.noValidate = true;

  const submitBtn = createButton({
    label: L("A08_Support_Submit"),
    variant: "filled",
    type: "submit",
  });
  submitBtn.classList.add("a08-support__submit");

  /* 이벤트 핸들러: 제출 시 1차 유효성 검사 */
  function onA08_Support_Submit_Click(event: Event): void {
    event.preventDefault();
    successMsg.hidden = true;
    nameField.setError();
    emailField.setError();
    subjectField.setError();
    messageField.setError();

    const name = nameField.input.value;
    const email = emailField.input.value;
    const phone = phoneField.input.value;
    const subject = subjectField.input.value;
    const message = messageField.textarea.value;

    // 필수값 검사
    let hasError = false;
    if (isBlank(name)) {
      nameField.setError(L("A08_Support_Error_Required"));
      hasError = true;
    }
    if (isBlank(email)) {
      emailField.setError(L("A08_Support_Error_Required"));
      hasError = true;
    }
    if (isBlank(subject)) {
      subjectField.setError(L("A08_Support_Error_Required"));
      hasError = true;
    }
    if (isBlank(message)) {
      messageField.setError(L("A08_Support_Error_Required"));
      hasError = true;
    }
    if (hasError) return;

    // 형식 검사
    if (!isValidEmail(email)) {
      emailField.setError(L("A08_Support_Error_Email"));
      return;
    }

    // API 호출: POST /api/a08/support
    (async () => {
      try {
        const response = await fetch("/api/a08/support", {
          method: "POST",
          credentials: "include",
          headers: { "Content-Type": "application/json" },
          body: JSON.stringify({ name, email, phone: phone || null, subject, message }),
        });
        if (!response.ok) {
          const error = (await response.json()) as { detail?: string };
          throw new Error(error.detail ?? "요청 실패");
        }
        form.reset();
        messageField.textarea.value = "";
        successMsg.hidden = false;
      } catch (err) {
        const msg = err instanceof Error ? err.message : "오류 발생";
        nameField.setError(msg);
      }
    })();
  }

  form.addEventListener("submit", onA08_Support_Submit_Click);
  form.append(
    nameField.root,
    emailField.root,
    phoneField.root,
    subjectField.root,
    messageField.root,
    submitBtn,
  );

  card.append(title, subtitle, successMsg, form);
  page.append(card);
  root.append(page);

  // 백그라운드에서 세션 정보 로드 (페이지 렌더링을 지연시키지 않음)
  (async () => {
    const sessionUser = await fetchSessionUser();
    if (sessionUser?.name) nameField.input.value = sessionUser.name;
    if (sessionUser?.email) emailField.input.value = sessionUser.email;
  })();
}