/* =============================================================================
 * ui_template_elements.ts
 * 공통 컴포넌트 및 그룹 템플릿 정의
 *
 * 원칙:
 *   - 모든 컴포넌트는 임의 스타일링 금지, 여기 규격을 최우선 상속/참조 (frontend.md §2).
 *   - 색상/간격은 CSS 클래스 + theme.css 변수로만 처리, JS 내 인라인 색상 금지.
 *   - 팩토리 함수는 HTMLElement를 반환하는 vanilla TS 패턴.
 *   - 스타일 규칙은 injectBaseStyles()로 1회 주입 (design.md 컴포넌트 명세 기반).
 * ========================================================================== */

/* -----------------------------------------------------------------------------
 * 0. 내부 유틸
 * -------------------------------------------------------------------------- */

/** 요소 생성 + 속성/클래스/자식 일괄 설정 헬퍼 */
function el<K extends keyof HTMLElementTagNameMap>(
  tag: K,
  options: {
    className?: string;
    text?: string;
    attrs?: Record<string, string>;
    children?: (HTMLElement | string)[];
  } = {},
): HTMLElementTagNameMap[K] {
  const node = document.createElement(tag);
  if (options.className) node.className = options.className;
  if (options.text !== undefined) node.textContent = options.text;
  if (options.attrs) {
    for (const [k, v] of Object.entries(options.attrs)) {
      node.setAttribute(k, v);
    }
  }
  if (options.children) {
    for (const child of options.children) {
      node.append(child);
    }
  }
  return node;
}

/* -----------------------------------------------------------------------------
 * 1. 버튼 (Button) — design.md: Filled Brand / Ghost Outlined / Pill Nav
 * -------------------------------------------------------------------------- */

export type ButtonVariant = "filled" | "ghost" | "pill" | "danger";

export interface ButtonOptions {
  /** 표시 텍스트 (i18n 결과 문자열을 전달) */
  label: string;
  variant?: ButtonVariant;
  /** 이벤트 핸들러 (frontend.md §4: on[페이지]_[기능]_[액션] 명명) */
  onClick?: (ev: MouseEvent) => void;
  disabled?: boolean;
  type?: "button" | "submit" | "reset";
  /** 앞쪽 아이콘 요소 (선택) */
  iconStart?: HTMLElement;
}

export function createButton(opts: ButtonOptions): HTMLButtonElement {
  const variant = opts.variant ?? "filled";
  const btn = el("button", {
    className: `ui-btn ui-btn--${variant}`,
    attrs: { type: opts.type ?? "button" },
  });
  if (opts.iconStart) {
    opts.iconStart.classList.add("ui-btn__icon");
    btn.append(opts.iconStart);
  }
  btn.append(el("span", { className: "ui-btn__label", text: opts.label }));
  if (opts.disabled) btn.disabled = true;
  if (opts.onClick) btn.addEventListener("click", opts.onClick);
  return btn;
}

/* -----------------------------------------------------------------------------
 * 2. 입력 필드 (Input Field) — design.md: 1px mist border, 8px radius, focus ring
 * -------------------------------------------------------------------------- */

export interface InputFieldOptions {
  /** 라벨 텍스트 (i18n 결과) */
  label?: string;
  /** placeholder (i18n 결과) */
  placeholder?: string;
  type?: "text" | "password" | "email" | "number" | "search";
  value?: string;
  required?: boolean;
  /** number 타입 범위 (1차 유효성 검사용, frontend.md §4) */
  min?: number;
  max?: number;
  onInput?: (value: string) => void;
}

export interface InputFieldHandle {
  /** 필드 컨테이너 (라벨 + 입력 + 에러 슬롯) */
  root: HTMLDivElement;
  input: HTMLInputElement;
  /** 에러 메시지 표시/해제. msg가 없으면 에러 해제. */
  setError: (msg?: string) => void;
}

export function createInputField(opts: InputFieldOptions): InputFieldHandle {
  const root = el("div", { className: "ui-field" });

  if (opts.label) {
    root.append(el("label", { className: "ui-field__label", text: opts.label }));
  }

  const input = el("input", {
    className: "ui-input",
    attrs: {
      type: opts.type ?? "text",
      ...(opts.placeholder ? { placeholder: opts.placeholder } : {}),
      ...(opts.required ? { required: "true" } : {}),
      ...(opts.min !== undefined ? { min: String(opts.min) } : {}),
      ...(opts.max !== undefined ? { max: String(opts.max) } : {}),
    },
  });
  if (opts.value !== undefined) input.value = opts.value;
  if (opts.onInput) {
    input.addEventListener("input", () => opts.onInput!(input.value));
  }

  // 에러 메시지 슬롯 (입력창 하단 표기, frontend.md §4)
  const errorSlot = el("span", { className: "ui-field__error", attrs: { role: "alert" } });

  root.append(input, errorSlot);

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

  return { root, input, setError };
}

/* -----------------------------------------------------------------------------
 * 3. 카드 / 패널 (Card) — design.md: white surface, 8px radius, shadow
 * -------------------------------------------------------------------------- */

export interface CardOptions {
  title?: string;
  /** 본문 자식 요소들 */
  body?: (HTMLElement | string)[];
  /** 그림자 강조 여부 (shadow-lg 사용) */
  raised?: boolean;
}

export function createCard(opts: CardOptions): HTMLDivElement {
  const card = el("div", {
    className: `ui-card${opts.raised ? " ui-card--raised" : ""}`,
  });
  if (opts.title) {
    card.append(el("h3", { className: "ui-card__title", text: opts.title }));
  }
  if (opts.body) {
    card.append(el("div", { className: "ui-card__body", children: opts.body }));
  }
  return card;
}

/* -----------------------------------------------------------------------------
 * 4. 태그 / 배지 (Tag / Pill) — design.md: 1440px radius pill
 * -------------------------------------------------------------------------- */

export type TagVariant = "accent" | "neutral" | "success" | "warning" | "danger";

export function createTag(label: string, variant: TagVariant = "neutral"): HTMLSpanElement {
  return el("span", { className: `ui-tag ui-tag--${variant}`, text: label });
}

/* -----------------------------------------------------------------------------
 * 5. 로딩 오버레이 (Loading Overlay) — frontend.md §4: API 호출 시 필수
 *    싱글턴 오버레이. show/hide로 참조 카운트 관리.
 * -------------------------------------------------------------------------- */

let overlayEl: HTMLDivElement | null = null;
let overlayCount = 0;

function ensureOverlay(): HTMLDivElement {
  if (overlayEl) return overlayEl;
  const spinner = el("div", { className: "ui-spinner", attrs: { "aria-hidden": "true" } });
  overlayEl = el("div", {
    className: "ui-overlay",
    attrs: { role: "status", "aria-live": "polite" },
    children: [spinner],
  });
  document.body.append(overlayEl);
  return overlayEl;
}

/** 로딩 스피너 오버레이 표시 (중첩 호출 안전) */
export function showLoadingOverlay(): void {
  overlayCount += 1;
  ensureOverlay().classList.add("is-active");
}

/** 로딩 스피너 오버레이 해제 (모든 참조 종료 시 실제 숨김) */
export function hideLoadingOverlay(): void {
  overlayCount = Math.max(0, overlayCount - 1);
  if (overlayCount === 0 && overlayEl) {
    overlayEl.classList.remove("is-active");
  }
}

/* -----------------------------------------------------------------------------
 * 6. 토스트 알림 (Toast) — 성공/에러 배너
 * -------------------------------------------------------------------------- */

export type ToastKind = "success" | "error" | "info" | "warning";

let toastContainer: HTMLDivElement | null = null;

function ensureToastContainer(): HTMLDivElement {
  if (toastContainer) return toastContainer;
  toastContainer = el("div", { className: "ui-toast-container" });
  document.body.append(toastContainer);
  return toastContainer;
}

/** 토스트 표시. durationMs 후 자동 소멸. */
export function showToast(message: string, kind: ToastKind = "info", durationMs = 3000): void {
  const toast = el("div", { className: `ui-toast ui-toast--${kind}`, text: message });
  ensureToastContainer().append(toast);
  // 진입 애니메이션 트리거
  requestAnimationFrame(() => toast.classList.add("is-visible"));
  window.setTimeout(() => {
    toast.classList.remove("is-visible");
    window.setTimeout(() => toast.remove(), 200);
  }, durationMs);
}

/* -----------------------------------------------------------------------------
 * 7. 워크플로우 3단 레이아웃 셸 (frontend.md §2)
 *    상단 헤더 + 좌측 고정 패널 + 우측 뷰어 영역.
 * -------------------------------------------------------------------------- */

export interface WorkflowShellOptions {
  /** 상단 페이지 타이틀 (i18n 결과) */
  title: string;
  /** 상단 진행 단계 라벨 배열 (i18n 결과) */
  steps?: string[];
  /** 현재 활성 단계 인덱스 */
  activeStep?: number;
}

export interface WorkflowShellHandle {
  root: HTMLDivElement;
  /** 좌측 입력 폼/설정 영역 (너비 고정) */
  leftPanel: HTMLDivElement;
  /** 우측 WebCAD 뷰어 / 결과 그리드 영역 */
  rightArea: HTMLDivElement;
}

export function createWorkflowShell(opts: WorkflowShellOptions): WorkflowShellHandle {
  // 상단 헤더
  const titleEl = el("h2", { className: "ui-wf__title", text: opts.title });
  const headerChildren: HTMLElement[] = [titleEl];

  if (opts.steps && opts.steps.length > 0) {
    const stepsEl = el("div", { className: "ui-wf__steps" });
    opts.steps.forEach((label, idx) => {
      const isActive = idx === (opts.activeStep ?? 0);
      stepsEl.append(
        el("span", {
          className: `ui-wf__step${isActive ? " is-active" : ""}`,
          text: label,
        }),
      );
    });
    headerChildren.push(stepsEl);
  }

  const header = el("header", { className: "ui-wf__header", children: headerChildren });
  const leftPanel = el("div", { className: "ui-wf__left" });
  const rightArea = el("div", { className: "ui-wf__right" });
  const bodyRow = el("div", { className: "ui-wf__body", children: [leftPanel, rightArea] });

  const root = el("div", { className: "ui-wf", children: [header, bodyRow] });
  return { root, leftPanel, rightArea };
}

/* =============================================================================
 * 8. 기본 컴포넌트 스타일 주입 (injectBaseStyles)
 *    theme.css 변수만 참조. 앱 진입 시 1회 호출.
 * ========================================================================== */

const BASE_STYLE_ID = "ui-template-elements-style";

const BASE_CSS = `
/* --- Button --- */
.ui-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-8);
  font-family: var(--font-body);
  font-size: var(--text-body);
  font-weight: var(--font-weight-medium);
  line-height: 1;
  border: 1px solid transparent;
  border-radius: var(--radius-buttons);
  padding: var(--spacing-16) var(--spacing-24);
  cursor: pointer;
  transition: background-color var(--transition-fast),
    border-color var(--transition-fast), color var(--transition-fast);
}
.ui-btn:disabled { opacity: 0.5; cursor: not-allowed; }
.ui-btn__icon { display: inline-flex; width: 16px; height: 16px; }

.ui-btn--filled {
  background-color: var(--color-primary);
  color: var(--color-primary-text);
  box-shadow: var(--shadow-sm);
}
.ui-btn--filled:hover:not(:disabled) { background-color: var(--color-royal-amethyst); }

.ui-btn--ghost {
  background-color: transparent;
  border-color: var(--color-primary);
  color: var(--color-primary);
}
.ui-btn--ghost:hover:not(:disabled) { background-color: var(--color-mist-violet); }

.ui-btn--pill {
  background-color: transparent;
  color: var(--color-plum-velvet);
  border-radius: var(--radius-pills);
  padding: var(--spacing-8) var(--spacing-16);
  font-size: var(--text-body-sm);
}
.ui-btn--pill:hover:not(:disabled),
.ui-btn--pill.is-active { background-color: var(--color-mist-violet); }

.ui-btn--danger {
  background-color: var(--color-danger);
  color: var(--color-canvas);
}

/* --- Input Field --- */
.ui-field { display: flex; flex-direction: column; gap: var(--spacing-4); }
.ui-field__label {
  font-size: var(--text-caption);
  font-weight: var(--font-weight-medium);
  color: var(--color-text-secondary);
}
.ui-input {
  font-family: var(--font-body);
  font-size: var(--text-body-sm);
  color: var(--color-text-body);
  background-color: var(--color-canvas);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-inputs);
  padding: 10px 14px;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}
.ui-input::placeholder { color: var(--color-text-muted); }
.ui-input:focus {
  outline: none;
  border-color: var(--color-focus-ring);
  box-shadow: 0 0 0 1px var(--color-focus-ring);
}
.ui-input--error { border-color: var(--color-danger); }
.ui-field__error {
  font-size: var(--text-caption);
  color: var(--color-danger);
  min-height: 0;
  visibility: hidden;
}
.ui-field__error.is-visible { visibility: visible; }

/* --- Card --- */
.ui-card {
  background-color: var(--color-surface-raised);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-cards);
  padding: var(--card-padding);
  box-shadow: var(--shadow-sm);
}
.ui-card--raised { box-shadow: var(--shadow-lg); border-color: transparent; }
.ui-card__title {
  font-family: var(--font-display);
  color: var(--color-plum-velvet);
  margin-bottom: var(--spacing-16);
}
.ui-card__body { display: flex; flex-direction: column; gap: var(--spacing-16); }

/* --- Tag / Pill --- */
.ui-tag {
  display: inline-flex;
  align-items: center;
  border-radius: var(--radius-pills);
  padding: var(--spacing-4) var(--spacing-16);
  font-size: var(--text-caption);
  font-weight: var(--font-weight-medium);
  line-height: 1.3;
}
.ui-tag--accent { background-color: var(--color-mist-violet); color: var(--color-royal-amethyst); }
.ui-tag--neutral { background-color: var(--color-paper); color: var(--color-slate); }
.ui-tag--success { background-color: var(--color-mist-violet); color: var(--color-success); }
.ui-tag--warning { background-color: var(--color-paper); color: var(--color-warning); }
.ui-tag--danger { background-color: var(--color-paper); color: var(--color-danger); }

/* --- Loading Overlay + Spinner --- */
.ui-overlay {
  position: fixed;
  inset: 0;
  display: none;
  align-items: center;
  justify-content: center;
  background-color: rgba(38, 17, 74, 0.24);
  z-index: var(--z-overlay);
}
.ui-overlay.is-active { display: flex; }
.ui-spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--color-mist-violet);
  border-top-color: var(--color-royal-amethyst);
  border-radius: var(--radius-pills);
  animation: ui-spin 0.8s linear infinite;
}
@keyframes ui-spin { to { transform: rotate(360deg); } }

/* --- Toast --- */
.ui-toast-container {
  position: fixed;
  top: var(--spacing-24);
  right: var(--spacing-24);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-8);
  z-index: var(--z-toast);
}
.ui-toast {
  padding: var(--spacing-16) var(--spacing-24);
  border-radius: var(--radius-cards);
  font-size: var(--text-body-sm);
  color: var(--color-canvas);
  box-shadow: var(--shadow-lg);
  opacity: 0;
  transform: translateX(16px);
  transition: opacity var(--transition-base), transform var(--transition-base);
}
.ui-toast.is-visible { opacity: 1; transform: translateX(0); }
.ui-toast--success { background-color: var(--color-success); }
.ui-toast--error { background-color: var(--color-danger); }
.ui-toast--warning { background-color: var(--color-warning); }
.ui-toast--info { background-color: var(--color-royal-amethyst); }

/* --- Workflow Shell (3단 레이아웃) --- */
.ui-wf { display: flex; flex-direction: column; height: 100%; }
.ui-wf__header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--wf-header-height);
  padding: 0 var(--spacing-24);
  border-bottom: 1px solid var(--color-border);
  background-color: var(--color-surface-raised);
}
.ui-wf__title { font-size: var(--text-subheading); }
.ui-wf__steps { display: flex; gap: var(--spacing-8); }
.ui-wf__step {
  padding: var(--spacing-4) var(--spacing-16);
  border-radius: var(--radius-pills);
  font-size: var(--text-caption);
  font-weight: var(--font-weight-medium);
  color: var(--color-slate);
  background-color: var(--color-paper);
}
.ui-wf__step.is-active {
  color: var(--color-royal-amethyst);
  background-color: var(--color-mist-violet);
}
.ui-wf__body { display: flex; flex: 1; min-height: 0; }
.ui-wf__left {
  width: var(--wf-left-panel-width);
  flex-shrink: 0;
  padding: var(--spacing-24);
  border-right: 1px solid var(--color-border);
  overflow-y: auto;
  background-color: var(--color-surface);
}
.ui-wf__right {
  flex: 1;
  min-width: 0;
  overflow: auto;
  background-color: var(--color-bg);
}
`;

/** 공통 컴포넌트 기본 스타일을 <head>에 1회 주입. 앱 진입 시 호출. */
export function injectBaseStyles(): void {
  if (document.getElementById(BASE_STYLE_ID)) return;
  const style = el("style", { attrs: { id: BASE_STYLE_ID } });
  style.textContent = BASE_CSS;
  document.head.append(style);
}