import * as THREE from "three";
import { OrbitControls } from "three/examples/jsm/controls/OrbitControls.js";
import { GLTFLoader } from "three/examples/jsm/loaders/GLTFLoader.js";
import { PLYLoader } from "three/examples/jsm/loaders/PLYLoader.js";
import { API_BASE_URL } from "@config/config_frontend";
import { fetchCachedBytes, fetchCachedJson } from "../A00_Common/b_asset_cache";
import { currentLanguageIndex, ui_locales } from "@ui/ui_template_locale";
import { createProgressCircle } from "@ui/ui_template_progress";
// 계획선 색은 2D 지도·B05 배수유역도와 한 곳에서 나온다 — 같은 선을 다른 색으로 그리지 않는다.
import { createTerrainCompass } from "./B04_PreProcess_UI_Compass";
import { routeLineColor } from "./B04_PreProcess_UI_MapRender";
import type { SurfaceBounds, SurfaceModelSummary } from "./B04_PreProcess_Api_Fetch";
import {
  bindCursorPivotControls,
  bindSurfaceViewerTheme,
  getTopFitDistance,
  TOP_VIEW_TILT,
  niceScaleDistance,
  SURFACE_CAMERA_FOV,
  targetPlaneMetersPerPixel,
  type SurfaceCameraState,
} from "./B04_PreProcess_UI_Camera";

/** 화면에 띄우는 등고 라벨 상한 — 긴 등고선부터 채운다. 조각이 많은 지형에서
 *  라벨이 수백 개가 되면 매 프레임 위치 재계산이 화면을 멈춰 세운다(2026-08-30). */
const MAX_CONTOUR_LABELS = 40;

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

export interface SurfaceTerrainViewer {
  root: HTMLElement;
  /** 표시 토글(축·서피스·등고선·간격) + 상태 줄. 페이지가 "모델 표시 옵션"에 넣는다. */
  optionsContent: HTMLElement;
  /** 스무딩 드롭다운 한 줄. 페이지가 "지표면 분석"에 넣는다. */
  smoothingField: HTMLElement;
  render: (projectId: string, models: readonly SurfaceModelSummary[]) => void;
  setReferenceBounds: (bounds: SurfaceBounds) => void;
  /** 계획노선(사업지 좌표계 m)을 3D 최고 표고 평면에 그린다. 빈 목록이면 걷어낸다. */
  setRoute: (points: ReadonlyArray<{ x: number; y: number }>) => void;
  setSelection: (sourceFilter: string, method: string) => void;
  /** 다른 모델(예: 라이다 지표면)을 반투명으로 겹쳐 본다. 빈 문자열이면 걷어낸다. */
  showOverlay: (sourceFilter: string, method: string, smooth: boolean) => Promise<boolean>;
  applyCameraState: (state: SurfaceCameraState) => void;
  onCameraChange: (listener: (state: SurfaceCameraState) => void) => void;
  onAxesVisibilityChange: (listener: (visible: boolean) => void) => void;
  isSmoothingEnabled: () => boolean;
  /** 스무딩 시작값을 정한다(확정본 저장값). 다시 그리지는 않는다. */
  setSmoothing: (enabled: boolean) => void;
  getContourInterval: () => number;
  /** 등고선 간격 시작값을 정한다(사용자가 B05에서 저장한 값). 다시 그리지는 않는다. */
  setContourInterval: (interval: number) => void;
  resetOptions: () => void;
  dispose: () => void;
}

export function createSurfaceTerrainViewer(): SurfaceTerrainViewer {
  const root = document.createElement("div");
  root.className = "terrain-model-group";

  const statusSpan = document.createElement("span");
  statusSpan.className = "terrain-status";
  statusSpan.style.fontSize = "var(--text-caption)";
  statusSpan.style.color = "var(--color-text-secondary)";
  statusSpan.textContent = "모델 선택 대기 중...";
  let activeFilter = "csf";
  let activeMethod = "dtm";

  const axesCheck = document.createElement("input");
  axesCheck.type = "checkbox";
  axesCheck.checked = false;

  const rightControls = document.createElement("div");
  rightControls.className = "viewer-options model-display-options";

  // Surface Toggle
  const surfLabel = document.createElement("label");
  surfLabel.className = "toggle-label toggle-button";
  const surfCheck = document.createElement("input");
  surfCheck.type = "checkbox";
  surfCheck.checked = true;
  surfLabel.append(surfCheck, document.createTextNode(" 서피스"));

  // 스무딩(tin/dtm 전용) — 지면 필터·서피스와 함께 "지표면 분석" 컨테이너로 옮겼다.
  // 주변 입력과 양식을 맞추려고 버튼이 아니라 드롭다운이다(2026-08-01 사용자 지시).
  // 상태·재렌더 배선은 여기 그대로 두고, 페이지는 이 엘리먼트를 원하는 자리에 놓기만 한다.
  const smoothLabel = document.createElement("label");
  smoothLabel.className = "b04-surface__field";
  const smoothCaption = document.createElement("span");
  smoothCaption.textContent = L("B04_Surface_Field_Smoothing");
  const smoothSelect = document.createElement("select");
  smoothSelect.className = "b04-surface__select";
  (
    [
      ["on", "B04_Surface_Smoothing_On"],
      ["off", "B04_Surface_Smoothing_Off"],
    ] as const
  ).forEach(([value, key]) => {
    const option = document.createElement("option");
    option.value = value;
    option.textContent = L(key);
    smoothSelect.append(option);
  });
  smoothSelect.value = "on";
  smoothLabel.append(smoothCaption, smoothSelect);

  // Contour Toggle
  const contourLabel = document.createElement("label");
  contourLabel.className = "toggle-label toggle-button";
  const contourCheck = document.createElement("input");
  contourCheck.type = "checkbox";
  contourCheck.checked = true;
  contourLabel.append(contourCheck, document.createTextNode(" 등고선"));

  // Contour Interval input form
  const intervalForm = document.createElement("form");
  intervalForm.className = "contour-interval-form";

  const intervalInput = document.createElement("input");
  intervalInput.type = "number";
  intervalInput.value = "1.0";
  intervalInput.step = "0.5";
  intervalInput.min = "0.5";
  intervalInput.className = "contour-interval-input";

  const intervalSubmit = document.createElement("button");
  intervalSubmit.type = "submit";
  intervalSubmit.textContent = "적용";
  intervalSubmit.className = "contour-interval-submit";

  intervalForm.append(
    document.createTextNode("간격 "),
    intervalInput,
    document.createTextNode("m "),
    intervalSubmit,
  );

  const axesLabel = document.createElement("label");
  axesLabel.className = "toggle-label toggle-button";
  axesLabel.append(axesCheck, document.createTextNode(" 축"));
  rightControls.append(axesLabel, surfLabel, contourLabel, intervalForm);

  // 표시 토글 묶음 + 상태 줄. 컨테이너(제목)는 페이지가 만든다 — 포인트 옵션과 한 칸을 쓴다.
  const optionsContent = document.createElement("div");
  optionsContent.className = "terrain-options-content";
  optionsContent.append(rightControls, statusSpan);

  // 3D View container
  const viewerArea = document.createElement("div");
  viewerArea.className = "three-viewer";
  viewerArea.style.position = "relative";
  viewerArea.style.borderRadius = "0 0 var(--radius-cards) var(--radius-cards)";
  viewerArea.style.overflow = "hidden";

  const canvas = document.createElement("canvas");
  canvas.className = "b04-surface-viewer__canvas";
  viewerArea.append(canvas);
  root.append(viewerArea);

  // Scale bar overlay
  const scaleBar = document.createElement("div");
  scaleBar.className = "b04-surface__scale";
  scaleBar.hidden = true;

  const scaleLabel = document.createElement("span");
  scaleBar.append(scaleLabel);
  viewerArea.append(scaleBar);

  // 방위 콤파스 — 축척 막대 반대편(우하단). 바늘 각도는 애니메이션 루프가 맞춘다.
  const compass = createTerrainCompass();
  viewerArea.append(compass.root);

  // Elevation bounds legend bar overlay (I-403)
  const legendBar = document.createElement("div");
  legendBar.style.position = "absolute";
  legendBar.style.top = "16px";
  legendBar.style.right = "16px";
  legendBar.style.background = "rgba(255, 255, 255, 0.9)";
  legendBar.style.border = "1px solid #cbd5e1";
  legendBar.style.borderRadius = "6px";
  legendBar.style.padding = "8px";
  legendBar.style.width = "50px";
  legendBar.style.display = "none"; // hidden until contours are loaded
  legendBar.style.flexDirection = "column";
  legendBar.style.alignItems = "center";
  legendBar.style.zIndex = "10";
  legendBar.style.boxShadow = "0 2px 6px rgba(0,0,0,0.08)";
  legendBar.style.pointerEvents = "none";

  const maxValSpan = document.createElement("span");
  maxValSpan.style.fontSize = "10px";
  maxValSpan.style.fontWeight = "bold";
  maxValSpan.style.color = "#b91c1c";
  maxValSpan.style.marginBottom = "4px";

  const gradientDiv = document.createElement("div");
  gradientDiv.style.width = "12px";
  gradientDiv.style.height = "120px";
  gradientDiv.style.background =
    "linear-gradient(to bottom, #d60000 0%, #ff5100 25%, #e6a100 50%, #228b22 75%, #3a85ff 100%)";
  gradientDiv.style.borderRadius = "2px";
  gradientDiv.style.border = "1px solid #94a3b8";

  const minValSpan = document.createElement("span");
  minValSpan.style.fontSize = "10px";
  minValSpan.style.fontWeight = "bold";
  minValSpan.style.color = "#1d4ed8";
  minValSpan.style.marginTop = "4px";

  legendBar.append(maxValSpan, gradientDiv, minValSpan);
  viewerArea.append(legendBar);

  // 뷰포트 정중앙 로딩 서클 — 메쉬 파일은 수십 MB라 내려받는 동안 화면이 비어 보인다.
  const progress = createProgressCircle({ overlay: true });
  progress.root.hidden = true;
  viewerArea.append(progress.root);

  /** 진행률(0~1, 모르면 null)과 문구를 표시한다. label이 null이면 서클을 감춘다. */
  function showProgress(ratio: number | null, label: string | null): void {
    progress.root.hidden = label === null;
    if (label !== null) progress.set(ratio, label);
  }

  // Three.js context variables
  let currentProjectId = "";
  let currentModelsList: readonly SurfaceModelSummary[] = [];
  let referenceBounds: SurfaceBounds | null = null;
  let cameraListener: ((state: SurfaceCameraState) => void) | null = null;
  let axesVisibilityListener: ((visible: boolean) => void) | null = null;
  let suppressCameraEvent = false;
  let smoothPreferred = true;
  let currentModelId: number | null = null;
  let currentModelSmooth = false;
  // 선택 변경 후 늦게 도착한 이전 로더 콜백이 장면을 오염시키지 않도록 세대를 추적한다.
  let loadGeneration = 0;

  const scene = new THREE.Scene();
  const releaseTheme = bindSurfaceViewerTheme((color) => {
    scene.background = new THREE.Color(color);
  });

  const camera = new THREE.PerspectiveCamera(SURFACE_CAMERA_FOV, 1, 0.01, 100000);
  const renderer = new THREE.WebGLRenderer({ canvas, antialias: true });
  renderer.setPixelRatio(Math.min(window.devicePixelRatio || 1, 2));

  const controls = new OrbitControls(camera, renderer.domElement);
  controls.enableDamping = true;
  controls.dampingFactor = 0.08;
  controls.screenSpacePanning = true;

  scene.add(new THREE.HemisphereLight(0xffffff, 0x445566, 1.8));
  const directional = new THREE.DirectionalLight(0xffffff, 1.5);
  directional.position.set(100, 180, 120);
  scene.add(directional);

  const axes = new THREE.AxesHelper(25);
  axes.visible = axesCheck.checked;
  scene.add(axes);

  const contourGroup = new THREE.Group();
  contourGroup.visible = contourCheck.checked;
  scene.add(contourGroup);

  // 계획노선 — 지표면에 드리우지 않고 **데이터 최고 표고 평면**에 수평으로 얹는다
  // (2026-09-01 사용자 확정). 노선과 측량 범위가 평면상 어디서 어긋나는지 보려는 것이라
  // 지형을 따라 오르내리면 오히려 판단이 어렵다.
  const routeGroup = new THREE.Group();
  scene.add(routeGroup);
  let routePoints: ReadonlyArray<{ x: number; y: number }> = [];

  let terrainMesh: THREE.Object3D | null = null;
  const labelElements: HTMLDivElement[] = [];
  // 라벨 목록이 바뀌거나 표시 옵션을 껐다 켰을 때는 카메라가 그대로여도 다시 배치해야 한다.
  let labelsDirty = true;
  // 회전·줌 중심을 커서 아래 지형 지점으로 (포인트클라우드 뷰어·B05와 공용 유틸).
  const releaseCursorPivot = bindCursorPivotControls({
    camera,
    controls,
    element: renderer.domElement,
    pickables: () => (terrainMesh ? [terrainMesh] : []),
    scene,
  });

  function disposeObject(obj: THREE.Object3D) {
    obj.traverse((child) => {
      const renderable = child as THREE.Mesh | THREE.Points | THREE.LineSegments;
      renderable.geometry?.dispose();
      const material = renderable.material;
      if (Array.isArray(material)) material.forEach((item) => item.dispose());
      else material?.dispose();
    });
  }

  function clearMesh() {
    if (terrainMesh) {
      scene.remove(terrainMesh);
      disposeObject(terrainMesh);
      terrainMesh = null;
    }
  }

  // ── 겹쳐 보기 메시 ─────────────────────────────────────────────────────────
  // 도엽등고 서피스 위에 라이다 지표면을 겹쳐 두 지형을 눈으로 대조한다
  // (2026-08-30 사용자 지시). 본 메시와 카메라·좌표계를 공유하므로 같은 자리에 겹친다.
  let overlayMesh: THREE.Object3D | null = null;
  let overlayGeneration = 0;

  function clearOverlay() {
    if (overlayMesh) {
      scene.remove(overlayMesh);
      disposeObject(overlayMesh);
      overlayMesh = null;
    }
  }

  async function loadOverlay(
    projectId: string,
    models: readonly SurfaceModelSummary[],
    sourceFilter: string,
    method: string,
    smooth: boolean,
  ): Promise<boolean> {
    const generation = ++overlayGeneration;
    clearOverlay();
    const match = models.find((model) => {
      const configured = model.generation_params?.source_filter;
      return (
        model.model_type.toLowerCase() === method.toLowerCase() &&
        typeof configured === "string" &&
        configured.toLowerCase() === sourceFilter.toLowerCase()
      );
    });
    if (!match) return false;
    const url = `${API_BASE_URL}/projects/${projectId}/surface/models/${match.id}/preview?smooth=${smooth}`;
    try {
      const buffer = await fetchCachedBytes(projectId, url);
      if (generation !== overlayGeneration) return false;
      return await new Promise<boolean>((resolve) => {
        new GLTFLoader().parse(
          buffer,
          "",
          (gltf) => {
            if (generation !== overlayGeneration) {
              disposeObject(gltf.scene);
              resolve(false);
              return;
            }
            // 겹친 두 면을 구분하려고 반투명 단색으로 덮어씌운다.
            gltf.scene.traverse((child) => {
              if (child instanceof THREE.Mesh) {
                child.material = new THREE.MeshStandardMaterial({
                  color: 0x60a5fa,
                  transparent: true,
                  opacity: 0.45,
                  side: THREE.DoubleSide,
                  flatShading: false,
                });
              }
            });
            overlayMesh = gltf.scene;
            scene.add(gltf.scene);
            resolve(true);
          },
          () => resolve(false),
        );
      });
    } catch {
      return false;
    }
  }

  function clearContours() {
    while (contourGroup.children.length > 0) {
      const child = contourGroup.children[0];
      contourGroup.remove(child);
      if (child instanceof THREE.LineSegments) {
        child.geometry.dispose();
        (child.material as THREE.Material).dispose();
      }
    }
    labelElements.forEach((el) => el.remove());
    labelElements.length = 0;
    labelsDirty = true;
    legendBar.style.display = "none";
  }

  function drawRoute(): void {
    while (routeGroup.children.length > 0) {
      const child = routeGroup.children[0];
      routeGroup.remove(child);
      if (child instanceof THREE.Line) {
        child.geometry.dispose();
        (child.material as THREE.Material).dispose();
      }
    }
    if (routePoints.length < 2 || !referenceBounds) return;
    // 뷰어 좌표 규약은 백엔드 scene_vertices와 같다: x, 높이, -y.
    const cx = (referenceBounds.x_min + referenceBounds.x_max) / 2;
    const cy = (referenceBounds.y_min + referenceBounds.y_max) / 2;
    const cz = (referenceBounds.z_min + referenceBounds.z_max) / 2;
    const planeY = referenceBounds.z_max - cz;
    const vertices = routePoints.map(
      (point) => new THREE.Vector3(point.x - cx, planeY, -(point.y - cy)),
    );
    const material = new THREE.LineBasicMaterial({
      color: new THREE.Color(routeLineColor()),
    });
    routeGroup.add(new THREE.Line(new THREE.BufferGeometry().setFromPoints(vertices), material));
    // 노선은 지형 로딩과 따로 도착한다. 지형이 이미 떠 있으면 노선까지 담도록 다시 맞춘다.
    if (terrainMesh) fitCamera(terrainMesh);
  }

  const getFitParams = (object: THREE.Object3D) => {
    const box = new THREE.Box3().setFromObject(object);
    // 계획노선은 최고 표고 평면에 있어 지형 상자 위·밖으로 걸친다. 지형만 보고 맞추면
    // 노선이 화면 밖으로 밀려 보이지 않는다 — 프레임에 같이 넣는다.
    if (routeGroup.children.length > 0) box.expandByObject(routeGroup);
    const center = box.getCenter(new THREE.Vector3());
    const size = box.getSize(new THREE.Vector3());
    const span = Math.max(size.x, size.y, size.z, 1);
    return { center, span };
  };

  /** 화면맞춤 기준 범위 — 지표면 범위에 계획노선까지 담는다.
   *
   * 카메라 타깃은 늘 지표면 중심(0,0,0)이라 범위를 한쪽으로만 늘려서는 소용이 없다.
   * 중심에서 가장 먼 노선 정점까지를 반폭으로 잡아 **대칭으로** 넓힌다. 그러지 않으면
   * 라이다가 노선의 일부만 덮을 때 나머지가 화면 밖으로 잘린다(2026-09-02 용화 실측:
   * 노선 2,136m 중 라이다는 1,400m만 덮어 오른쪽이 캔버스 밖으로 나갔다). */
  const fitBounds = (): SurfaceBounds | null => {
    if (!referenceBounds || routePoints.length < 2) return referenceBounds;
    const cx = (referenceBounds.x_min + referenceBounds.x_max) / 2;
    const cy = (referenceBounds.y_min + referenceBounds.y_max) / 2;
    let halfX = (referenceBounds.x_max - referenceBounds.x_min) / 2;
    let halfY = (referenceBounds.y_max - referenceBounds.y_min) / 2;
    for (const point of routePoints) {
      halfX = Math.max(halfX, Math.abs(point.x - cx));
      halfY = Math.max(halfY, Math.abs(point.y - cy));
    }
    return {
      ...referenceBounds,
      x_min: cx - halfX,
      x_max: cx + halfX,
      y_min: cy - halfY,
      y_max: cy + halfY,
    };
  };

  const fitCamera = (object: THREE.Object3D) => {
    const { span } = getFitParams(object);
    const aspect = viewerArea.clientWidth / Math.max(viewerArea.clientHeight, 1);
    const bounds = fitBounds();
    const distance = bounds ? getTopFitDistance(bounds, aspect) : span * 1.2;
    controls.target.set(0, 0, 0);
    // 정확히 수직이면 lookAt이 화면 방향을 못 정해 첫 드래그에 화면이 뒤집힌다.
    camera.position.set(0, distance, distance * TOP_VIEW_TILT);
    camera.near = Math.max(distance / 10000, 0.01);
    camera.far = distance * 100;
    camera.updateProjectionMatrix();
    controls.update();
  };

  function emitCameraState(): void {
    if (suppressCameraEvent || !cameraListener) return;
    const offset = camera.position.clone().sub(controls.target);
    const distance = Math.max(offset.length(), 0.001);
    offset.normalize();
    cameraListener({
      direction: [offset.x, offset.y, offset.z],
      distanceMeters: distance,
      targetMeters: [controls.target.x, controls.target.y, controls.target.z],
    });
  }

  function applyCameraState(state: SurfaceCameraState): void {
    suppressCameraEvent = true;
    controls.target.set(...state.targetMeters);
    camera.position
      .set(...state.direction)
      .multiplyScalar(Math.max(state.distanceMeters, 0.001))
      .add(controls.target);
    camera.lookAt(controls.target);
    controls.update();
    suppressCameraEvent = false;
  }

  function syncSmoothingSupport(): void {
    const supported = activeMethod === "tin" || activeMethod === "dtm";
    smoothSelect.disabled = !supported;
    smoothSelect.value = supported && smoothPreferred ? "on" : "off";
    smoothLabel.classList.toggle("is-disabled", !supported);
    smoothLabel.title = supported ? "" : L("B04_Surface_Smoothing_Unsupported");
  }

  /** 지금 스무딩을 적용하는 상태인가. */
  function smoothingOn(): boolean {
    return !smoothSelect.disabled && smoothSelect.value === "on";
  }

  // Load mesh and contours
  async function updateSelectedModel() {
    if (!currentProjectId || currentModelsList.length === 0) return;

    clearMesh();
    clearContours();
    currentModelId = null;
    scaleBar.hidden = true;
    statusSpan.textContent = "모델 조회 중...";
    showProgress(null, "모델 조회 중…");

    // 1. Find matching model in list
    // model_type is TIN / DTM / NURBS / Implicit / Meshfree (we match activeMethod)
    // model_file_path contains the activeFilter (e.g. csf, pmf, grid_min_z)
    const match = currentModelsList.find((m) => {
      const typeMatches = m.model_type.toLowerCase() === activeMethod.toLowerCase();
      const configuredFilter = m.generation_params?.source_filter;
      const filterMatches =
        (typeof configuredFilter === "string" &&
          configuredFilter.toLowerCase() === activeFilter.toLowerCase()) ||
        Boolean(m.model_file_path?.toLowerCase().includes(activeFilter.toLowerCase()));
      return typeMatches && filterMatches;
    });

    if (!match) {
      statusSpan.textContent = "일치하는 완성된 모델을 찾을 수 없습니다.";
      showProgress(null, null);
      return;
    }

    const modelId = match.id;
    const isSmooth = (activeMethod === "tin" || activeMethod === "dtm") && smoothingOn();
    currentModelId = modelId;
    currentModelSmooth = isSmooth;
    const generation = ++loadGeneration;

    statusSpan.textContent = "3D 메쉬 파일 다운로드 중...";
    showProgress(0, "3D 메쉬 내려받는 중…");
    const previewUrl = `${API_BASE_URL}/projects/${currentProjectId}/surface/models/${modelId}/preview?smooth=${isSmooth}`;

    try {
      // 브라우저 보관함에 있으면 그대로 쓰고, 없을 때만 내려받는다(새로고침이 빨라진다).
      const buffer = await fetchCachedBytes(currentProjectId, previewUrl, {
        onProgress: (ratio) => {
          if (generation !== loadGeneration) return;
          showProgress(ratio, "3D 메쉬 내려받는 중…");
        },
      });
      if (generation !== loadGeneration) return;

      if (activeMethod === "meshfree") {
        const geometry = new PLYLoader().parse(buffer);
        geometry.computeBoundingSphere();
        const material = new THREE.PointsMaterial({
          size: 0.35,
          vertexColors: geometry.hasAttribute("color"),
          sizeAttenuation: true,
        });
        const points = new THREE.Points(geometry, material);
        points.visible = surfCheck.checked;
        terrainMesh = points;
        scene.add(points);
        fitCamera(points);
        showProgress(1, "등고선을 그리는 중…");
        await loadSelectedContours(modelId, isSmooth);
        showProgress(null, null);
      } else {
        new GLTFLoader().parse(
          buffer,
          "",
          async (gltf) => {
            if (generation !== loadGeneration) {
              disposeObject(gltf.scene);
              return;
            }
            gltf.scene.traverse((child) => {
              if (child instanceof THREE.Mesh) {
                child.material.side = THREE.DoubleSide;
                child.material.vertexColors = child.geometry.hasAttribute("color");
              }
            });
            gltf.scene.visible = surfCheck.checked;
            terrainMesh = gltf.scene;
            scene.add(gltf.scene);
            fitCamera(gltf.scene);
            showProgress(1, "등고선을 그리는 중…");
            await loadSelectedContours(modelId, isSmooth);
            showProgress(null, null);
          },
          () => {
            if (generation !== loadGeneration) return;
            statusSpan.textContent = "3D 메쉬 파일이 없거나 로드할 수 없습니다.";
            showProgress(null, null);
          },
        );
      }
    } catch (e) {
      statusSpan.textContent = "3D 파일 로드에 실패했습니다.";
      showProgress(null, null);
    }
  }

  async function loadContourLines(
    modelId: number,
    isSmooth: boolean,
    recalculate = false,
  ): Promise<boolean> {
    const interval = parseFloat(intervalInput.value) || 1.0;
    const projectId = currentProjectId;
    const contourUrl = `${API_BASE_URL}/projects/${projectId}/surface/models/${modelId}/contour?interval=${interval}&smooth=${isSmooth}&recalculate=${recalculate}`;

    try {
      // 등고선도 보관함에서 먼저 찾는다 — 같은 파일을 새로고침마다 다시 내려받지 않는다.
      const data = await fetchCachedJson<any>(projectId, contourUrl);
      if (
        currentProjectId !== projectId ||
        currentModelId !== modelId ||
        currentModelSmooth !== isSmooth ||
        (parseFloat(intervalInput.value) || 1.0) !== interval
      ) {
        return false;
      }

      clearContours();

      const bounds = data.bounds;
      if (!bounds) return false;

      const cx = (bounds.x[0] + bounds.x[1]) / 2;
      const cy = (bounds.y[0] + bounds.y[1]) / 2;
      const cz = (bounds.z[0] + bounds.z[1]) / 2;

      const transform = (coords: [number, number, number][]) => {
        return coords.map(([x_model, y_model, z_model]) => {
          const x_scene = x_model - cx;
          const y_scene = z_model - cz;
          const z_scene = -(y_model - cy);
          return new THREE.Vector3(x_scene, y_scene, z_scene);
        });
      };

      let minH = Infinity;
      let maxH = -Infinity;
      // 등고선 한 가닥마다 3D 객체를 만들면 수백 개가 되어 그리기가 느려진다.
      // 주곡선·보조곡선 두 덩어리로 합쳐 객체 2개만 만든다(2026-08-01).
      const majorPoints: THREE.Vector3[] = [];
      const minorPoints: THREE.Vector3[] = [];
      const labelCandidates: {
        level: number;
        position: THREE.Vector3;
        length: number;
      }[] = [];

      data.contours.forEach((c: any) => {
        if (c.level < minH) minH = c.level;
        if (c.level > maxH) maxH = c.level;

        const points = transform(c.coordinates);
        if (points.length < 2) return;

        const isMajor = c.level % (interval * 5) === 0;
        const bucket = isMajor ? majorPoints : minorPoints;
        for (let i = 0; i < points.length - 1; i++) {
          bucket.push(points[i], points[i + 1]);
        }

        // 라벨은 여기서 만들지 않고 후보만 모은다 — 등고선이 잘게 쪼개지면 조각마다
        // 라벨이 붙어 수백 개가 되고, 매 프레임 위치 재계산이 화면을 멈춰 세운다
        // (2026-08-30 사용자 보고). 아래에서 긴 것부터 상한만큼만 만든다.
        if (isMajor && points.length > 4) {
          let length = 0;
          for (let i = 0; i < points.length - 1; i++) {
            length += points[i].distanceTo(points[i + 1]);
          }
          labelCandidates.push({
            level: c.level,
            position: points[Math.floor(points.length / 2)],
            length,
          });
        }
      });

      labelCandidates.sort((a, b) => b.length - a.length);
      for (const candidate of labelCandidates.slice(0, MAX_CONTOUR_LABELS)) {
        const labelPos = candidate.position;
        const labelDiv = document.createElement("div");
        labelDiv.className = "contour-label";
        labelDiv.innerText = `${Math.round(candidate.level)}m`;
        labelDiv.style.position = "absolute";
        labelDiv.style.background = "rgba(255, 255, 255, 0.85)";
        labelDiv.style.border = "1px solid #d97706";
        labelDiv.style.color = "#b45309";
        labelDiv.style.padding = "1px 4px";
        labelDiv.style.borderRadius = "3px";
        labelDiv.style.fontSize = "9px";
        labelDiv.style.fontWeight = "bold";
        labelDiv.style.pointerEvents = "none";
        labelDiv.style.zIndex = "5";
        labelDiv.style.transform = "translate(-50%, -50%)";

        (labelDiv as any).__updateLabelPos = () => {
          if (!contourCheck.checked) {
            labelDiv.style.display = "none";
            return;
          }
          const proj = labelPos.clone().project(camera);
          const x = (proj.x * 0.5 + 0.5) * viewerArea.clientWidth;
          const y = (-(proj.y * 0.5) + 0.5) * viewerArea.clientHeight;

          if (proj.z > 1) {
            labelDiv.style.display = "none";
          } else {
            labelDiv.style.display = "block";
            labelDiv.style.left = `${x}px`;
            labelDiv.style.top = `${y}px`;
          }
        };

        viewerArea.appendChild(labelDiv);
        labelElements.push(labelDiv);
        labelsDirty = true;
      }

      // 합쳐 둔 점들을 주곡선·보조곡선 각각 한 덩어리로 올린다.
      [
        { points: minorPoints, color: 0xf59e0b },
        { points: majorPoints, color: 0xd97706 },
      ].forEach(({ points, color }) => {
        if (points.length === 0) return;
        const geometry = new THREE.BufferGeometry().setFromPoints(points);
        const material = new THREE.LineBasicMaterial({
          color,
          transparent: true,
          opacity: 0.8,
        });
        contourGroup.add(new THREE.LineSegments(geometry, material));
      });

      if (minH !== Infinity && maxH !== -Infinity) {
        const nearestMin10 = Math.round(minH / 10) * 10;
        const nearestMax10 = Math.round(maxH / 10) * 10;
        maxValSpan.textContent = `${nearestMax10}m`;
        minValSpan.textContent = `${nearestMin10}m`;
        legendBar.style.display = "flex";
      } else {
        legendBar.style.display = "none";
      }
      return true;
    } catch (e) {
      legendBar.style.display = "none";
      return false;
    }
  }

  async function loadSelectedContours(
    modelId: number,
    isSmooth: boolean,
    recalculate = false,
  ): Promise<void> {
    const projectId = currentProjectId;
    const interval = parseFloat(intervalInput.value) || 1.0;
    statusSpan.textContent = `등고선 ${interval}m 계산 중...`;
    const loaded = await loadContourLines(modelId, isSmooth, recalculate);
    if (
      currentProjectId === projectId &&
      currentModelId === modelId &&
      currentModelSmooth === isSmooth &&
      (parseFloat(intervalInput.value) || 1.0) === interval
    ) {
      statusSpan.textContent = loaded
        ? `${activeFilter.toUpperCase()} · ${activeMethod.toUpperCase()} · 등고선 ${interval}m`
        : "등고선 계산 또는 조회에 실패했습니다.";
    }
  }

  // Animation render loop
  let animationFrameId = 0;
  let hasConnected = false;
  // 라벨 재계산 여부 판단용 — 직전 프레임의 카메라 자세.
  const cameraMatrixSnapshot = new THREE.Matrix4();
  function animate() {
    if (!root.isConnected) {
      if (!hasConnected) {
        animationFrameId = requestAnimationFrame(animate);
      } else {
        cancelAnimationFrame(animationFrameId);
        clearMesh();
        clearContours();
        releaseTheme();
        releaseCursorPivot();
        controls.dispose();
        renderer.dispose();
      }
      return;
    }
    hasConnected = true;
    controls.update();

    // Render scale bar dynamically
    if (terrainMesh && terrainMesh.visible) {
      scaleBar.hidden = false;
      compass.setVisible(true);
      compass.update(
        camera.position.x - controls.target.x,
        camera.position.y - controls.target.y,
        camera.position.z - controls.target.z,
      );
      const dist = camera.position.distanceTo(controls.target);
      const metersPerPixel = targetPlaneMetersPerPixel(dist, viewerArea.clientHeight);
      const roughMeters = 100 * metersPerPixel;
      const prettyMeters = niceScaleDistance(roughMeters);
      scaleBar.style.width = `${prettyMeters / metersPerPixel}px`;
      scaleLabel.textContent =
        prettyMeters >= 1000 ? `${(prettyMeters / 1000).toFixed(0)} km` : `${prettyMeters} m`;
    } else {
      scaleBar.hidden = true;
      compass.setVisible(false);
    }

    // 등고 라벨 위치 — 화면이 실제로 움직였을 때만 다시 계산한다(매 프레임 재계산은 낭비).
    if (labelsDirty || !cameraMatrixSnapshot.equals(camera.matrixWorldInverse)) {
      labelsDirty = false;
      cameraMatrixSnapshot.copy(camera.matrixWorldInverse);
      labelElements.forEach((label) => {
        if (typeof (label as any).__updateLabelPos === "function") {
          (label as any).__updateLabelPos();
        }
      });
    }

    renderer.render(scene, camera);
    animationFrameId = requestAnimationFrame(animate);
  }

  // Event Listeners
  axesCheck.addEventListener("change", () => {
    axes.visible = axesCheck.checked;
    axesVisibilityListener?.(axesCheck.checked);
  });

  surfCheck.addEventListener("change", () => {
    if (terrainMesh) {
      terrainMesh.visible = surfCheck.checked;
    }
  });

  smoothSelect.addEventListener("change", () => {
    smoothPreferred = smoothSelect.value === "on";
    updateSelectedModel();
  });

  contourCheck.addEventListener("change", () => {
    contourGroup.visible = contourCheck.checked;
    labelElements.forEach((el) => {
      el.style.display = contourCheck.checked ? "block" : "none";
    });
    labelsDirty = true;
  });

  intervalForm.addEventListener("submit", async (e) => {
    e.preventDefault();
    const interval = Number(intervalInput.value);
    if (!Number.isFinite(interval) || interval < 0.5 || currentModelId === null) return;
    intervalSubmit.disabled = true;
    await loadSelectedContours(currentModelId, currentModelSmooth, true);
    intervalSubmit.disabled = false;
  });

  controls.addEventListener("change", emitCameraState);

  // Resize handler
  const resizeObserver = new ResizeObserver((entries) => {
    for (const entry of entries) {
      const width = entry.contentRect.width || 800;
      const height = entry.contentRect.height || 520;
      camera.aspect = width / height;
      camera.updateProjectionMatrix();
      renderer.setSize(width, height);
    }
  });
  resizeObserver.observe(viewerArea);

  animationFrameId = requestAnimationFrame(animate);

  return {
    root,
    optionsContent,
    smoothingField: smoothLabel,
    render(projectId, models) {
      currentProjectId = projectId;
      currentModelsList = models;
      updateSelectedModel();
    },
    setReferenceBounds(bounds) {
      referenceBounds = bounds;
      drawRoute();
    },
    setRoute(points) {
      routePoints = points;
      drawRoute();
    },
    setSelection(sourceFilter, method) {
      activeFilter = sourceFilter;
      activeMethod = method;
      syncSmoothingSupport();
    },
    showOverlay(sourceFilter, method, smooth) {
      if (!sourceFilter) {
        clearOverlay();
        return Promise.resolve(false);
      }
      return loadOverlay(currentProjectId, currentModelsList, sourceFilter, method, smooth);
    },
    applyCameraState,
    onCameraChange(listener) {
      cameraListener = listener;
    },
    onAxesVisibilityChange(listener) {
      axesVisibilityListener = listener;
    },
    isSmoothingEnabled() {
      return smoothingOn();
    },
    setSmoothing(enabled) {
      smoothPreferred = enabled;
      syncSmoothingSupport();
    },
    setContourInterval(interval) {
      if (Number.isFinite(interval) && interval > 0) intervalInput.value = String(interval);
    },
    getContourInterval() {
      return Number.parseFloat(intervalInput.value);
    },
    resetOptions() {
      axesCheck.checked = false;
      axes.visible = false;
      axesVisibilityListener?.(false);
      surfCheck.checked = true;
      smoothPreferred = true;
      syncSmoothingSupport();
      contourCheck.checked = true;
      contourGroup.visible = true;
      intervalInput.value = "1.0";
      if (terrainMesh) terrainMesh.visible = true;
      void updateSelectedModel();
    },
    dispose() {
      cancelAnimationFrame(animationFrameId);
      resizeObserver.disconnect();
      releaseTheme();
      releaseCursorPivot();
      clearMesh();
      clearContours();
      controls.dispose();
      renderer.dispose();
    },
  };
}