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 { bindCursorPivotControls, TOP_VIEW_TILT } from "../B04_PreProcess/B04_PreProcess_UI_Camera";
import {
  createRouteMarkers,
  modelToScene,
  sceneToModel,
  type ModelBounds,
  type RouteMarkers,
  type RoutePointKind,
  type SectionStationMarker,
} from "./B05_Profile_UI_Markers";

const LIGHT_VIEWER_BACKGROUND = 0xf5f7fa;
const DARK_VIEWER_BACKGROUND = 0x251f38;

function disposeObject(object: THREE.Object3D | null): void {
  object?.traverse((child) => {
    if (
      child instanceof THREE.Mesh ||
      child instanceof THREE.Points ||
      child instanceof THREE.Line
    ) {
      child.geometry.dispose();
      const materials = Array.isArray(child.material) ? child.material : [child.material];
      materials.forEach((material) => material.dispose());
    }
  });
}

export interface RouteViewer {
  root: HTMLElement;
  markers: RouteMarkers;
  loadSurface: (
    projectId: string,
    modelId: number,
    method: string,
    smooth: boolean,
    interval: number,
    bounds: ModelBounds,
  ) => Promise<void>;
  reloadContours: (interval: number) => Promise<void>;
  setSurfaceVisible: (visible: boolean) => void;
  /** 지표면 흑백 표시 — 무지개 고도색이 헷갈릴 때 명도만 남긴다(정점색 1회 변환, 성능 영향 없음). */
  setSurfaceGrayscale: (grayscale: boolean) => void;
  setContoursVisible: (visible: boolean) => void;
  setAxesVisible: (visible: boolean) => void;
  setStationLinesVisible: (visible: boolean) => void;
  /** 구조물(비정규) 측점의 번호·이름 라벨 표시 토글. */
  setStationLabelsVisible: (visible: boolean) => void;
  renderStationLines: (stations: SectionStationMarker[], halfWidth: number) => void;
  setView: (view: "iso" | "top" | "front" | "side") => void;
  beginMoveSelected: () => void;
  /** 화면(client) 좌표 아래 지형의 모델 좌표 — 3D 우클릭 구조물 배치용(2026-08-19). */
  modelPointAt: (clientX: number, clientY: number) => { x: number; y: number; z: number } | null;
  dispose: () => void;
}

export function createRouteViewer(): RouteViewer {
  const root = document.createElement("div");
  root.className = "b05-route__viewport";
  const status = document.createElement("div");
  status.className = "b05-route__viewer-status";
  status.textContent = "확정 지표면을 불러오는 중입니다.";
  const canvas = document.createElement("canvas");
  root.append(canvas, status);

  const scene = new THREE.Scene();
  const systemDarkTheme = window.matchMedia("(prefers-color-scheme: dark)");

  function updateSceneBackground(): void {
    const theme = document.documentElement.getAttribute("data-theme");
    const dark = theme === "dark" || (theme !== "light" && systemDarkTheme.matches);
    if (!dark) {
      scene.background = new THREE.Color(LIGHT_VIEWER_BACKGROUND);
      return;
    }
    const surfaceRaised = getComputedStyle(document.documentElement)
      .getPropertyValue("--color-surface-raised")
      .trim();
    scene.background = new THREE.Color(
      surfaceRaised && CSS.supports("color", surfaceRaised)
        ? surfaceRaised
        : DARK_VIEWER_BACKGROUND,
    );
  }

  const themeObserver = new MutationObserver(updateSceneBackground);
  themeObserver.observe(document.documentElement, {
    attributes: true,
    attributeFilter: ["data-theme"],
  });
  systemDarkTheme.addEventListener("change", updateSceneBackground);
  updateSceneBackground();
  const camera = new THREE.PerspectiveCamera(45, 1, 0.1, 100000);
  camera.position.set(100, 120, 100);
  const renderer = new THREE.WebGLRenderer({ canvas, antialias: true });
  renderer.setPixelRatio(Math.min(devicePixelRatio, 2));
  const controls = new OrbitControls(camera, canvas);
  controls.enableDamping = true;
  scene.add(new THREE.HemisphereLight(0xffffff, 0x64748b, 2.2));
  const directional = new THREE.DirectionalLight(0xffffff, 2.2);
  directional.position.set(100, 200, 100);
  scene.add(directional);
  const axes = new THREE.AxesHelper(30);
  axes.visible = false;
  scene.add(axes);

  let terrain: THREE.Object3D | null = null;
  const contours = new THREE.Group();
  scene.add(contours);
  let bounds: ModelBounds | null = null;
  let current: { projectId: string; modelId: number; smooth: boolean; interval: number } | null =
    null;
  let movingSelected = false;
  let dragCandidate: { id: string; pointerId: number; x: number; y: number } | null = null;
  let draggingMarker = false;
  let lastDragPoint: { x: number; y: number; z: number } | null = null;
  /**
   * 모델 좌표 (x, y) 자리의 지형 표고. 지형 위에서 수직으로 광선을 쏴 맞은 높이를 돌려준다.
   * 계획노선 CSV로 만든 점처럼 표고가 없는 자리를 지형에 얹을 때 쓴다.
   */
  function terrainElevation(x: number, y: number): number | null {
    if (!terrain || !bounds) return null;
    const origin = modelToScene({ x, y, z: bounds.z[1] + 100 }, bounds);
    const raycaster = new THREE.Raycaster(origin, new THREE.Vector3(0, -1, 0));
    const hit = raycaster.intersectObject(terrain, true)[0];
    return hit ? sceneToModel(hit.point, bounds).z : null;
  }

  const markers = createRouteMarkers(scene, () => bounds, terrainElevation);
  // 회전·줌 중심을 커서 아래 지형 지점으로 (B04 뷰어들과 공용 유틸).
  // 마커를 잡고 있는 동안에는 회전을 넘겨 드래그 이동이 우선하게 한다.
  const releaseCursorPivot = bindCursorPivotControls({
    camera,
    controls,
    element: canvas,
    pickables: () => (terrain ? [terrain] : []),
    blocked: () => dragCandidate !== null || draggingMarker || movingSelected,
    scene,
  });

  function clearContours(): void {
    disposeObject(contours);
    contours.clear();
  }

  function resize(): void {
    const width = Math.max(1, root.clientWidth);
    const height = Math.max(1, root.clientHeight);
    renderer.setSize(width, height, false);
    camera.aspect = width / height;
    camera.updateProjectionMatrix();
  }
  const resizeObserver = new ResizeObserver(resize);
  resizeObserver.observe(root);

  function fit(view: "iso" | "top" | "front" | "side" = "top"): void {
    if (!bounds) return;
    const width = bounds.x[1] - bounds.x[0];
    const depth = bounds.y[1] - bounds.y[0];
    const distance = Math.max(width, depth, 20) * 1.35;
    controls.target.set(0, 0, 0);
    const positions = {
      iso: [distance, distance, distance],
      // 정확히 수직이면 lookAt이 화면 방향을 못 정해 첫 드래그에 화면이 뒤집힌다.
      top: [0, distance, distance * TOP_VIEW_TILT],
      front: [0, distance * 0.25, distance],
      side: [distance, distance * 0.25, 0],
    } as const;
    const [x, y, z] = positions[view];
    camera.position.set(x, y, z);
    camera.near = Math.max(0.1, distance / 1000);
    camera.far = distance * 10;
    camera.updateProjectionMatrix();
    controls.update();
  }

  async function reloadContours(interval: number): Promise<void> {
    if (!current || !bounds) return;
    current.interval = interval;
    // 등고선도 보관함에서 먼저 찾는다 — 같은 파일을 새로고침마다 다시 내려받지 않는다.
    const data = await fetchCachedJson<{
      contours: Array<{ level: number; coordinates: [number, number, number][] }>;
    }>(
      current.projectId,
      `${API_BASE_URL}/projects/${current.projectId}/surface/models/${current.modelId}/contour?interval=${interval}&smooth=${current.smooth}`,
    );
    clearContours();
    // 등고선 한 가닥마다 3D 객체를 만들면 수백 개가 된다. 주곡선·보조곡선 두 덩어리로 합친다.
    const majorPoints: THREE.Vector3[] = [];
    const minorPoints: THREE.Vector3[] = [];
    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;
    data.contours.forEach((contour) => {
      const points = contour.coordinates.map(
        ([x, y, z]) => new THREE.Vector3(x - cx, z - cz + 0.15, -(y - cy)),
      );
      if (points.length < 2) return;
      const bucket = contour.level % (interval * 5) === 0 ? majorPoints : minorPoints;
      for (let index = 0; index < points.length - 1; index += 1) {
        bucket.push(points[index], points[index + 1]);
      }
    });
    [
      { points: minorPoints, color: 0xf59e0b },
      { points: majorPoints, color: 0xd97706 },
    ].forEach(({ points, color }) => {
      if (points.length === 0) return;
      contours.add(
        new THREE.LineSegments(
          new THREE.BufferGeometry().setFromPoints(points),
          new THREE.LineBasicMaterial({ color, transparent: true, opacity: 0.75 }),
        ),
      );
    });
  }

  /** 화면(client) 좌표 아래 지형의 모델 좌표 — 우클릭 구조물 배치 등 외부 픽에도 쓴다. */
  function terrainPointAt(
    clientX: number,
    clientY: number,
  ): { x: number; y: number; z: number } | null {
    if (!terrain || !bounds) return null;
    const rect = canvas.getBoundingClientRect();
    const pointer = new THREE.Vector2(
      ((clientX - rect.left) / rect.width) * 2 - 1,
      -((clientY - rect.top) / rect.height) * 2 + 1,
    );
    const raycaster = new THREE.Raycaster();
    raycaster.setFromCamera(pointer, camera);
    const hit = raycaster.intersectObject(terrain, true)[0];
    return hit ? sceneToModel(hit.point, bounds) : null;
  }

  function terrainPoint(
    event: PointerEvent | DragEvent,
  ): { x: number; y: number; z: number } | null {
    return terrainPointAt(event.clientX, event.clientY);
  }

  canvas.addEventListener("dragover", (event) => event.preventDefault());
  canvas.addEventListener("drop", (event) => {
    event.preventDefault();
    const kind = event.dataTransfer?.getData("pointType") as RoutePointKind;
    const point = terrainPoint(event);
    if (point && ["bp", "ep", "cp", "ap", "fp"].includes(kind)) markers.place(kind, point);
  });
  function markerHit(event: PointerEvent): THREE.Object3D | undefined {
    const rect = canvas.getBoundingClientRect();
    const pointer = new THREE.Vector2(
      ((event.clientX - rect.left) / rect.width) * 2 - 1,
      -((event.clientY - rect.top) / rect.height) * 2 + 1,
    );
    const raycaster = new THREE.Raycaster();
    raycaster.setFromCamera(pointer, camera);
    return raycaster.intersectObject(markers.group, true)[0]?.object;
  }

  function finishMarkerInteraction(selectCandidate: boolean): void {
    if (dragCandidate && (draggingMarker || selectCandidate)) {
      markers.selectPoint(dragCandidate.id);
    }
    if (dragCandidate && canvas.hasPointerCapture(dragCandidate.pointerId)) {
      canvas.releasePointerCapture(dragCandidate.pointerId);
    }
    controls.enabled = true;
    dragCandidate = null;
    draggingMarker = false;
    lastDragPoint = null;
  }

  function handlePointerDown(event: PointerEvent): void {
    if (event.button !== 0) return;
    const hit = markerHit(event);
    const pointId = markers.pointIdForObject(hit);
    if (pointId) {
      dragCandidate = {
        id: pointId,
        pointerId: event.pointerId,
        x: event.clientX,
        y: event.clientY,
      };
      draggingMarker = false;
      lastDragPoint = null;
      canvas.setPointerCapture(event.pointerId);
      event.preventDefault();
      event.stopPropagation();
      return;
    }
    if (hit) {
      markers.selectObject(hit);
      event.stopPropagation();
      return;
    }
    if (movingSelected) {
      const point = terrainPoint(event);
      if (point) markers.moveSelected(point);
      movingSelected = false;
    } else {
      markers.selectObject(undefined);
    }
  }

  function handlePointerMove(event: PointerEvent): void {
    if (!dragCandidate || event.pointerId !== dragCandidate.pointerId) return;
    event.preventDefault();
    event.stopPropagation();
    if (
      !draggingMarker &&
      Math.hypot(event.clientX - dragCandidate.x, event.clientY - dragCandidate.y) > 3
    ) {
      draggingMarker = true;
      controls.enabled = false;
    }
    if (!draggingMarker) return;
    const point = terrainPoint(event);
    if (!point) return;
    lastDragPoint = point;
    markers.movePoint(dragCandidate.id, point);
  }

  function handlePointerUp(event: PointerEvent): void {
    if (!dragCandidate || event.pointerId !== dragCandidate.pointerId) return;
    event.preventDefault();
    event.stopPropagation();
    if (draggingMarker) {
      const point = terrainPoint(event) ?? lastDragPoint;
      if (point) markers.movePoint(dragCandidate.id, point);
    }
    finishMarkerInteraction(!draggingMarker);
  }

  function handlePointerExit(event: PointerEvent): void {
    if (!dragCandidate || event.pointerId !== dragCandidate.pointerId) return;
    event.preventDefault();
    event.stopPropagation();
    finishMarkerInteraction(false);
  }

  canvas.addEventListener("pointerdown", handlePointerDown, true);
  canvas.addEventListener("pointermove", handlePointerMove, true);
  canvas.addEventListener("pointerup", handlePointerUp, true);
  canvas.addEventListener("pointerleave", handlePointerExit, true);
  canvas.addEventListener("pointercancel", handlePointerExit, true);

  let frame = 0;
  function animate(): void {
    frame = requestAnimationFrame(animate);
    controls.update();
    renderer.render(scene, camera);
  }
  animate();

  // 지표면 흑백 표시(2026-08-05 사용자 요청). 정점색 배열을 한 번 바꿔치기하는 것뿐이라
  // (원본은 userData에 보관, 재질·셰이더 교체 없음) 로딩·회전 속도에 영향이 없다.
  let surfaceGrayscale = false;
  function applySurfaceGrayscale(): void {
    terrain?.traverse((child) => {
      const geometry = (child as THREE.Mesh).geometry as THREE.BufferGeometry | undefined;
      const color = geometry?.getAttribute("color") as THREE.BufferAttribute | undefined;
      if (!geometry || !color) return;
      const target = color.array as Float32Array;
      if (!child.userData.originalColors) child.userData.originalColors = target.slice();
      const original = child.userData.originalColors as Float32Array;
      const stride = color.itemSize;
      if (surfaceGrayscale) {
        for (let i = 0; i + 2 < original.length; i += stride) {
          const gray = 0.299 * original[i] + 0.587 * original[i + 1] + 0.114 * original[i + 2];
          target[i] = target[i + 1] = target[i + 2] = gray;
        }
      } else {
        target.set(original);
      }
      color.needsUpdate = true;
    });
  }

  return {
    root,
    markers,
    async loadSurface(projectId, modelId, method, smooth, interval, nextBounds) {
      bounds = nextBounds;
      current = { projectId, modelId, smooth, interval };
      if (terrain) {
        scene.remove(terrain);
        disposeObject(terrain);
      }
      const url = `${API_BASE_URL}/projects/${projectId}/surface/models/${modelId}/preview?smooth=${smooth}`;
      // 브라우저 보관함에 있으면 그대로 쓰고, 없을 때만 내려받는다(새로고침이 빨라진다).
      const buffer = await fetchCachedBytes(projectId, url);
      terrain = await new Promise<THREE.Object3D>((resolve, reject) => {
        if (method === "meshfree") {
          const geometry = new PLYLoader().parse(buffer);
          resolve(new THREE.Points(geometry, new THREE.PointsMaterial({ size: 0.35 })));
        } else {
          new GLTFLoader().parse(buffer, "", (gltf) => resolve(gltf.scene), reject);
        }
      });
      terrain.traverse((child) => {
        if (child instanceof THREE.Mesh) child.material.side = THREE.DoubleSide;
      });
      scene.add(terrain);
      // 흑백 토글이 켜진 채 모델을 다시 불러와도 상태를 유지한다.
      applySurfaceGrayscale();
      fit("top");
      markers.renderMarkers();
      await reloadContours(interval);
      // 로딩이 끝나면 안내문을 지운다 — 조작법 설명이 화면에 계속 떠 있을 이유가
      // 없다(2026-08-19 사용자 지시). 로딩·이동 중 안내는 그대로 쓴다.
      status.textContent = "";
    },
    reloadContours,
    setSurfaceVisible(visible) {
      if (terrain) terrain.visible = visible;
    },
    setSurfaceGrayscale(grayscale) {
      if (surfaceGrayscale === grayscale) return;
      surfaceGrayscale = grayscale;
      applySurfaceGrayscale();
    },
    setContoursVisible(visible) {
      contours.visible = visible;
    },
    setAxesVisible(visible) {
      axes.visible = visible;
    },
    setStationLinesVisible: markers.setStationLinesVisible,
    setStationLabelsVisible: markers.setStationLabelsVisible,
    renderStationLines: markers.renderStationLines,
    setView: fit,
    beginMoveSelected() {
      movingSelected = true;
      status.textContent = "선택한 포인트를 이동할 지형 위치를 클릭하세요.";
    },
    modelPointAt: terrainPointAt,
    dispose() {
      cancelAnimationFrame(frame);
      resizeObserver.disconnect();
      themeObserver.disconnect();
      systemDarkTheme.removeEventListener("change", updateSceneBackground);
      canvas.removeEventListener("pointerdown", handlePointerDown, true);
      canvas.removeEventListener("pointermove", handlePointerMove, true);
      canvas.removeEventListener("pointerup", handlePointerUp, true);
      canvas.removeEventListener("pointerleave", handlePointerExit, true);
      canvas.removeEventListener("pointercancel", handlePointerExit, true);
      releaseCursorPivot();
      markers.dispose();
      clearContours();
      disposeObject(terrain);
      controls.dispose();
      renderer.dispose();
    },
  };
}