// M3 live scan view — consumes /ws/pointcloud (see backend/pointcloud_codec.py
// for the exact binary layout) and renders into #pointcloud-canvas with
// three.js. One reused BufferGeometry with pre-allocated typed arrays,
// overwritten in place per frame (needsUpdate=true) to avoid GC churn at
// the stream's 3-5Hz.
import * as THREE from "three";
import { OrbitControls } from "/vendor/three/OrbitControls.js";

const MAGIC = "PCF1";

// Must match backend config.py POINTCLOUD_PROFILES max_points — sizes the
// pre-allocated buffers, so it can't just read the count off the wire.
const PROFILE_MAX_POINTS = { desktop: 20000, phone: 7000 };

function pickProfile() {
  return window.innerWidth < 768 ? "phone" : "desktop";
}

export function initPointcloudView() {
  const canvas = document.getElementById("pointcloud-canvas");
  const emptyState = document.getElementById("scan-empty");
  const profile = pickProfile();
  const maxPoints = PROFILE_MAX_POINTS[profile];

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

  const scene = new THREE.Scene();
  scene.background = new THREE.Color(0x0a0e14);

  const camera = new THREE.PerspectiveCamera(60, 1, 0.05, 500);
  // FAST-LIO's "camera_init" world frame is z-up (LiDAR convention), not
  // three.js's default y-up — set the camera's up vector to match so
  // OrbitControls orbits around the right axis.
  camera.up.set(0, 0, 1);
  camera.position.set(0, -8, 5);

  const controls = new OrbitControls(camera, canvas);
  controls.enableDamping = true;
  controls.dampingFactor = 0.08;

  const grid = new THREE.GridHelper(40, 40, 0x2a3040, 0x1a1f28);
  grid.rotation.x = Math.PI / 2; // GridHelper defaults to the XZ plane (y-up); rotate into XY (z-up)
  scene.add(grid);

  const positions = new Float32Array(maxPoints * 3);
  const colors = new Float32Array(maxPoints * 3);
  const geometry = new THREE.BufferGeometry();
  geometry.setAttribute("position", new THREE.BufferAttribute(positions, 3));
  geometry.setAttribute("color", new THREE.BufferAttribute(colors, 3));
  geometry.setDrawRange(0, 0);
  const material = new THREE.PointsMaterial({ size: 0.035, vertexColors: true, sizeAttenuation: true });
  scene.add(new THREE.Points(geometry, material));

  // Small marker at the current sensor pose (position + heading).
  const poseGizmo = new THREE.Mesh(
    new THREE.ConeGeometry(0.15, 0.4, 12),
    new THREE.MeshBasicMaterial({ color: 0x5b8cff }),
  );
  poseGizmo.rotation.x = Math.PI / 2; // ConeGeometry points +y by default; point it along +x (forward) instead
  poseGizmo.visible = false;
  scene.add(poseGizmo);

  let hasCentered = false;
  let running = true;
  let paused = false;
  let viewMode = "orbit"; // or "lidar"
  const latestPose = { position: new THREE.Vector3(), quaternion: new THREE.Quaternion(), valid: false };
  const lookTarget = new THREE.Vector3();
  const FORWARD = new THREE.Vector3(1, 0, 0); // body-frame +x — matches the poseGizmo's forward convention below

  function resize() {
    const w = canvas.clientWidth, h = canvas.clientHeight;
    if (w === 0 || h === 0) return;
    renderer.setSize(w, h, false);
    camera.aspect = w / h;
    camera.updateProjectionMatrix();
  }
  new ResizeObserver(resize).observe(canvas);
  resize();

  function updateCameraForLidarView() {
    if (!latestPose.valid) return;
    camera.position.copy(latestPose.position);
    lookTarget.copy(FORWARD).applyQuaternion(latestPose.quaternion).add(latestPose.position);
    camera.up.set(0, 0, 1);
    camera.lookAt(lookTarget);
  }

  function animate() {
    if (!running) return;
    requestAnimationFrame(animate);
    if (paused) return;
    if (viewMode === "lidar") {
      updateCameraForLidarView();
    } else {
      controls.update();
    }
    renderer.render(scene, camera);
  }
  animate();

  function applyFrame(buf) {
    const view = new DataView(buf);
    if (String.fromCharCode(view.getUint8(0), view.getUint8(1), view.getUint8(2), view.getUint8(3)) !== MAGIC) return;
    let off = 4;
    off += 4;  // frame_seq — unused client-side for now
    off += 8;  // timestamp
    const poseFlag = view.getUint32(off, true); off += 4;
    if (poseFlag) {
      const x = view.getFloat32(off, true); const y = view.getFloat32(off + 4, true); const z = view.getFloat32(off + 8, true);
      const qx = view.getFloat32(off + 12, true), qy = view.getFloat32(off + 16, true),
            qz = view.getFloat32(off + 20, true), qw = view.getFloat32(off + 24, true);
      off += 28;
      poseGizmo.position.set(x, y, z);
      poseGizmo.quaternion.set(qx, qy, qz, qw);
      poseGizmo.visible = true;
      latestPose.position.set(x, y, z);
      latestPose.quaternion.set(qx, qy, qz, qw);
      latestPose.valid = true;
      if (!hasCentered) {
        controls.target.set(x, y, z);
        camera.position.set(x, y - 8, z + 5);
        hasCentered = true;
      }
    }
    const n = view.getUint32(off, true); off += 4;

    const count = Math.min(n, maxPoints);
    positions.set(new Float32Array(buf, off, count * 3));
    const intensity = new Uint8Array(buf, off + n * 3 * 4, count);
    for (let i = 0; i < count; i++) {
      const t = intensity[i] / 255;
      // Cool-to-warm ramp by intensity — no camera colour to draw from
      // (LiDAR-only), so intensity is the only per-point signal worth encoding.
      colors[i * 3] = 0.15 + 0.65 * t;
      colors[i * 3 + 1] = 0.35 + 0.35 * (1 - Math.abs(t - 0.5) * 2);
      colors[i * 3 + 2] = 0.75 - 0.55 * t;
    }
    geometry.attributes.position.needsUpdate = true;
    geometry.attributes.color.needsUpdate = true;
    geometry.setDrawRange(0, count);

    emptyState.classList.toggle("hidden", count > 0);
  }

  function connect() {
    const proto = location.protocol === "https:" ? "wss:" : "ws:";
    const ws = new WebSocket(`${proto}//${location.host}/ws/pointcloud?profile=${profile}`);
    ws.binaryType = "arraybuffer";
    ws.onmessage = (ev) => applyFrame(ev.data);
    ws.onclose = () => { if (running) setTimeout(connect, 1500); };
    ws.onerror = () => ws.close();
  }
  connect();

  return {
    setPaused(p) { paused = p; },
    // "orbit" — free OrbitControls camera (default). "lidar" — camera locked
    // to the sensor's live position/heading, first-person. Disabling
    // OrbitControls in lidar mode (not just skipping controls.update()) stops
    // it from silently accumulating drag input it never gets to apply, which
    // would otherwise jump the view on switching back to orbit.
    setViewMode(mode) {
      viewMode = mode;
      controls.enabled = mode === "orbit";
    },
  };
}