/**
 * SceneManager — Three.js scene setup, lighting, camera, OrbitControls.
 * Loaded as a plain script; class is defined on the global scope.
 */

class SceneManager {
  constructor() {
    this.scene = null;
    this.camera = null;
    this.renderer = null;
    this.controls = null;
    this.detectorMarker = null;

    // Default camera position and target for reset — top-down view
    this.defaultCameraPosition = { x: 0, y: 700, z: 0 };
    this.defaultCameraTarget = { x: 0, y: 0, z: 0 };
  }

  /**
   * Initialise the Three.js scene inside the given container element.
   * @param {HTMLElement} container
   * @param {object} [options]
   * @param {number} [options.detectorCol] - detector column x-index
   * @param {number} [options.nx] - grid width in cells
   * @param {number} [options.ny] - grid height in cells
   */
  init(container, options) {
    var opts = options || {};
    var nx = opts.nx || 300;
    var ny = opts.ny || 200;
    var detectorCol = opts.detectorCol != null ? opts.detectorCol : Math.floor(nx * 0.85);

    // Scene
    this.scene = new THREE.Scene();
    this.scene.background = new THREE.Color(0x2a2a3e);

    // Camera — adjust distance based on aspect ratio so the full plane is visible
    var w = Math.max(container.clientWidth, 1);
    var h = Math.max(container.clientHeight, 1);
    var aspect = w / h;
    // On narrow/portrait screens, zoom out more to see the full plane
    var zoomFactor = aspect < 0.8 ? 1.8 : (aspect < 1.2 ? 1.5 : (aspect < 1.6 ? 1.15 : 1.0));
    this._zoomFactor = zoomFactor;
    this.defaultTopPosition = { x: 0, y: 700 * zoomFactor, z: 0 };

    this.camera = new THREE.PerspectiveCamera(60, aspect, 0.1, 3000);
    this.camera.position.set(
      this.defaultCameraPosition.x,
      this.defaultCameraPosition.y * zoomFactor,
      this.defaultCameraPosition.z
    );
    this.camera.lookAt(
      this.defaultCameraTarget.x,
      this.defaultCameraTarget.y,
      this.defaultCameraTarget.z
    );

    // Renderer — wrapped in try/catch for WebGL unavailability
    try {
      this.renderer = new THREE.WebGLRenderer({ antialias: true });
    } catch (e) {
      var msg = document.createElement('p');
      msg.textContent =
        'WebGL is not supported in your browser. Please use a modern browser with WebGL support.';
      msg.style.cssText = 'color:#e0e0e0;padding:2rem;text-align:center;';
      container.appendChild(msg);
      return;
    }
    this.renderer.setSize(container.clientWidth, Math.max(container.clientHeight, 1));
    this.renderer.setPixelRatio(window.devicePixelRatio || 1);
    container.appendChild(this.renderer.domElement);

    // OrbitControls — rotate (left-drag), zoom (scroll), pan (right-drag)
    this.controls = new THREE.OrbitControls(this.camera, this.renderer.domElement);
    this.controls.target.set(
      this.defaultCameraTarget.x,
      this.defaultCameraTarget.y,
      this.defaultCameraTarget.z
    );
    this.controls.enableDamping = true;
    this.controls.dampingFactor = 0.1;
    this.controls.update();

    // Lighting — multiple sources for vivid colors
    var dirLight = new THREE.DirectionalLight(0xffffff, 1.0);
    dirLight.position.set(100, 400, 200);
    this.scene.add(dirLight);

    var dirLight2 = new THREE.DirectionalLight(0xccddff, 0.5);
    dirLight2.position.set(-200, 300, -100);
    this.scene.add(dirLight2);

    var ambientLight = new THREE.AmbientLight(0x8888aa, 0.8);
    this.scene.add(ambientLight);

    // Hemisphere light for natural diffused illumination
    var hemiLight = new THREE.HemisphereLight(0xccccff, 0x444466, 0.6);
    this.scene.add(hemiLight);

    // Detector marker — vertical line at the detector column position
    this._addDetectorMarker(detectorCol, ny, nx);
  }

  /**
   * Add a semi-transparent screen at the detector column.
   * The wave surface is centered at origin, so we convert grid coords
   * to world coords: worldX = -surfaceWidth/2 + detectorCol * dx.
   * @param {number} detectorCol - x position in grid coordinates
   * @param {number} ny - grid height
   * @private
   */
  _addDetectorMarker(detectorCol, ny, nx) {
    nx = nx || 800;
    var dx = 1.0;
    this._nx = nx;
    this._ny = ny;
    var surfaceWidth = (nx - 1) * dx;
    var surfaceDepth = (ny - 1) * dx;

    // Convert grid column to world X (surface is centered at origin)
    var worldX = -surfaceWidth / 2 + detectorCol * dx;

    // Semi-transparent plane spanning the full depth and a reasonable height
    var screenHeight = this._elementHeight || 30;
    var geometry = new THREE.PlaneGeometry(surfaceDepth, screenHeight);
    var material = new THREE.MeshBasicMaterial({
      color: 0x00ff88,
      transparent: true,
      opacity: 0.15,
      side: THREE.DoubleSide,
      depthWrite: false
    });

    this.detectorMarker = new THREE.Mesh(geometry, material);
    // Rotate so the plane faces along the X axis (stands upright in XZ plane)
    this.detectorMarker.rotation.y = Math.PI / 2;
    this.detectorMarker.position.set(worldX, screenHeight / 2 - 5, 0);

    this.scene.add(this.detectorMarker);
  }

  /**
   * Update the height of the detector marker.
   * @param {number} height
   */
  updateDetectorHeight(height) {
    if (!this.detectorMarker || !this.scene) return;
    var oldPos = this.detectorMarker.position;
    this.scene.remove(this.detectorMarker);
    if (this.detectorMarker.geometry) this.detectorMarker.geometry.dispose();

    var nx = this._nx || 800;
    var surfaceDepth = ((this._ny || 600) - 1) * 1.0;
    var geometry = new THREE.PlaneGeometry(surfaceDepth, height);
    this.detectorMarker.geometry = geometry;
    this.detectorMarker.position.set(oldPos.x, height / 2 - 5, 0);
    this.scene.add(this.detectorMarker);
  }

  /** Restore the camera to its default position and lookAt target. */
  resetCamera() {
    if (!this.camera || !this.controls) return;

    this.camera.position.set(
      this.defaultCameraPosition.x,
      this.defaultCameraPosition.y,
      this.defaultCameraPosition.z
    );
    this.controls.target.set(
      this.defaultCameraTarget.x,
      this.defaultCameraTarget.y,
      this.defaultCameraTarget.z
    );
    this.camera.lookAt(
      this.defaultCameraTarget.x,
      this.defaultCameraTarget.y,
      this.defaultCameraTarget.z
    );
    this.controls.update();
  }

  /**
   * Switch the bottom interactive camera to a specific view.
   * @param {'top'|'angle'} mode
   */
  setBottomView(mode) {
    if (!this.camera || !this.controls) return;
    var wasDamping = this.controls.enableDamping;
    this.controls.enableDamping = false;
    var zf = this._zoomFactor || 1.0;
    
    if (mode === 'top') {
      this.camera.position.set(0, 700 * zf, 1);
      this.controls.target.set(0, 0, 0);
    } else if (mode === '135') {
      this.camera.position.set(300 * zf, 400 * zf, -350 * zf);
      this.controls.target.set(0, 0, 0);
    } else {
      this.camera.position.set(-300 * zf, 400 * zf, 400 * zf);
      this.controls.target.set(0, 0, 0);
    }
    this.camera.lookAt(0, 0, 0);
    this.controls.update();
    this.controls.enableDamping = wasDamping;
  }

  /**
   * Update renderer size and camera aspect ratio.
   * @param {number} width
   * @param {number} height
   */
  resize(width, height) {
    var w = Math.max(width, 1);
    var h = Math.max(height, 1);

    if (this.camera) {
      this.camera.aspect = w / h;
      this.camera.updateProjectionMatrix();
    }
    if (this.renderer) {
      this.renderer.setSize(w, h);
    }
    this.containerWidth = w;
    this.containerHeight = h;
  }

  render() {
    if (!this.renderer || !this.scene || !this.camera) return;
    if (this.controls) this.controls.update();
    this.renderer.render(this.scene, this.camera);
  }
}

window.SceneManager = SceneManager;