import * as THREE from 'three';

/**
 * Camera that contains a sphere (2026-11-03): keeps the view direction of `position → target`, moves the target to the
 * sphere centre, and backs off until the sphere fits both the vertical and the horizontal field of view.
 */
export function fitCamera(
  position: THREE.Vector3,
  target: THREE.Vector3,
  sphere: THREE.Sphere,
  fovDeg: number,
  aspect: number,
  margin = 1.1,
): { position: THREE.Vector3; target: THREE.Vector3 } {
  const halfV = THREE.MathUtils.degToRad(fovDeg / 2);
  // The narrower of the two half-angles decides how far back the camera must stand.
  const halfH = Math.atan(Math.tan(halfV) * aspect);
  const halfFov = Math.min(halfV, halfH);
  const fit = (sphere.radius / Math.sin(halfFov)) * margin;
  const dir = position.clone().sub(target);
  const current = dir.length();
  const dist = Math.max(current, fit);
  dir.normalize();
  return {
    position: sphere.center.clone().add(dir.multiplyScalar(dist)),
    target: sphere.center.clone(),
  };
}