export const add = (a, b) => a.map((v, i) => v + b[i]);
export const sub = (a, b) => a.map((v, i) => v - b[i]);
export const mul = (a, s) => a.map((v) => v * s);
export const dot = (a, b) => a[0] * b[0] + a[1] * b[1] + a[2] * b[2];
export const cross = (a, b) => [
  a[1] * b[2] - a[2] * b[1],
  a[2] * b[0] - a[0] * b[2],
  a[0] * b[1] - a[1] * b[0],
];
export const unit = (a) => mul(a, 1 / (Math.hypot(...a) || 1));
export const point = (p, i) => Array.from(p.subarray(i * 3, i * 3 + 3));
export const clamp = (n, a, b) => Math.max(a, Math.min(b, n));

// Bound apparent scale along the viewport's shorter side, in either orientation.
export function clampZoom(zoom, rect) {
  const scale = Math.min(1, rect.width / rect.height);
  return clamp(zoom * scale, 0.2, 14) / scale;
}

// Orthographic camera: the same basis drives rendering, rays and grab planes.
export function cameraBasis(yaw, pitch) {
  const forward = [
    Math.sin(yaw) * Math.cos(pitch),
    Math.sin(pitch),
    Math.cos(yaw) * Math.cos(pitch),
  ];
  // Analytic basis remains defined at the top/bottom cardinal views.
  const right = [Math.cos(yaw), 0, -Math.sin(yaw)];
  return { right, up: cross(forward, right), forward };
}