// Simple 4×4 matrix helpers (column-major) — exported so consumers can build
// their own orbit / trackball controls.

export function mat4Perspective(
  fov: number,
  aspect: number,
  near: number,
  far: number,
): Float32Array {
  const f = 1.0 / Math.tan(fov / 2);
  const nf = 1 / (near - far);
  // prettier-ignore
  return new Float32Array([
    f / aspect, 0, 0, 0,
    0, f, 0, 0,
    0, 0, (far + near) * nf, -1,
    0, 0, 2 * far * near * nf, 0,
  ]);
}

export function mat4Multiply(a: Float32Array, b: Float32Array): Float32Array {
  const out = new Float32Array(16);
  for (let i = 0; i < 4; i++) {
    for (let j = 0; j < 4; j++) {
      out[j * 4 + i] =
        a[0 * 4 + i] * b[j * 4 + 0] +
        a[1 * 4 + i] * b[j * 4 + 1] +
        a[2 * 4 + i] * b[j * 4 + 2] +
        a[3 * 4 + i] * b[j * 4 + 3];
    }
  }
  return out;
}

export function mat4RotateY(angle: number): Float32Array {
  const c = Math.cos(angle),
    s = Math.sin(angle);
  // prettier-ignore
  return new Float32Array([
    c, 0, s, 0,
    0, 1, 0, 0,
    -s, 0, c, 0,
    0, 0, 0, 1,
  ]);
}

export function mat4RotateZ(angle: number): Float32Array {
  const c = Math.cos(angle),
    s = Math.sin(angle);
  // prettier-ignore
  return new Float32Array([
    c, s, 0, 0,
    -s, c, 0, 0,
    0, 0, 1, 0,
    0, 0, 0, 1,
  ]);
}

export function mat4RotateX(angle: number): Float32Array {
  const c = Math.cos(angle),
    s = Math.sin(angle);
  // prettier-ignore
  return new Float32Array([
    1, 0, 0, 0,
    0, c, -s, 0,
    0, s, c, 0,
    0, 0, 0, 1,
  ]);
}

export function mat4Ortho(
  left: number,
  right: number,
  bottom: number,
  top: number,
  near: number,
  far: number,
): Float32Array {
  const lr = 1 / (left - right);
  const bt = 1 / (bottom - top);
  const nf = 1 / (near - far);
  // prettier-ignore
  return new Float32Array([
    -2 * lr, 0, 0, 0,
    0, -2 * bt, 0, 0,
    0, 0, 2 * nf, 0,
    (left + right) * lr, (top + bottom) * bt, (far + near) * nf, 1,
  ]);
}

export function mat4Translate(x: number, y: number, z: number): Float32Array {
  // prettier-ignore
  return new Float32Array([
    1, 0, 0, 0,
    0, 1, 0, 0,
    0, 0, 1, 0,
    x, y, z, 1,
  ]);
}