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``````use crate::geom::Point3;
use crate::glam::{EulerRot, Mat4, Quat, Vec3};

/// Orientation properties for **Drawing** a **Primitive**.
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum Properties {
/// The orientation described by an angle along each axis.
Axes(Vec3),
/// The orientation described by looking at some other point.
LookAt(Point3),
/// Angle described by quarternion.
Quat(Quat),
}

impl Properties {
pub fn transform(&self) -> Mat4 {
match *self {
Properties::Axes(v) => Mat4::from_euler(EulerRot::XYZ, v.x, v.y, v.z),
Properties::LookAt(p) => {
let eye = Vec3::ZERO;
let up = Vec3::Y;
Mat4::look_at_rh(eye, p, up)
}
Properties::Quat(q) => Mat4::from_quat(q),
}
}

/// If the `Properties` was set to the `LookAt` variant, this method switches to the `Axes`
/// variant.
///
/// If the `Properties` is already `Axes`, nothing changes.
pub fn switch_to_axes(&mut self) {
if let Properties::LookAt(_) = *self {
*self = Properties::Axes(Vec3::ZERO);
}
}
}

/// An API for setting the **orientation::Properties**.
pub trait SetOrientation: Sized {
/// Provide a mutable reference to the **orientation::Properties** for updating.
fn properties(&mut self) -> &mut Properties;

// Describing orientation via a target.

/// Describe orientation via the vector that points to the given target.
fn look_at(mut self, target: Point3) -> Self {
*self.properties() = Properties::LookAt(target);
self
}

// Absolute orientation.

/// Specify the orientation around the *x* axis as an absolute value in radians.
fn x_radians(mut self, x: f32) -> Self {
self.properties().switch_to_axes();
expect_axes(self.properties()).x = x;
self
}

/// Specify the orientation around the *y* axis as an absolute value in radians.
fn y_radians(mut self, y: f32) -> Self {
self.properties().switch_to_axes();
expect_axes(self.properties()).y = y;
self
}

/// Specify the orientation around the *z* axis as an absolute value in radians.
fn z_radians(mut self, z: f32) -> Self {
self.properties().switch_to_axes();
expect_axes(self.properties()).z = z;
self
}

/// Specify the orientation around the *x* axis as an absolute value in degrees.
fn x_degrees(self, x: f32) -> Self {
}

/// Specify the orientation around the *y* axis as an absolute value in degrees.
fn y_degrees(self, y: f32) -> Self {
}

/// Specify the orientation around the *z* axis as an absolute value in degrees.
fn z_degrees(self, z: f32) -> Self {
}

/// Specify the orientation around the *x* axis as a number of turns around the axis.
fn x_turns(self, x: f32) -> Self {
}

/// Specify the orientation around the *y* axis as a number of turns around the axis.
fn y_turns(self, y: f32) -> Self {
}

/// Specify the orientation around the *z* axis as a number of turns around the axis.
fn z_turns(self, z: f32) -> Self {
}

/// Specify the orientation along each axis with the given **Vector** of radians.
///
fn radians(self, v: Vec3) -> Self {
}

/// Specify the orientation along each axis with the given **Vector** of degrees.
///
/// This has the same affect as calling `self.x_degrees(v.x).y_degrees(v.y).z_degrees(v.z)`.
fn degrees(self, v: Vec3) -> Self {
self.x_degrees(v.x).y_degrees(v.y).z_degrees(v.z)
}

/// Specify the orientation along each axis with the given **Vector** of "turns".
///
/// This has the same affect as calling `self.x_turns(v.x).y_turns(v.y).z_turns(v.z)`.
fn turns(self, v: Vec3) -> Self {
self.x_turns(v.x).y_turns(v.y).z_turns(v.z)
}

/// Specify the orientation with the given euler orientation in radians.
fn euler(self, e: Vec3) -> Self {
}

/// Specify the orientation with the given **Quaternion**.
fn quaternion(mut self, q: Quat) -> Self {
*self.properties() = Properties::Quat(q);
self
}

// Higher level methods.

/// Specify the "pitch" of the orientation in radians.
///
/// This has the same effect as calling `x_radians`.
fn pitch(self, pitch: f32) -> Self {
}

/// Specify the "yaw" of the orientation in radians.
///
/// This has the same effect as calling `y_radians`.
fn yaw(self, yaw: f32) -> Self {
}

/// Specify the "roll" of the orientation in radians.
///
/// This has the same effect as calling `z_radians`.
fn roll(self, roll: f32) -> Self {
}

/// Assuming we're looking at a 2D plane, positive values cause a clockwise rotation where the
/// given value is specified in radians.
///
/// This is equivalent to calling the `z_radians` or `roll` methods.
fn rotate(self, radians: f32) -> Self {
}
}

impl SetOrientation for Properties {
fn properties(&mut self) -> &mut Properties {
self
}
}

impl Default for Properties {
fn default() -> Self {
Properties::Axes(Vec3::ZERO)
}
}

// Expects the `Axes` variant from the given properties.
fn expect_axes(p: &mut Properties) -> &mut Vec3 {
match *p {
Properties::Axes(ref mut axes) => axes,
Properties::LookAt(_) => panic!("expected `Axes`, found `LookAt`"),
Properties::Quat(_) => panic!("expected `Axes`, found `Quat`"),
}
}
``````