use glam::{Affine3A, Mat3, Mat4, vec3};

pub(crate) fn rotation(yaw: f32, pitch: f32) -> Mat3 {
	let (ys, yc) = yaw.sin_cos();
	let (ps, pc) = pitch.sin_cos();
	Mat3::from_cols_array_2d(&[[0., 0., -1.], [-1., 0., 0.], [0., 1., 0.]])
		* Mat3::from_cols_array_2d(&[[pc, 0., -ps], [0., 1., 0.], [ps, 0., pc]])
		* Mat3::from_cols_array_2d(&[[yc, -ys, 0.], [ys, yc, 0.], [0., 0., 1.]])
}

pub(crate) fn view(yaw: f32, pitch: f32, distance: f32) -> Affine3A {
	Affine3A::from_mat3_translation(rotation(yaw, pitch), vec3(0., 0., distance))
}

pub(crate) fn projection(fovy: f32, aspect: f32) -> Mat4 {
	Mat4::perspective_lh(fovy, aspect, 0.1, 10.0)
}

#[cfg(test)]
mod tests {
	use super::*;

	use glam::Vec3;
	use std::f32::consts::PI;

	#[test]
	fn test_rotation() {
		let mut ok = true;
		for (yaw, pitch, x, y, z) in [
			(0.0, 0.0, [0., 0., -1.], [-1., 0., 0.], [0., 1., 0.]),
			(0.5, 0.0, [1., 0., 0.], [0., 0., -1.], [0., 1., 0.]),
			(0.0, 0.5, [0., -1., 0.], [-1., 0., 0.], [0., 0., -1.]),
			(0.5, 0.5, [1., 0., 0.], [0., -1., 0.], [0., 0., -1.]),
		] {
			let m = rotation(yaw * PI, pitch * PI);
			if !m.abs_diff_eq(Mat3::from_cols_array_2d(&[x, y, z]), 1e-3) {
				ok = false;
				println!("Wrong rotation for {}, {}", 180. * yaw, 180. * pitch);
				println!("X: expected: {}, actual: {}", Vec3::from_array(x), m.x_axis);
				println!("Y: expected: {}, actual: {}", Vec3::from_array(y), m.y_axis);
				println!("Z: expected: {}, actual: {}", Vec3::from_array(z), m.z_axis);
			}
		}
		if !ok {
			panic!();
		}
	}

	#[test]
	fn test_view() {
		let mut ok = true;
		for (yaw, pitch, x1, y1, z1) in [
			(0.0, 0.0, [0., 0., 2.], [-1., 0., 3.], [0., 1., 3.]),
			(0.5, 0.0, [1., 0., 3.], [0., 0., 2.], [0., 1., 3.]),
			(0.0, 0.5, [0., -1., 3.], [-1., 0., 3.], [0., 0., 2.]),
			(0.5, 0.5, [1., 0., 3.], [0., -1., 3.], [0., 0., 2.]),
		] {
			let m = view(yaw * PI, pitch * PI, 3.);
			for (label, world, expected) in
				[('X', Vec3::X, x1), ('Y', Vec3::Y, y1), ('Z', Vec3::Z, z1)]
			{
				let expected = Vec3::from_array(expected);
				let actual = m.transform_point3(world);
				if !actual.abs_diff_eq(expected, 1e-3) {
					ok = false;
					println!(
						"Wrong transform for {}, {}: for {label}, expected: {expected}, got: {actual}",
						180. * yaw,
						180. * pitch
					);
				}
			}
		}
		if !ok {
			panic!();
		}
	}
}