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use crate::{
  num::{DefaultFloat, Float},
  vec::{Vec3, Vector},
};
use std::{
  array::LengthAtMost32,
  marker::PhantomData,
  ops::{Add, Mul, Neg},
};

#[derive(Debug, Copy, Clone, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct Ray<T = DefaultFloat, V = Vec3<T>> {
  pub pos: V,
  pub dir: V,
  // TODO should I add a time field here?
  // It makes it much cleaner to declare structs using this
  phantom: PhantomData<T>,
}

impl<T, V> Ray<T, V> {
  /// Returns a new ray with the given position and direction
  pub fn new(pos: V, dir: V) -> Self {
    Ray {
      pos,
      dir,
      phantom: PhantomData,
    }
  }
}
impl<T: Float, V> Ray<T, V>
where
  V: Add<Output = V> + Mul<T, Output = V> + Copy,
{
  /// Returns the position along a ray that corresponds to some parameter T
  pub fn at(&self, t: T) -> V { self.pos + self.dir * t }
  pub fn step(&mut self, t: T) { self.pos = self.pos + (self.dir * t) }
}

impl<T: Float, const N: usize> Ray<T, Vector<T, N>>
where
  [T; N]: LengthAtMost32,
{
  /// Sets the length of this ray to the given amount
  pub fn set_length(&mut self, t: T) { self.dir = self.dir.norm() * t; }
}

impl<T, V> Ray<T, V>
where
  V: Neg<Output = V> + Copy,
{
  /// Flips the direction of this ray
  pub fn flip(&self) -> Self { Ray::new(self.pos, -self.dir) }
}