//!
//! Provides some useful 2d geometry functions.
//!
//! Why the name? Not sure. Duck Duck Goose.
#[macro_use]
extern crate more_asserts;


extern crate axgeom;

///2d bot library where a bot is a 2d particle with mass.
pub mod bot;

pub mod grid;

use num_traits::Float;
use num_traits::NumAssign;
use num_traits::Zero;
use ordered_float::NotNan;
use axgeom::vec2;
use axgeom::Rect;
use axgeom::Vec2;
use core::ops::Neg;

///Basic Number Trait
pub trait MyNum: Zero + Copy + NumAssign + PartialOrd + Neg<Output = Self> {}
impl<T: Zero + Copy + NumAssign + PartialOrd + Neg<Output = Self>> MyNum for T {}

///NotNan f64
pub type F64n = NotNan<f64>;
///NotNan f64
pub type F32n = NotNan<f32>;

///convert an array of elements of type B to type A.
pub fn array2_inner_into<B: Copy, A: From<B>>(a: [B; 2]) -> [A; 2] {
    let x = A::from(a[0]);
    let y = A::from(a[1]);
    [x, y]
}

use core::convert::TryFrom;

///convert an array of elements of type B to type A.
pub fn array2_inner_try_into<B: Copy, A: TryFrom<B>>(a: [B; 2]) -> Result<[A; 2], A::Error> {
    let x = A::try_from(a[0]);
    let y = A::try_from(a[1]);
    match (x, y) {
        (Ok(x), Ok(y)) => Ok([x, y]),
        (Ok(_), Err(e)) => Err(e),
        (Err(e), Ok(_)) => Err(e),
        (Err(e1), Err(_)) => Err(e1),
    }
}

///Passed to gravitate.
pub trait GravityTrait {
    type N: Float;
    fn pos(&self) -> Vec2<Self::N>;
    fn mass(&self) -> Self::N;
    fn apply_force(&mut self, arr: Vec2<Self::N>);
}

///Returns the force to be exerted to the first object.
///The force to the second object can be retrieved simply by negating the first.
pub fn gravitate<T: GravityTrait, K: GravityTrait<N = T::N>>(
    a: &mut T,
    b: &mut K,
    min: T::N,
    gravity_const: T::N,
) -> Result<(), ErrTooClose> {
    let p1 = a.pos();
    let p2 = b.pos();
    let m1 = a.mass();
    let m2 = b.mass();

    let diff = p2 - p1;
    let dis_sqr = diff.magnitude2();

    if dis_sqr > min {
        //newtons law of gravitation (modified for 2d??? divide by len instead of sqr)
        let force = gravity_const * (m1 * m2) / dis_sqr;

        let dis = Float::sqrt(dis_sqr);

        let final_vec = diff * (force / dis);

        a.apply_force(final_vec);
        b.apply_force(-final_vec);
        Ok(())
    } else {
        Err(ErrTooClose)
    }
}

///Passed to repel
pub trait RepelTrait {
    type N: Float;
    fn pos(&self) -> Vec2<Self::N>;
    fn add_force(&mut self, force: Vec2<Self::N>);
}

///If we repel too close, because of the inverse square we might get overlow problems.
pub struct ErrTooClose;

///Repel one object by simply not calling add_force on the other.
pub fn repel_one<B: RepelTrait>(
    bot1: &mut B,
    pos: Vec2<B::N>,
    closest: B::N,
    mag: B::N,
) -> Result<(), ErrTooClose> {
    let a = bot1;

    let pos1 = a.pos();
    let pos2 = pos;

    let diff = pos2 - pos1;

    let len_sqr = diff.magnitude2();

    if len_sqr < closest {
        return Err(ErrTooClose);
    }

    let len = Float::sqrt(len_sqr);
    let mag = mag / len;

    let force = diff.normalize_to(mag);

    a.add_force(-force);

    Ok(())
}

///Repel two objects.
pub fn repel<B: RepelTrait>(
    bot1: &mut B,
    bot2: &mut B,
    closest: B::N,
    mag: B::N,
) -> Result<(), ErrTooClose> {
    let a = bot1;
    let b = bot2;

    let pos1 = a.pos();
    let pos2 = b.pos();
    let diff = pos2 - pos1;

    let len_sqr = diff.magnitude2();

    if len_sqr < closest {
        return Err(ErrTooClose);
    }

    let len = len_sqr.sqrt();
    let mag = mag / len;

    let force = diff.normalize_to(mag);

    a.add_force(-force);
    b.add_force(force);

    Ok(())
}

///Generic trait to collide with border
pub trait BorderCollideTrait {
    type N: MyNum;
    fn pos_vel_mut(&mut self) -> (&mut Vec2<Self::N>, &mut Vec2<Self::N>);
}

///Collides and bounces an object with a border
pub fn collide_with_border<B: BorderCollideTrait>(
    a: &mut B,
    rect2: &axgeom::Rect<B::N>,
    drag: B::N,
) {
    let xx = rect2.get_range(axgeom::XAXIS);
    let yy = rect2.get_range(axgeom::YAXIS);

    let (pos, vel) = &mut a.pos_vel_mut();

    if pos.x < xx.start {
        pos.x = xx.start;
        vel.x = -vel.x;
        vel.x *= drag;
    }
    if pos.x > xx.end {
        pos.x = xx.end;
        vel.x = -vel.x;
        vel.x *= drag;
    }
    if pos.y < yy.start {
        pos.y = yy.start;
        vel.y = -vel.y;
        vel.y *= drag;
    }
    if pos.y > yy.end {
        pos.y = yy.end;
        vel.y = -vel.y;
        vel.y *= drag;
    }
}

///Forces a position to be within the specified rect.
#[inline(always)]
pub fn stop_wall<N: MyNum>(pos: &mut Vec2<N>, rect: Rect<N>) {
    let start = vec2(rect.x.start, rect.y.start);
    let dim = vec2(rect.x.end, rect.y.end);
    if pos.x > dim.x {
        pos.x = dim.x;
    } else if pos.x < start.x {
        pos.x = start.x;
    }

    if pos.y > dim.y {
        pos.y = dim.y;
    } else if pos.y < start.y {
        pos.y = start.y;
    }
}

///Wraps the first point around the rectangle made between (0,0) and dim.
pub fn wrap_position<N: MyNum>(a: &mut Vec2<N>, dim: Rect<N>) {
    let ((a_, b), (c, d)) = dim.get();

    let start = vec2(a_, c);
    let dim = vec2(b, d);

    if a.x > dim.x {
        a.x = start.x
    } else if a.x < start.x {
        a.x = dim.x;
    }

    if a.y > dim.y {
        a.y = start.y;
    } else if a.y < start.y {
        a.y = dim.y;
    }
}

///Describes a cardinal direction..
pub enum WallSide {
    Above,
    Below,
    LeftOf,
    RightOf,
}

///Returns which cardinal direction the specified rectangle is closest to.
pub fn collide_with_rect<N: Float>(
    botr: &axgeom::Rect<N>,
    wallr: &axgeom::Rect<N>,
) -> Option<WallSide> {
    let wallx = wallr.get_range(axgeom::XAXIS);
    let wally = wallr.get_range(axgeom::YAXIS);

    let center_bot = botr.derive_center();
    let center_wall = wallr.derive_center();

    let ratio = (wallx.end - wallx.start) / (wally.end - wally.start);

    //Assuming perfect square
    let p1 = vec2(N::one(), ratio);
    let p2 = vec2(N::zero() - N::one(), ratio);

    let diff = center_bot - center_wall;

    let d1 = p1.dot(diff);
    let d2 = p2.dot(diff);
    let zero = N::zero();

    use std::cmp::Ordering::*;

    let ans = match [d1.partial_cmp(&zero)?, d2.partial_cmp(&zero)?] {
        [Less, Less] => {
            //top
            WallSide::Above
        }
        [Less, Equal] => {
            //topstart
            WallSide::Above
        }
        [Less, Greater] => {
            //start
            WallSide::LeftOf
        }
        [Greater, Less] => {
            //end
            WallSide::RightOf
        }
        [Greater, Equal] => {
            //bottom end
            WallSide::Below
        }
        [Greater, Greater] => {
            //bottom
            WallSide::Below
        }
        [Equal, Less] => {
            //top end
            WallSide::Above
        }
        [Equal, Equal] => {
            //Directly in the center
            WallSide::Above
        }
        [Equal, Greater] => {
            //bottom start
            WallSide::Below
        }
    };
    Some(ans)
}
/*

///A Ray.
#[derive(Debug, Copy, Clone)]
pub struct Ray<N> {
    pub point: Vec2<N>,
    pub dir: Vec2<N>,
}


impl<N:Copy+core::ops::Add<Output=N>+core::ops::Mul<Output=N>> Ray<N>{

    #[inline(always)]
    pub fn point_at_tval(&self,tval:N)->Vec2<N>{
        self.point+self.dir*tval
    }
}

impl<N> Ray<N> {
    pub fn new(point: Vec2<N>, dir: Vec2<N>) -> Ray<N> {
        Ray { point, dir }
    }

    pub fn inner_into<B: From<N>>(self) -> Ray<B> {
        let point = self.point.inner_into();
        let dir = self.dir.inner_into();
        Ray { point, dir }
    }
    pub fn inner_try_into<B: TryFrom<N>>(self) -> Result<Ray<B>, B::Error> {
        let point = self.point.inner_try_into();
        let dir = self.dir.inner_try_into();
        match (point, dir) {
            (Ok(point), Ok(dir)) => Ok(Ray { point, dir }),
            (Err(e), Ok(_)) => Err(e),
            (Ok(_), Err(e)) => Err(e),
            (Err(e), Err(_)) => Err(e),
        }
    }
}



///Given a ray and an axis aligned line, return the tvalue,and x coordinate
pub fn ray_compute_intersection_tvalue<A: axgeom::Axis, N: MyNum>(
    ray: &Ray<N>,
    axis: A,
    line: N,
) -> Option<(N)> {
    if axis.is_xaxis() {
        if ray.dir.x == N::zero() {
            if ray.point.x == line {
                Some(N::zero())
            } else {
                None
            }
        } else {
            let t = (line - ray.point.x) / ray.dir.x;
            if t >= N::zero() {
                Some(t)
            } else {
                None
            }
        }
    } else {
        if ray.dir.y == N::zero() {
            if ray.point.y == line {
                Some(N::zero())
            } else {
                None
            }
        } else {
            let t = (line - ray.point.y) / ray.dir.y;
            if t >= N::zero() {
                Some(t)
            } else {
                None
            }
        }
    }
}

fn ray_1d<N: Float>(point: N, dir: N, range: &axgeom::Range<N>) -> IntersectsBotResult<N> {
    use core::cmp::Ordering::*;
    match range.contains_ext(point) {
        Less => {
            if dir < N::zero() {
                IntersectsBotResult::NoHit
            } else {
                IntersectsBotResult::Hit(range.start - point)
            }
        }
        Greater => {
            if dir > N::zero() {
                IntersectsBotResult::NoHit
            } else {
                IntersectsBotResult::Hit(point - range.end)
            }
        }
        Equal => IntersectsBotResult::Inside,
    }
}

use roots;
use roots::*;
///Checks if a ray intersects a circle.
pub fn ray_intersects_circle<N: Float + roots::FloatType>(
    ray: &Ray<N>,
    center: Vec2<N>,
    radius: N,
) -> IntersectsBotResult<N> {
    //https://math.stackexchange.com/questions/311921/get-location-of-vector-circle-intersection
    //circle
    //(x-center.x)^2+(y-center.y)^2=r2
    //ray
    //x(t)=ray.dir.x*t+ray.point.x
    //y(t)=ray.dir.y*t+ray.point.y
    //
    //solve for t.
    //
    //
    //we get:
    //
    //𝑎𝑡^2+𝑏𝑡+𝑐=0
    //
    //
    //
    //
    let zz = <N as FloatType>::zero();
    let two = <N as FloatType>::two();

    let a = ray.dir.x.powi(2) + ray.dir.y.powi(2);
    let b = two * ray.dir.x * (ray.point.x - center.x) + two * ray.dir.y * (ray.point.y - center.y);
    let c = (ray.point.x - center.x).powi(2) + (ray.point.y - center.y).powi(2) - radius.powi(2);

    match find_roots_quadratic(a, b, c) {
        Roots::No(_) => IntersectsBotResult::NoHit,
        Roots::One([a]) => {
            if a < zz {
                IntersectsBotResult::NoHit
            } else {
                IntersectsBotResult::Hit(a)
            }
        }
        Roots::Two([a, b]) => {
            let (closer, further) = if a < b { (a, b) } else { (b, a) };

            if closer < zz && further < zz {
                IntersectsBotResult::NoHit
            } else if closer < zz && further > zz {
                IntersectsBotResult::Inside
            } else {
                IntersectsBotResult::Hit(closer)
            }
        }
        _ => unreachable!(),
    }
}








///Returns if a ray intersects a box.
pub fn ray_intersects_box<N: Float + core::fmt::Debug>(
    ray: &Ray<N>,
    rect: &axgeom::Rect<N>,
) -> IntersectsBotResult<N> {
    let point = ray.point;
    let dir = ray.dir;

    let ((x1, x2), (y1, y2)) = rect.get();

    let (tmin, tlen) = if dir.x != N::zero() {
        let tx1 = (x1 - point.x) / dir.x;
        let tx2 = (x2 - point.x) / dir.x;

        (tx1.min(tx2), tx1.max(tx2))
    } else if point.x < x1 || point.x > x2 {
        return IntersectsBotResult::NoHit; // parallel AND outside box : no intersection possible
    } else {
        return ray_1d(point.y, dir.y, &rect.y);
    };

    let (tmin, tlen) = if dir.y != N::zero() {
        let ty1 = (y1 - point.y) / dir.y;
        let ty2 = (y2 - point.y) / dir.y;

        let k1 = tmin.max(ty1.min(ty2));
        let k2 = tlen.min(ty1.max(ty2));
        (k1, k2)
    } else if point.y < y1 || point.y > y2 {
        return IntersectsBotResult::NoHit; // parallel AND outside box : no intersection possible
    } else {
        (tmin, tlen)
    };

    //TODO figure out inequalities!
    if tmin <= N::zero() && tlen >= N::zero() {
        return IntersectsBotResult::Inside;
    }

    if tmin <= N::zero() && tlen < N::zero() {
        return IntersectsBotResult::NoHit;
    }

    if tlen >= tmin {
        IntersectsBotResult::Hit(tmin)
    } else {
        IntersectsBotResult::NoHit
    }
}

///Describes if a ray hit a rectangle.
#[derive(Copy, Clone, Debug)]
pub enum IntersectsBotResult<N> {
    Hit(N),
    Inside,
    NoHit,
}

*/