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use crate::{
    geom::{Circle, Line, Rectangle, Scalar, Shape, Transform, Triangle, Vector},
    graphics::{Color, GpuTriangle, Image, Mesh}
};
use std::iter;

/// Some object that can be drawn to the screen
pub trait Drawable {
    /// Draw the object to the Mesh
    fn draw<'a>(&self, mesh: &mut Mesh, background: Background<'a>, transform: Transform, z: impl Scalar);
}

/// The background to use for a given drawable
///
/// While each Drawable can define its own behavior, the recommended behavior
/// is that the Image be applied in proportion to the relative position of
/// the vertices. This means the left-most vertex should use the left edge
/// of the image, the right-most vertex should use the right edge of the image, etc.
#[derive(Copy, Clone)]
pub enum Background<'a> {
    /// A uniform color background
    Col(Color),
    /// A textured background
    Img(&'a Image),
    /// A color and image blended multiplicatively
    Blended(&'a Image, Color)
}

impl<'a> Background<'a> {
    /// Return either the stored Image or None
    pub fn image(&self) -> Option<&Image> {
        match self {
            Background::Col(_) => None,
            Background::Img(img) | Background::Blended(img, _) => Some(img),
        }
    }

    /// Return either the stored Color or Color::WHITE
    pub fn color(&self) -> Color {
        match self {
            Background::Col(color) |Background::Blended(_, color) => *color,
            Background::Img(_) => Color::WHITE,
        }
    }
}

impl<'a> From<Color> for Background<'a> {
    fn from(col: Color) -> Self {
        Background::Col(col)
    }
}

impl<'a> From<&'a Image> for Background<'a> {
    fn from(img: &'a Image) -> Self {
        Background::Img(img)
    }
}

impl<'a> From<(&'a Image, Color)> for Background<'a> {
    fn from((img, col): (&'a Image, Color)) -> Self {
        Background::Blended(img, col)
    }
}

impl Drawable for Vector {
    fn draw<'a>(&self, mesh: &mut Mesh, bkg: Background<'a>, trans: Transform, z: impl Scalar) {
        Rectangle::new(*self, Vector::ONE).draw(mesh, bkg, trans, z);
    }
}

impl Drawable for Rectangle {
    fn draw<'a>(&self, mesh: &mut Mesh, bkg: Background<'a>, trans: Transform, z: impl Scalar) {
        let trans = Transform::translate(self.top_left() + self.size() / 2)
            * trans
            * Transform::translate(-self.size() / 2)
            * Transform::scale(self.size());
        let tex_trans = bkg.image().map(|img| img.projection(Rectangle::new_sized((1, 1))));
        let offset = mesh.add_positioned_vertices(
            [Vector::ZERO, Vector::X, Vector::ONE, Vector::Y].iter().cloned(), trans, tex_trans, bkg);
        mesh.triangles.push(GpuTriangle::new(offset, [0, 1, 2], z, bkg));
        mesh.triangles.push(GpuTriangle::new(offset, [2, 3, 0], z, bkg));
    }
}


impl Drawable for Circle {
    fn draw<'a>(&self, mesh: &mut Mesh, bkg: Background<'a>, trans: Transform, z: impl Scalar) {
        let trans = Transform::translate(self.center())
            * trans
            * Transform::scale(Vector::ONE * self.radius);
        let tex_trans = bkg.image().map(|img| img.projection(Rectangle::new((-1,-1), (2,2))));
        let offset = mesh.add_positioned_vertices(CIRCLE_POINTS.iter().cloned(), trans, tex_trans, bkg);
        mesh.triangles.extend(iter::repeat(z)
            .take(CIRCLE_POINTS.len() - 1)
            .enumerate()
            .map(|(index, z)| GpuTriangle::new(offset, [0, index as u32, index as u32 + 1], z, bkg)));
    }
}

impl Drawable for Triangle {
    fn draw<'a>(&self, mesh: &mut Mesh, bkg: Background<'a>, trans: Transform, z: impl Scalar) {
        let trans = Transform::translate(self.center())
            * trans
            * Transform::translate(-self.center());
        let tex_transform = bkg.image().map(|image| image.projection(self.bounding_box()));
        let offset = mesh.add_positioned_vertices([self.a, self.b, self.c].iter().cloned(),
            trans, tex_transform, bkg);
        mesh.triangles.push(GpuTriangle::new(offset, [0, 1, 2], z, bkg));
    }
}

impl Drawable for Line {
    fn draw<'a>(&self, mesh: &mut Mesh, bkg: Background<'a>, trans: Transform, z: impl Scalar) {
        // create rectangle in right size
        let rect = Rectangle::new((self.a.x, self.a.y + self.t / 2.0), (self.a.distance(self.b), self.t));

        let trans = Transform::translate((self.a + self.b) / 2 - rect.center())
            * trans
            * Transform::rotate((self.b - self.a).angle());
        rect.draw(mesh, bkg, trans, z);
    }
}


// Until there's serious compile-time calculations in Rust,
// it's best to just pre-write the points on a rasterized circle

// Python script to generate the array:
/*
import math
from math import pi


def points_on_circumference(center=(0, 0), r=50, n=100):
    n -= 1
    return [
        (
            center[0]+(math.cos(2 * pi / n * x) * r),  # x
            center[1] + (math.sin(2 * pi / n * x) * r)  # y

        ) for x in range(0, n + 1)]


number_of_points = 64
points = points_on_circumference(center=(0,0),r=1, n=number_of_points)

print("const CIRCLE_POINTS: [Vector; %i] = [" % number_of_points)

for point in points:
    print("    Vector { x: %s, y: %s }," % (point[0], point[1]))

print("];")
*/

const CIRCLE_POINTS: [Vector; 64] = [
    Vector { x: 1.0, y: 0.0 },
    Vector { x: 0.9950307753654014, y: 0.09956784659581666 },
    Vector { x: 0.9801724878485438, y: 0.19814614319939758 },
    Vector { x: 0.9555728057861407, y: 0.2947551744109042 },
    Vector { x: 0.9214762118704076, y: 0.38843479627469474 },
    Vector { x: 0.8782215733702285, y: 0.47825397862131824 },
    Vector { x: 0.8262387743159949, y: 0.5633200580636221 },
    Vector { x: 0.766044443118978, y: 0.6427876096865394 },
    Vector { x: 0.6982368180860729, y: 0.7158668492597184 },
    Vector { x: 0.6234898018587336, y: 0.7818314824680298 },
    Vector { x: 0.5425462638657594, y: 0.8400259231507714 },
    Vector { x: 0.4562106573531629, y: 0.8898718088114687 },
    Vector { x: 0.365341024366395, y: 0.9308737486442042 },
    Vector { x: 0.27084046814300516, y: 0.962624246950012 },
    Vector { x: 0.17364817766693022, y: 0.9848077530122081 },
    Vector { x: 0.07473009358642417, y: 0.9972037971811801 },
    Vector { x: -0.024930691738072913, y: 0.9996891820008162 },
    Vector { x: -0.12434370464748516, y: 0.9922392066001721 },
    Vector { x: -0.22252093395631434, y: 0.9749279121818236 },
    Vector { x: -0.31848665025168454, y: 0.9479273461671317 },
    Vector { x: -0.41128710313061156, y: 0.9115058523116731 },
    Vector { x: -0.5000000000000002, y: 0.8660254037844385 },
    Vector { x: -0.58374367223479, y: 0.8119380057158564 },
    Vector { x: -0.6616858375968595, y: 0.7497812029677341 },
    Vector { x: -0.7330518718298263, y: 0.6801727377709194 },
    Vector { x: -0.7971325072229225, y: 0.6038044103254774 },
    Vector { x: -0.8532908816321556, y: 0.5214352033794981 },
    Vector { x: -0.900968867902419, y: 0.43388373911755823 },
    Vector { x: -0.9396926207859084, y: 0.3420201433256685 },
    Vector { x: -0.969077286229078, y: 0.24675739769029342 },
    Vector { x: -0.9888308262251285, y: 0.14904226617617428 },
    Vector { x: -0.9987569212189223, y: 0.04984588566069704 },
    Vector { x: -0.9987569212189223, y: -0.04984588566069723 },
    Vector { x: -0.9888308262251285, y: -0.14904226617617447 },
    Vector { x: -0.969077286229078, y: -0.24675739769029362 },
    Vector { x: -0.9396926207859084, y: -0.34202014332566866 },
    Vector { x: -0.9009688679024191, y: -0.433883739117558 },
    Vector { x: -0.8532908816321555, y: -0.5214352033794983 },
    Vector { x: -0.7971325072229224, y: -0.6038044103254775 },
    Vector { x: -0.7330518718298262, y: -0.6801727377709195 },
    Vector { x: -0.6616858375968594, y: -0.7497812029677342 },
    Vector { x: -0.5837436722347898, y: -0.8119380057158565 },
    Vector { x: -0.4999999999999996, y: -0.8660254037844388 },
    Vector { x: -0.4112871031306116, y: -0.9115058523116731 },
    Vector { x: -0.3184866502516841, y: -0.9479273461671318 },
    Vector { x: -0.2225209339563146, y: -0.9749279121818236 },
    Vector { x: -0.12434370464748495, y: -0.9922392066001721 },
    Vector { x: -0.024930691738073156, y: -0.9996891820008162 },
    Vector { x: 0.07473009358642436, y: -0.9972037971811801 },
    Vector { x: 0.17364817766693083, y: -0.984807753012208 },
    Vector { x: 0.2708404681430051, y: -0.962624246950012 },
    Vector { x: 0.3653410243663954, y: -0.9308737486442041 },
    Vector { x: 0.45621065735316285, y: -0.8898718088114687 },
    Vector { x: 0.5425462638657597, y: -0.8400259231507713 },
    Vector { x: 0.6234898018587334, y: -0.7818314824680299 },
    Vector { x: 0.698236818086073, y: -0.7158668492597183 },
    Vector { x: 0.7660444431189785, y: -0.6427876096865389 },
    Vector { x: 0.8262387743159949, y: -0.563320058063622 },
    Vector { x: 0.8782215733702288, y: -0.4782539786213178 },
    Vector { x: 0.9214762118704076, y: -0.38843479627469474 },
    Vector { x: 0.9555728057861408, y: -0.2947551744109039 },
    Vector { x: 0.9801724878485438, y: -0.19814614319939772 },
    Vector { x: 0.9950307753654014, y: -0.09956784659581641 },
    Vector { x: 1.0, y: 0.0 },
];