// Some notes on terminology as used in this project:
//
// Body frame (or body-fixed frame):
//   - A coordinate frame that moves and rotates with the body.
//   - The origin of the body is fixed at the origin of this frame, and points on the body
//     have constant coordinates relative to the origin. For example, the ship's nose
//     is always at a fixed distance along the x-axis in this frame.
//
// Local frame (or co-moving frame):
//   - A coordinate frame that moves with the object's position (e.g., center of mass) 
//     but does not rotate with it.
//   - Points on the body may rotate relative to this frame as the object rotates in space.
//
// World frame (or inertial frame):
//   - A fixed coordinate frame that does not move or rotate with the body.
//   - All positions and orientations of the object are expressed relative to this absolute frame.
//
// This should be consistent with standard terminology.

use std::f64;
use std::collections::HashSet;

use wasm_bindgen::prelude::*;
use wasm_bindgen::JsCast;
use web_sys::{CanvasRenderingContext2d, HtmlCanvasElement};
use web_sys::console;

mod cga;
use cga::CGA;

const PI: f64 = f64::consts::PI;
const TWO_PI: f64 = 2.*PI;
const ERROR: f64 = 0.0001;

const WIDTH: f64 = 600.;
const HEIGHT: f64 = 600.;
const CENTER_X: f64 = 300.;
const CENTER_Y: f64 = 300.;
const RADIUS: f64 = 250.;

const BACKGROUND: &str = "#ffffff";
const BLACK: &str      = "#000000";
const RED: &str        = "#ff0000";
const GREEN: &str      = "#00ff00";
const BLUE: &str       = "#0000ff";

const SCALAR: usize = 0; 
const E1: usize = 1;
const E2: usize = 2;
//const E3: usize = 3;
//const E4: usize = 4;
//const E5: usize = 5;
const E12: usize = 6;
const E13: usize = 7;
const E14: usize = 8;
const E15: usize = 9;
const E23: usize = 10;
const E24: usize = 11;
const E25: usize = 12;
const E34: usize = 13;
const E35: usize = 14;
const E45: usize = 15;
//const E123: usize = 16;
//const E124: usize = 17;
//const E125: usize = 18;
//const E134: usize = 19;
//const E135: usize = 20;
//const E145: usize = 21;
//const E234: usize = 22;
//const E235: usize = 23;
//const E245: usize = 24;
//const E345: usize = 25;
//const E1234: usize = 26;
//const E1235: usize = 27;
//const E1245: usize = 28;
//const E1345: usize = 29;
//const E2345: usize = 30;
//const E12345: usize = 31;

const DRAG: f64 = 1.;
const ACCEL_STR: f64 = 1.;

struct Ship {
    com_rotor: CGA,
    verts: (CGA, CGA, CGA),
    vel: CGA,
    orientation: CGA,
}

impl Ship {
    fn update(&mut self, dt_s: f64, keys: &HashSet<String>) {
        let vel = self.vel.clone(); //Velocity at beginning of frame
        let mut vel_2 = self.vel.clone();

        let mut a_vec = - DRAG * &vel_2;

        if keys.contains("w") {
            let orient = &self.orientation; //Transforms body frame to local frame
            let pos = &self.com_rotor; //Transforms local frame to world frame
            let accel_body = ACCEL_STR * CGA::e15(); //The acceleration in the body frame.
            let accel_local = orient * accel_body * orient.Reverse(); //The acceleration in the local frame.
            let accel_world = pos * accel_local * pos.Reverse(); //The acceleration in the world frame.
            a_vec = a_vec - accel_world; //Sum of drag and thrust.
        }

        if keys.contains("q") {
            self.orientation = bivector_exponential(&(dt_s * CGA::e12())) * &self.orientation;
        }

        if keys.contains("e") {
            self.orientation = bivector_exponential(&(-dt_s * CGA::e12())) * &self.orientation;
        }


        vel_2 = vel_2 + a_vec*dt_s; //Velocity at end of frame
        let vel_3 = 0.5*(vel+&vel_2);
        let delta = vel_3 * dt_s;
        let pos = bivector_exponential(&delta)*&self.com_rotor; //Update position.
        self.vel = vel_2;
        self.com_rotor = pos;

    }

    fn draw(&self, context: &CanvasRenderingContext2d) {
        let origin = gen_hyperbolic_point(&CGA::zero()); //Origin in the body frame.
        let orient_rotor = &self.orientation; //Transforms body frame to local frame.
        let com = &self.com_rotor; //Transforms local frame to world frame.
        let v0_rotor = com*orient_rotor*bivector_exponential(&self.verts.0); //Combined transformation to locate a vertex of the ship in the world frame.
        let v1_rotor = com*orient_rotor*bivector_exponential(&self.verts.1); //Combined transformation ...
        let v2_rotor = com*orient_rotor*bivector_exponential(&self.verts.2); //Combined transformation ...
        let p0 = &v0_rotor*&origin*&v0_rotor.Reverse(); //Produce a vertex of the ship in the world frame.
        let p1 = &v1_rotor*&origin*&v1_rotor.Reverse(); //...
        let p2 = &v2_rotor*&origin*&v2_rotor.Reverse(); //...

        draw_point(context, &(com*&origin*com.Reverse()));
        draw_point(context, &p0);
        draw_point(context, &p1);
        draw_point(context, &p2);
        draw_line_between(context, &p0, &p1);
        draw_line_between(context, &p1, &p2);
        draw_line_between(context, &p2, &p0);

        //Construct and draw line pointing straight ahead, to help orient the player.
        let com_p = com * gen_hyperbolic_point(&CGA::zero()) * com.Reverse();
        let delta_gen = com * orient_rotor * CGA::e14() * &orient_rotor.Reverse() * com.Reverse();
        let dot = delta_gen | &com_p;
        let line = CGA::e4() ^ com_p ^ dot ^ CGA::e3();
        draw_line(context, &line);


    }
}

enum Geometry {
    Circle(f64, f64, f64), //x,y,r
    Line(f64, f64, f64), //x,r,theta
    Null,
}

/* Translation of a Euclidean Point. Need to use hyperbolic*/
fn point_to_cga(x: f64, y: f64) -> CGA {
    let x_vec = CGA::e1();
    let y_vec = CGA::e2();
    let _z_vec =CGA::e3(); //This game assumes everything takes place in the plane.
    let e_vec = CGA::e4();
    let e_bar = CGA::e5();
    let n_vec = &e_vec + &e_bar; //Null vector for the point at infinity.
    let n_bar = &e_vec - &e_bar; //Null vector for the origin.

    let mut ux = x;
    let mut uy = y;
    let mut mag_sqr = ux*ux + uy*uy;
    if mag_sqr > 1. {
        ux /= mag_sqr.sqrt();
        uy /= mag_sqr.sqrt();
        mag_sqr = 1.;
    }

    0.5*mag_sqr*n_vec + ux*x_vec + uy*y_vec - 0.5*n_bar //F(x) = 1/2(x^2 n + 2x - nbar) = -1/2(x-e)n(x-e)
} 

fn point_to_screen_space(x: f64, y: f64) -> (f64, f64) {
    let screen_x = x*RADIUS + CENTER_X;
    let screen_y = y*RADIUS + CENTER_Y;
    (screen_x, screen_y)
}

fn draw_point(context: &CanvasRenderingContext2d, point: &CGA) {
    //Naively assume we are given a valid point
    let (x,y) = get_hyperbolic_point(point);
    let (x,y) = point_to_screen_space(x, y);

    context.begin_path();
    context.set_fill_style_str(RED);
    context.arc(x, y, 2., 0., TWO_PI).unwrap();
    context.fill();

    let (x,y) = get_point(point);
    let (x,y) = point_to_screen_space(x,y);

    context.begin_path();
    context.set_fill_style_str(BLUE);
    context.arc(x, y, 2., 0., TWO_PI).unwrap();
    context.fill();

}

//TODO Integrate into get geometry
fn get_hyperbolic_point(point: &CGA) -> (f64, f64) {
    let n_bar = CGA::e4() - CGA::e5();

    //Construct r hat dir for the point.
    let mut x = point[E1];
    let mut y = point[E2];
    let mag_sqr = x*x + y*y;
    if mag_sqr > ERROR {
        x /= mag_sqr.sqrt();
        y /= mag_sqr.sqrt();
        //(x,y) is a unit vector pointing in the direction of our point
    } else {
        //mag_sqr is too small to be confident in our vector.
        //Assume vector is at the origin.
        return (0., 0.);
    }

    //A normalized hyperbolic point in the full CGA satisfies p dot e4 = -1, 
    //where e4 is the positive squaring conformal vector.
    let norm = -(point | CGA::e4())[SCALAR];
    //Get the normalize component of the n term. Note n dot n = 0 and n dot n_bar = 2
    let n_term = (0.5/norm) * (point | &n_bar)[SCALAR];
    //Solve for r^2
    let r_sqr = n_term/(1.+n_term);
    let r = r_sqr.sqrt();
    (r*x,r*y)
}

fn get_point(point: &CGA) -> (f64, f64) {
    let x = point[E1];
    let y = point[E2];
    let n = CGA::e4()+CGA::e5();
    let norm = -(point | &n)[SCALAR];
    (x/norm, y/norm)
}

fn get_geometry(circle: &CGA) -> Geometry {
    //Naively assume we are given a valid line/circle
    let n_bar = CGA::e4() - CGA::e5();
    let n_vec = CGA::e4() + CGA::e5();
    let dual = (&circle).Dual();
    let l = (&dual | &n_vec)[SCALAR];
    let c = (&dual | &n_bar)[SCALAR];
    let a = (&dual | CGA::e1())[SCALAR];
    let b = (&dual | CGA::e2())[SCALAR];

    if l.abs() < ERROR {
        //LINE
        let theta = (-a).atan2(b);
        let norm_sqr = a*a + b*b;
        if norm_sqr < ERROR*ERROR {
            return Geometry::Null;
        }
        let x = a*c/norm_sqr/2.;
        let y = b*c/norm_sqr/2.;
        return Geometry::Line(x,y,theta);
    } else {
        //Circle
        let c_x = a/l;
        let c_y = b/l;
        let r_sqr = c_x*c_x + c_y*c_y + c/l;
        let r = r_sqr.sqrt();
        return Geometry::Circle(-c_x, -c_y, r);
    }
}

fn draw_line(context: &CanvasRenderingContext2d, line: &CGA) {
    context.begin_path();
    context.set_stroke_style_str(GREEN);

    let geometry = get_geometry(line);
    match geometry {
        Geometry::Circle(x,y,r) => {
            let (canvas_x, canvas_y) = point_to_screen_space(x, y);
            let canvas_r = r*RADIUS;
            context.arc(canvas_x, canvas_y, canvas_r, 0., TWO_PI).unwrap();
        },
            Geometry::Line(x,y,theta) => {
                let (p1x, p1y) = (x - theta.cos(), y - theta.sin());
                let (p2x, p2y) = (x + theta.cos(), y + theta.sin());
                let (canvas_x1, canvas_y1) = point_to_screen_space(p1x, p1y);
                let (canvas_x2, canvas_y2) = point_to_screen_space(p2x, p2y);
                //draw_point(&context, &point_to_cga(x,y));
                context.move_to(canvas_x1, canvas_y1);
                context.line_to(canvas_x2, canvas_y2);
            },
            Geometry::Null => {},
    }
    context.stroke();
}

fn draw_line_between(context: &CanvasRenderingContext2d, a: &CGA, b: &CGA) {
    let line = CGA::e4() ^ a ^ b ^ CGA::e3();
    let geometry = get_geometry(&line);
    context.begin_path();
    context.set_stroke_style_str(GREEN);
    match geometry {
        Geometry::Circle(x,y,r) => {
            let (a_x, a_y) = get_point(a);
            let (b_x, b_y) = get_point(b);
            let mut theta_a = (a_y-y).atan2(a_x-x);
            let mut theta_b = (b_y-y).atan2(b_x-x);
            if theta_a < 0. {
                theta_a += TWO_PI;
            }
            if theta_b < 0. {
                theta_b += TWO_PI;
            }
            let mut delta = theta_b - theta_a;
            if delta < -PI {
                delta += TWO_PI;
            } else if delta > PI {
                delta -= TWO_PI;
            }
            let (x,y) = point_to_screen_space(x,y);
            let r = RADIUS*r;
            if delta < 0. {
                if theta_a + delta < 0. {
                    context.arc(x, y, r, 0., theta_a).unwrap();
                    context.arc(x, y, r, theta_a + delta + TWO_PI, TWO_PI).unwrap();
                } else {
                    context.arc(x, y, r, theta_a + delta, theta_a).unwrap();
                }
            } else {
                if theta_a + delta > TWO_PI {
                    context.arc(x, y, r, theta_a, TWO_PI).unwrap();
                    context.arc(x, y, r, 0., theta_a + delta - TWO_PI).unwrap();
                } else {
                    context.arc(x, y, r, theta_a, theta_a + delta).unwrap();
                }
            }
        },
        _ => {},
    }
    context.stroke();
}

fn _get_hyperbolic_translation(vec: &CGA) -> CGA {
    let vec_sqr = (vec * vec)[SCALAR];
    if vec_sqr >= 1. {
        panic!("Translation Vector Out of Bounds");
    }
    let t = 1.0 / ( 1. - vec_sqr).sqrt() * ( CGA::new(1., SCALAR) + CGA::e5()*vec);
    t
}

fn gen_hyperbolic_point(vec: &CGA) -> CGA {
    let vec_sqr = (vec * vec)[SCALAR];
    if vec_sqr >= 1. {
        panic!("Vector out of bounds");
    }
    let n = CGA::e4() + CGA::e5();
    let p = 1. / (1. - vec_sqr)*(vec_sqr*n/*CGA::new(vec_sqr, SCALAR)*/ + 2.*vec - (CGA::e4() - CGA::e5()));
    p
}

fn bivector_exponential(bivector: &CGA) -> CGA {
    //Explicitly take only the bivector part.
    //The library doesn't provide a grade 2 selection.
    let a = bivector[E12];
    let b = bivector[E13];
    let c = bivector[E14];
    let d = bivector[E15];
    let e = bivector[E23];
    let f = bivector[E24];
    let g = bivector[E25];
    let h = bivector[E34];
    let i = bivector[E35];
    let j = bivector[E45];

    let bivector = a*CGA::e12() + b*CGA::e13() + c*CGA::e14() 
        + d*CGA::e15()  + e*CGA::e23() + f*CGA::e24() + g*CGA::e25()
        + h*CGA::e34() + i *CGA::e35() + j*CGA::e45();
    let sqr = (&bivector*&bivector)[SCALAR];
    if sqr.abs() < ERROR {
        CGA::new(1., SCALAR) + bivector
    } else if sqr < 0. {
        let theta = sqr.abs().sqrt();
        CGA::new(theta.cos(), SCALAR) + theta.sin()/theta*bivector //Division by theta to normalize bivector
    } else {
        let t = sqr.sqrt();
        CGA::new(t.cosh(), SCALAR) + t.sinh()/t*bivector //Division by t to normalize the bivector
    }
}

struct Asteroid {
    circle: CGA,
    vel: CGA,
}

impl Asteroid {
    fn new() -> Asteroid {
        let v = 0.1;
        let (v_x, v_y) = (v * 1.0_f64.cos(), v*1.0_f64.sin());
        let vel = v_x*CGA::e15() + v_y*CGA::e25();
        Self::new_from_coords(0.0_f64, 0.0_f64, 0.1_f64, vel)
    }

    fn new_from_coords(x: f64, y: f64, r: f64, vel: CGA) -> Asteroid {
        let (a_x, a_y) = (x + r * 0.0_f64.cos(), y + r * 0.0_f64.sin());
        let (b_x, b_y) = (x + r * 1.0_f64.cos(), y + r * 1.0_f64.sin());
        let (c_x, c_y) = (x + r * 2.0_f64.cos(), y + r * 2.0_f64.sin());
        let a = point_to_cga(a_x, a_y);
        let b = point_to_cga(b_x, b_y);
        let c = point_to_cga(c_x, c_y);
        let circle = a^b^c^CGA::e3();
        Asteroid { circle, vel }
    }

    fn update(&mut self, dt_s: f64) {
        let vel = &self.vel;
        let delta = vel * dt_s;
        let vel_rotor = bivector_exponential(&delta);
        let circle = &vel_rotor*&self.circle*&vel_rotor.Reverse();
        self.circle = circle;
    }

    fn draw(&self, context: &CanvasRenderingContext2d) {
        draw_line(context, &self.circle);
    }
}

#[wasm_bindgen]
pub struct Game {
    context: CanvasRenderingContext2d,
    ship: Ship,
    asteroids: Vec::<Asteroid>,
    keys: HashSet<String>,
}

#[wasm_bindgen]
impl Game {
#[wasm_bindgen(constructor)]
    pub fn new(canvas_id: &str) -> Self {
        let window = web_sys::window().unwrap();
        let document = window.document().unwrap();
        let canvas = document
            .get_element_by_id(canvas_id)
            .ok_or_else( || JsValue::from_str("Canvas not found")).unwrap()
            .dyn_into::<HtmlCanvasElement>().unwrap();
        canvas.set_width(WIDTH as u32);
        canvas.set_height(HEIGHT as u32);
        let context = canvas
            .get_context("2d").unwrap()
            .ok_or_else( || JsValue::from_str("Failed to get context")).unwrap()
            .dyn_into::<CanvasRenderingContext2d>().unwrap();

        let tx_gen = CGA::e15();
        let ty_gen = CGA::e25();

        let ship = Ship {
            com_rotor: CGA::new(1., SCALAR),
            verts: (-0.1*&tx_gen, 0.05*&tx_gen+0.02*&ty_gen, 0.05*&tx_gen-0.02*ty_gen),
            vel: CGA::zero(),
            orientation: CGA::new(1., SCALAR),
        };

        Game { 
            context: context,
            ship,
            asteroids: vec![Asteroid::new()],
            keys: HashSet::new(),
        }
    }

    pub fn draw(&self) {
        self.context.begin_path();
        self.context.set_fill_style_str(BACKGROUND);
        self.context.fill_rect(0.0, 0.0, WIDTH, HEIGHT);
        self.context.fill();
        self.context.set_stroke_style_str(BLACK);
        self.context.arc(CENTER_X, CENTER_Y, RADIUS, 0., TWO_PI).unwrap();
        self.context.stroke();
        self.ship.draw(&self.context);
        for asteroid in &self.asteroids {
            asteroid.draw(&self.context);
        }
    }

    pub fn update(&mut self, dt_m: f64) {
        let dt_s = if dt_m > 100. {
            0.1
        } else {
            dt_m / 1000.
        };

        for asteroid in &mut self.asteroids {
            asteroid.update(dt_s);
        }

        self.ship.update(dt_s, &self.keys);
    }

    pub fn key_down(&mut self, key: String) {
        self.keys.insert(key);
    }

    pub fn key_up(&mut self, key: String) {
        self.keys.remove(&key);
    }
}



// Start entry point
#[wasm_bindgen(start)]
pub fn start() -> Result<(), JsValue> {
//    let _ship = Ship { _pos: point_to_cga(0.,0.), _vel: CGA::zero(), _orientation: CGA::zero() };

/*
    // Grab document and canvas
    let window = web_sys::window().unwrap();
    let document = window.document().unwrap();
    let canvas = document
        .get_element_by_id("game-canvas")
        .unwrap()
        .dyn_into::<HtmlCanvasElement>()?;

    canvas.set_width(WIDTH as u32);
canvas.set_height(HEIGHT as u32);

    let context = canvas
        .get_context("2d")?
        .unwrap()
        .dyn_into::<CanvasRenderingContext2d>().unwrap();

    //Set up play area.
    context.begin_path();
    context.set_fill_style_str(BACKGROUND);
    context.fill_rect(0.0, 0.0, WIDTH, HEIGHT);
    context.fill();
    context.set_stroke_style_str(BLACK);
    context.arc(CENTER_X, CENTER_Y, RADIUS, 0., TWO_PI).unwrap();
    context.stroke();
*/
    /* //Testing example lines and circles.
       let point = point_to_cga(0.,0.);
       draw_point(&context, &point);

       let p1 = point_to_cga(0.9, 0.0);
       draw_point(&context, &p1);
       let p2 = point_to_cga(0.0, 0.9);
       draw_point(&context, &p2);
       let p3 = point_to_cga(0.7, 0.6);
       draw_point(&context, &p3);
       let circle = &p1 ^ &p2 ^ &p3 ^ &CGA::e3(); //wedge e3 to force into the plane
       draw_line(&context, &circle);

       let p1 = point_to_cga(0.9, 0.2);
       draw_point(&context, &p1);
       let p2 = point_to_cga(-0.9, -0.);
       draw_point(&context, &p2);
       let p3 = point_to_cga(0., 0.1);
       draw_point(&context, &p3);
       let circle = &p1 ^ &p2 ^ &p3 ^ &CGA::e3();
       draw_line(&context, &circle);

       let p1 = point_to_cga(0.9, 0.1);
       draw_point(&context, &p1);
       let p2 = point_to_cga(-0.9, -0.1);
       draw_point(&context, &p2);
       let p3 = point_to_cga(0., 0.0);
       draw_point(&context, &p3);
       let circle = &p1 ^ &p2 ^ &p3 ^ &CGA::e3();
       draw_line(&context, &circle);

       let p1 = point_to_cga(0.9, 0.);
       draw_point(&context, &p1);
       let p2 = point_to_cga(0.9, -0.1);
       draw_point(&context, &p2);
       let circle = &p1 ^ &p2 ^ &CGA::e4() ^ &CGA::e3(); //Wedge e4 to create a circle through p1 and p1 that is tangent to the unit circle.
       draw_line(&context, &circle);

       let p1 = point_to_cga(0.9, 0.);
       draw_point(&context, &p1);
       let p2 = point_to_cga(0.9, -0.1);
       draw_point(&context, &p2);
       let circle = &p1 ^ &p2 ^ &CGA::e5() ^ &CGA::e3(); //Orthogonal to the line at infinity
       draw_line(&context, &circle);*/

    Ok(())
}