class Vec2 {
    x: number;
    y: number;
    constructor(x: number, y: number) {
        this.x = x;
        this.y = y;
    }

    add(v: Vec2): Vec2 {
        return new Vec2(this.x + v.x, this.y + v.y);
    }

    sub(v: Vec2): Vec2 {
        return new Vec2(this.x - v.x, this.y - v.y);
    }

    mul(multiplicand: number): Vec2 {
        return new Vec2(this.x * multiplicand, this.y * multiplicand);
    }

    div(divisor: number): Vec2 {
        return new Vec2(this.x / divisor, this.y / divisor);
    }

    dot(v: Vec2): number {
        return this.x * v.x + this.y * v.y;
    }

    length(): number {
        return Math.sqrt(this.dot(this));
    }

    normalize(): Vec2 {
        return this.div(this.length());
    }

    cos_angle_to(other: Vec2): number {
        return this.dot(other) / (this.length() * other.length());
    }

    angle_to(other: Vec2): number {
        return Math.acos(this.cos_angle_to(other));
    }
}

class Vec3 {
    // x, right, y forward, z up
    x: number;
    y: number;
    z: number;
    constructor(x: number, y: number, z: number) {
        this.x = x;
        this.y = y;
        this.z = z;
    }

    add(v: Vec3): Vec3 {
        return new Vec3(this.x + v.x, this.y + v.y, this.z + v.z);
    }

    sub(v: Vec3): Vec3 {
        return new Vec3(this.x - v.x, this.y - v.y, this.z - v.z);
    }

    mul(multiplicand: number): Vec3 {
        return new Vec3(this.x * multiplicand, this.y * multiplicand, this.z * multiplicand);
    }

    div(divisor: number): Vec3 {
        return new Vec3(this.x / divisor, this.y / divisor, this.z / divisor);
    }

    dot(v: Vec3): number {
        return this.x * v.x + this.y * v.y + this.z * v.z;
    }

    length(): number {
        return Math.sqrt(this.dot(this));
    }

    normalize(): Vec2 {
        return this.div(this.length());
    }

    cos_angle_to(other: Vec3): number {
        return this.dot(other) / (this.length() * other.length());
    }

    angle_to(other: Vec3): number {
        return Math.acos(this.cos_angle_to(other));
    }

    // maps angle 0 to angle phi
    rotate_about_z(phi: number): Vec3 {
        let sp = Math.sin(phi);
        let cp = Math.cos(phi);
        return new Vec3(
            cp * this.x - sp * this.y,
            sp * this.x + cp * this.y,
            this.z
        );
    }

    // maps angle 0 to angle theta
    rotate_about_x(theta: number): Vec3 {
        let st = Math.sin(theta);
        let ct = Math.cos(theta);
        return new Vec3(
            this.x,
            ct * this.y - st * this.z,
            st * this.y + ct * this.z,
        );
    }
}

interface ProjectedPoint {
    screen_space: Vec2, // [0, width[x[0, height[
    camera_space: Vec2, // [-1, 1]x[-1, 1]
    distance: number, // world units
    screen_margin: Vec2, // pixels, negative = outside of screen
    behind: boolean,

    xhat_screen: Vec2,
    yhat_screen: Vec2,
    zhat_screen: Vec2,
}

class CameraProjection {
    origin: Vec3;
    yaw: number;
    pitch: number;
    fov: number;
    width: number;
    height: number;

    constructor(origin: Vec3, yaw: number, pitch: number, fov: number, width: number, height: number) {
        this.origin = origin;
        this.yaw = yaw;
        this.pitch = pitch;
        this.fov = fov;
        this.width = width;
        this.height = height;
    }

    world_to_camera(point: Vec3, respect_origin: boolean): Vec3 {
        if (respect_origin) {
            point = point.sub(this.origin);
        }
        return point.rotate_about_z(-this.yaw).rotate_about_x(-this.pitch);
    }

    camera_to_world(point: Vec3, respect_origin: boolean): Vec3 {
        point = point.rotate_about_x(this.pitch).rotate_about_z(this.yaw);
        if (respect_origin) {
            point = point.add(this.origin);
        }
        return point;
    }

    project(point: Vec3, respect_origin: boolean): ProjectedPoint {
        let camera_space_3 = this.world_to_camera(point, respect_origin);
        let scale = 1 / Math.tan(this.fov / 2);
        let camera_space = new Vec2(scale * camera_space_3.x / camera_space_3.y, scale * camera_space_3.z / camera_space_3.y);
        let screen_space = new Vec2(this.width / 2 + camera_space.x / 2 * this.width, this.height / 2 - camera_space.y / 2 * this.width);

        let self = this;
        function vec_screen(origin: Vec3, v: Vec3) {
            // TODO: PLEASE DO THIS ANALYTICALLY FOR THE LOVE OF GOD

            let h = 0.00001;
            let camera_space_3 = self.world_to_camera(origin, true);
            let camera_space = new Vec2(scale * camera_space_3.x / camera_space_3.y, scale * camera_space_3.z / camera_space_3.y);
            let screen_space = new Vec2((0.5 * camera_space.x) * self.width, (-0.5 * camera_space.y) * self.width);

            let v_camera_space_3 = self.world_to_camera(origin.add(v.mul(h)), true);
            let v_camera_space = new Vec2(scale * v_camera_space_3.x / v_camera_space_3.y, scale * v_camera_space_3.z / v_camera_space_3.y);
            let v_screen_space = new Vec2((0.5 * v_camera_space.x) * self.width, (-0.5 * v_camera_space.y) * self.width);
            let diff = (v_screen_space.sub(screen_space)).div(h);

            return diff;
        }

        let distance = camera_space_3.y;
        let behind = camera_space_3.y <= 0;
        let margin_x = Math.min(screen_space.x, this.width - screen_space.x);
        let margin_y = Math.min(screen_space.y, this.height - screen_space.y);

        // We want the
        let origin_camera_space = camera_space_3;
        if (camera_space.x < -1) {
            // We want to move origin's x such that camera_space.x == -1
            // scale * camera_space_3.x / camera_space_3.y == -1
            // camera_space_3.x = -camera_space_3.y / scale
            origin_camera_space.x = -camera_space_3.y / scale;
        }
        // All of these are similar
        if (camera_space.x > 1) {
            origin_camera_space.x = camera_space_3.y / scale;
        }
        if (camera_space.y < -1) {
            origin_camera_space.z = -camera_space_3.y / scale;
        }
        if (camera_space.y > 1) {
            origin_camera_space.z = camera_space_3.y / scale;
        }
        let origin = this.camera_to_world(origin_camera_space, true);

        return {
            screen_space: screen_space,
            camera_space: camera_space,
            distance: distance,
            screen_margin: new Vec2(margin_x, margin_y),
            behind: behind,
            xhat_screen: vec_screen(origin, new Vec3(1, 0, 0)),
            yhat_screen: vec_screen(origin, new Vec3(0, 1, 0)),
            zhat_screen: vec_screen(origin, new Vec3(0, 0, 1)),
        };
    }

    view_vector(): Vec3 {
        let yhat = new Vec3(0, 1, 0);
        return yhat.rotate_about_x(this.pitch).rotate_about_z(this.yaw);
    }
}

type RGB = {r: number, g: number, b: number};

interface Drawable {
    at: Vec3;
    render(at: ProjectedPoint, camera: CameraProjection, ctx: CanvasRenderingContext2D): boolean;
}

class Ball {
    at: Vec3;
    color: RGB;
    size: number;
    constructor(at: Vec3, color: RGB, size: number) {
        this.at = at;
        this.color = color;
        this.size = size;
    }
    render(at: ProjectedPoint, cam: CameraProjection, ctx: CanvasRenderingContext2D): boolean {
        let x_amount = Math.sqrt(Math.pow(at.xhat_screen.x, 2) + Math.pow(at.yhat_screen.x, 2) + Math.pow(at.zhat_screen.x, 2));
        let y_amount = Math.sqrt(Math.pow(at.xhat_screen.y, 2) + Math.pow(at.yhat_screen.y, 2) + Math.pow(at.zhat_screen.y, 2));

        for (let a = 0; a < 2; a++) {
            ctx.fillStyle = `rgb(${this.color.r * a}, ${this.color.g * a}, ${this.color.b * a})`;
            ctx.beginPath();
            ctx.ellipse(
                at.screen_space.x, at.screen_space.y,
                this.size * x_amount + 1 - a, this.size * y_amount + 1 - a,
                0,
                0, Math.PI * 2
            );
            ctx.fill();
        }
        return true;
    }
}

class Shadow {
    at: Vec3;
    size: number;
    constructor(at: Vec2, size: number) {
        this.at = new Vec3(at.x, at.y, 0);
        this.size = size;
    }

    up(): Vec3 {
        return new Vec3(0, 0, 1);
    }

    render(at: ProjectedPoint, cam: CameraProjection, ctx: CanvasRenderingContext2D): boolean {
        // in world space, we have x_w^2 + y_w^2 = r^2
        // in screen space, [ x_w y_w z_w ] is transformed to [ x_s y_s ]
        // by the basis vectors x->at.xhat_screen, y->at.yhat_screen, z->at.zhat_screen
        // x_s = x_s_hat * x_w + y_s_hat * y_w + z_s_hat * z_w
        // TODO: Actually use this to render the ellipse

        ctx.fillStyle = "black";
        ctx.beginPath();

        let x_amount = Math.sqrt(Math.pow(at.xhat_screen.x, 2) + Math.pow(at.yhat_screen.x, 2));
        let y_amount = Math.sqrt(Math.pow(at.xhat_screen.y, 2) + Math.pow(at.yhat_screen.y, 2));

        ctx.ellipse(
            at.screen_space.x, at.screen_space.y,
            this.size * x_amount,
            this.size * y_amount,
            0, // rotation
            0, Math.PI * 2,
        );
        ctx.fill();
        return true;
    }
}

const FPS = 60;
let should_draw_gizmo = false;
let canvas = document.getElementById("frame") as HTMLCanvasElement;
let width = window.innerWidth;
let height = window.innerHeight;
//width = Math.min(width, height);
//height = width;

canvas.width = width;
canvas.height = height;
canvas.style.width = `${width}px`;
canvas.style.height = `${height}px`;

let ctx: CanvasRenderingContext2D = canvas.getContext("2d") as CanvasRenderingContext2D;
let at = new Vec3(0, -10, 5);
let camera = new CameraProjection(at, 0, Math.atan(at.z/at.y), 60 * Math.PI / 180 * 1, width, height);

let pressing = new Set();

document.addEventListener("keydown", e => {
    pressing.add(e.code);
    if (e.code === "Space") {
        should_draw_gizmo = !should_draw_gizmo;
    }
});

document.addEventListener("keyup", e => {
    pressing.delete(e.code);
});

function step() {
    let delta = 1 / FPS;
    if (pressing.has("ShiftLeft")) {
        delta *= 0.2;
    }
    if (pressing.has("AltLeft")) {
        delta *= 5;
    }
    let position_delta = new Vec3(0, 0, 0);
    if (pressing.has("KeyW")) {
        position_delta.y += delta;
    }
    if (pressing.has("KeyA")) {
        position_delta.x -= delta;
    }
    if (pressing.has("KeyS")) {
        position_delta.y -= delta;
    }
    if (pressing.has("KeyD")) {
        position_delta.x += delta;
    }
    if (pressing.has("KeyQ")) {
        position_delta.z += delta;
    }
    if (pressing.has("KeyZ")) {
        position_delta.z -= delta;
    }
    camera.origin = camera.origin.add(position_delta.rotate_about_z(camera.yaw));

    if (pressing.has("ArrowRight")) {
        camera.yaw -= delta;
    }
    if (pressing.has("ArrowLeft")) {
        camera.yaw += delta;
    }
    if (pressing.has("ArrowUp")) {
        camera.pitch += delta;
    }
    if (pressing.has("ArrowDown")) {
        camera.pitch -= delta;
    }
    redraw(camera);
    if (should_draw_gizmo) {
        draw_gizmo(ctx, camera);
    }
}

function get_objects(t): Array<Drawable> {
    let objects: Array<Drawable> = [];
    for (let x = 5; x >= -5; x--) {
        for (let y = 5; y >= -5; y--) {
            objects.push(new Ball(new Vec3(x, y, 1), {r: 100+x*10, g: 100+y*10, b: 100}, 0.3));
            objects.push(new Shadow(new Vec2(x, y), 0.3));
        }
    }
    return objects;
}

let start = new Date();
function redraw(camera: CameraProjection) {
    ctx.clearRect(0, 0, width, height);

    let objects = get_objects(new Date().getTime() - start.getTime());
    let rendered = objects
        .map(o => {return {object: o, at: camera.project(o.at, true )}})
        .filter(r => !r.at.behind)
        .sort((a, b) => -(a.at.distance - b.at.distance));

    for (let x of rendered) {
        x.object.render(x.at, camera, ctx);
    }
}


function draw_gizmo(ctx: CanvasRenderingContext2D, cam: CameraProjection) {
    let size = 0.6;
    let distance_away = 3;

    let v = new Vec3(0.0, distance_away, 0.0).rotate_about_x(camera.pitch).rotate_about_z(camera.yaw);
    let gizmo_world = cam.origin.add(v);
    // temporarily set the FOV to a known value so the gizmo doesn't depend on the camera FOV
    let old_fov = cam.fov;
    //camera.fov = Math.PI / 4;

    let gizmo_screen = cam.project(gizmo_world, true);

    let directions = [
        { dir: gizmo_screen.xhat_screen, color: "rgb(0, 0, 255)" },
        { dir: gizmo_screen.yhat_screen, color: "rgb(0, 180, 0)" },
        { dir: gizmo_screen.zhat_screen, color: "rgb(255, 0, 0)" },
    ];

    for (let direction of directions) {
        ctx.beginPath();
        ctx.strokeStyle = direction.color;
        ctx.lineWidth = 4;
        let start = gizmo_screen.screen_space;
        let end = gizmo_screen.screen_space.add(direction.dir.mul(size));
        ctx.moveTo(start.x, start.y);
        ctx.lineTo(end.x, end.y);
        ctx.stroke();
    }

    camera.fov = old_fov;
}

setInterval(step, 1000 / FPS);