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());
    }
}

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());
    }

    // 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 {
    camera_space: Vec2, // [-1, 1]x[-1, 1]
    distance: number,
    in_view: boolean, // outside view?
    behind: boolean,
}

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

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

    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 distance = camera_space_3.y;
        let behind = camera_space_3.y <= 0;
        let in_view = !behind;// && (camera_space.x >= -1 && camera_space.x <= 1 && camera_space.y >= -1 && camera_space.y < 1);
        return {
            camera_space: camera_space,
            distance: distance,
            in_view: in_view,
            behind: behind,
        };
    }
}

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;
    constructor(at: Vec3, color: RGB) {
        this.at = at;
        this.color = color;
    }
    render(at: ProjectedPoint, cam: CameraProjection, ctx: CanvasRenderingContext2D): boolean {
        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.arc((at.camera_space.x / 2 + 0.5) * width, (-at.camera_space.y / 2 + 0.5) * height, 100 / at.distance + 1 - a, 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; height: ${height}px;`;

let ctx: CanvasRenderingContext2D = canvas.getContext("2d") as CanvasRenderingContext2D;
let camera = new CameraProjection(new Vec3(0, -10, 5), 0, -0.5, 60 * Math.PI / 180 * 1);

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);
    }
}

let objects: Array<Drawable> = [];
for (let x = 5; x >= -5; x--) {
    for (let y = 5; y >= -5; y--) {
        for (let z = -1; z <= 1; z += 2) {
            objects.push(new Ball(new Vec3(x, y, z), {r: 100+x*10, g: 100+y*10, b: 100+50*z}));
        }
    }
}

function redraw(camera: CameraProjection) {
    ctx.clearRect(0, 0, width, height);

    let rendered = objects
        .map(o => {return {object: o, at: camera.project(o.at, true )}})
        .filter(r => r.at.in_view)
        .sort((a, b) => -(a.at.distance - b.at.distance));

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

const DIRECTIONS = [
    {dir: new Vec3(1, 0, 0), color: "rgb(0, 0, 255)"},
    {dir: new Vec3(0, 1, 0), color: "rgb(0, 180, 0)"},
    {dir: new Vec3(0, 0, 1), color: "rgb(255, 0, 0)"},
];

function draw_gizmo(ctx: CanvasRenderingContext2D, cam: CameraProjection) {
    let size = 100;
    let at = new Vec2(width / 2, width / 2);

    let old_fov = camera.fov;
    camera.fov = Math.PI / 4;

    let distance = 100;
    let gizmo_at = camera.camera_to_world(new Vec3(0, distance, 0), false);

    for (let direction of DIRECTIONS) {
        let gizmo_up = gizmo_at.add(direction.dir);
        let up_cam = camera.project(gizmo_up, false);
        let xy = up_cam.camera_space.mul(distance);
        xy = xy.mul(size / 3);

        ctx.beginPath();
        ctx.strokeStyle = direction.color;
        ctx.lineWidth = 4;
        ctx.moveTo(at.x, at.y);
        ctx.lineTo(at.x + xy.x, at.y - xy.y);
        ctx.stroke();
    }

    camera.fov = old_fov;
}

setInterval(step, 1000 / FPS);