homework/work in class/canvas_2/main.js

const canvas = document.getElementById('canvas')
const ctx    = canvas.getContext('2d')

const width  = canvas.width;
const height = canvas.height;

let current;
let selection = []

const tools = {
    graffity: {
        mousemove(e){ //e.buttons 0b00000x11 & 0b00000100 == x
            (e.buttons & 0b001) && new Circle(e.layerX, e.layerY, +size.value, color.value)
        }
    },

    circle: {
        mousedown(e){
            current = new Circle(e.layerX,e.layerY, 1, color.value)
        },
        mousemove(e){
            if (!current) return;

            current.radius = current.distanceTo(e.layerX, e.layerY)
            Drawable.drawAll()
        },
        mouseup(e){
            current = null
        }
    },

    line: { //ctrl-c ctrl-v в rectangle. Так же добавьте его в <select id='tool'>
        mousedown(e){
            current = new Line(e.layerX, e.layerY, 0, 0, color.value, +size.value)
        },
        mousemove(e){
            if (!current) return;

            current.width = e.layerX - current.x
            current.height = e.layerY - current.y

            Drawable.drawAll()
        },
        mouseup(e){
            current = null
        }
    },

    rectangle: { 
        mousedown(e){
            current = new Rectangle(e.layerX, e.layerY, 0, 0, color.value, +size.value)
        },
        mousemove(e){
            if (!current) return;

            current.width = e.layerX - current.x
            current.height = e.layerY - current.y

            Drawable.drawAll()
        },
        mouseup(e){
            current = null
        }
    },

    ellipse: { 
        mousedown(e){
            current = new Ellips(e.layerX, e.layerY, 0, 0, color.value, +size.value)
        },
        mousemove(e){
            if (!current) return;

            current.width = e.layerX - current.x
            current.height = e.layerY - current.y

            Drawable.drawAll()
        },
        mouseup(e){
            current = null
        }
    },

    select: {
        click(e){
            console.log(e)
            let found = Drawable.instances.filter(c => c.in && c.in(e.layerX, e.layerY));
            if (found.length){
                if (e.ctrlKey){
                    selection.push(found.pop());
                }
                else {
                    selection = [found.pop()];
                }
            }
            else {
                if (!e.ctrlKey) selection = []
            }

            Drawable.drawAll(selection)
        },
        mousedown(e){
            //
        },
        mousemove(e){

        },
        mouseup(e){
            //x,y, w, h прямоугольника
            //selection - только те элеменеты Drawable.instances которые в границах прямоугольника.
        },
    }
}

function superHandler(evt){
    let t = tools[tool.value]
    if (typeof t[evt.type] === 'function')
        t[evt.type].call(this, evt)
}

canvas.onmousemove = superHandler
canvas.onmouseup   = superHandler
canvas.onmousedown = superHandler
canvas.onclick = superHandler

////

function Drawable(){
    Drawable.addInstance(this);   
}

const distance = (x1,y1, x2, y2) => ((x1-x2)**2 + (y1-y2)**2)**0.5

Drawable.prototype.draw = function(){};
Drawable.prototype.distanceTo = function(x,y){
    if (typeof this.x !== 'number' ||
        typeof this.y !== 'number'){
        return NaN
    }
    return distance(this.x, this.y, x, y)
};
Drawable.instances = [];
Drawable.addInstance = function(item){
    Drawable.instances.push(item);
}

Drawable.drawAll = function(selection=[]){
    ctx.clearRect(0,0,width,height);
    Drawable.forAll(item => item.draw())
    selection.forEach(item  => item.draw(true))
}

Drawable.forAll = function(callback){
    for(var i = 0; i<Drawable.instances.length;i++){
        callback(Drawable.instances[i])
    }
}

class Circle extends Drawable {
    //__proto__: Drawable.prototype
    constructor(x,y,radius, color){
        super()
        this.x = x;
        this.y = y;
        this.radius = radius;
        this.color = color;

        this.draw(); 
    }

    draw(selected){
        ctx.beginPath();
        ctx.arc(this.x, this.y, this.radius, 0, 2 * Math.PI);
        ctx.closePath();
        ctx.fillStyle = this.color;
        if (selected){
            ctx.lineWidth = 2
            ctx.stroke();
        }
        ctx.fill();
    }

    in(x,y){
        return this.distanceTo(x,y) < this.radius
    }

    inBounds(x,y,w,h){ // x = 100, this.x = 102, w = 5
        return  this.x >= x && this.x <= x + w &&
                this.y >= y && this.y <= y + h 
    }
}

class Line extends Drawable { //смочь скопировать в Rectangle и поменять отприсовку
    constructor(x,y, width, height, color, lineWidth){
        super()
        this.x      = x;
        this.y      = y;
        this.width  = width;
        this.height = height;
        this.color  = color;
        this.lineWidth  = lineWidth;

        this.draw(); 
    }
    
    draw(selected){
        ctx.beginPath();
        ctx.moveTo(this.x, this.y);
        ctx.lineTo(this.x + this.width, this.y + this.height);
        ctx.closePath();
        ctx.strokeStyle = this.color;
        ctx.lineWidth   = this.lineWidth
        ctx.stroke();
    }

    in(x, y) {
        let rotateLine = Math.atan2(this.height, this.width)
        let rotCursor = Math.atan2(y - this.y, x - this.x)
        let distanceToPoint = distance(x, y, this.x, this.y)
        let angleLine = rotCursor - rotateLine
        let rotateX = Math.cos(angleLine) * distanceToPoint
        let rotateY = Math.sin(angleLine) * distanceToPoint
        return rotateX >= 0 && rotateX <= this.length && rotateY <= this.lineWidth/2 && rotateY >= -this.lineWidth/2
    }
    get length(){
        return this.distanceTo(this.x + this.width, this.y + this.height)
    }
} 

class Rectangle extends Drawable { 
    constructor(x,y, width, height, color, lineWidth){
        super()
        this.x      = x;
        this.y      = y;
        this.width  = width;
        this.height = height;
        this.color  = color;
        this.lineWidth = lineWidth;

        this.draw(); 
    }
    
    draw(selected){
        ctx.beginPath();
        ctx.rect(this.x, this.y, this.width, this.height);
        ctx.closePath();
        ctx.fillStyle = this.color;
        ctx.lineWidth = 2;
        ctx.fill();
        ctx.stroke();
    }

    in(x, y) {
        return  this.x <= x &&this.x <= this.x + this.width && 
                this.y <= y && this.y <= this.y + this.height
    }
} 

class Ellips extends Drawable { 
    constructor(x, y, width, height, color, lineWidth){
        super()
        this.x      = x;
        this.y      = y;
        this.width  = width;
        this.height = height;
        this.color  = color;
        this.lineWidth = lineWidth;

        this.draw(); 
    }
    
    draw(selected){
        ctx.beginPath();
        ctx.ellipse(this.x + this.width / 2, this.y + this.height / 2, this.width / 2, this.height / 2, 0, 0, 2 * Math.PI);
        ctx.closePath();
        ctx.fillStyle = this.color;
        ctx.lineWidth = 2;
        ctx.fill();
        ctx.stroke();
    }

    in(x, y) {
        const rx = this.width / 2
        const ry = this.height / 2
        const h = this.x + rx
        const k = this.y + ry

        return ((((x - h) ** 2) / ((rx) ** 2)) + (((y - k) ** 2) / ((ry) ** 2))) <= 1
    }
} 

color.onchange = () => {
    selection.forEach(c => c.color = color.value)
    Drawable.drawAll(selection)
}

document.getElementById('delete').onclick = () =>{
    Drawable.instances = Drawable.instances.filter(item => !selection.includes(item))
    selection = []
    Drawable.drawAll()
}

//new Line(0,0,100,100, "red")
////new Circle(30,30,10, "red")

////canvas.onmousemove = function(e){
////}

//undo.onclick = function(){
    //Drawable.instances.pop()
    ////Drawable.instances = []
    //Drawable.drawAll()
//}