btcpayserver/BTCPayServer/wwwroot/crowdfund/services/fireworks.js

addLoadEvent(function(){
var c = document.getElementById("fireworks");
var ctx = c.getContext("2d");

var cH;
var cW;
var bgColor = srvModel.animationColors[0];
var animations = [];

var colorPicker = (function() {
    var colors = srvModel.animationColors;
    var index = 0;
    function next() {
        index = index++ < colors.length-1 ? index : 0;
        return colors[index];
    }
    function current() {
        return colors[index]
    }
    return {
        next: next,
        current: current
    }
})();

function removeAnimation(animation) {
    var index = animations.indexOf(animation);
    if (index > -1) animations.splice(index, 1);
}

function calcPageFillRadius(x, y) {
    var l = Math.max(x - 0, cW - x);
    var h = Math.max(y - 0, cH - y);
    return Math.sqrt(Math.pow(l, 2) + Math.pow(h, 2));
}

function handleEvent(e) {
    if (e.touches) {
        e.preventDefault();
        e = e.touches[0];
    }
    var currentColor = colorPicker.current();
    var nextColor = colorPicker.next();
    var targetR = calcPageFillRadius(e.pageX, e.pageY);
    var rippleSize = Math.min(200, (cW * .4));
    var minCoverDuration = 750;

    var pageFill = new Circle({
        x: e.pageX,
        y: e.pageY,
        r: 0,
        fill: nextColor
    });
    var fillAnimation = anime({
        targets: pageFill,
        r: targetR,
        duration:  Math.max(targetR / 2 , minCoverDuration ),
        easing: "easeOutQuart",
        complete: function(){
            bgColor = pageFill.fill;
            removeAnimation(fillAnimation);
        }
    });

    var ripple = new Circle({
        x: e.pageX,
        y: e.pageY,
        r: 0,
        fill: currentColor,
        stroke: {
            width: 3,
            color: currentColor
        },
        opacity: 1
    });
    var rippleAnimation = anime({
        targets: ripple,
        r: rippleSize,
        opacity: 0,
        easing: "easeOutExpo",
        duration: 900,
        complete: removeAnimation
    });

    var particles = [];
    for (var i=0; i<32; i++) {
        var particle = new Circle({
            x: e.pageX,
            y: e.pageY,
            fill: currentColor,
            r: anime.random(24, 48)
        })
        particles.push(particle);
    }
    var particlesAnimation = anime({
        targets: particles,
        x: function(particle){
            return particle.x + anime.random(rippleSize, -rippleSize);
        },
        y: function(particle){
            return particle.y + anime.random(rippleSize * 1.15, -rippleSize * 1.15);
        },
        r: 0,
        easing: "easeOutExpo",
        duration: anime.random(1000,1300),
        complete: removeAnimation
    });
    animations.push(fillAnimation, rippleAnimation, particlesAnimation);
}

function extend(a, b){
    for(var key in b) {
        if(b.hasOwnProperty(key)) {
            a[key] = b[key];
        }
    }
    return a;
}

var Circle = function(opts) {
    extend(this, opts);
}

Circle.prototype.draw = function() {
    ctx.globalAlpha = this.opacity || 1;
    ctx.beginPath();
    ctx.arc(this.x, this.y, this.r, 0, 2 * Math.PI, false);
    if (this.stroke) {
        ctx.strokeStyle = this.stroke.color;
        ctx.lineWidth = this.stroke.width;
        ctx.stroke();
    }
    if (this.fill) {
        ctx.fillStyle = this.fill;
        ctx.fill();
    }
    ctx.closePath();
    ctx.globalAlpha = 1;
}

anime({
    duration: Infinity,
    update: function() {
        ctx.fillStyle = bgColor;
        ctx.fillRect(0, 0, cW, cH);
        animations.forEach(function(anim) {
            anim.animatables.forEach(function(animatable) {
                animatable.target.draw();
            });
        });
    }
});

var resizeCanvas = function() {
    cW = window.innerWidth;
    cH = window.innerHeight;
    c.width = cW * devicePixelRatio;
    c.height = cH * devicePixelRatio;
    ctx.scale(devicePixelRatio, devicePixelRatio);
};

(function init() {
    resizeCanvas();
    
    window.addEventListener("resize", resizeCanvas);
})();

window.fireworks = function(){
    var fauxClick = new Event("mousedown");
    fauxClick.pageX = anime.random( 0, cW );
    fauxClick.pageY = anime.random(0, cH );

    var middleSpaceX = cW * 0.6;
    var middleSpaceY = cH * 0.6;
    var middleSpaceX1 = middleSpaceX /2;
    var middleSpaceX2 = middleSpaceX1 + middleSpaceX;
    var middleSpaceY1 = middleSpaceY /2;
    var middleSpaceY2 = middleSpaceY1 + middleSpaceY;
    while(true){
        if(fauxClick.pageX > middleSpaceX1 && fauxClick.pageX < middleSpaceX2){
            fauxClick.pageX = anime.random( 0, cW );
            continue;
        }
        if(fauxClick.pageY > middleSpaceY1 && fauxClick.pageY < middleSpaceY2){
            fauxClick.pageY = anime.random( 0, cH );
            continue;
        }
        break;
    }
    handleEvent(fauxClick)
};
});