function d(x1, y1, x2, y2){
    return Math.sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1));
}

function areCircleColliding(c1, c2){
    return d(c1.x, c1.y, c2.x, c2.y) < c1.r + c2.r;
}

class Player{
    constructor(x, y, color){
        this.x = x;
        this.y = y;
        this.r = 20;
        this.speed = 5;
        this.color = color;
        this.reload_time = 20;
        this.reload = 0;
        this.hp = 20;
    }
    shoot(tX, tY){
        if (this.reload <= 0){
            b.push(new Bullet(this.x, this.y, tX, tY, this.color));
            this.reload = this.reload_time;
        }
    }
    update(){
        this.reload--;
        for (let i=0; i<b.length; ++i){
            if (b[i].color != this.color && areCircleColliding(b[i], this)){
                this.hp--;
                b[i] = b[b.length-1];
                b.pop();
                --i;
            }
        }
        if (this.x < 0) this.x = 0;
        if (this.x > 800) this.x = 800;
        if (this.y < 0) this.y = 0;
        if (this.y > 600) this.y = 600;
    }
    moveKeyboard(){
        if (isKeyPressed[87]) this.y -= this.speed;
        if (isKeyPressed[83]) this.y += this.speed;
        if (isKeyPressed[65]) this.x -= this.speed;
        if (isKeyPressed[68]) this.x += this.speed;
    }
    moveEnemy(){
        let xrun=0, yrun=0, mint=-1;
        for (let i=0; i<b.length; ++i){
            if (b[i].color != this.color){
                let alpha = Math.atan2(b[i].dy, b[i].dx) - Math.atan2(this.y-b[i].y, this.x - b[i].x);
                //console.log("alpha:", alpha);
                let dist = d(this.x, this.y, b[i].x, b[i].y) * Math.cos(alpha);
                //console.log("dist:", dist);
                let t = Math.max(dist/b[i].speed, 0);
                //console.log("t:", t);
                let bx = b[i].x + b[i].dx*t;
                let by = b[i].y + b[i].dy*t;
                if (d(bx, by, this.x, this.y) < this.r + b[i].r + this.r){
                    if (mint==-1 || t < mint){
                        mint = t;
                        xrun = bx;
                        yrun = by;
                    }
                }
            }
        }
        if (mint != -1){
            let dist = d(xrun, yrun, this.x, this.y);
            let dx = (this.x-xrun)/dist*this.speed;
            let dy = (this.y-yrun)/dist*this.speed;
            if (dist == 0){
                dx = 0
                dy = this.speed;
            }
            this.x += dx;
            this.y += dy;
        }
        let ind = -1, mind = -1;
        for (let i=0; i<p.length; ++i){
            if (p[i].color != this.color && (mind == -1 || mind > d(this.x, this.y, p[i].x, p[i].y))){
                ind = i;
                mind = d(this.x, this.y, p[i].x, p[i].y);
            }
        }
        if (ind != -1){
            this.shoot(p[ind].x, p[ind].y);
        }
    }
    draw(){
        if (this.hp <= 0) return;
        context.fillStyle = this.color;
        context.beginPath();
        context.arc(this.x, this.y, this.r, 0, 2*Math.PI);
        context.fill();
    }
};

class Bullet{
    constructor(x, y, tX, tY, color){
        this.x = x;
        this.y = y;
        this.r = 5;
        this.color = color;
        this.speed = 12;
        let dist = d(x, y, tX, tY);
        this.dx = (tX-x)/dist*this.speed;
        this.dy = (tY-y)/dist*this.speed;
    }
    update(){
        this.x += this.dx;
        this.y += this.dy;
    }
    draw(){
        context.fillStyle = this.color;
        context.beginPath();
        context.arc(this.x, this.y, this.r, 0, 2*Math.PI);
        context.fill();
    }
};

var p = [];
for (let i=0; i<13; ++i){
    if (i%2 == 0){
        p[i] = new Player(Math.random()*800, Math.random()*600, "blue");
    }else{
        p[i] = new Player(Math.random()*800, Math.random()*600, "red");
    }
}
var b = [];

function update() {
    for (let i=0; i<p.length; ++i){
        if (p[i].hp <= 0){
            p[i] = p[p.length-1];
            p.pop();
            i--;
        }else{
            p[i].update();
            p[i].moveEnemy();
        }
    }
    for (let i=0; i<b.length; ++i) b[i].update();
}
function draw() {
    for (let i=0; i<p.length; ++i){
        p[i].draw();
    }
    for (let i=0; i<b.length; ++i) b[i].draw();
};
function keyup(key) {
};
function mouseup() {
    p[0].shoot(mouseX, mouseY);
};