app.js

'use strict';

var height = $(window).height();
var width = $(window).width();

var game = new Phaser.Game(width, height, Phaser.AUTO, 'aws-serverless-samfarm', {
    preload: preload,
    create: create,
    update: update
});

var sprites;
var DESIRED_SAM_COUNT = 1;
var CURRENT_SAM_COUNT = 1;
var MAX_SAM_CHANGE = 10;
var LAST_CHANGE_TIME = Date.now();
var GET_SAM_COUNT_URL = 'https://68eks9w83m.execute-api.us-east-1.amazonaws.com/Prod/sam';
var TIME_BETWEEN_COUNT_UPDATE_MS = 4000;

function preload() {
    game.load.spritesheet('spinner', 'squirrel.png', 64, 64);
    game.scale.scaleMode = Phaser.ScaleManager.SHOW_ALL;
}

function create() {
    game.stage.disableVisibilityChange = true;
    game.stage.backgroundColor = '#967da7';
    sprites = game.add.physicsGroup(Phaser.Physics.ARCADE);
    createSprites(DESIRED_SAM_COUNT);
}

function createSprites(numberOfSprites) {
    for (var i = 0; i < numberOfSprites; i++) {
        var initX = game.rnd.integerInRange(100, width - 100);
        var initY = game.rnd.integerInRange(32, height - 32);
        var velX = game.rnd.integerInRange(-200, 200);
        var velY = game.rnd.integerInRange(-200, 200);

        var s = sprites.create(initX, initY, 'spinner');
        s.body.velocity.set(velX, velY);
        s.scale.setTo(1.4, 1.4);
    }

    sprites.setAll('body.collideWorldBounds', true);
    sprites.setAll('body.bounce.x', 1);
    sprites.setAll('body.bounce.y', 1);
}

function update() {
    game.physics.arcade.collide(sprites);

    var countToChange = DESIRED_SAM_COUNT - CURRENT_SAM_COUNT;

    samCountUpdate(countToChange);
}

function samCountUpdate(samCountChange) {

    var currTime = Date.now();

    // Only update the number of SAMs on the screen every second
    if (currTime - LAST_CHANGE_TIME > 1000) {

        // If we are increasing the amount of SAMs on the screen, take the min of the requested change value and
        // the max number that can be updated at a time.
        if (samCountChange > 0) {
            samCountChange = Math.min(samCountChange, MAX_SAM_CHANGE);

            createSprites(samCountChange);
            CURRENT_SAM_COUNT += samCountChange;
            LAST_CHANGE_TIME = currTime;

        } else if (samCountChange < 0) {
            // Else if we are decreasing the amount of SAMs on the screen, take the max of the negative change value and
            // the maximum that can be changed at a time
            samCountChange = Math.abs(Math.max(samCountChange, -MAX_SAM_CHANGE));

            // For each of the SAMs that are being removed, kill it's sprite
            for (var i = 0; i < samCountChange; i++) {
                sprites.children[i].kill();
            }

            // Remove killed SAMs from the array
            sprites.children.splice(0, samCountChange);

            CURRENT_SAM_COUNT -= samCountChange;
            LAST_CHANGE_TIME = currTime;
        }
    }
}

// Every X seconds as defined in the variable TIME_BETWEEN_COUNT_UPDATE_MS, call our API endpoint to tell use how many
// SAMs should be on the screen.
setInterval(() => {
    // Make frontend call to lambda
    $.get({
        url: GET_SAM_COUNT_URL
    }).done(function(data) {
        DESIRED_SAM_COUNT = data;
    });

}, TIME_BETWEEN_COUNT_UPDATE_MS);