Traffic Light Simulator

var northBound = document.getElementById("northBound");
var southBound = document.getElementById("southBound");
var eastBound = document.getElementById("eastBound");
var westBound = document.getElementById("westBound");

var signalGreen = "light-green";
var signalYellow = "light-yellow";
var signalRed = "light-red";

var greenTimer = 10000;
var yellowTimer = 3000;

var stopSimulation = false;


// Lights work on two groups
// North and South are one group
// East and West are another group
// Only one group can be active at a time
var norSouActive = false;

function startSimulation() {
    console.log('DEBUG: Triggered start simulation');
    setupSimulation();
};

function stopSimulation() {
    stopSimulation = true;
    console.log('stopping simulation...');
};

function setupSimulation() {
    // North and South traffic go first
    norSouActive = true;
    console.log('initializing norSouGroup to green');
    switchNorthSouthGroup('g');

    // Ensure West and East are stopped
    console.log('initializing easWesGroup to red');
    switchEastWestGroup('r');

    runSimulation();
};

function runSimulation() {
    console.log('prepareForChange timer...');
    setTimeout(prepareForChange, greenTimer);
    console.log('changeGroup...');
    changeGroup();
    console.log('runSimulation');
    runSimulation();
};

function prepareForChange() {
    if(norSouActive) {
        switchNorthSouthGroup('y');
        setTimeout(changeGroup(), yellowTimer);
    } else {
        switchEastWestGroup('y');
        setTimeout(changeGroup(), yellowTimer);
    }
};

function changeGroup() {
    if(norSouActive) {
        switchNorthSouthGroup('r');
        switchEastWestGroup('g');
    } else {
        switchEastWestGroup('r');
        switchNorthSouthGroup('g');
    }
};

// g - green y - yellow r - red
function switchEastWestGroup(status) {
    switch(status) {
        case "g":
            westBound.className = "grid-item " + signalGreen;
            eastBound.className = "grid-item " + signalGreen;
            break;
        case "y":
            westBound.className = "grid-item " + signalYellow;
            eastBound.className = "grid-item " + signalYellow;
            break;
        case "r":
            westBound.className = "grid-item " + signalRed;
            eastBound.className = "grid-item " + signalRed;
            break;
    }
};

// g - green y - yellow r - red
function switchNorthSouthGroup(status) {
    switch(status) {
        case "g":
            northBound.className = "grid-item " + signalGreen;
            southBound.className = "grid-item " + signalGreen;
            break;
        case "y":
            northBound.className = "grid-item " + signalYellow;
            southBound.className = "grid-item " + signalYellow;
            break;
        case "r":
            northBound.className = "grid-item " + signalRed;
            southBound.className = "grid-item " + signalRed;
            break;
    }
};