import fpsNative = require("fps-meter/fps-native");

var callbacks = {},

idCounter = 0,

_minFps = 1000,

framesRendered = 0,

frameStartTime = 0;

function doFrame(currentTimeMillis: number) {

var fps = 0;

if (frameStartTime > 0) {

// take the span in milliseconds

var timeSpan = (currentTimeMillis - frameStartTime);

framesRendered++;

if (timeSpan > 1000) {

fps = framesRendered * 1000 / timeSpan;

if (fps < _minFps) {

_minFps = fps;

}

notify(fps);

frameStartTime = currentTimeMillis;

framesRendered = 0;

}

} else {

frameStartTime = currentTimeMillis;

}

}

var native: fpsNative.FPSCallback;

function ensureNative() {

if (!native) {

native = new fpsNative.FPSCallback(doFrame);

}

}

export function reset() {

_minFps = 1000;

frameStartTime = 0;

framesRendered = 0;

}

export function running(): boolean {

if (!native) {

return false;

}

return native.running;

}

export function minFps(): number {

return _minFps;

}

export function start() {

ensureNative();

native.start();

}

export function stop() {

if (!native) {

return;

}

native.stop();

reset();

}

export function addCallback(callback: (fps: number, minFps?: number) => void): number {

var id = idCounter;

callbacks[id] = callback;

idCounter++;

return id;

}

export function removeCallback(id: number) {

if (id in callbacks) {

delete callbacks[id];

}

}

function notify(fps) {

var callback: Function;

for (var id in callbacks) {

callback = callbacks[id];

callback(fps, _minFps);

}

}