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

class FrameHandlerImpl extends NSObject {

private _owner: WeakRef<FPSCallback>;

public static initWithOwner(owner: WeakRef<FPSCallback>): FrameHandlerImpl {

let handler = <FrameHandlerImpl>FrameHandlerImpl.new();

handler._owner = owner;

return handler;

}

public handleFrame(sender: CADisplayLink): void {

let owner = this._owner.get();

if (owner) {

owner._handleFrame(sender);

}

}

public static ObjCExposedMethods = {

"handleFrame": { returns: interop.types.void, params: [CADisplayLink] }

};

}

export class FPSCallback implements definition.FPSCallback {

public running: boolean;

private onFrame: Function;

private displayLink: CADisplayLink;

private impl: FrameHandlerImpl;

constructor(onFrame: (currentTimeMillis: number) => void) {

this.onFrame = onFrame;

this.impl = FrameHandlerImpl.initWithOwner(new WeakRef(this));

this.displayLink = CADisplayLink.displayLinkWithTargetSelector(this.impl, "handleFrame");

this.displayLink.paused = true;

this.displayLink.addToRunLoopForMode(NSRunLoop.currentRunLoop(), NSDefaultRunLoopMode);

// UIScrollView (including in UIITableView) will run a loop in UITrackingRunLoopMode during scrolling.

// If we do not add the CADisplayLink in this mode, it would appear paused during scrolling.

this.displayLink.addToRunLoopForMode(NSRunLoop.currentRunLoop(), UITrackingRunLoopMode);

}

public start() {

if (this.running) {

return;

}

this.running = true;

this.displayLink.paused = false;

}

public stop() {

if (!this.running) {

return;

}

this.displayLink.paused = true;

this.running = false;

}

public _handleFrame(sender: CADisplayLink) {

if (!this.running) {

return;

}

// timestamp is CFTimeInterval, which is in seconds, the onFrame callback expects millis, so multiply by 1000

this.onFrame(sender.timestamp * 1000);

}

}