<!-- Info.plist -->
<key>CADisableMinimumFrameDurationOnPhone</key>
<true/>

// ❌ WRONG: Implicit 60fps (default)
let mtkView = MTKView(frame: frame, device: device)
mtkView.delegate = self
// Running at 60fps even on ProMotion!

// ✅ CORRECT: Explicit 120fps request
let mtkView = MTKView(frame: frame, device: device)
mtkView.preferredFramesPerSecond = 120
mtkView.isPaused = false
mtkView.enableSetNeedsDisplay = false  // Continuous, not on-demand
mtkView.delegate = self

// ❌ WRONG: Timer-based render loop (drifts, wastes frame time)
Timer.scheduledTimer(withTimeInterval: 1.0/120.0, repeats: true) { _ in
    self.render()
}

// ❌ WRONG: Default CADisplayLink (may hint 60)
let displayLink = CADisplayLink(target: self, selector: #selector(render))
displayLink.add(to: .main, forMode: .common)

// ✅ CORRECT: Explicit frame rate range
let displayLink = CADisplayLink(target: self, selector: #selector(render))
displayLink.preferredFrameRateRange = CAFrameRateRange(
    minimum: 80,      // Minimum acceptable
    maximum: 120,     // Preferred maximum
    preferred: 120    // What you want
)
displayLink.add(to: .main, forMode: .common)

// 30Hz and 60Hz get priority scheduling
let prioritizedRange = CAFrameRateRange(
    minimum: 30,
    maximum: 60,
    preferred: 60
)
displayLink.preferredFrameRateRange = prioritizedRange

class MetalRenderer: NSObject, CAMetalDisplayLinkDelegate {
    var displayLink: CAMetalDisplayLink?
    var metalLayer: CAMetalLayer!

    func setupDisplayLink() {
        displayLink = CAMetalDisplayLink(metalLayer: metalLayer)
        displayLink?.delegate = self
        displayLink?.preferredFrameRateRange = CAFrameRateRange(
            minimum: 60,
            maximum: 120,
            preferred: 120
        )
        // Control render latency (in frames)
        displayLink?.preferredFrameLatency = 2
        displayLink?.add(to: .main, forMode: .common)
    }

    func metalDisplayLink(_ link: CAMetalDisplayLink, needsUpdate update: CAMetalDisplayLink.Update) {
        // update.drawable - The drawable to render to
        // update.targetTimestamp - Deadline to finish rendering
        // update.targetPresentationTimestamp - When frame will display

        guard let drawable = update.drawable else { return }

        let workingTime = update.targetTimestamp - CACurrentMediaTime()
        // workingTime = seconds available before deadline

        // Render to drawable...
        renderFrame(to: drawable)
    }
}

// Check programmatically
if ProcessInfo.processInfo.isLowPowerModeEnabled {
    // System caps display to 60Hz
}

// Observe changes
NotificationCenter.default.addObserver(
    forName: .NSProcessInfoPowerStateDidChange,
    object: nil,
    queue: .main
) { _ in
    let isLowPower = ProcessInfo.processInfo.isLowPowerModeEnabled
    self.adjustRenderingForPowerState(isLowPower)
}

// Check thermal state
switch ProcessInfo.processInfo.thermalState {
case .nominal, .fair:
    preferredFramesPerSecond = 120
case .serious, .critical:
    preferredFramesPerSecond = 60  // Reduce proactively
@unknown default:
    break
}

// Observe thermal changes
NotificationCenter.default.addObserver(
    forName: ProcessInfo.thermalStateDidChangeNotification,
    object: nil,
    queue: .main
) { _ in
    self.adjustForThermalState()
}

func draw(in view: MTKView) {
    guard let commandBuffer = commandQueue.makeCommandBuffer() else { return }

    // Your rendering code...

    commandBuffer.addCompletedHandler { buffer in
        let gpuTime = buffer.gpuEndTime - buffer.gpuStartTime
        let gpuMs = gpuTime * 1000

        if gpuMs > 8.33 {
            print("⚠️ GPU: \(String(format: "%.2f", gpuMs))ms exceeds 120Hz budget")
        }
    }

    commandBuffer.commit()
}

// If you can't sustain 8.33ms, explicitly target 60 for smooth cadence
if averageGpuTime > 8.33 && averageGpuTime <= 16.67 {
    mtkView.preferredFramesPerSecond = 60
}

// BAD: Inconsistent intervals despite ~40 FPS average
Frame 1: 25ms
Frame 2: 40ms  ← stutter
Frame 3: 25ms
Frame 4: 40ms  ← stutter

// GOOD: Consistent intervals at 30 FPS
Frame 1: 33ms
Frame 2: 33ms
Frame 3: 33ms
Frame 4: 33ms

func draw(in view: MTKView) {
    guard let commandBuffer = commandQueue.makeCommandBuffer(),
          let drawable = view.currentDrawable else { return }

    // Render to drawable...

    // Present with minimum 33ms between frames (30 FPS target)
    commandBuffer.present(drawable, afterMinimumDuration: 0.033)
    commandBuffer.commit()
}

// Present at specific Mach absolute time
let presentTime = CACurrentMediaTime() + 0.033
commandBuffer.present(drawable, atTime: presentTime)

drawable.addPresentedHandler { drawable in
    let actualTime = drawable.presentedTime
    if actualTime == 0.0 {
        // Frame was dropped!
        print("⚠️ Frame dropped")
    } else {
        print("Frame presented at: \(actualTime)")
    }
}

class SmoothRenderer: NSObject, MTKViewDelegate {
    private var targetFrameDuration: CFTimeInterval = 1.0 / 60.0  // 60 FPS target

    func draw(in view: MTKView) {
        guard let commandBuffer = commandQueue.makeCommandBuffer(),
              let drawable = view.currentDrawable else { return }

        renderScene(to: drawable)

        // Use frame pacing to ensure consistent intervals
        commandBuffer.present(drawable, afterMinimumDuration: targetFrameDuration)
        commandBuffer.commit()
    }

    func adjustTargetFrameRate(canSustain fps: Int) {
        switch fps {
        case 90...:
            targetFrameDuration = 1.0 / 120.0
        case 50...:
            targetFrameDuration = 1.0 / 60.0
        default:
            targetFrameDuration = 1.0 / 30.0
        }
    }
}

Expected Frame Lifetime = Begin Time → Presentation Time
Actual Frame Lifetime = Begin Time → Actual Vsync

Hitch Duration = Actual - Expected

// ❌ This says 120 even when system caps you to 60
let maxFPS = UIScreen.main.maximumFramesPerSecond
// Reports capability, not actual rate!

// ✅ Measure from CADisplayLink timing
@objc func displayLinkCallback(_ link: CADisplayLink) {
    // Time available to prepare next frame
    let workingTime = link.targetTimestamp - CACurrentMediaTime()

    // Actual interval since last callback
    if lastTimestamp > 0 {
        let interval = link.timestamp - lastTimestamp
        let actualFPS = 1.0 / interval
    }
    lastTimestamp = link.timestamp
}

MTL_HUD_ENABLED=1

import MetricKit

class MetricsManager: NSObject, MXMetricManagerSubscriber {
    func didReceive(_ payloads: [MXMetricPayload]) {
        for payload in payloads {
            if let animationMetrics = payload.animationMetrics {
                // Ratio of time spent hitching during scroll
                let scrollHitchRatio = animationMetrics.scrollHitchTimeRatio

                // Ratio of time spent hitching in all animations
                if #available(iOS 17.0, *) {
                    let hitchRatio = animationMetrics.hitchTimeRatio
                }

                analyzeHitchMetrics(scrollHitchRatio: scrollHitchRatio)
            }
        }
    }
}

// Register for metrics
MXMetricManager.shared.add(metricsManager)

class AdaptiveRenderer: NSObject, MTKViewDelegate {
    private var recentFrameTimes: [Double] = []
    private let sampleCount = 30
    private var targetFrameDuration: CFTimeInterval = 1.0 / 60.0

    func draw(in view: MTKView) {
        guard let commandBuffer = commandQueue.makeCommandBuffer(),
              let drawable = view.currentDrawable else { return }

        let startTime = CACurrentMediaTime()
        renderScene(to: drawable)
        let frameTime = (CACurrentMediaTime() - startTime) * 1000

        updateTargetRate(frameTime: frameTime, view: view)

        commandBuffer.present(drawable, afterMinimumDuration: targetFrameDuration)
        commandBuffer.commit()
    }

    private func updateTargetRate(frameTime: Double, view: MTKView) {
        recentFrameTimes.append(frameTime)
        if recentFrameTimes.count > sampleCount {
            recentFrameTimes.removeFirst()
        }

        let avgFrameTime = recentFrameTimes.reduce(0, +) / Double(recentFrameTimes.count)
        let thermal = ProcessInfo.processInfo.thermalState
        let lowPower = ProcessInfo.processInfo.isLowPowerModeEnabled

        // Constrain based on what we can sustain AND system state
        if lowPower || thermal >= .serious {
            view.preferredFramesPerSecond = 30
            targetFrameDuration = 1.0 / 30.0
        } else if avgFrameTime < 7.0 && thermal == .nominal {
            view.preferredFramesPerSecond = 120
            targetFrameDuration = 1.0 / 120.0
        } else if avgFrameTime < 14.0 {
            view.preferredFramesPerSecond = 60
            targetFrameDuration = 1.0 / 60.0
        } else {
            view.preferredFramesPerSecond = 30
            targetFrameDuration = 1.0 / 30.0
        }
    }
}

class FrameDropMonitor {
    private var expectedPresentTime: CFTimeInterval = 0
    private var dropCount = 0

    func trackFrame(drawable: MTLDrawable, expectedInterval: CFTimeInterval) {
        drawable.addPresentedHandler { [weak self] drawable in
            guard let self = self else { return }

            if drawable.presentedTime == 0.0 {
                self.dropCount += 1
                print("⚠️ Frame dropped (total: \(self.dropCount))")
            } else if self.expectedPresentTime > 0 {
                let actualInterval = drawable.presentedTime - self.expectedPresentTime
                let variance = abs(actualInterval - expectedInterval)

                if variance > expectedInterval * 0.5 {
                    print("⚠️ Frame timing variance: \(variance * 1000)ms")
                }
            }

            self.expectedPresentTime = drawable.presentedTime
        }
    }
}