punktfunk/clients/apple/Sources/PunktfunkKit/PunktfunkConnection.swift

// Swift wrapper around the punktfunk-core C ABI's punktfunk/1 connection API.
//
// Threading contract (mirrors the C header): one PunktfunkConnection is pumped from a single
// video thread via nextAU(); nextAudio() runs on its own (single) drain thread, and
// nextRumble()/nextHidOutput() share one feedback drain thread (two core planes, one puller
// each — polling them sequentially from one thread is within the contract); the core keeps
// per-plane borrow slots, so the planes never alias. send() is enqueue-only and safe
// alongside all of them. The pointers inside an AU/audio packet are only valid until the
// next call of the same kind, so we copy into Data here — the copies are small and keep the
// Swift side memory-safe.
//
// Trust: pass the host's pinned certificate fingerprint (the host logs it at startup, and
// `hostFingerprint` reports what a trust-on-first-use connect observed — persist it, e.g.
// in UserDefaults keyed by host, and pin it from then on).
//
// close() is safe from any thread: it flags the pullers to exit at their next poll
// boundary, then takes the per-plane locks (each held across its blocking C poll), so the
// handle is never freed under an in-flight call — the C contract ("never close with a
// next_au/next_audio call in flight") is enforced here rather than left to callers. After
// close, the pull methods throw `.closed` and the threads unwind on their own.

import Foundation
import PunktfunkCore

// cbindgen's C17-compatible header spells the typedefs as plain integers
// (`typedef int32_t PunktfunkStatus`, `typedef uint8_t PunktfunkInputKind`) while the enum
// constants import as a distinct same-named Swift type — bridge by raw value once here.
private let statusOK: Int32 = PUNKTFUNK_STATUS_OK.rawValue
private let statusNoFrame: Int32 = PUNKTFUNK_STATUS_NO_FRAME.rawValue
private let statusClosed: Int32 = PUNKTFUNK_STATUS_CLOSED.rawValue

/// One reassembled, FEC-recovered, decrypted access unit (Annex-B HEVC from the host).
public struct AccessUnit: Sendable {
    public let data: Data
    public let ptsNs: UInt64
    public let frameIndex: UInt32
    public let flags: UInt32
}

/// One Opus audio packet (48 kHz stereo, 5 ms frames) — decode with AVAudioConverter
/// (`kAudioFormatOpus`) or libopus into an AVAudioEngine source node.
public struct AudioPacket: Sendable {
    public let data: Data
    public let ptsNs: UInt64
    public let seq: UInt32
}

public enum PunktfunkClientError: Error {
    /// Connect failed — wrong host/port, timeout, or a certificate-pin mismatch.
    case connectFailed
    /// `pinSHA256` was non-nil but not exactly 32 bytes. Failing closed: connecting
    /// unpinned when the caller asked for verification would be a silent trust downgrade.
    case invalidPin
    /// Pairing rejected — wrong PIN.
    case wrongPIN
    case closed
    case status(Int32)
}

/// This client's persistent self-signed identity. Generate ONCE with `generateIdentity()`,
/// store both PEMs (Keychain), present on every connect — the certificate's fingerprint is
/// how hosts recognize this client after pairing.
public struct ClientIdentity: Sendable {
    public let certPEM: String
    public let keyPEM: String
    public init(certPEM: String, keyPEM: String) {
        self.certPEM = certPEM
        self.keyPEM = keyPEM
    }
}

/// Generate a fresh client identity (self-signed cert + key, PEM).
public func generateIdentity() throws -> ClientIdentity {
    var cert = [CChar](repeating: 0, count: 4096)
    var key = [CChar](repeating: 0, count: 4096)
    let rc = punktfunk_generate_identity(&cert, UInt(cert.count), &key, UInt(key.count))
    guard rc == PUNKTFUNK_STATUS_OK.rawValue else {
        throw PunktfunkClientError.status(rc)
    }
    return ClientIdentity(certPEM: String(cString: cert), keyPEM: String(cString: key))
}

/// Run the PIN pairing ceremony: the host displays a 4-digit PIN (its log/UI), the user
/// types it here. On success the host stores this client's identity and the returned
/// fingerprint is the host's now-VERIFIED identity — persist it and pass it as `pinSHA256`
/// to every later connect. Throws `.wrongPIN` when the proof is rejected.
public func pair(
    host: String, port: UInt16 = 9777,
    identity: ClientIdentity, pin: String, name: String,
    timeoutMs: UInt32 = 90_000
) throws -> Data {
    var observed = [UInt8](repeating: 0, count: 32)
    // The C header types PunktfunkStatus as a bare int32 (C17, no enum import), so the ABI
    // functions return Int32 directly — compare against the enum constants' rawValue, the
    // same bridging the connection methods use (statusOK etc.).
    let rc = host.withCString { cs in
        identity.certPEM.withCString { cert in
            identity.keyPEM.withCString { key in
                pin.withCString { p in
                    name.withCString { n in
                        punktfunk_pair(cs, port, cert, key, p, n, &observed, timeoutMs)
                    }
                }
            }
        }
    }
    switch rc {
    case PUNKTFUNK_STATUS_OK.rawValue: return Data(observed)
    case PUNKTFUNK_STATUS_CRYPTO.rawValue: throw PunktfunkClientError.wrongPIN
    default: throw PunktfunkClientError.status(rc)
    }
}

/// `withCString` over an optional — nil maps to a NULL C pointer.
func withOptionalCString<R>(_ s: String?, _ body: (UnsafePointer<CChar>?) -> R) -> R {
    guard let s else { return body(nil) }
    return s.withCString { body($0) }
}

public final class PunktfunkConnection {
    private var handle: OpaquePointer?
    /// Set by close() before it contends for the plane locks: the pullers see it at their
    /// next poll boundary and exit, so close() can't be starved by back-to-back polls
    /// (NSLock is not fair).
    private var closeRequested = false
    /// Serializes send()/close() against each other and guards `handle`/`closeRequested`.
    private let abiLock = NSLock()
    /// Held across the blocking next_au call; close() takes it (same plane-lock → abiLock
    /// order as the pullers) so it can never free the handle under an in-flight poll.
    private let pumpLock = NSLock()
    /// Same role for the audio drain thread (its own plane in the core).
    private let audioLock = NSLock()
    /// Same role for the feedback drain thread (rumble + HID-output — two core planes,
    /// drained sequentially by one thread).
    private let feedbackLock = NSLock()

    /// Negotiated session mode (host-confirmed).
    public private(set) var width: UInt32 = 0
    public private(set) var height: UInt32 = 0
    public private(set) var refreshHz: UInt32 = 0

    /// SHA-256 fingerprint of the certificate the host presented (32 bytes). After a
    /// trust-on-first-use connect, persist this and pass it as `pinSHA256` next time.
    public private(set) var hostFingerprint: Data = Data()

    /// Compositor preference for the host's per-session virtual output (the
    /// `PUNKTFUNK_COMPOSITOR_*` ABI values). `.auto` lets the host auto-detect from its
    /// running desktop; a concrete backend is honored only if available on the host right
    /// now — else the host falls back to auto-detect and logs the real choice.
    public enum Compositor: UInt32, CaseIterable, Sendable {
        case auto = 0
        case kwin = 1
        case wlroots = 2
        case mutter = 3
        case gamescope = 4

        /// Loose name parsing for env/dev hooks ("kde" and "sway" are accepted aliases,
        /// mirroring the host's `CompositorPref::from_name`).
        public init?(name: String) {
            switch name.lowercased() {
            case "auto": self = .auto
            case "kwin", "kde": self = .kwin
            case "wlroots", "sway", "hyprland": self = .wlroots
            case "mutter", "gnome": self = .mutter
            case "gamescope": self = .gamescope
            default: return nil
            }
        }
    }

    /// Which virtual gamepad the host creates for this session's pads (the
    /// `PUNKTFUNK_GAMEPAD_*` ABI values). `.auto` lets the host decide (its env var, else
    /// X-Box 360); `.dualSense` is honored only on hosts with UHID (Linux) — games then see
    /// a real DualSense and their lightbar / adaptive-trigger writes come back on the
    /// HID-output plane (`nextHidOutput`). The host's actual choice is `resolvedGamepad`.
    public enum GamepadType: UInt32, CaseIterable, Sendable {
        case auto = 0
        case xbox360 = 1
        case dualSense = 2

        /// Loose name parsing for env/dev hooks, mirroring the host's
        /// `GamepadPref::from_name`.
        public init?(name: String) {
            switch name.lowercased() {
            case "auto", "default": self = .auto
            case "xbox", "xbox360", "x360", "uinput": self = .xbox360
            case "dualsense", "ds", "ps5": self = .dualSense
            default: return nil
            }
        }
    }

    /// The virtual gamepad backend the host actually resolved (the Welcome's echo of the
    /// requested `gamepad`). `.auto` = an older host that didn't say — assume Xbox 360, no
    /// DualSense feedback.
    public private(set) var resolvedGamepad: GamepadType = .auto

    /// Connect and start a session at the requested mode (the host creates a native virtual
    /// output at exactly this size/refresh). Blocks up to `timeoutMs`.
    ///
    /// `pinSHA256`: the host's expected certificate fingerprint (exactly 32 bytes, else
    /// `invalidPin` is thrown — never silently downgraded); nil = trust on first use
    /// (check `hostFingerprint` afterwards). A pinned mismatch throws.
    ///
    /// `identity`: this client's persistent identity (from `generateIdentity()`, stored in
    /// the Keychain) — presented so a host recognizes a paired client. nil = anonymous;
    /// hosts running `--require-pairing` reject anonymous sessions.
    ///
    /// `compositor`: which backend should drive the virtual output host-side (see
    /// `Compositor`; `.auto` = host decides).
    ///
    /// `gamepad`: which virtual pad the host creates for this session's controllers (see
    /// `GamepadType`; `.auto` = host decides). Check `resolvedGamepad` afterwards.
    public init(
        host: String, port: UInt16 = 9777,
        width: UInt32, height: UInt32, refreshHz: UInt32,
        pinSHA256: Data? = nil,
        identity: ClientIdentity? = nil,
        compositor: Compositor = .auto,
        gamepad: GamepadType = .auto,
        timeoutMs: UInt32 = 10_000
    ) throws {
        if let pin = pinSHA256, pin.count != 32 { throw PunktfunkClientError.invalidPin }
        var observed = [UInt8](repeating: 0, count: 32)
        handle = host.withCString { cs in
            withOptionalCString(identity?.certPEM) { cert in
                withOptionalCString(identity?.keyPEM) { key in
                    if let pin = pinSHA256 {
                        return pin.withUnsafeBytes { p in
                            punktfunk_connect_ex2(
                                cs, port, width, height, refreshHz, compositor.rawValue,
                                gamepad.rawValue,
                                p.bindMemory(to: UInt8.self).baseAddress, &observed,
                                cert, key, timeoutMs)
                        }
                    }
                    return punktfunk_connect_ex2(
                        cs, port, width, height, refreshHz, compositor.rawValue,
                        gamepad.rawValue,
                        nil, &observed, cert, key, timeoutMs)
                }
            }
        }
        guard handle != nil else { throw PunktfunkClientError.connectFailed }
        hostFingerprint = Data(observed)
        var w: UInt32 = 0, h: UInt32 = 0, hz: UInt32 = 0
        _ = punktfunk_connection_mode(handle, &w, &h, &hz)
        self.width = w
        self.height = h
        self.refreshHz = hz
        var gp: UInt32 = 0
        _ = punktfunk_connection_gamepad(handle, &gp)
        resolvedGamepad = GamepadType(rawValue: gp) ?? .auto
    }

    /// Ask the host to switch the live session to a new mode (window resized) — no
    /// reconnect. Non-blocking; on acceptance the stream continues at the new mode (the
    /// first new-mode AU is an IDR with fresh parameter sets — `AnnexB.formatDescription`
    /// refresh-on-IDR already handles it) and `currentMode()` reflects the switch.
    public func requestMode(width: UInt32, height: UInt32, refreshHz: UInt32) {
        abiLock.lock()
        defer { abiLock.unlock() }
        guard let h = handle, !closeRequested else { return }
        _ = punktfunk_connection_request_mode(h, width, height, refreshHz)
    }

    /// The currently active session mode (updated by accepted `requestMode` switches).
    public func currentMode() -> (width: UInt32, height: UInt32, refreshHz: UInt32) {
        abiLock.lock()
        defer { abiLock.unlock() }
        var w: UInt32 = 0, h: UInt32 = 0, hz: UInt32 = 0
        if let hd = handle, !closeRequested {
            _ = punktfunk_connection_mode(hd, &w, &h, &hz)
        }
        return (w, h, hz)
    }

    /// Pull the next access unit; nil on timeout, throws `.closed` once the session ended.
    /// Call from a single pump thread.
    public func nextAU(timeoutMs: UInt32 = 100) throws -> AccessUnit? {
        pumpLock.lock()
        defer { pumpLock.unlock() }
        guard let h = liveHandle() else { throw PunktfunkClientError.closed }

        var frame = PunktfunkFrame()
        let rc = punktfunk_connection_next_au(h, &frame, timeoutMs)
        switch rc {
        case statusOK:
            guard let base = frame.data, frame.len > 0 else { return nil }
            let data = Data(bytes: base, count: Int(frame.len)) // copy: ptr valid only until next call
            return AccessUnit(
                data: data, ptsNs: frame.pts_ns,
                frameIndex: frame.frame_index, flags: frame.flags)
        case statusNoFrame:
            return nil
        case statusClosed:
            throw PunktfunkClientError.closed
        default:
            throw PunktfunkClientError.status(rc)
        }
    }

    /// Pull the next Opus audio packet; nil on timeout, throws `.closed` once the session
    /// ended. Drain from a dedicated audio thread — packets arrive every 5 ms (the core
    /// buffers 320 ms and drops the newest when the puller lags).
    public func nextAudio(timeoutMs: UInt32 = 100) throws -> AudioPacket? {
        audioLock.lock()
        defer { audioLock.unlock() }
        guard let h = liveHandle() else { throw PunktfunkClientError.closed }

        var pkt = PunktfunkAudioPacket()
        let rc = punktfunk_connection_next_audio(h, &pkt, timeoutMs)
        switch rc {
        case statusOK:
            guard let base = pkt.data, pkt.len > 0 else { return nil }
            let data = Data(bytes: base, count: Int(pkt.len)) // copy: ptr valid only until next call
            return AudioPacket(data: data, ptsNs: pkt.pts_ns, seq: pkt.seq)
        case statusNoFrame:
            return nil
        case statusClosed:
            throw PunktfunkClientError.closed
        default:
            throw PunktfunkClientError.status(rc)
        }
    }

    /// Pull the next force-feedback update for the GCController haptics engine:
    /// `(pad, lowFrequency, highFrequency)` with 0...0xFFFF amplitudes, (0, 0) = stop.
    /// Drain from the (single) feedback thread, alongside `nextHidOutput`.
    public func nextRumble(timeoutMs: UInt32 = 0) throws -> (pad: UInt16, low: UInt16, high: UInt16)? {
        feedbackLock.lock()
        defer { feedbackLock.unlock() }
        guard let h = liveHandle() else { throw PunktfunkClientError.closed }

        var pad: UInt16 = 0, low: UInt16 = 0, high: UInt16 = 0
        let rc = punktfunk_connection_next_rumble(h, &pad, &low, &high, timeoutMs)
        switch rc {
        case statusOK:
            return (pad, low, high)
        case statusNoFrame:
            return nil
        case statusClosed:
            throw PunktfunkClientError.closed
        default:
            throw PunktfunkClientError.status(rc)
        }
    }

    /// One DualSense feedback event a game wrote to the host's virtual pad — replay it on
    /// the real controller (GCDeviceLight, GCControllerPlayerIndex,
    /// GCDualSenseAdaptiveTrigger). Only a `.dualSense` session emits these.
    public enum HidOutputEvent: Sendable, Equatable {
        /// Lightbar color.
        case led(pad: UInt8, r: UInt8, g: UInt8, b: UInt8)
        /// Player-indicator LEDs (low 5 bits).
        case playerLEDs(pad: UInt8, bits: UInt8)
        /// Adaptive-trigger effect: `which` 0 = L2, 1 = R2; `effect` is the raw DualSense
        /// trigger parameter block (mode byte + params, ≤ 11 bytes) — parse with
        /// `DualSenseTriggerEffect`.
        case triggerEffect(pad: UInt8, which: UInt8, effect: [UInt8])
    }

    /// Pull the next DualSense feedback event (lightbar / player LEDs / adaptive triggers);
    /// nil on timeout, throws `.closed` once the session ended. Drain from the (single)
    /// feedback thread, alongside `nextRumble`. Nothing ever arrives unless
    /// `resolvedGamepad == .dualSense` — poll with a short timeout, never spin.
    public func nextHidOutput(timeoutMs: UInt32 = 0) throws -> HidOutputEvent? {
        feedbackLock.lock()
        defer { feedbackLock.unlock() }
        guard let h = liveHandle() else { throw PunktfunkClientError.closed }

        var out = PunktfunkHidOutput()
        let rc = punktfunk_connection_next_hidout(h, &out, timeoutMs)
        switch rc {
        case statusOK:
            switch Int32(out.kind) {
            case PUNKTFUNK_HIDOUT_LED:
                return .led(pad: out.pad, r: out.r, g: out.g, b: out.b)
            case PUNKTFUNK_HIDOUT_PLAYER_LEDS:
                return .playerLEDs(pad: out.pad, bits: out.player_bits)
            case PUNKTFUNK_HIDOUT_TRIGGER:
                // The fixed C array imports as a tuple — copy out the valid prefix.
                let len = Int(min(out.effect_len, UInt8(PUNKTFUNK_HID_EFFECT_MAX)))
                let effect = withUnsafeBytes(of: out.effect) { Array($0.prefix(len)) }
                return .triggerEffect(pad: out.pad, which: out.which, effect: effect)
            default:
                return nil // unknown kind from a newer host — skip (forward-compatible)
            }
        case statusNoFrame:
            return nil
        case statusClosed:
            throw PunktfunkClientError.closed
        default:
            throw PunktfunkClientError.status(rc)
        }
    }

    /// Send one input event (delivered to the host as a QUIC datagram). Thread-safe;
    /// silently dropped after close.
    public func send(_ event: PunktfunkInputEvent) {
        var ev = event
        abiLock.lock()
        defer { abiLock.unlock() }
        guard let h = handle, !closeRequested else { return }
        _ = punktfunk_connection_send_input(h, &ev)
    }

    /// Close the connection and free the handle. Safe from any thread, idempotent; waits
    /// for in-flight pulls (≤ their timeouts) before tearing down.
    public func close() {
        abiLock.lock()
        closeRequested = true
        abiLock.unlock()
        pumpLock.lock() // pullers exit at their next poll boundary, releasing these
        audioLock.lock()
        feedbackLock.lock()
        abiLock.lock()
        let h = handle
        handle = nil
        abiLock.unlock()
        feedbackLock.unlock()
        audioLock.unlock()
        pumpLock.unlock()
        if let h {
            punktfunk_connection_close(h) // joins the connection's internal Rust threads
        }
    }

    /// Send one Opus mic frame (48 kHz) to the host, where it feeds a virtual
    /// microphone source the host's apps can record. Non-blocking enqueue, safe
    /// alongside the pull threads (same discipline as `send`). `seq`/`ptsNs` are the
    /// caller's own counters (host uses them only for diagnostics); empty `opus` is a
    /// DTX silence frame.
    public func sendMic(_ opus: Data, seq: UInt32, ptsNs: UInt64) {
        abiLock.lock()
        defer { abiLock.unlock() }
        guard let h = handle, !closeRequested else { return }
        opus.withUnsafeBytes { p in
            _ = punktfunk_connection_send_mic(
                h, p.bindMemory(to: UInt8.self).baseAddress, UInt(opus.count), seq, ptsNs)
        }
    }

    /// Send one DualSense touchpad contact to the host's virtual pad (rich-input plane).
    /// `x`/`y` are normalized 0...65535 across the touchpad, origin top-left, +y down.
    /// Non-blocking enqueue (same discipline as `send`); pointless on non-DualSense
    /// sessions — the host ignores it there.
    public func sendTouchpad(pad: UInt8 = 0, finger: UInt8, active: Bool, x: UInt16, y: UInt16) {
        abiLock.lock()
        defer { abiLock.unlock() }
        guard let h = handle, !closeRequested else { return }
        var rich = PunktfunkRichInput()
        rich.kind = UInt8(PUNKTFUNK_RICH_TOUCHPAD)
        rich.pad = pad
        rich.finger = finger
        rich.active = active ? 1 : 0
        rich.x = x
        rich.y = y
        _ = punktfunk_connection_send_rich_input(h, &rich)
    }

    /// Send one DualSense motion sample to the host's virtual pad (rich-input plane). The
    /// values are raw DualSense sensor units, written verbatim into the virtual pad's input
    /// report — convert with `GamepadCapture`'s scale constants (gyro: rad/s → 20 LSB per
    /// deg/s; accel: g → 10000 LSB per g).
    public func sendMotion(
        pad: UInt8 = 0,
        gyro: (Int16, Int16, Int16), accel: (Int16, Int16, Int16)
    ) {
        abiLock.lock()
        defer { abiLock.unlock() }
        guard let h = handle, !closeRequested else { return }
        var rich = PunktfunkRichInput()
        rich.kind = UInt8(PUNKTFUNK_RICH_MOTION)
        rich.pad = pad
        rich.gyro = gyro
        rich.accel = accel
        _ = punktfunk_connection_send_rich_input(h, &rich)
    }

    deinit { close() }

    /// Snapshot the handle unless close is pending (callers hold their plane lock).
    private func liveHandle() -> OpaquePointer? {
        abiLock.lock()
        defer { abiLock.unlock() }
        return closeRequested ? nil : handle
    }
}

// Convenience constructors for the wire input events (field semantics match
// punktfunk_core::input::InputEvent; see punktfunk_core.h).
public extension PunktfunkInputEvent {
    private static func make(
        _ kind: UInt32, code: UInt32, x: Int32, y: Int32, flags: UInt32 = 0
    ) -> PunktfunkInputEvent {
        PunktfunkInputEvent(kind: UInt8(kind), _pad: (0, 0, 0), code: code, x: x, y: y, flags: flags)
    }
    static func mouseMove(dx: Int32, dy: Int32) -> PunktfunkInputEvent {
        make(PUNKTFUNK_INPUT_KIND_MOUSE_MOVE.rawValue, code: 0, x: dx, y: dy)
    }
    /// GameStream button ids: 1=left 2=middle 3=right 4=X1 5=X2 (host maps to evdev BTN_*).
    static func mouseButton(_ button: UInt32, down: Bool) -> PunktfunkInputEvent {
        make(
            (down ? PUNKTFUNK_INPUT_KIND_MOUSE_BUTTON_DOWN : PUNKTFUNK_INPUT_KIND_MOUSE_BUTTON_UP).rawValue,
            code: button, x: 0, y: 0)
    }
    /// `vk` is a Windows virtual-key code (the host's vk_to_evdev table consumes these).
    static func key(_ vk: UInt32, down: Bool) -> PunktfunkInputEvent {
        make((down ? PUNKTFUNK_INPUT_KIND_KEY_DOWN : PUNKTFUNK_INPUT_KIND_KEY_UP).rawValue, code: vk, x: 0, y: 0)
    }
    /// WHEEL_DELTA(120)-scaled; positive = up (vertical) / right (horizontal) — the
    /// convention Moonlight/SDL use; the host maps onto the ei/wl axes.
    static func scroll(_ delta: Int32, horizontal: Bool = false) -> PunktfunkInputEvent {
        make(PUNKTFUNK_INPUT_KIND_MOUSE_SCROLL.rawValue, code: horizontal ? 1 : 0, x: delta, y: 0)
    }

    // Gamepad (wire contract in punktfunk_core::input::gamepad): one transition per event,
    // `pad` = controller index, accumulated host-side into a virtual Xbox 360 or DualSense
    // pad (the session's negotiated `GamepadType`).

    /// `button` is a GameStream buttonFlags bit (A=0x1000 B=0x2000 X=0x4000 Y=0x8000,
    /// dpad=0x1/2/4/8, start=0x10 back=0x20 LS=0x40 RS=0x80 LB=0x100 RB=0x200 guide=0x400,
    /// touchpad click=0x100000 — DualSense sessions only, the xpad has no such button).
    static func gamepadButton(_ button: UInt32, down: Bool, pad: UInt32 = 0) -> PunktfunkInputEvent {
        make(
            PUNKTFUNK_INPUT_KIND_GAMEPAD_BUTTON.rawValue,
            code: button, x: down ? 1 : 0, y: 0, flags: pad)
    }

    /// Axis ids: 0=LSX 1=LSY 2=RSX 3=RSY (−32768...32767, XInput convention: +y = UP —
    /// `GCControllerDirectionPad.yAxis` already matches, no flip), 4=LT 5=RT (0...255).
    static func gamepadAxis(_ axis: UInt32, value: Int32, pad: UInt32 = 0) -> PunktfunkInputEvent {
        make(PUNKTFUNK_INPUT_KIND_GAMEPAD_AXIS.rawValue, code: axis, x: value, y: 0, flags: pad)
    }

    // Touch (host-side: libei ei_touchscreen on the virtual output). `id` distinguishes
    // fingers and is reusable after touchUp; coordinates are absolute pixels on the
    // client's touch surface, whose size rides in `flags` so the host can rescale —
    // the surface dimensions must each fit in 16 bits. Built for the iOS variant
    // (UITouch → these); nothing on macOS emits them yet.

    static func touchDown(
        id: UInt32, x: Int32, y: Int32, surfaceWidth: UInt32, surfaceHeight: UInt32
    ) -> PunktfunkInputEvent {
        make(
            PUNKTFUNK_INPUT_KIND_TOUCH_DOWN.rawValue, code: id, x: x, y: y,
            flags: ((surfaceWidth & 0xFFFF) << 16) | (surfaceHeight & 0xFFFF))
    }

    static func touchMove(
        id: UInt32, x: Int32, y: Int32, surfaceWidth: UInt32, surfaceHeight: UInt32
    ) -> PunktfunkInputEvent {
        make(
            PUNKTFUNK_INPUT_KIND_TOUCH_MOVE.rawValue, code: id, x: x, y: y,
            flags: ((surfaceWidth & 0xFFFF) << 16) | (surfaceHeight & 0xFFFF))
    }

    static func touchUp(id: UInt32) -> PunktfunkInputEvent {
        make(PUNKTFUNK_INPUT_KIND_TOUCH_UP.rawValue, code: id, x: 0, y: 0)
    }
}