From 53789ebd7530579b43c5a500c52a3373b4a545f7 Mon Sep 17 00:00:00 2001
From: Siyuan Miao <i@xswan.net>
Date: Wed, 17 Sep 2025 17:21:27 +0200
Subject: [PATCH] clean up code

---
 hidrpc.go | 121 +++++++++++++++++++++++++++++-------------------------
 usb.go    |   4 --
 2 files changed, 64 insertions(+), 61 deletions(-)

diff --git a/hidrpc.go b/hidrpc.go
index 62eb8491..7475b358 100644
--- a/hidrpc.go
+++ b/hidrpc.go
@@ -39,63 +39,7 @@ func handleHidRPCMessage(message hidrpc.Message, session *Session) {
 		rpcCancelKeyboardMacro()
 		return
 	case hidrpc.TypeKeypressKeepAliveReport:
-		session.keepAliveJitterLock.Lock()
-		defer session.keepAliveJitterLock.Unlock()
-
-		now := time.Now()
-
-		// Tunables
-		// Keep in mind
-		// macOS default: 15 * 15 = 225ms https://discussions.apple.com/thread/1316947?sortBy=rank
-		// Linux default: 250ms https://man.archlinux.org/man/kbdrate.8.en
-		// Windows default: 1s `HKEY_CURRENT_USER\Control Panel\Accessibility\Keyboard Response\AutoRepeatDelay`
-
-		const expectedRate = 50 * time.Millisecond       // expected keepalive interval
-		const maxLateness = 50 * time.Millisecond        // max jitter we'll tolerate OR jitter budget
-		const baseExtension = expectedRate + maxLateness // 100ms extension on perfect tick
-
-		const maxStaleness = 225 * time.Millisecond // discard ancient packets outright
-
-		// 1) Staleness guard: ensures packets that arrive far beyond the life of a valid key hold
-		// (e.g. after a network stall, retransmit burst, or machine sleep) are ignored outright.
-		// This prevents “zombie” keepalives from reviving a key that should already be released.
-		if !session.lastTimerResetTime.IsZero() && now.Sub(session.lastTimerResetTime) > maxStaleness {
-			return
-		}
-
-		validTick := true
-		timerExtension := baseExtension
-
-		if !session.lastKeepAliveArrivalTime.IsZero() {
-			timeSinceLastTick := now.Sub(session.lastKeepAliveArrivalTime)
-			lateness := timeSinceLastTick - expectedRate
-
-			if lateness > 0 {
-				if lateness <= maxLateness {
-					// --- Small lateness (within jitterBudget) ---
-					// This is normal jitter (e.g., Wi-Fi contention).
-					// We still accept the tick, but *reduce the extension*
-					// so that the total hold time stays aligned with REAL client side intent.
-					timerExtension -= lateness
-				} else {
-					// --- Large lateness (beyond jitterBudget) ---
-					// This is likely a retransmit stall or ordering delay.
-					// We reject the tick entirely and DO NOT extend,
-					// so the auto-release still fires on time.
-					validTick = false
-				}
-			}
-		}
-
-		if validTick {
-			// Only valid ticks update our state and extend the timer.
-			session.lastKeepAliveArrivalTime = now
-			session.lastTimerResetTime = now
-			if ug := getUsbGadget(); ug != nil {
-				ug.DelayAutoReleaseWithDuration(timerExtension)
-			}
-		}
-		// On a miss: do not advance any state — keeps baseline stable.
+		rpcErr = handleHidRPCKeypressKeepAlive(session)
 	case hidrpc.TypePointerReport:
 		pointerReport, err := message.PointerReport()
 		if err != nil {
@@ -159,6 +103,69 @@ func onHidMessage(msg hidQueueMessage, session *Session) {
 	}
 }
 
+// Tunables
+// Keep in mind
+// macOS default: 15 * 15 = 225ms https://discussions.apple.com/thread/1316947?sortBy=rank
+// Linux default: 250ms https://man.archlinux.org/man/kbdrate.8.en
+// Windows default: 1s `HKEY_CURRENT_USER\Control Panel\Accessibility\Keyboard Response\AutoRepeatDelay`
+
+const expectedRate = 50 * time.Millisecond       // expected keepalive interval
+const maxLateness = 50 * time.Millisecond        // max jitter we'll tolerate OR jitter budget
+const baseExtension = expectedRate + maxLateness // 100ms extension on perfect tick
+
+const maxStaleness = 225 * time.Millisecond // discard ancient packets outright
+
+func handleHidRPCKeypressKeepAlive(session *Session) error {
+	session.keepAliveJitterLock.Lock()
+	defer session.keepAliveJitterLock.Unlock()
+
+	now := time.Now()
+
+	// 1) Staleness guard: ensures packets that arrive far beyond the life of a valid key hold
+	// (e.g. after a network stall, retransmit burst, or machine sleep) are ignored outright.
+	// This prevents “zombie” keepalives from reviving a key that should already be released.
+	if !session.lastTimerResetTime.IsZero() && now.Sub(session.lastTimerResetTime) > maxStaleness {
+		return nil
+	}
+
+	validTick := true
+	timerExtension := baseExtension
+
+	if !session.lastKeepAliveArrivalTime.IsZero() {
+		timeSinceLastTick := now.Sub(session.lastKeepAliveArrivalTime)
+		lateness := timeSinceLastTick - expectedRate
+
+		if lateness > 0 {
+			if lateness <= maxLateness {
+				// --- Small lateness (within jitterBudget) ---
+				// This is normal jitter (e.g., Wi-Fi contention).
+				// We still accept the tick, but *reduce the extension*
+				// so that the total hold time stays aligned with REAL client side intent.
+				timerExtension -= lateness
+			} else {
+				// --- Large lateness (beyond jitterBudget) ---
+				// This is likely a retransmit stall or ordering delay.
+				// We reject the tick entirely and DO NOT extend,
+				// so the auto-release still fires on time.
+				validTick = false
+			}
+		}
+	}
+
+	if !validTick {
+		return nil
+	}
+	// Only valid ticks update our state and extend the timer.
+	session.lastKeepAliveArrivalTime = now
+	session.lastTimerResetTime = now
+	if gadget != nil {
+		gadget.DelayAutoReleaseWithDuration(timerExtension)
+	}
+
+	// On a miss: do not advance any state — keeps baseline stable.
+	return nil
+}
+
 func handleHidRPCKeyboardInput(message hidrpc.Message) error {
 	switch message.Type() {
 	case hidrpc.TypeKeypressReport:
diff --git a/usb.go b/usb.go
index d7ddf605..99287a30 100644
--- a/usb.go
+++ b/usb.go
@@ -8,10 +8,6 @@ import (
 
 var gadget *usbgadget.UsbGadget
 
-func getUsbGadget() *usbgadget.UsbGadget {
-	return gadget
-}
-
 // initUsbGadget initializes the USB gadget.
 // call it only after the config is loaded.
 func initUsbGadget() {