From 98c68ccd0df3e976c3b7992968852e6ae0b9595c Mon Sep 17 00:00:00 2001
From: Přemysl Eric Janouch <p@janouch.name>
Date: Sat, 9 Nov 2024 10:27:24 +0100
Subject: WIP: xA: make sending work somehow

---
 xA/xA.go | 54 ++++++++++++++++++++++++++++--------------------------
 1 file changed, 28 insertions(+), 26 deletions(-)

diff --git a/xA/xA.go b/xA/xA.go
index 3934849..b9f79ec 100644
--- a/xA/xA.go
+++ b/xA/xA.go
@@ -15,6 +15,7 @@ import (
 	"net"
 	"os"
 	"slices"
+	"sync"
 	"time"
 
 	"fyne.io/fyne/v2"
@@ -167,6 +168,9 @@ var (
 	backendAddress string
 	backendContext context.Context
 	backendCancel  context.CancelFunc
+	backendConn    net.Conn
+
+	backendLock sync.Mutex
 
 	// Connection state:
 
@@ -231,20 +235,27 @@ func relayReadMessage(r io.Reader) (m RelayEventMessage, ok bool) {
 	return m, true
 }
 
-func relayWriteMessage(conn net.Conn, data RelayCommandData) bool {
+func relaySend(data RelayCommandData, callback callback) bool {
+	backendLock.Lock()
+	defer backendLock.Unlock()
+
 	m := RelayCommandMessage{
 		CommandSeq: commandSeq,
 		Data:       data,
 	}
+	if callback != nil {
+		commandCallbacks[m.CommandSeq] = callback
+	}
 	commandSeq++
 
+	// TODO(p): Handle errors better.
 	b, ok := m.AppendTo(make([]byte, 4))
 	if !ok {
 		log.Println("Command serialization failed")
 		return false
 	}
 	binary.BigEndian.PutUint32(b[:4], uint32(len(b)-4))
-	if _, err := conn.Write(b); err != nil {
+	if _, err := backendConn.Write(b); err != nil {
 		log.Println("Command send failed: " + err.Error())
 		return false
 	}
@@ -255,15 +266,6 @@ func relayWriteMessage(conn net.Conn, data RelayCommandData) bool {
 	return true
 }
 
-func relaySend(data RelayCommandData, callback callback) {
-	if callback != nil {
-		commandCallbacks[commandSeq] = callback
-	}
-
-	// TODO(p): Get the net.Conn from somewhere.
-	//relayWriteMessage(nil, data)
-}
-
 // --- Buffers -----------------------------------------------------------------
 
 func bufferByName(name string) *buffer {
@@ -619,7 +621,9 @@ func relayProcessBufferLine(b *buffer, m *RelayEventDataBufferLine) {
 func relayProcessCallbacks(
 	commandSeq uint32, err string, response *RelayResponseData) {
 	if handler, ok := commandCallbacks[commandSeq]; !ok {
-		// TODO(p): Warn about an unawaited response.
+		if *debug {
+			log.Printf("unawaited response: %+v\n", *response)
+		}
 	} else {
 		delete(commandCallbacks, commandSeq)
 		if handler != nil {
@@ -833,27 +837,25 @@ func relayRun() {
 	backendContext, backendCancel = context.WithCancel(context.Background())
 	defer backendCancel()
 
-	conn, err := net.Dial("tcp", backendAddress)
+	var err error
+	backendLock.Lock()
+	backendConn, err = net.Dial("tcp", backendAddress)
+	backendLock.Unlock()
 	if err != nil {
 		log.Println("Connection failed: " + err.Error())
 		// TODO(p): Display errors to the user.
 		return
 	}
-	defer conn.Close()
-
-	// TODO(p): How to send messages?
-	//  - It would probably make the most sense to have either a chan
-	//    (which makes code synchronize), or a locked slice.
-	//  - But I also need to wake the sender up somehow,
-	//    so maybe use a channel after all.
-	//     - Or maybe use a channel just for the signalling.
-	//  - Sending (semi-)synchronously is also an option, perhaps.
-	// TODO(p): Handle any errors here.
-	_ = relayWriteMessage(conn, RelayCommandData{
+	defer backendConn.Close()
+
+	// TODO(p): Figure out locking.
+	//  - Messages are currently sent (semi-)synchronously, directly.
+	//  - Is the net.Conn actually async-safe?
+	relaySend(RelayCommandData{
 		Variant: &RelayCommandDataHello{Version: RelayVersion},
-	})
+	}, nil)
 
-	relayMessages := relayMakeReceiver(backendContext, conn)
+	relayMessages := relayMakeReceiver(backendContext, backendConn)
 	for {
 		select {
 		case m, ok := <-relayMessages:
-- 
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