fix #1531

AWAY status should be tracked per-session:

1. With auto-away enabled, away status is aggregated across sessions
   (if any session is not away, the client is not away, else use
   the away status that was set most recently)
2. With auto-away disabled, we get the legacy behavior where AWAY
   applies directly to the client

irc/client.go

@@ -78,8 +78,6 @@ type Client struct {
 	accountName        string // display name of the account: uncasefolded, '*' if not logged in
 	accountRegDate     time.Time
 	accountSettings    AccountSettings
-	away               bool
-	autoAway           bool
 	awayMessage        string
 	brbTimer           BrbTimer
 	channels           ChannelSet
@@ -177,6 +175,9 @@ type Session struct {
 
 	quitMessage string
 
+	awayMessage string
+	awayAt      time.Time
+
 	capabilities caps.Set
 	capState     caps.State
 	capVersion   caps.Version
@@ -486,8 +487,6 @@ func (server *Server) AddAlwaysOnClient(account ClientAccount, channelToStatus m
 	}
 
 	if persistenceEnabled(config.Accounts.Multiclient.AutoAway, client.accountSettings.AutoAway) {
-		client.autoAway = true
-		client.away = true
 		client.awayMessage = client.t("User is currently disconnected")
 	}
 }
@@ -675,7 +674,7 @@ func (client *Client) run(session *Session) {
 			session.playResume()
 			session.resumeDetails = nil
 			client.brbTimer.Disable()
-			client.SetAway(false, "") // clear BRB message if any
+			session.SetAway("") // clear BRB message if any
 		} else {
 			client.playReattachMessages(session)
 		}
@@ -1458,15 +1457,13 @@ func (client *Client) destroy(session *Session) {
 		client.dirtyBits |= IncludeLastSeen
 	}
 
-	autoAway := false
+	becameAutoAway := false
 	var awayMessage string
-	if alwaysOn && !client.away && remainingSessions == 0 &&
-		persistenceEnabled(config.Accounts.Multiclient.AutoAway, client.accountSettings.AutoAway) {
-		autoAway = true
-		client.autoAway = true
-		client.away = true
-		awayMessage = config.languageManager.Translate(client.languages, `User is currently disconnected`)
-		client.awayMessage = awayMessage
+	if alwaysOn && persistenceEnabled(config.Accounts.Multiclient.AutoAway, client.accountSettings.AutoAway) {
+		wasAway := client.awayMessage != ""
+		client.setAutoAwayNoMutex(config)
+		awayMessage = client.awayMessage
+		becameAutoAway = !wasAway && awayMessage != ""
 	}
 
 	if client.registrationTimer != nil {
@@ -1523,7 +1520,7 @@ func (client *Client) destroy(session *Session) {
 		client.server.stats.Remove(registered, invisible, operator)
 	}
 
-	if autoAway {
+	if becameAutoAway {
 		dispatchAwayNotify(client, true, awayMessage)
 	}