fix #536

irc/channel.go

@@ -624,12 +624,16 @@ func (channel *Channel) Join(client *Client, key string, isSajoin bool, rb *Resp
 	// TODO #259 can be implemented as Flush(false) (i.e., nonblocking) while holding joinPartMutex
 	rb.Flush(true)
 
+	channel.autoReplayHistory(client, rb, message.Msgid)
+}
+
+func (channel *Channel) autoReplayHistory(client *Client, rb *ResponseBuffer, skipMsgid string) {
 	// autoreplay any messages as necessary
 	config := channel.server.Config()
 	var items []history.Item
-	if rb.session.zncPlaybackTimes != nil && (rb.session.zncPlaybackTimes.targets == nil || rb.session.zncPlaybackTimes.targets[chcfname]) {
+	if rb.session.zncPlaybackTimes != nil && (rb.session.zncPlaybackTimes.targets == nil || rb.session.zncPlaybackTimes.targets[channel.NameCasefolded()]) {
 		items, _ = channel.history.Between(rb.session.zncPlaybackTimes.after, rb.session.zncPlaybackTimes.before, false, config.History.ChathistoryMax)
-	} else {
+	} else if !rb.session.HasHistoryCaps() {
 		var replayLimit int
 		customReplayLimit := client.AccountSettings().AutoreplayLines
 		if customReplayLimit != nil {
@@ -648,7 +652,7 @@ func (channel *Channel) Join(client *Client, key string, isSajoin bool, rb *Resp
 	// remove the client's own JOIN line from the replay
 	numItems := len(items)
 	for i := len(items) - 1; 0 <= i; i-- {
-		if items[i].Message.Msgid == message.Msgid {
+		if items[i].Message.Msgid == skipMsgid {
 			// zero'ed items will not be replayed because their `Type` field is not recognized
 			items[i] = history.Item{}
 			numItems--

irc/client.go

@@ -162,6 +162,13 @@ func (session *Session) SetDestroyed() {
 	atomic.StoreUint32(&session.destroyed, 1)
 }
 
+// returns whether the client supports a smart history replay cap,
+// and therefore autoreplay-on-join and similar should be suppressed
+func (session *Session) HasHistoryCaps() bool {
+	// TODO the chathistory cap will go here as well
+	return session.capabilities.Has(caps.ZNCPlayback)
+}
+
 // WhoWas is the subset of client details needed to answer a WHOWAS query
 type WhoWas struct {
 	nick           string
@@ -473,6 +480,13 @@ func (client *Client) playReattachMessages(session *Session) {
 	client.server.playRegistrationBurst(session)
 	for _, channel := range session.client.Channels() {
 		channel.playJoinForSession(session)
+		// clients should receive autoreplay-on-join lines, if applicable;
+		// if they negotiated znc.in/playback or chathistory, they will receive nothing,
+		// because those caps disable autoreplay-on-join and they haven't sent the relevant
+		// *playback PRIVMSG or CHATHISTORY command yet
+		rb := NewResponseBuffer(session)
+		channel.autoReplayHistory(client, rb, "")
+		rb.Send(true)
 	}
 }
 

irc/znc.go

@@ -73,8 +73,21 @@ func zncPlaybackHandler(client *Client, command string, params []string, rb *Res
 
 	var targets map[string]bool
 
-	// OK: the user's PMs get played back immediately on receiving this,
-	// then we save the timestamps in the session to handle replay on future channel joins
+	// three cases:
+	// 1. the user's PMs get played back immediately upon receiving this
+	// 2. if this is a new connection (from the server's POV), save the information
+	// and use it to process subsequent joins
+	// 3. if this is a reattach (from the server's POV), immediately play back
+	// history for channels that the client is already joined to. In this scenario,
+	// there are three total attempts to play the history:
+	//     3.1. During the initial reattach (no-op because the *playback privmsg
+	//          hasn't been received yet, but they negotiated the znc.in/playback
+	//          cap so we know we're going to receive it later)
+	//     3.2  Upon receiving the *playback privmsg, i.e., now: we should play
+	//          the relevant history lines
+	//     3.3  When the client sends a subsequent redundant JOIN line for those
+	//          channels; redundant JOIN is a complete no-op so we won't replay twice
+
 	config := client.server.Config()
 	if params[1] == "*" {
 		items, _ := client.history.Between(after, before, false, config.History.ChathistoryMax)
@@ -95,4 +108,9 @@ func zncPlaybackHandler(client *Client, command string, params []string, rb *Res
 		before:  before,
 		targets: targets,
 	}
+
+	for _, channel := range client.Channels() {
+		channel.autoReplayHistory(client, rb, "")
+		rb.Flush(true)
+	}
 }