From 424f676254ea144b752afde694c0b1c5cf2388ad Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Tue, 13 Apr 2021 18:15:30 +0200
Subject: [PATCH] Store last internal msg ID in DB when detaching

References: https://todo.sr.ht/~emersion/soju/98
---
 db.go   | 29 ++++++++++++++++++-----------
 user.go | 26 +++++++++++++++++++-------
 2 files changed, 37 insertions(+), 18 deletions(-)

diff --git a/db.go b/db.go
index e2c90a7..4147a7c 100644
--- a/db.go
+++ b/db.go
@@ -109,10 +109,12 @@ func parseFilter(filter string) (MessageFilter, error) {
 }
 
 type Channel struct {
-	ID       int64
-	Name     string
-	Key      string
-	Detached bool
+	ID   int64
+	Name string
+	Key  string
+
+	Detached              bool
+	DetachedInternalMsgID string
 
 	RelayDetached MessageFilter
 	ReattachOn    MessageFilter
@@ -161,6 +163,7 @@ CREATE TABLE Channel (
 	name VARCHAR(255) NOT NULL,
 	key VARCHAR(255),
 	detached INTEGER NOT NULL DEFAULT 0,
+	detached_internal_msgid VARCHAR(255),
 	relay_detached INTEGER NOT NULL DEFAULT 0,
 	reattach_on INTEGER NOT NULL DEFAULT 0,
 	detach_after INTEGER NOT NULL DEFAULT 0,
@@ -245,6 +248,7 @@ var migrations = []string{
 			UNIQUE(network, target, client)
 		);
 	`,
+	"ALTER TABLE Channel ADD COLUMN detached_internal_msgid VARCHAR(255)",
 }
 
 type DB struct {
@@ -546,7 +550,9 @@ func (db *DB) ListChannels(networkID int64) ([]Channel, error) {
 	db.lock.RLock()
 	defer db.lock.RUnlock()
 
-	rows, err := db.db.Query(`SELECT id, name, key, detached, relay_detached, reattach_on, detach_after, detach_on
+	rows, err := db.db.Query(`SELECT
+			id, name, key, detached, detached_internal_msgid,
+			relay_detached, reattach_on, detach_after, detach_on
 		FROM Channel
 		WHERE network = ?`, networkID)
 	if err != nil {
@@ -557,12 +563,13 @@ func (db *DB) ListChannels(networkID int64) ([]Channel, error) {
 	var channels []Channel
 	for rows.Next() {
 		var ch Channel
-		var key sql.NullString
+		var key, detachedInternalMsgID sql.NullString
 		var detachAfter int64
-		if err := rows.Scan(&ch.ID, &ch.Name, &key, &ch.Detached, &ch.RelayDetached, &ch.ReattachOn, &detachAfter, &ch.DetachOn); err != nil {
+		if err := rows.Scan(&ch.ID, &ch.Name, &key, &ch.Detached, &detachedInternalMsgID, &ch.RelayDetached, &ch.ReattachOn, &detachAfter, &ch.DetachOn); err != nil {
 			return nil, err
 		}
 		ch.Key = key.String
+		ch.DetachedInternalMsgID = detachedInternalMsgID.String
 		ch.DetachAfter = time.Duration(detachAfter) * time.Second
 		channels = append(channels, ch)
 	}
@@ -583,14 +590,14 @@ func (db *DB) StoreChannel(networkID int64, ch *Channel) error {
 	var err error
 	if ch.ID != 0 {
 		_, err = db.db.Exec(`UPDATE Channel
-			SET network = ?, name = ?, key = ?, detached = ?, relay_detached = ?, reattach_on = ?, detach_after = ?, detach_on = ?
+			SET network = ?, name = ?, key = ?, detached = ?, detached_internal_msgid = ?, relay_detached = ?, reattach_on = ?, detach_after = ?, detach_on = ?
 			WHERE id = ?`,
-			networkID, ch.Name, key, ch.Detached, ch.RelayDetached, ch.ReattachOn, detachAfter, ch.DetachOn, ch.ID)
+			networkID, ch.Name, key, ch.Detached, toNullString(ch.DetachedInternalMsgID), ch.RelayDetached, ch.ReattachOn, detachAfter, ch.DetachOn, ch.ID)
 	} else {
 		var res sql.Result
-		res, err = db.db.Exec(`INSERT INTO Channel(network, name, key, detached, relay_detached, reattach_on, detach_after, detach_on)
+		res, err = db.db.Exec(`INSERT INTO Channel(network, name, key, detached, detached_internal_msgid, relay_detached, reattach_on, detach_after, detach_on)
 			VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
-			networkID, ch.Name, key, ch.Detached, ch.RelayDetached, ch.ReattachOn, detachAfter, ch.DetachOn)
+			networkID, ch.Name, key, ch.Detached, toNullString(ch.DetachedInternalMsgID), ch.RelayDetached, ch.ReattachOn, detachAfter, ch.DetachOn)
 		if err != nil {
 			return err
 		}
diff --git a/user.go b/user.go
index 8052234..e2e06ee 100644
--- a/user.go
+++ b/user.go
@@ -232,9 +232,20 @@ func (net *network) detach(ch *Channel) {
 	if ch.Detached {
 		return
 	}
-	ch.Detached = true
+
 	net.user.logger.Printf("network %q: detaching channel %q", net.GetName(), ch.Name)
 
+	ch.Detached = true
+
+	if net.user.msgStore != nil {
+		nameCM := net.casemap(ch.Name)
+		lastID, err := net.user.msgStore.LastMsgID(net, nameCM, time.Now())
+		if err != nil {
+			net.user.logger.Printf("failed to get last message ID for channel %q: %v", ch.Name, err)
+		}
+		ch.DetachedInternalMsgID = lastID
+	}
+
 	if net.conn != nil {
 		uch := net.conn.channels.Value(ch.Name)
 		if uch != nil {
@@ -255,9 +266,13 @@ func (net *network) attach(ch *Channel) {
 	if !ch.Detached {
 		return
 	}
-	ch.Detached = false
+
 	net.user.logger.Printf("network %q: attaching channel %q", net.GetName(), ch.Name)
 
+	detachedMsgID := ch.DetachedInternalMsgID
+	ch.Detached = false
+	ch.DetachedInternalMsgID = ""
+
 	var uch *upstreamChannel
 	if net.conn != nil {
 		uch = net.conn.channels.Value(ch.Name)
@@ -276,12 +291,9 @@ func (net *network) attach(ch *Channel) {
 			forwardChannel(dc, uch)
 		}
 
-		lastDelivered := net.delivered.LoadID(ch.Name, dc.clientName)
-		if lastDelivered == "" {
-			return
+		if detachedMsgID != "" {
+			dc.sendTargetBacklog(net, ch.Name, detachedMsgID)
 		}
-
-		dc.sendTargetBacklog(net, ch.Name, lastDelivered)
 	})
 }