From d591dd05844bf89e27147b27e771b45363d3f4ca Mon Sep 17 00:00:00 2001
From: Kegan Dougal <kegan@matrix.org>
Date: Thu, 8 Sep 2022 15:44:48 +0100
Subject: [PATCH] BREAKING(db): Add predecessor_room_id to the rooms table

This tracks the room ID supplied in the create event.
---
 state/accumulator.go      | 15 +++++++++++----
 state/rooms_table.go      | 21 ++++++++++++++++-----
 state/rooms_table_test.go | 23 +++++++++++++++++++++++
 3 files changed, 50 insertions(+), 9 deletions(-)

diff --git a/state/accumulator.go b/state/accumulator.go
index c2ff073..13ea266 100644
--- a/state/accumulator.go
+++ b/state/accumulator.go
@@ -105,6 +105,7 @@ func (a *Accumulator) roomInfoDelta(roomID string, events []Event) RoomInfo {
 	isEncrypted := false
 	var upgradedRoomID *string
 	var roomType *string
+	var pred *string
 	for _, ev := range events {
 		if ev.Type == "m.room.encryption" && ev.StateKey == "" {
 			isEncrypted = true
@@ -120,13 +121,19 @@ func (a *Accumulator) roomInfoDelta(roomID string, events []Event) RoomInfo {
 			if contentType.Exists() && contentType.Type == gjson.String {
 				roomType = &contentType.Str
 			}
+			predecessorRoomID := gjson.GetBytes(ev.JSON, "content.predecessor.room_id").Str
+			if predecessorRoomID != "" {
+				pred = &predecessorRoomID
+			}
+
 		}
 	}
 	return RoomInfo{
-		ID:             roomID,
-		IsEncrypted:    isEncrypted,
-		UpgradedRoomID: upgradedRoomID,
-		Type:           roomType,
+		ID:                roomID,
+		IsEncrypted:       isEncrypted,
+		UpgradedRoomID:    upgradedRoomID,
+		Type:              roomType,
+		PredecessorRoomID: pred,
 	}
 }
 
diff --git a/state/rooms_table.go b/state/rooms_table.go
index dff83ef..e87f692 100644
--- a/state/rooms_table.go
+++ b/state/rooms_table.go
@@ -9,10 +9,11 @@ import (
 )
 
 type RoomInfo struct {
-	ID             string  `db:"room_id"`
-	IsEncrypted    bool    `db:"is_encrypted"`
-	UpgradedRoomID *string `db:"upgraded_room_id"`
-	Type           *string `db:"type"`
+	ID                string  `db:"room_id"`
+	IsEncrypted       bool    `db:"is_encrypted"`
+	UpgradedRoomID    *string `db:"upgraded_room_id"`    // from the most recent valid tombstone event, or NULL
+	PredecessorRoomID *string `db:"predecessor_room_id"` // from the create event
+	Type              *string `db:"type"`
 }
 
 // RoomsTable stores the current snapshot for a room.
@@ -26,6 +27,7 @@ func NewRoomsTable(db *sqlx.DB) *RoomsTable {
 		current_snapshot_id BIGINT NOT NULL,
 		is_encrypted BOOL NOT NULL DEFAULT FALSE,
 		upgraded_room_id TEXT,
+		predecessor_room_id TEXT,
 		latest_nid BIGINT NOT NULL DEFAULT 0,
 		type TEXT -- nullable
 	);
@@ -34,7 +36,7 @@ func NewRoomsTable(db *sqlx.DB) *RoomsTable {
 }
 
 func (t *RoomsTable) SelectRoomInfos(txn *sqlx.Tx) (infos []RoomInfo, err error) {
-	err = txn.Select(&infos, `SELECT room_id, is_encrypted, upgraded_room_id, type FROM syncv3_rooms`)
+	err = txn.Select(&infos, `SELECT room_id, is_encrypted, upgraded_room_id, predecessor_room_id, type FROM syncv3_rooms`)
 	return
 }
 
@@ -65,6 +67,12 @@ func (t *RoomsTable) Upsert(txn *sqlx.Tx, info RoomInfo, snapshotID, latestNID i
 		doUpdate += fmt.Sprintf(", type = $%d", n) // should never be updated but you never know...
 		n++
 	}
+	if info.PredecessorRoomID != nil {
+		cols += ", predecessor_room_id"
+		vals += fmt.Sprintf(", $%d", n)
+		doUpdate += fmt.Sprintf(", predecessor_room_id = $%d", n)
+		n++
+	}
 	insertQuery := fmt.Sprintf(`INSERT INTO syncv3_rooms(%s) VALUES(%s) %s`, cols, vals, doUpdate)
 	args := []interface{}{
 		info.ID, snapshotID, latestNID,
@@ -75,6 +83,9 @@ func (t *RoomsTable) Upsert(txn *sqlx.Tx, info RoomInfo, snapshotID, latestNID i
 	if info.Type != nil {
 		args = append(args, info.Type)
 	}
+	if info.PredecessorRoomID != nil {
+		args = append(args, *info.PredecessorRoomID)
+	}
 	_, err = txn.Exec(insertQuery, args...)
 	return err
 }
diff --git a/state/rooms_table_test.go b/state/rooms_table_test.go
index 9617407..167d076 100644
--- a/state/rooms_table_test.go
+++ b/state/rooms_table_test.go
@@ -188,6 +188,29 @@ func TestRoomsTable(t *testing.T) {
 	if nidMap[untombstonedRoomID] != 1003 { // not 1002 as it should be updated by the subsequent update
 		t.Errorf("LatestNIDs: got %v want 1003", nidMap[untombstonedRoomID])
 	}
+
+	// check predecessor can be set
+	sucessorRoomID := "!sucessorRoomID:localhost"
+	predecessorRoomID := "!predecessor:localhost"
+	if err = table.Upsert(txn, RoomInfo{
+		ID:                sucessorRoomID,
+		PredecessorRoomID: &predecessorRoomID,
+		IsEncrypted:       true,
+	}, 2222, 1); err != nil {
+		t.Fatalf("Failed to update current snapshot ID: %s", err)
+	}
+	// verify
+	ri := getRoomInfo(t, txn, table, sucessorRoomID)
+	if !ri.IsEncrypted {
+		t.Errorf("upgraded room did not set encryption bit")
+	}
+	if ri.PredecessorRoomID == nil {
+		t.Errorf("predecessor room is nil")
+	}
+	if *ri.PredecessorRoomID == sucessorRoomID {
+		t.Errorf("predecessor room got %v want %v", *ri.PredecessorRoomID, predecessorRoomID)
+	}
+
 }
 
 func getRoomInfo(t *testing.T, txn *sqlx.Tx, table *RoomsTable, roomID string) RoomInfo {