feat(multiplayer): deliver allocated server rosters

server/store/assignment_sql.go

@@ -69,6 +69,11 @@ const AssignmentSelectSQL = `SELECT match_id, player_id, allocation_id, server_i
 FROM assignments
 WHERE match_id = $1 AND player_id = $2 AND expires_at > $3`
 
+const AssignmentRosterSelectSQL = `SELECT allocation_id, server_id, join_authorisation
+FROM assignments
+WHERE match_id = $1 AND server_id = $2 AND expires_at > $3
+ORDER BY slot, player_id`
+
 func validateDurableAssignment(assignment DurableAssignment) error {
 	if assignment.MatchID == "" || assignment.PlayerID == "" || assignment.AllocationID == "" || assignment.ServerID == "" || assignment.Slot < 0 || assignment.Slot > 5 || (assignment.Region != "EU" && assignment.Region != "NA") || assignment.ClientBuild == "" || assignment.ProtocolVersion < 1 || (assignment.Transport != "enet" && assignment.Transport != "steam_sdr") || assignment.Endpoint == "" || assignment.JoinAuthorisation == "" || len(assignment.ManifestDigest) == 0 || assignment.ExpiresAt.IsZero() || assignment.Revision < 0 {
 		return fmt.Errorf("invalid durable assignment")
@@ -187,3 +192,43 @@ func GetAssignment(ctx context.Context, db *sql.DB, playerID, matchID string, no
 	}
 	return assignment, nil
 }
+
+// GetAssignmentRoster returns the complete signed roster for an allocated
+// server. It is intentionally server-scoped rather than player-scoped and is
+// called only after workload authentication at the API boundary. All rows
+// must belong to one allocation; a partial or mixed allocation is unsafe to
+// hand to the game process.
+func GetAssignmentRoster(ctx context.Context, db *sql.DB, matchID, serverID string, now time.Time) ([][]byte, error) {
+	if db == nil || matchID == "" || serverID == "" || now.IsZero() {
+		return nil, fmt.Errorf("invalid assignment roster arguments")
+	}
+	rows, err := db.QueryContext(ctx, AssignmentRosterSelectSQL, matchID, serverID, now)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var allocationID string
+	var roster [][]byte
+	for rows.Next() {
+		var rowAllocation, rowServer, encoded string
+		if err := rows.Scan(&rowAllocation, &rowServer, &encoded); err != nil {
+			return nil, err
+		}
+		if rowServer != serverID || rowAllocation == "" || (allocationID != "" && allocationID != rowAllocation) {
+			return nil, fmt.Errorf("assignment roster contains mixed allocation")
+		}
+		decoded, err := base64.RawURLEncoding.DecodeString(encoded)
+		if err != nil || len(decoded) == 0 {
+			return nil, fmt.Errorf("assignment roster contains invalid envelope")
+		}
+		allocationID = rowAllocation
+		roster = append(roster, decoded)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	if len(roster) == 0 {
+		return nil, sql.ErrNoRows
+	}
+	return roster, nil
+}