fix(multiplayer): fence client queue cancellation states

server/store/queue_sql.go

@@ -6,6 +6,7 @@ import (
 	"crypto/sha256"
 	"database/sql"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"time"
 
@@ -42,8 +43,12 @@ RETURNING ticket_id, player_id, playlist, state, client_build, protocol_version,
 	QueueTicketCancelSQL = `UPDATE queue_tickets SET state = 'CANCELLED',
     revision = revision + 1, expires_at = $4
 WHERE ticket_id = $1 AND player_id = $2 AND revision = $3
-  AND state NOT IN ('COMPLETED', 'CANCELLED', 'EXPIRED', 'FAILED')
+  AND state IN ('QUEUED', 'PROPOSED')
 RETURNING ticket_id, player_id, playlist, state, client_build, protocol_version, enqueued_at, expires_at, revision, predicted_rtt`
+	QueueMutationFailureSQL = `SELECT player_id, state, revision, expires_at
+FROM queue_tickets
+WHERE ticket_id = $1
+FOR UPDATE`
 	QueueCooldownSelectSQL = `SELECT ends_at
 FROM penalties
 WHERE player_id = $1 AND playlist = $2
@@ -294,7 +299,10 @@ func mutateQueueTicket(ctx context.Context, db *sql.DB, playerID, ticketID, idem
 		var record queueTicketRecord
 		var predictedRTT []byte
 		if err := tx.QueryRowContext(ctx, mutationSQL, ticketID, playerID, expectedRevision, now).Scan(&record.TicketID, &record.PlayerID, &record.Playlist, &record.State, &record.ClientBuild, &record.ProtocolVersion, &record.EnqueuedAt, &record.ExpiresAt, &record.Revision, &predictedRTT); err != nil {
-			return fmt.Errorf("queue mutation rejected: %w", err)
+			if !errors.Is(err, sql.ErrNoRows) {
+				return fmt.Errorf("queue mutation rejected: %w", err)
+			}
+			return classifyQueueMutationFailure(ctx, tx, playerID, ticketID, expectedRevision, now)
 		}
 		if err := json.Unmarshal(predictedRTT, &record.PredictedRTT); err != nil {
 			return fmt.Errorf("decode queue RTT: %w", err)
@@ -315,6 +323,29 @@ func mutateQueueTicket(ctx context.Context, db *sql.DB, playerID, ticketID, idem
 	return ticket, err
 }
 
+func classifyQueueMutationFailure(ctx context.Context, tx *sql.Tx, playerID, ticketID string, expectedRevision uint64, now time.Time) error {
+	var owner, state string
+	var revision uint64
+	var expiresAt time.Time
+	err := tx.QueryRowContext(ctx, QueueMutationFailureSQL, ticketID).Scan(&owner, &state, &revision, &expiresAt)
+	if errors.Is(err, sql.ErrNoRows) {
+		return domain.ErrTicketNotFound
+	}
+	if err != nil {
+		return err
+	}
+	if owner != playerID {
+		return domain.ErrNotTicketOwner
+	}
+	if (state == string(domain.Queued) || state == string(domain.Proposed)) && !now.Before(expiresAt) {
+		return domain.ErrTicketExpired
+	}
+	if revision != expectedRevision {
+		return domain.ErrStaleRevision
+	}
+	return fmt.Errorf("%w: %s in %s", domain.ErrConflict, "queue mutation", state)
+}
+
 func queueTicketRecordFromDomain(ticket domain.QueueTicket) queueTicketRecord {
 	return queueTicketRecord{TicketID: ticket.TicketID, PlayerID: ticket.PlayerID, ProposalID: ticket.ProposalID, MatchID: ticket.MatchID, Playlist: string(ticket.Playlist), State: string(ticket.State), ClientBuild: ticket.Candidate.ClientBuild, ProtocolVersion: ticket.Candidate.ProtocolVersion, EnqueuedAt: ticket.EnqueuedAt, ExpiresAt: ticket.ExpiresAt, Revision: ticket.Revision, PredictedRTT: ticket.Candidate.PredictedRTT}
 }