feat: persist ranked season rollovers

server/store/season_sql.go

@@ -0,0 +1,64 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"time"
+
+	"github.com/cosmic-clash/cosmic-clash/server/domain"
+)
+
+const SeasonRatingLockSQL = `SELECT player_id, rating, deviation, volatility, ranked_games, revision
+FROM ratings
+WHERE player_id = $1
+FOR UPDATE`
+
+const SeasonRolloverInsertSQL = `INSERT INTO ranked_season_rollovers
+    (player_id, season_id, rating, deviation, volatility, ranked_games, rolled_over_at)
+VALUES ($1, $2, $3, $4, $5, $6, $7)
+ON CONFLICT (player_id, season_id) DO NOTHING`
+
+const SeasonRatingUpdateSQL = `UPDATE ratings
+SET rating = $2, deviation = $3, volatility = $4, revision = revision + 1, updated_at = $5
+WHERE player_id = $1`
+
+// ApplyRankedSeasonRollover persists the domain rollover exactly once. The
+// marker insert and rating update share one SERIALIZABLE transaction, so a
+// retry after a worker failure cannot apply compression twice or leave a
+// marker without its corresponding rating snapshot.
+func ApplyRankedSeasonRollover(ctx context.Context, db *sql.DB, playerID, seasonID string, profile domain.RankedProfile, now time.Time) (domain.RankedProfile, bool, error) {
+	if playerID == "" {
+		return domain.RankedProfile{}, false, fmt.Errorf("player ID is required")
+	}
+	updated, _, err := domain.ApplySeasonRollover(profile, seasonID)
+	if err != nil {
+		return domain.RankedProfile{}, false, err
+	}
+	applied := false
+	err = RunSerializable(ctx, db, DefaultSerializableAttempts, func(ctx context.Context, tx *sql.Tx) error {
+		if _, err := tx.ExecContext(ctx, SeasonRatingLockSQL, playerID); err != nil {
+			return err
+		}
+		result, err := tx.ExecContext(ctx, SeasonRolloverInsertSQL, playerID, seasonID, updated.Value, updated.RD, updated.Volatility, updated.RankedGames, now)
+		if err != nil {
+			return err
+		}
+		changed, err := result.RowsAffected()
+		if err != nil {
+			return err
+		}
+		if changed == 0 {
+			return nil
+		}
+		if _, err := tx.ExecContext(ctx, SeasonRatingUpdateSQL, playerID, updated.Value, updated.RD, updated.Volatility, now); err != nil {
+			return err
+		}
+		applied = true
+		return nil
+	})
+	if err != nil {
+		return domain.RankedProfile{}, false, err
+	}
+	return updated, applied, nil
+}