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 db == nil || playerID == "" || seasonID == "" || now.IsZero() {
		return domain.RankedProfile{}, false, fmt.Errorf("invalid season rollover arguments")
	}
	// The caller's profile is only a validation-compatible hint. The durable
	// row is authoritative because a result update may have committed after the
	// caller read its snapshot but before this transaction acquired the lock.
	_ = profile
	var updated domain.RankedProfile
	applied := false
	err := RunSerializable(ctx, db, DefaultSerializableAttempts, func(ctx context.Context, tx *sql.Tx) error {
		var locked domain.RankedProfile
		var lockedPlayerID string
		var revision int64
		if err := tx.QueryRowContext(ctx, SeasonRatingLockSQL, playerID).Scan(&lockedPlayerID, &locked.Value, &locked.RD, &locked.Volatility, &locked.RankedGames, &revision); err != nil {
			return err
		}
		if lockedPlayerID != playerID {
			return fmt.Errorf("locked unexpected rating row")
		}
		var err error
		updated, _, err = domain.ApplySeasonRollover(locked, seasonID)
		if 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 {
			updated = locked
			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
}