scrabble-game/backend/internal/social/robotfriends.go

package social

import (
	"context"
	"fmt"
	"slices"
	"time"

	"github.com/google/uuid"
	"go.uber.org/zap"
)

// robotFriendRequestTTL is how long a per-game disguised-robot friend request is kept
// after its game has finished before the reaper deletes it. It is a sibling of
// friendRequestTTL; the request is housekeeping for the in-game "request sent" state,
// so it is purged once the finished game is well past its lobby lifetime.
const robotFriendRequestTTL = 7 * 24 * time.Hour

// robotFriendRequestReapInterval is how often the reaper sweeps expired rows.
const robotFriendRequestReapInterval = time.Hour

// RobotFriendRequest is one per-game friend request to a disguised-robot opponent: the
// row id, the game name the player saw, and the game + seat it was sent in (so the
// in-game scoreboard can re-mark that seat as already requested).
type RobotFriendRequest struct {
	ID          uuid.UUID
	DisplayName string
	GameID      uuid.UUID
	Seat        int
}

// RequestInGame sends a friend request to addresseeID for requesterID from within gameID.
// A human is requested normally (the friendships table, via SendFriendRequest). A
// disguised-robot opponent is instead recorded per-game in robot_friend_requests — never
// the shared robot account — so the matchmaker keeps robots free, the same robot stays
// un-requested in the requester's other games (under its other names), and the in-game
// "request sent" state is pinned to this seat rather than the shared account. The robot
// ignores the request (it never becomes a friendship); the reaper deletes the row once
// the game is long finished. It is the entry point for the in-game add-friend control;
// the friend-code path goes elsewhere.
func (svc *Service) RequestInGame(ctx context.Context, requesterID, addresseeID, gameID uuid.UUID) error {
	if requesterID == addresseeID {
		return ErrSelfRelation
	}
	// A guest cannot use friends: a durable-account feature (the UI hides it).
	if acc, err := svc.accounts.GetByID(ctx, requesterID); err != nil {
		return err
	} else if acc.IsGuest {
		return ErrGuestForbidden
	}
	isRobot, err := svc.accounts.IsRobot(ctx, addresseeID)
	if err != nil {
		return err
	}
	if !isRobot {
		return svc.SendFriendRequest(ctx, requesterID, addresseeID)
	}
	if gameID == uuid.Nil {
		return ErrNotParticipant
	}
	seats, _, _, err := svc.games.Participants(ctx, gameID)
	if err != nil {
		return err
	}
	seat := slices.Index(seats, addresseeID)
	if seat < 0 {
		return ErrNotParticipant
	}
	name, _ := svc.games.SeatName(ctx, gameID, addresseeID)
	return svc.store.insertRobotFriendRequest(ctx, requesterID, gameID, seat, addresseeID, name)
}

// ListRobotFriendRequests returns requesterID's per-game disguised-robot friend
// requests, newest first.
func (svc *Service) ListRobotFriendRequests(ctx context.Context, requesterID uuid.UUID) ([]RobotFriendRequest, error) {
	return svc.store.listRobotFriendRequests(ctx, requesterID)
}

// insertRobotFriendRequest records a per-game robot friend request; a duplicate (same
// requester, game, seat) is ignored.
func (s *Store) insertRobotFriendRequest(ctx context.Context, requester, gameID uuid.UUID, seat int, robotID uuid.UUID, name string) error {
	id, err := uuid.NewV7()
	if err != nil {
		return fmt.Errorf("social: new robot friend request id: %w", err)
	}
	const q = `INSERT INTO backend.robot_friend_requests (id, requester_id, game_id, seat, robot_id, display_name)
VALUES ($1, $2, $3, $4, $5, $6)
ON CONFLICT (requester_id, game_id, seat) DO NOTHING`
	if _, err := s.db.ExecContext(ctx, q, id, requester, gameID, int16(seat), robotID, name); err != nil {
		return fmt.Errorf("social: insert robot friend request: %w", err)
	}
	return nil
}

// listRobotFriendRequests returns requester's robot friend requests, newest first.
func (s *Store) listRobotFriendRequests(ctx context.Context, requester uuid.UUID) ([]RobotFriendRequest, error) {
	const q = `SELECT id, display_name, game_id, seat FROM backend.robot_friend_requests
WHERE requester_id = $1 ORDER BY created_at DESC`
	rows, err := s.db.QueryContext(ctx, q, requester)
	if err != nil {
		return nil, fmt.Errorf("social: list robot friend requests: %w", err)
	}
	defer rows.Close()
	var out []RobotFriendRequest
	for rows.Next() {
		var r RobotFriendRequest
		var seat int16
		if err := rows.Scan(&r.ID, &r.DisplayName, &r.GameID, &seat); err != nil {
			return nil, fmt.Errorf("social: scan robot friend request: %w", err)
		}
		r.Seat = int(seat)
		out = append(out, r)
	}
	return out, rows.Err()
}

// ReapExpiredRobotFriendRequests deletes every per-game robot friend request whose game has
// been finished for longer than robotFriendRequestTTL, reporting how many rows were removed.
// Rows for active (not-yet-finished) games are kept so the in-game "request sent" state
// survives. It backs the RobotFriendRequestReaper and is directly callable in tests.
func (svc *Service) ReapExpiredRobotFriendRequests(ctx context.Context) (int64, error) {
	return svc.store.deleteExpiredRobotFriendRequests(ctx, svc.now().Add(-robotFriendRequestTTL))
}

// deleteExpiredRobotFriendRequests removes robot friend requests whose game has been
// finished since before cutoff, reporting how many rows were deleted.
func (s *Store) deleteExpiredRobotFriendRequests(ctx context.Context, cutoff time.Time) (int64, error) {
	const q = `DELETE FROM backend.robot_friend_requests r
USING backend.games g
WHERE r.game_id = g.game_id AND g.status = 'finished' AND g.finished_at < $1`
	res, err := s.db.ExecContext(ctx, q, cutoff)
	if err != nil {
		return 0, fmt.Errorf("social: delete expired robot friend requests: %w", err)
	}
	n, err := res.RowsAffected()
	if err != nil {
		return 0, fmt.Errorf("social: delete expired robot friend requests rows: %w", err)
	}
	return n, nil
}

// RobotFriendRequestReaper periodically reaps expired per-game disguised-robot friend
// requests via Service.ReapExpiredRobotFriendRequests. It mirrors the account.GuestReaper:
// one background goroutine, started once from main.
type RobotFriendRequestReaper struct {
	svc *Service
	log *zap.Logger
}

// NewRobotFriendRequestReaper constructs a reaper over svc. log may be nil.
func NewRobotFriendRequestReaper(svc *Service, log *zap.Logger) *RobotFriendRequestReaper {
	if log == nil {
		log = zap.NewNop()
	}
	return &RobotFriendRequestReaper{svc: svc, log: log}
}

// Interval is the reaper's sweep cadence, for the startup log line.
func (r *RobotFriendRequestReaper) Interval() time.Duration { return robotFriendRequestReapInterval }

// Retention is the reaper's post-finish retention window, for the startup log line.
func (r *RobotFriendRequestReaper) Retention() time.Duration { return robotFriendRequestTTL }

// Run reaps expired robot friend requests on each tick until ctx is cancelled.
func (r *RobotFriendRequestReaper) Run(ctx context.Context) {
	ticker := time.NewTicker(robotFriendRequestReapInterval)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			n, err := r.svc.ReapExpiredRobotFriendRequests(ctx)
			if err != nil {
				r.log.Warn("robot friend request reap failed", zap.Error(err))
			} else if n > 0 {
				r.log.Info("reaped expired robot friend requests", zap.Int64("count", n))
			}
		}
	}
}