feat: game lobby service

lobby/internal/service/cancelgame/service.go

@@ -0,0 +1,170 @@
+// Package cancelgame implements the `lobby.game.cancel` message type. It
+// transitions a game record to `cancelled` from one of the allowed source
+// statuses (`draft`, `enrollment_open`, `ready_to_start`, `start_failed`)
+// after enforcing admin-or-owner authorization. Any other source status is
+// rejected with game.ErrConflict.
+package cancelgame
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
+	"time"
+
+	"galaxy/lobby/internal/domain/common"
+	"galaxy/lobby/internal/domain/game"
+	"galaxy/lobby/internal/logging"
+	"galaxy/lobby/internal/ports"
+	"galaxy/lobby/internal/service/shared"
+	"galaxy/lobby/internal/telemetry"
+)
+
+// cancellableStatuses enumerates the source statuses from which a game may
+// transition directly to `cancelled`. The set mirrors the allowed
+// transitions defined in `internal/domain/game/status.go` and the
+// PLAN.md exit criteria.
+var cancellableStatuses = map[game.Status]struct{}{
+	game.StatusDraft:          {},
+	game.StatusEnrollmentOpen: {},
+	game.StatusReadyToStart:   {},
+	game.StatusStartFailed:    {},
+}
+
+// Service executes the cancel-game use case.
+type Service struct {
+	games     ports.GameStore
+	clock     func() time.Time
+	logger    *slog.Logger
+	telemetry *telemetry.Runtime
+}
+
+// Dependencies groups the collaborators used by Service.
+type Dependencies struct {
+	// Games mediates the CAS status transition and the result read.
+	Games ports.GameStore
+
+	// Clock supplies the wall-clock used for UpdatedAt. Defaults to
+	// time.Now when nil.
+	Clock func() time.Time
+
+	// Logger records structured service-level events. Defaults to
+	// slog.Default when nil.
+	Logger *slog.Logger
+
+	// Telemetry records the `lobby.game.transitions` counter on each
+	// successful cancellation. Optional; nil disables metric emission.
+	Telemetry *telemetry.Runtime
+}
+
+// NewService constructs one Service with deps.
+func NewService(deps Dependencies) (*Service, error) {
+	if deps.Games == nil {
+		return nil, errors.New("new cancel game service: nil game store")
+	}
+
+	clock := deps.Clock
+	if clock == nil {
+		clock = time.Now
+	}
+	logger := deps.Logger
+	if logger == nil {
+		logger = slog.Default()
+	}
+
+	return &Service{
+		games:     deps.Games,
+		clock:     clock,
+		logger:    logger.With("service", "lobby.cancelgame"),
+		telemetry: deps.Telemetry,
+	}, nil
+}
+
+// Input stores the arguments required to cancel one game.
+type Input struct {
+	// Actor identifies the caller.
+	Actor shared.Actor
+
+	// GameID identifies the target game record.
+	GameID common.GameID
+}
+
+// Handle authorizes the actor, checks the source status, transitions the
+// record to `cancelled`, and returns the post-transition snapshot.
+func (service *Service) Handle(ctx context.Context, input Input) (game.Game, error) {
+	if service == nil {
+		return game.Game{}, errors.New("cancel game: nil service")
+	}
+	if ctx == nil {
+		return game.Game{}, errors.New("cancel game: nil context")
+	}
+	if err := input.Actor.Validate(); err != nil {
+		return game.Game{}, fmt.Errorf("cancel game: actor: %w", err)
+	}
+	if err := input.GameID.Validate(); err != nil {
+		return game.Game{}, fmt.Errorf("cancel game: %w", err)
+	}
+
+	record, err := service.games.Get(ctx, input.GameID)
+	if err != nil {
+		return game.Game{}, fmt.Errorf("cancel game: %w", err)
+	}
+
+	if err := authorize(input.Actor, record); err != nil {
+		return game.Game{}, err
+	}
+
+	if _, ok := cancellableStatuses[record.Status]; !ok {
+		return game.Game{}, fmt.Errorf(
+			"cancel game: status %q cannot be cancelled: %w",
+			record.Status, game.ErrConflict,
+		)
+	}
+
+	at := service.clock().UTC()
+	err = service.games.UpdateStatus(ctx, ports.UpdateStatusInput{
+		GameID:       input.GameID,
+		ExpectedFrom: record.Status,
+		To:           game.StatusCancelled,
+		Trigger:      game.TriggerCommand,
+		At:           at,
+	})
+	if err != nil {
+		return game.Game{}, fmt.Errorf("cancel game: %w", err)
+	}
+
+	service.telemetry.RecordGameTransition(ctx,
+		string(record.Status),
+		string(game.StatusCancelled),
+		string(game.TriggerCommand),
+	)
+
+	updated, err := service.games.Get(ctx, input.GameID)
+	if err != nil {
+		return game.Game{}, fmt.Errorf("cancel game: %w", err)
+	}
+
+	logArgs := []any{
+		"game_id", updated.GameID.String(),
+		"from_status", string(record.Status),
+		"to_status", string(updated.Status),
+		"trigger", string(game.TriggerCommand),
+		"actor_kind", string(input.Actor.Kind),
+	}
+	logArgs = append(logArgs, logging.ContextAttrs(ctx)...)
+	service.logger.InfoContext(ctx, "game cancelled", logArgs...)
+
+	return updated, nil
+}
+
+// authorize enforces admin OR private-owner access to the record.
+func authorize(actor shared.Actor, record game.Game) error {
+	if actor.IsAdmin() {
+		return nil
+	}
+	if record.GameType == game.GameTypePrivate && actor.UserID == record.OwnerUserID {
+		return nil
+	}
+	return fmt.Errorf("%w: actor is not authorized to cancel game %q",
+		shared.ErrForbidden, record.GameID.String())
+}