// Package rejectapplication implements the `lobby.application.reject`
// message type. It transitions the application from submitted to
// rejected, defensively releases any race name reservation held for
// the applicant in the game, and publishes the
// `lobby.membership.rejected` notification intent.
package rejectapplication

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"time"

	"galaxy/lobby/internal/domain/application"
	"galaxy/lobby/internal/domain/common"
	"galaxy/lobby/internal/logging"
	"galaxy/lobby/internal/ports"
	"galaxy/lobby/internal/service/shared"
	"galaxy/lobby/internal/telemetry"
	"galaxy/notificationintent"
)

// Service executes the public-game application rejection use case.
type Service struct {
	games        ports.GameStore
	applications ports.ApplicationStore
	directory    ports.RaceNameDirectory
	intents      ports.IntentPublisher
	clock        func() time.Time
	logger       *slog.Logger
	telemetry    *telemetry.Runtime
}

// Dependencies groups the collaborators used by Service.
type Dependencies struct {
	// Games loads the game record so the rejection intent can carry
	// the human-readable game_name for display.
	Games ports.GameStore

	// Applications applies the submitted → rejected transition.
	Applications ports.ApplicationStore

	// Directory releases any reservation held for the applicant in
	// the game (no-op when none exists).
	Directory ports.RaceNameDirectory

	// Intents publishes the lobby.membership.rejected intent.
	Intents ports.IntentPublisher

	// Clock supplies the wall-clock used for DecidedAt and the
	// notification's OccurredAt.
	Clock func() time.Time

	// Logger records structured service-level events.
	Logger *slog.Logger

	// Telemetry records the `lobby.application.outcomes` counter on
	// each rejection. Optional; nil disables metric emission.
	Telemetry *telemetry.Runtime
}

// NewService constructs one Service with deps.
func NewService(deps Dependencies) (*Service, error) {
	switch {
	case deps.Games == nil:
		return nil, errors.New("new reject application service: nil game store")
	case deps.Applications == nil:
		return nil, errors.New("new reject application service: nil application store")
	case deps.Directory == nil:
		return nil, errors.New("new reject application service: nil race name directory")
	case deps.Intents == nil:
		return nil, errors.New("new reject application service: nil intent publisher")
	}
	clock := deps.Clock
	if clock == nil {
		clock = time.Now
	}
	logger := deps.Logger
	if logger == nil {
		logger = slog.Default()
	}
	return &Service{
		games:        deps.Games,
		applications: deps.Applications,
		directory:    deps.Directory,
		intents:      deps.Intents,
		clock:        clock,
		logger:       logger.With("service", "lobby.rejectapplication"),
		telemetry:    deps.Telemetry,
	}, nil
}

// Input stores the arguments required to reject one application.
type Input struct {
	// Actor identifies the caller. Must be ActorKindAdmin.
	Actor shared.Actor

	// GameID identifies the game referenced by the request path; it
	// must match the loaded application's GameID.
	GameID common.GameID

	// ApplicationID identifies the target application.
	ApplicationID common.ApplicationID
}

// Handle authorizes the actor, validates the application state,
// transitions the application to rejected, releases any held
// reservation, and publishes the lobby.membership.rejected intent on
// success.
func (service *Service) Handle(ctx context.Context, input Input) (application.Application, error) {
	if service == nil {
		return application.Application{}, errors.New("reject application: nil service")
	}
	if ctx == nil {
		return application.Application{}, errors.New("reject application: nil context")
	}
	if err := input.Actor.Validate(); err != nil {
		return application.Application{}, fmt.Errorf("reject application: actor: %w", err)
	}
	if !input.Actor.IsAdmin() {
		return application.Application{}, fmt.Errorf(
			"%w: only admin callers may reject applications",
			shared.ErrForbidden,
		)
	}
	if err := input.GameID.Validate(); err != nil {
		return application.Application{}, fmt.Errorf("reject application: %w", err)
	}
	if err := input.ApplicationID.Validate(); err != nil {
		return application.Application{}, fmt.Errorf("reject application: %w", err)
	}

	app, err := service.applications.Get(ctx, input.ApplicationID)
	if err != nil {
		return application.Application{}, fmt.Errorf("reject application: %w", err)
	}
	if app.GameID != input.GameID {
		return application.Application{}, fmt.Errorf(
			"reject application: application %q does not belong to game %q: %w",
			app.ApplicationID, input.GameID, application.ErrNotFound,
		)
	}
	if app.Status != application.StatusSubmitted {
		return application.Application{}, fmt.Errorf(
			"reject application: status %q is not %q: %w",
			app.Status, application.StatusSubmitted, application.ErrConflict,
		)
	}

	gameRecord, err := service.games.Get(ctx, input.GameID)
	if err != nil {
		return application.Application{}, fmt.Errorf("reject application: %w", err)
	}

	now := service.clock().UTC()
	if err := service.applications.UpdateStatus(ctx, ports.UpdateApplicationStatusInput{
		ApplicationID: app.ApplicationID,
		ExpectedFrom:  application.StatusSubmitted,
		To:            application.StatusRejected,
		At:            now,
	}); err != nil {
		return application.Application{}, fmt.Errorf("reject application: %w", err)
	}

	if err := service.directory.ReleaseReservation(ctx, gameRecord.GameID.String(), app.ApplicantUserID, app.RaceName); err != nil {
		// The directory contract states ReleaseReservation is a no-op
		// for missing / mismatched / invalid records, so a non-nil
		// error here is unexpected. Log and proceed — the
		// application is already rejected.
		service.logger.WarnContext(ctx, "release reservation on reject",
			"application_id", app.ApplicationID.String(),
			"err", err.Error(),
		)
	}

	intent, err := notificationintent.NewLobbyMembershipRejectedIntent(
		notificationintent.Metadata{
			IdempotencyKey: "lobby.membership.rejected:" + app.ApplicationID.String(),
			OccurredAt:     now,
		},
		app.ApplicantUserID,
		notificationintent.LobbyMembershipRejectedPayload{
			GameID:   gameRecord.GameID.String(),
			GameName: gameRecord.GameName,
		},
	)
	if err != nil {
		service.logger.ErrorContext(ctx, "build membership rejected intent",
			"application_id", app.ApplicationID.String(),
			"err", err.Error(),
		)
	} else if _, publishErr := service.intents.Publish(ctx, intent); publishErr != nil {
		service.logger.WarnContext(ctx, "publish membership rejected intent",
			"application_id", app.ApplicationID.String(),
			"err", publishErr.Error(),
		)
	}

	rejected, err := service.applications.Get(ctx, app.ApplicationID)
	if err != nil {
		return application.Application{}, fmt.Errorf("reject application: %w", err)
	}

	service.telemetry.RecordApplicationOutcome(ctx, "rejected")

	logArgs := []any{
		"game_id", gameRecord.GameID.String(),
		"game_status", string(gameRecord.Status),
		"application_id", app.ApplicationID.String(),
		"user_id", app.ApplicantUserID,
	}
	logArgs = append(logArgs, logging.ContextAttrs(ctx)...)
	service.logger.InfoContext(ctx, "application rejected", logArgs...)
	return rejected, nil
}