// Package submitapplication implements the `lobby.application.submit`
// message type. It validates the request against the public-game
// enrollment rules, calls UserService for eligibility, checks race name
// availability through the Race Name Directory, persists the new
// submitted application via ApplicationStore, and publishes the
// `lobby.application.submitted` notification intent.
package submitapplication

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

	"galaxy/lobby/internal/domain/application"
	"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"
	"galaxy/notificationintent"
)

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

// Dependencies groups the collaborators used by Service.
type Dependencies struct {
	// Games loads the target game record for enrollment validation.
	Games ports.GameStore

	// Memberships is consulted for the active-member roster count used
	// to enforce the max_players + start_gap_players capacity guard.
	Memberships ports.MembershipStore

	// Applications persists the new submitted record.
	Applications ports.ApplicationStore

	// Users resolves the synchronous eligibility snapshot.
	Users ports.UserService

	// Directory checks race name availability.
	Directory ports.RaceNameDirectory

	// Intents publishes the lobby.application.submitted intent.
	Intents ports.IntentPublisher

	// IDs mints the new opaque application identifier.
	IDs ports.IDGenerator

	// Clock supplies the wall-clock used for CreatedAt and the
	// notification's OccurredAt. 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.application.outcomes` counter on each
	// successful submission. 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 submit application service: nil game store")
	case deps.Memberships == nil:
		return nil, errors.New("new submit application service: nil membership store")
	case deps.Applications == nil:
		return nil, errors.New("new submit application service: nil application store")
	case deps.Users == nil:
		return nil, errors.New("new submit application service: nil user service")
	case deps.Directory == nil:
		return nil, errors.New("new submit application service: nil race name directory")
	case deps.Intents == nil:
		return nil, errors.New("new submit application service: nil intent publisher")
	case deps.IDs == nil:
		return nil, errors.New("new submit application service: nil id generator")
	}
	clock := deps.Clock
	if clock == nil {
		clock = time.Now
	}
	logger := deps.Logger
	if logger == nil {
		logger = slog.Default()
	}
	return &Service{
		games:        deps.Games,
		memberships:  deps.Memberships,
		applications: deps.Applications,
		users:        deps.Users,
		directory:    deps.Directory,
		intents:      deps.Intents,
		ids:          deps.IDs,
		clock:        clock,
		logger:       logger.With("service", "lobby.submitapplication"),
		telemetry:    deps.Telemetry,
	}, nil
}

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

	// GameID identifies the target game.
	GameID common.GameID

	// RaceName stores the desired in-game name in original casing.
	RaceName string
}

// Handle validates input, authorizes the actor, verifies eligibility and
// race name availability, persists the new submitted application, and
// publishes the lobby.application.submitted intent on success.
func (service *Service) Handle(ctx context.Context, input Input) (application.Application, error) {
	if service == nil {
		return application.Application{}, errors.New("submit application: nil service")
	}
	if ctx == nil {
		return application.Application{}, errors.New("submit application: nil context")
	}
	if err := input.Actor.Validate(); err != nil {
		return application.Application{}, fmt.Errorf("submit application: actor: %w", err)
	}
	if !input.Actor.IsUser() {
		return application.Application{}, fmt.Errorf(
			"%w: only authenticated users may submit applications",
			shared.ErrForbidden,
		)
	}
	if err := input.GameID.Validate(); err != nil {
		return application.Application{}, fmt.Errorf("submit application: %w", err)
	}

	gameRecord, err := service.games.Get(ctx, input.GameID)
	if err != nil {
		return application.Application{}, fmt.Errorf("submit application: %w", err)
	}
	if gameRecord.GameType != game.GameTypePublic {
		return application.Application{}, fmt.Errorf(
			"submit application: game %q is not public: %w",
			gameRecord.GameID, game.ErrConflict,
		)
	}
	if gameRecord.Status != game.StatusEnrollmentOpen {
		return application.Application{}, fmt.Errorf(
			"submit application: game %q is not in enrollment_open: %w",
			gameRecord.GameID, game.ErrConflict,
		)
	}

	eligibility, err := service.users.GetEligibility(ctx, input.Actor.UserID)
	if err != nil {
		return application.Application{}, fmt.Errorf(
			"submit application: %w: %w",
			shared.ErrServiceUnavailable, err,
		)
	}
	if !eligibility.Exists || !eligibility.CanJoinGame {
		return application.Application{}, fmt.Errorf(
			"%w: user is not eligible to join games",
			shared.ErrEligibilityDenied,
		)
	}

	if err := service.checkRosterCapacity(ctx, gameRecord); err != nil {
		return application.Application{}, err
	}

	availability, err := service.directory.Check(ctx, input.RaceName, input.Actor.UserID)
	if err != nil {
		return application.Application{}, fmt.Errorf("submit application: %w", err)
	}
	if availability.Taken {
		return application.Application{}, fmt.Errorf(
			"submit application: race name held by another user: %w",
			ports.ErrNameTaken,
		)
	}

	applicationID, err := service.ids.NewApplicationID()
	if err != nil {
		return application.Application{}, fmt.Errorf("submit application: %w", err)
	}

	now := service.clock().UTC()
	record, err := application.New(application.NewApplicationInput{
		ApplicationID:   applicationID,
		GameID:          input.GameID,
		ApplicantUserID: input.Actor.UserID,
		RaceName:        input.RaceName,
		Now:             now,
	})
	if err != nil {
		return application.Application{}, fmt.Errorf("submit application: %w", err)
	}

	if err := service.applications.Save(ctx, record); err != nil {
		return application.Application{}, fmt.Errorf("submit application: %w", err)
	}

	intent, err := notificationintent.NewPublicLobbyApplicationSubmittedIntent(
		notificationintent.Metadata{
			IdempotencyKey: "lobby.application.submitted:" + record.ApplicationID.String(),
			OccurredAt:     now,
		},
		notificationintent.LobbyApplicationSubmittedPayload{
			GameID:          gameRecord.GameID.String(),
			GameName:        gameRecord.GameName,
			ApplicantUserID: record.ApplicantUserID,
			ApplicantName:   record.RaceName,
		},
	)
	if err != nil {
		// Building the intent failed: this is a programmer error
		// (mismatched payload contract), not a transport failure.
		// Log and proceed — the application is already committed.
		service.logger.ErrorContext(ctx, "build application submitted intent",
			"application_id", record.ApplicationID.String(),
			"err", err.Error(),
		)
	} else if _, publishErr := service.intents.Publish(ctx, intent); publishErr != nil {
		// Notification degradation per README §Notification Contracts:
		// do not roll back business state.
		service.logger.WarnContext(ctx, "publish application submitted intent",
			"application_id", record.ApplicationID.String(),
			"err", publishErr.Error(),
		)
	}

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

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

// checkRosterCapacity counts active memberships for gameRecord and
// returns game.ErrConflict when the roster has reached the gap-window
// upper bound (max_players + start_gap_players).
func (service *Service) checkRosterCapacity(ctx context.Context, gameRecord game.Game) error {
	cap := gameRecord.MaxPlayers + gameRecord.StartGapPlayers
	count, err := shared.CountActiveMemberships(ctx, service.memberships, gameRecord.GameID)
	if err != nil {
		return fmt.Errorf("submit application: %w", err)
	}
	if count >= cap {
		return fmt.Errorf(
			"submit application: roster full (%d active >= %d cap): %w",
			count, cap, game.ErrConflict,
		)
	}
	return nil
}