// Package createinvite implements the `lobby.invite.create` message type. It
// validates the request against the private-game enrollment rules, persists
// the new created invite via InviteStore, and publishes the
// `lobby.invite.created` notification intent to the invitee.
package createinvite

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

	"galaxy/lobby/internal/domain/common"
	"galaxy/lobby/internal/domain/game"
	"galaxy/lobby/internal/domain/invite"
	"galaxy/lobby/internal/domain/membership"
	"galaxy/lobby/internal/logging"
	"galaxy/lobby/internal/ports"
	"galaxy/lobby/internal/service/shared"
	"galaxy/lobby/internal/telemetry"
	"galaxy/notificationintent"
)

// Service executes the private-game invite creation use case.
type Service struct {
	games       ports.GameStore
	invites     ports.InviteStore
	memberships ports.MembershipStore
	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

	// Invites persists the new created invite record and is scanned for
	// existing active invites that block re-invite.
	Invites ports.InviteStore

	// Memberships supplies the active-roster count for the capacity guard
	// and is scanned for an existing active membership of the invitee.
	Memberships ports.MembershipStore

	// Intents publishes the lobby.invite.created intent.
	Intents ports.IntentPublisher

	// IDs mints the new opaque invite 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.invite.outcomes` counter on each
	// successful create. 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 create invite service: nil game store")
	case deps.Invites == nil:
		return nil, errors.New("new create invite service: nil invite store")
	case deps.Memberships == nil:
		return nil, errors.New("new create invite service: nil membership store")
	case deps.Intents == nil:
		return nil, errors.New("new create invite service: nil intent publisher")
	case deps.IDs == nil:
		return nil, errors.New("new create invite 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,
		invites:     deps.Invites,
		memberships: deps.Memberships,
		intents:     deps.Intents,
		ids:         deps.IDs,
		clock:       clock,
		logger:      logger.With("service", "lobby.createinvite"),
		telemetry:   deps.Telemetry,
	}, nil
}

// Input stores the arguments required to create one invite.
type Input struct {
	// Actor identifies the caller. Must be the private-game owner.
	Actor shared.Actor

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

	// InviteeUserID stores the platform user id of the invited user.
	InviteeUserID string
}

// Handle authorizes the actor, validates the game state, refuses duplicate
// active invites and active memberships, persists the new created invite,
// and publishes the lobby.invite.created intent on success.
func (service *Service) Handle(ctx context.Context, input Input) (invite.Invite, error) {
	if service == nil {
		return invite.Invite{}, errors.New("create invite: nil service")
	}
	if ctx == nil {
		return invite.Invite{}, errors.New("create invite: nil context")
	}
	if err := input.Actor.Validate(); err != nil {
		return invite.Invite{}, fmt.Errorf("create invite: actor: %w", err)
	}
	if !input.Actor.IsUser() {
		return invite.Invite{}, fmt.Errorf(
			"%w: only private-game owners may create invites",
			shared.ErrForbidden,
		)
	}
	if err := input.GameID.Validate(); err != nil {
		return invite.Invite{}, fmt.Errorf("create invite: %w", err)
	}
	inviteeUserID := strings.TrimSpace(input.InviteeUserID)

	gameRecord, err := service.games.Get(ctx, input.GameID)
	if err != nil {
		return invite.Invite{}, fmt.Errorf("create invite: %w", err)
	}
	if gameRecord.GameType != game.GameTypePrivate {
		return invite.Invite{}, fmt.Errorf(
			"create invite: game %q is not private: %w",
			gameRecord.GameID, game.ErrConflict,
		)
	}
	if gameRecord.Status != game.StatusEnrollmentOpen {
		return invite.Invite{}, fmt.Errorf(
			"create invite: game %q is not in enrollment_open: %w",
			gameRecord.GameID, game.ErrConflict,
		)
	}
	if gameRecord.OwnerUserID != input.Actor.UserID {
		return invite.Invite{}, fmt.Errorf(
			"%w: actor is not the owner of game %q",
			shared.ErrForbidden, gameRecord.GameID,
		)
	}

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

	if err := service.checkNoActiveInvite(ctx, gameRecord.GameID, inviteeUserID); err != nil {
		return invite.Invite{}, err
	}
	if err := service.checkNoActiveMembership(ctx, gameRecord.GameID, inviteeUserID); err != nil {
		return invite.Invite{}, err
	}

	inviteID, err := service.ids.NewInviteID()
	if err != nil {
		return invite.Invite{}, fmt.Errorf("create invite: %w", err)
	}

	now := service.clock().UTC()
	record, err := invite.New(invite.NewInviteInput{
		InviteID:      inviteID,
		GameID:        gameRecord.GameID,
		InviterUserID: input.Actor.UserID,
		InviteeUserID: inviteeUserID,
		Now:           now,
		ExpiresAt:     gameRecord.EnrollmentEndsAt,
	})
	if err != nil {
		return invite.Invite{}, fmt.Errorf("create invite: %w", err)
	}

	if err := service.invites.Save(ctx, record); err != nil {
		return invite.Invite{}, fmt.Errorf("create invite: %w", err)
	}

	inviterName := service.resolveInviterName(ctx, gameRecord.GameID, input.Actor.UserID)

	intent, err := notificationintent.NewLobbyInviteCreatedIntent(
		notificationintent.Metadata{
			IdempotencyKey: "lobby.invite.created:" + record.InviteID.String(),
			OccurredAt:     now,
		},
		record.InviteeUserID,
		notificationintent.LobbyInviteCreatedPayload{
			GameID:        gameRecord.GameID.String(),
			GameName:      gameRecord.GameName,
			InviterUserID: record.InviterUserID,
			InviterName:   inviterName,
		},
	)
	if err != nil {
		service.logger.ErrorContext(ctx, "build invite created intent",
			"invite_id", record.InviteID.String(),
			"err", err.Error(),
		)
	} else if _, publishErr := service.intents.Publish(ctx, intent); publishErr != nil {
		service.logger.WarnContext(ctx, "publish invite created intent",
			"invite_id", record.InviteID.String(),
			"err", publishErr.Error(),
		)
	}

	service.telemetry.RecordInviteOutcome(ctx, "created")

	logArgs := []any{
		"game_id", record.GameID.String(),
		"game_status", string(gameRecord.Status),
		"invite_id", record.InviteID.String(),
		"inviter_user_id", record.InviterUserID,
		"invitee_user_id", record.InviteeUserID,
	}
	logArgs = append(logArgs, logging.ContextAttrs(ctx)...)
	service.logger.InfoContext(ctx, "invite created", logArgs...)
	return record, nil
}

// checkRosterCapacity counts active memberships for gameRecord and returns
// game.ErrConflict when the roster has reached the gap-window upper bound.
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("create invite: %w", err)
	}
	if count >= cap {
		return fmt.Errorf(
			"create invite: roster full (%d active >= %d cap): %w",
			count, cap, game.ErrConflict,
		)
	}
	return nil
}

// checkNoActiveInvite enforces the README invariant that the invitee has no
// existing active invite for the same game. The Redis InviteStore does not
// maintain a (game, invitee) uniqueness index, so the service performs the
// scan; see the design notes.
func (service *Service) checkNoActiveInvite(ctx context.Context, gameID common.GameID, inviteeUserID string) error {
	existing, err := service.invites.GetByGame(ctx, gameID)
	if err != nil {
		return fmt.Errorf("create invite: %w", err)
	}
	for _, record := range existing {
		if record.Status == invite.StatusCreated && record.InviteeUserID == inviteeUserID {
			return fmt.Errorf(
				"create invite: invitee %q already has an active invite to game %q: %w",
				inviteeUserID, gameID, invite.ErrConflict,
			)
		}
	}
	return nil
}

// checkNoActiveMembership enforces the README invariant that the invitee is
// not already an active member of the game.
func (service *Service) checkNoActiveMembership(ctx context.Context, gameID common.GameID, inviteeUserID string) error {
	existing, err := service.memberships.GetByGame(ctx, gameID)
	if err != nil {
		return fmt.Errorf("create invite: %w", err)
	}
	for _, record := range existing {
		if record.Status == membership.StatusActive && record.UserID == inviteeUserID {
			return fmt.Errorf(
				"create invite: invitee %q already has an active membership in game %q: %w",
				inviteeUserID, gameID, membership.ErrConflict,
			)
		}
	}
	return nil
}

// resolveInviterName returns the owner's confirmed in-game race name when the
// owner already has an active membership in the game. Otherwise it falls
// back to the owner's user id, matching README §Invite Lifecycle.
func (service *Service) resolveInviterName(ctx context.Context, gameID common.GameID, ownerUserID string) string {
	records, err := service.memberships.GetByGame(ctx, gameID)
	if err != nil {
		service.logger.WarnContext(ctx, "resolve inviter name: load memberships",
			"game_id", gameID.String(),
			"err", err.Error(),
		)
		return ownerUserID
	}
	for _, record := range records {
		if record.UserID == ownerUserID && record.Status == membership.StatusActive {
			return record.RaceName
		}
	}
	return ownerUserID
}