// Package redeeminvite implements the `lobby.invite.redeem` message type. It
// validates the invitee against the private-game enrollment rules, reserves
// the chosen race name, transitions the invite from created to redeemed,
// creates the matching active membership, opens the gap window when the new
// approved count equals max_players, and publishes the
// `lobby.invite.redeemed` notification intent to the private-game owner.
package redeeminvite

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"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 redemption use case.
type Service struct {
	games       ports.GameStore
	invites     ports.InviteStore
	memberships ports.MembershipStore
	directory   ports.RaceNameDirectory
	users       ports.UserService
	gapStore    ports.GapActivationStore
	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 status verification and the
	// owner notification recipient.
	Games ports.GameStore

	// Invites loads the target invite and applies the
	// created → redeemed transition.
	Invites ports.InviteStore

	// Memberships persists the new active membership and supplies the
	// approved-count for the gap-window decision and capacity guard.
	Memberships ports.MembershipStore

	// Directory canonicalizes the race name and reserves it for the
	// invitee.
	Directory ports.RaceNameDirectory

	// Users resolves the synchronous eligibility snapshot for both the
	// inviter and the invitee. uses it to short-circuit
	// redemption when either party has been permanently blocked or
	// soft-deleted between invite creation and the redeem attempt.
	Users ports.UserService

	// GapStore records the gap-window activation timestamp when the new
	// approved count equals max_players.
	GapStore ports.GapActivationStore

	// Intents publishes the lobby.invite.redeemed intent to the owner.
	Intents ports.IntentPublisher

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

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

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

	// Telemetry records the `lobby.invite.outcomes` and
	// `lobby.membership.changes` counters. 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 redeem invite service: nil game store")
	case deps.Invites == nil:
		return nil, errors.New("new redeem invite service: nil invite store")
	case deps.Memberships == nil:
		return nil, errors.New("new redeem invite service: nil membership store")
	case deps.Directory == nil:
		return nil, errors.New("new redeem invite service: nil race name directory")
	case deps.Users == nil:
		return nil, errors.New("new redeem invite service: nil user service")
	case deps.GapStore == nil:
		return nil, errors.New("new redeem invite service: nil gap activation store")
	case deps.Intents == nil:
		return nil, errors.New("new redeem invite service: nil intent publisher")
	case deps.IDs == nil:
		return nil, errors.New("new redeem 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,
		directory:   deps.Directory,
		users:       deps.Users,
		gapStore:    deps.GapStore,
		intents:     deps.Intents,
		ids:         deps.IDs,
		clock:       clock,
		logger:      logger.With("service", "lobby.redeeminvite"),
		telemetry:   deps.Telemetry,
	}, nil
}

// Input stores the arguments required to redeem one invite.
type Input struct {
	// Actor identifies the caller. Must be the invitee.
	Actor shared.Actor

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

	// InviteID identifies the target invite.
	InviteID common.InviteID

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

// Handle authorizes the invitee, validates the invite + game state, reserves
// the race name, transitions the invite, persists the active membership,
// opens the gap window if appropriate, and publishes the
// lobby.invite.redeemed intent on success.
func (service *Service) Handle(ctx context.Context, input Input) (membership.Membership, error) {
	if service == nil {
		return membership.Membership{}, errors.New("redeem invite: nil service")
	}
	if ctx == nil {
		return membership.Membership{}, errors.New("redeem invite: nil context")
	}
	if err := input.Actor.Validate(); err != nil {
		return membership.Membership{}, fmt.Errorf("redeem invite: actor: %w", err)
	}
	if !input.Actor.IsUser() {
		return membership.Membership{}, fmt.Errorf(
			"%w: only the invited user may redeem an invite",
			shared.ErrForbidden,
		)
	}
	if err := input.GameID.Validate(); err != nil {
		return membership.Membership{}, fmt.Errorf("redeem invite: %w", err)
	}
	if err := input.InviteID.Validate(); err != nil {
		return membership.Membership{}, fmt.Errorf("redeem invite: %w", err)
	}

	inv, err := service.invites.Get(ctx, input.InviteID)
	if err != nil {
		return membership.Membership{}, fmt.Errorf("redeem invite: %w", err)
	}
	if inv.GameID != input.GameID {
		// Defensive: opaque ids must not leak across games.
		return membership.Membership{}, fmt.Errorf(
			"redeem invite: invite %q does not belong to game %q: %w",
			inv.InviteID, input.GameID, invite.ErrNotFound,
		)
	}
	if inv.InviteeUserID != input.Actor.UserID {
		return membership.Membership{}, fmt.Errorf(
			"%w: invite is addressed to a different user",
			shared.ErrForbidden,
		)
	}
	if inv.Status != invite.StatusCreated {
		return membership.Membership{}, fmt.Errorf(
			"redeem invite: status %q is not %q: %w",
			inv.Status, invite.StatusCreated, invite.ErrConflict,
		)
	}

	gameRecord, err := service.games.Get(ctx, input.GameID)
	if err != nil {
		return membership.Membership{}, fmt.Errorf("redeem invite: %w", err)
	}
	if gameRecord.GameType != game.GameTypePrivate {
		return membership.Membership{}, fmt.Errorf(
			"redeem invite: game %q is not private: %w",
			gameRecord.GameID, game.ErrConflict,
		)
	}
	if gameRecord.Status != game.StatusEnrollmentOpen {
		return membership.Membership{}, fmt.Errorf(
			"redeem invite: game %q is not in enrollment_open: %w",
			gameRecord.GameID, game.ErrConflict,
		)
	}

	// cascade guard: a permanent_block or DeleteUser on the
	// inviter or the invitee makes the invite untusable. Return
	// subject_not_found so the caller sees the same outcome as if the
	// invite never existed, even when the user-lifecycle cascade has
	// not yet flipped the invite to revoked.
	if err := service.requireActiveParty(ctx, inv.InviterUserID, "inviter"); err != nil {
		return membership.Membership{}, err
	}
	if err := service.requireActiveParty(ctx, input.Actor.UserID, "invitee"); err != nil {
		return membership.Membership{}, err
	}

	cap := gameRecord.MaxPlayers + gameRecord.StartGapPlayers
	currentActive, err := shared.CountActiveMemberships(ctx, service.memberships, gameRecord.GameID)
	if err != nil {
		return membership.Membership{}, fmt.Errorf("redeem invite: %w", err)
	}
	if currentActive >= cap {
		return membership.Membership{}, fmt.Errorf(
			"redeem invite: roster full (%d active >= %d cap): %w",
			currentActive, cap, game.ErrConflict,
		)
	}

	canonical, err := service.directory.Canonicalize(input.RaceName)
	if err != nil {
		return membership.Membership{}, fmt.Errorf("redeem invite: %w", err)
	}

	if err := service.directory.Reserve(ctx, gameRecord.GameID.String(), input.Actor.UserID, input.RaceName); err != nil {
		return membership.Membership{}, fmt.Errorf("redeem invite: %w", err)
	}

	now := service.clock().UTC()
	updateErr := service.invites.UpdateStatus(ctx, ports.UpdateInviteStatusInput{
		InviteID:     inv.InviteID,
		ExpectedFrom: invite.StatusCreated,
		To:           invite.StatusRedeemed,
		At:           now,
		RaceName:     input.RaceName,
	})
	if updateErr != nil {
		// Concurrent mutation lost the CAS race. Release the
		// reservation we just made so it does not orphan; the user
		// may retry redeem later under the same canonical key.
		if releaseErr := service.directory.ReleaseReservation(ctx, gameRecord.GameID.String(), input.Actor.UserID, input.RaceName); releaseErr != nil {
			service.logger.WarnContext(ctx, "release reservation after redeem cas failure",
				"invite_id", inv.InviteID.String(),
				"err", releaseErr.Error(),
			)
		}
		return membership.Membership{}, fmt.Errorf("redeem invite: %w", updateErr)
	}

	membershipID, err := service.ids.NewMembershipID()
	if err != nil {
		return membership.Membership{}, fmt.Errorf("redeem invite: %w", err)
	}
	memberRecord, err := membership.New(membership.NewMembershipInput{
		MembershipID: membershipID,
		GameID:       gameRecord.GameID,
		UserID:       input.Actor.UserID,
		RaceName:     input.RaceName,
		CanonicalKey: canonical,
		Now:          now,
	})
	if err != nil {
		return membership.Membership{}, fmt.Errorf("redeem invite: %w", err)
	}
	if err := service.memberships.Save(ctx, memberRecord); err != nil {
		return membership.Membership{}, fmt.Errorf("redeem invite: %w", err)
	}

	// Gap-window trigger: count after Save now includes the new
	// membership, so if it equals max_players we just crossed the
	// threshold. The worker reads gap_activated_at to time
	// out the gap; auto-transition to ready_to_start is its job.
	if currentActive+1 == gameRecord.MaxPlayers {
		if err := service.gapStore.MarkActivated(ctx, gameRecord.GameID, now); err != nil {
			service.logger.WarnContext(ctx, "mark gap activation",
				"game_id", gameRecord.GameID.String(),
				"err", err.Error(),
			)
		}
	}

	intent, err := notificationintent.NewLobbyInviteRedeemedIntent(
		notificationintent.Metadata{
			IdempotencyKey: "lobby.invite.redeemed:" + inv.InviteID.String(),
			OccurredAt:     now,
		},
		gameRecord.OwnerUserID,
		notificationintent.LobbyInviteRedeemedPayload{
			GameID:        gameRecord.GameID.String(),
			GameName:      gameRecord.GameName,
			InviteeUserID: memberRecord.UserID,
			InviteeName:   memberRecord.RaceName,
		},
	)
	if err != nil {
		service.logger.ErrorContext(ctx, "build invite redeemed intent",
			"invite_id", inv.InviteID.String(),
			"err", err.Error(),
		)
	} else if _, publishErr := service.intents.Publish(ctx, intent); publishErr != nil {
		service.logger.WarnContext(ctx, "publish invite redeemed intent",
			"invite_id", inv.InviteID.String(),
			"err", publishErr.Error(),
		)
	}

	service.telemetry.RecordInviteOutcome(ctx, "redeemed")
	service.telemetry.RecordMembershipChange(ctx, "activated")

	logArgs := []any{
		"game_id", gameRecord.GameID.String(),
		"game_status", string(gameRecord.Status),
		"invite_id", inv.InviteID.String(),
		"membership_id", memberRecord.MembershipID.String(),
		"user_id", memberRecord.UserID,
		"race_name", memberRecord.RaceName,
		"canonical_key", string(memberRecord.CanonicalKey),
	}
	logArgs = append(logArgs, logging.ContextAttrs(ctx)...)
	service.logger.InfoContext(ctx, "invite redeemed", logArgs...)
	return memberRecord, nil
}

// requireActiveParty fetches the eligibility snapshot for userID and
// returns shared.ErrSubjectNotFound when the user no longer exists or
// has been permanently blocked. Transport failures wrap
// shared.ErrServiceUnavailable so the caller can map to HTTP 503.
func (service *Service) requireActiveParty(ctx context.Context, userID, role string) error {
	eligibility, err := service.users.GetEligibility(ctx, userID)
	if err != nil {
		return fmt.Errorf("redeem invite: %w of %s: %w", shared.ErrServiceUnavailable, role, err)
	}
	if !eligibility.Exists || eligibility.PermanentBlocked {
		return fmt.Errorf("redeem invite: %s no longer active: %w", role, shared.ErrSubjectNotFound)
	}
	return nil
}