// Package accountdeletion implements the trusted `DeleteUser` soft-delete
// command owned by User Service.
package accountdeletion

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

	"galaxy/user/internal/domain/common"
	"galaxy/user/internal/ports"
	"galaxy/user/internal/service/shared"
	"galaxy/user/internal/telemetry"
)

const adminInternalAPISource = common.Source("admin_internal_api")

// Input stores one trusted `DeleteUser` command request.
type Input struct {
	// UserID identifies the regular-user account to soft-delete.
	UserID string

	// ReasonCode stores the machine-readable mutation reason.
	ReasonCode string

	// Actor stores the audit actor metadata attached to the mutation.
	Actor ActorInput
}

// ActorInput stores one transport-facing audit actor payload.
type ActorInput struct {
	// Type stores the machine-readable actor type.
	Type string

	// ID stores the optional stable actor identifier.
	ID string
}

// Result stores one trusted `DeleteUser` command outcome.
type Result struct {
	// UserID identifies the soft-deleted account.
	UserID string `json:"user_id"`

	// DeletedAt stores the committed soft-delete timestamp.
	DeletedAt time.Time `json:"deleted_at"`
}

// Service executes the explicit trusted `DeleteUser` soft-delete command.
type Service struct {
	accounts           ports.UserAccountStore
	clock              ports.Clock
	lifecyclePublisher ports.UserLifecyclePublisher
	logger             *slog.Logger
	telemetry          *telemetry.Runtime
}

// NewService constructs one `DeleteUser` use case without optional
// observability hooks.
func NewService(
	accounts ports.UserAccountStore,
	clock ports.Clock,
	lifecyclePublisher ports.UserLifecyclePublisher,
) (*Service, error) {
	return NewServiceWithObservability(accounts, clock, lifecyclePublisher, nil, nil)
}

// NewServiceWithObservability constructs one `DeleteUser` use case with
// optional observability hooks.
func NewServiceWithObservability(
	accounts ports.UserAccountStore,
	clock ports.Clock,
	lifecyclePublisher ports.UserLifecyclePublisher,
	logger *slog.Logger,
	telemetryRuntime *telemetry.Runtime,
) (*Service, error) {
	switch {
	case accounts == nil:
		return nil, fmt.Errorf("account deletion service: user account store must not be nil")
	case clock == nil:
		return nil, fmt.Errorf("account deletion service: clock must not be nil")
	case lifecyclePublisher == nil:
		return nil, fmt.Errorf("account deletion service: lifecycle publisher must not be nil")
	default:
		return &Service{
			accounts:           accounts,
			clock:              clock,
			lifecyclePublisher: lifecyclePublisher,
			logger:             logger,
			telemetry:          telemetryRuntime,
		}, nil
	}
}

// Execute soft-deletes the account identified by input.UserID. The command is
// idempotent per `user_id`: calling it after the account is already
// soft-deleted returns `subject_not_found` and does not re-publish the
// lifecycle event.
func (service *Service) Execute(ctx context.Context, input Input) (result Result, err error) {
	outcome := shared.ErrorCodeInternalError
	userIDString := strings.TrimSpace(input.UserID)
	reasonCodeValue := strings.TrimSpace(input.ReasonCode)
	actorTypeValue := strings.TrimSpace(input.Actor.Type)
	actorIDValue := strings.TrimSpace(input.Actor.ID)
	defer func() {
		if service.telemetry != nil {
			service.telemetry.RecordUserLifecycleMutation(ctx, "delete", outcome)
		}
		shared.LogServiceOutcome(service.logger, ctx, "delete user completed", err,
			"use_case", "delete_user",
			"command", "delete",
			"outcome", outcome,
			"user_id", userIDString,
			"source", adminInternalAPISource.String(),
			"reason_code", reasonCodeValue,
			"actor_type", actorTypeValue,
			"actor_id", actorIDValue,
		)
	}()

	if ctx == nil {
		outcome = shared.ErrorCodeInvalidRequest
		return Result{}, shared.InvalidRequest("context must not be nil")
	}

	userID, err := shared.ParseUserID(input.UserID)
	if err != nil {
		outcome = shared.MetricOutcome(err)
		return Result{}, err
	}
	userIDString = userID.String()

	reasonCode, err := shared.ParseReasonCode(input.ReasonCode)
	if err != nil {
		outcome = shared.MetricOutcome(err)
		return Result{}, err
	}
	reasonCodeValue = reasonCode.String()

	actor, err := parseActor(input.Actor)
	if err != nil {
		outcome = shared.MetricOutcome(err)
		return Result{}, err
	}
	actorTypeValue = actor.Type.String()
	actorIDValue = actor.ID.String()

	record, err := service.accounts.GetByUserID(ctx, userID)
	switch {
	case err == nil:
	case errors.Is(err, ports.ErrNotFound):
		outcome = shared.ErrorCodeSubjectNotFound
		return Result{}, shared.SubjectNotFound()
	default:
		outcome = shared.ErrorCodeServiceUnavailable
		return Result{}, shared.ServiceUnavailable(err)
	}
	if record.IsDeleted() {
		outcome = shared.ErrorCodeSubjectNotFound
		return Result{}, shared.SubjectNotFound()
	}

	now := service.clock.Now().UTC()
	record.UpdatedAt = now
	record.DeletedAt = &now

	if err := service.accounts.Update(ctx, record); err != nil {
		switch {
		case errors.Is(err, ports.ErrNotFound):
			outcome = shared.ErrorCodeSubjectNotFound
			return Result{}, shared.SubjectNotFound()
		case errors.Is(err, ports.ErrConflict):
			outcome = shared.ErrorCodeConflict
			return Result{}, shared.Conflict()
		default:
			outcome = shared.ErrorCodeServiceUnavailable
			return Result{}, shared.ServiceUnavailable(err)
		}
	}

	outcome = "success"
	result = Result{
		UserID:    userID.String(),
		DeletedAt: now,
	}
	publishDeleted(ctx, service.lifecyclePublisher, service.telemetry, service.logger, userID, now, actor, reasonCode)

	return result, nil
}

func parseActor(input ActorInput) (common.ActorRef, error) {
	ref := common.ActorRef{
		Type: common.ActorType(shared.NormalizeString(input.Type)),
		ID:   common.ActorID(shared.NormalizeString(input.ID)),
	}
	if err := ref.Validate(); err != nil {
		if ref.Type.IsZero() {
			return common.ActorRef{}, shared.InvalidRequest("actor.type must not be empty")
		}
		return common.ActorRef{}, shared.InvalidRequest(err.Error())
	}

	return ref, nil
}

func publishDeleted(
	ctx context.Context,
	publisher ports.UserLifecyclePublisher,
	telemetryRuntime *telemetry.Runtime,
	logger *slog.Logger,
	userID common.UserID,
	occurredAt time.Time,
	actor common.ActorRef,
	reasonCode common.ReasonCode,
) {
	if publisher == nil {
		return
	}

	event := ports.UserLifecycleEvent{
		EventType:  ports.UserLifecycleDeletedEventType,
		UserID:     userID,
		OccurredAt: occurredAt,
		Source:     adminInternalAPISource,
		Actor:      actor,
		ReasonCode: reasonCode,
	}
	if err := publisher.PublishUserLifecycleEvent(ctx, event); err != nil {
		if telemetryRuntime != nil {
			telemetryRuntime.RecordEventPublicationFailure(ctx, string(ports.UserLifecycleDeletedEventType))
		}
		shared.LogEventPublicationFailure(logger, ctx, string(ports.UserLifecycleDeletedEventType), err,
			"use_case", "delete_user",
			"user_id", userID.String(),
			"source", adminInternalAPISource.String(),
			"reason_code", reasonCode.String(),
			"actor_type", actor.Type.String(),
			"actor_id", actor.ID.String(),
		)
	}
}