package user

import (
	"context"
	"encoding/json"
	"errors"
	"strings"
	"time"

	domain "knowfoolery/backend/services/user-service/internal/domain/user"
	sharederrors "knowfoolery/backend/shared/domain/errors"
	sharedtypes "knowfoolery/backend/shared/domain/types"
	sharedsecurity "knowfoolery/backend/shared/infra/security"
)

// Service orchestrates user use-cases.
type Service struct {
	repo domain.Repository
}

// NewService creates a new user service.
func NewService(repo domain.Repository) *Service {
	return &Service{repo: repo}
}

// Register creates or returns an existing user (idempotent behavior).
func (s *Service) Register(ctx context.Context, in RegisterInput) (*domain.User, error) {
	zitadelID, email, err := validateIdentity(in)
	if err != nil {
		return nil, err
	}
	displayName, consentVersion, consentSource, err := sanitizeRegistrationInput(in)
	if err != nil {
		return nil, err
	}
	existing, err := s.findExistingUser(ctx, zitadelID, email)
	if err != nil {
		return nil, err
	}
	if existing != nil {
		return existing, nil
	}

	now := time.Now().UTC()
	created, err := s.repo.Create(ctx, &domain.User{
		ZitadelUserID:  zitadelID,
		Email:          email,
		EmailVerified:  false,
		DisplayName:    displayName,
		ConsentVersion: consentVersion,
		ConsentGivenAt: now,
		ConsentSource:  consentSource,
	})
	if err != nil {
		return nil, err
	}
	return created, nil
}

// GetProfile returns a user profile by id.
func (s *Service) GetProfile(ctx context.Context, id string) (*domain.User, error) {
	if strings.TrimSpace(id) == "" {
		return nil, domain.ErrValidationFailed
	}
	return s.repo.GetByID(ctx, id)
}

// UpdateProfile updates mutable profile fields.
func (s *Service) UpdateProfile(ctx context.Context, id string, in UpdateProfileInput) (*domain.User, error) {
	if strings.TrimSpace(id) == "" {
		return nil, domain.ErrValidationFailed
	}

	displayName := sharedsecurity.SanitizePlayerName(in.DisplayName)
	if displayName == "" {
		return nil, domain.ErrValidationFailed
	}

	consentVersion := strings.TrimSpace(in.ConsentVersion)
	if consentVersion == "" || len(consentVersion) > 32 {
		return nil, domain.ErrValidationFailed
	}

	consentSource := strings.TrimSpace(in.ConsentSource)
	if consentSource == "" {
		consentSource = "web"
	}
	if len(consentSource) > 32 {
		return nil, domain.ErrValidationFailed
	}

	return s.repo.UpdateProfile(ctx, id, displayName, domain.ConsentRecord{
		Version: consentVersion,
		GivenAt: time.Now().UTC(),
		Source:  consentSource,
	})
}

// VerifyEmail sets email verified flag.
func (s *Service) VerifyEmail(ctx context.Context, id string) (*domain.User, error) {
	if strings.TrimSpace(id) == "" {
		return nil, domain.ErrValidationFailed
	}
	return s.repo.MarkEmailVerified(ctx, id)
}

// DeleteUser soft-deletes a user and writes audit.
func (s *Service) DeleteUser(ctx context.Context, id, actorUserID string) error {
	if strings.TrimSpace(id) == "" {
		return domain.ErrValidationFailed
	}
	return s.repo.SoftDelete(ctx, id, actorUserID)
}

// AdminListUsers lists users with pagination and filters.
func (s *Service) AdminListUsers(
	ctx context.Context,
	in ListUsersInput,
) ([]*domain.User, int64, sharedtypes.Pagination, error) {
	pagination := sharedtypes.Pagination{Page: in.Page, PageSize: in.PageSize}
	pagination.Normalize()

	items, total, err := s.repo.List(ctx, pagination, domain.ListFilter{
		Email:          strings.ToLower(strings.TrimSpace(in.Email)),
		DisplayName:    strings.TrimSpace(in.DisplayName),
		CreatedAfter:   in.CreatedAfter,
		CreatedBefore:  in.CreatedBefore,
		IncludeDeleted: in.IncludeDeleted,
	})
	if err != nil {
		return nil, 0, pagination, err
	}
	return items, total, pagination, nil
}

// AdminExportUser builds GDPR export payload and writes audit log.
func (s *Service) AdminExportUser(ctx context.Context, id, actorUserID string) (*ExportBundle, error) {
	if strings.TrimSpace(id) == "" {
		return nil, domain.ErrValidationFailed
	}

	u, err := s.repo.GetByID(ctx, id)
	if err != nil {
		return nil, err
	}

	logs, err := s.repo.AuditLogsByUserID(ctx, id)
	if err != nil {
		return nil, err
	}

	meta := map[string]string{"operation": domain.AuditActionGDPRExport}
	metaJSON, _ := json.Marshal(meta)
	_ = s.repo.WriteAuditLog(ctx, domain.AuditLogEntry{
		ActorUserID:  actorUserID,
		TargetUserID: id,
		Action:       domain.AuditActionGDPRExport,
		MetadataJSON: string(metaJSON),
	})

	return &ExportBundle{User: u, AuditLogs: logs}, nil
}

func isNotFoundError(err error) bool {
	if err == nil {
		return false
	}
	var domainErr *sharederrors.DomainError
	if errors.As(err, &domainErr) {
		return domainErr.Code == sharederrors.CodeUserNotFound
	}
	return false
}

func validateIdentity(in RegisterInput) (string, string, error) {
	zitadelID := strings.TrimSpace(in.ActorZitadelUserID)
	email := strings.ToLower(strings.TrimSpace(in.ActorEmail))
	if zitadelID == "" || email == "" {
		return "", "", domain.ErrUnauthorized
	}
	if !sharedsecurity.IsValidEmail(email) {
		return "", "", domain.ErrValidationFailed
	}
	return zitadelID, email, nil
}

func sanitizeRegistrationInput(in RegisterInput) (string, string, string, error) {
	displayName := sharedsecurity.SanitizePlayerName(in.DisplayName)
	if displayName == "" {
		return "", "", "", domain.ErrValidationFailed
	}

	consentVersion := strings.TrimSpace(in.ConsentVersion)
	if consentVersion == "" || len(consentVersion) > 32 {
		return "", "", "", domain.ErrValidationFailed
	}

	consentSource := strings.TrimSpace(in.ConsentSource)
	if consentSource == "" {
		consentSource = "web"
	}
	if len(consentSource) > 32 {
		return "", "", "", domain.ErrValidationFailed
	}
	return displayName, consentVersion, consentSource, nil
}

func (s *Service) findExistingUser(
	ctx context.Context,
	zitadelID string,
	email string,
) (*domain.User, error) {
	existing, err := s.repo.GetByZitadelUserID(ctx, zitadelID)
	if err == nil && existing != nil {
		return existing, nil
	}
	if !isNotFoundError(err) {
		return nil, err
	}

	existing, err = s.repo.GetByEmail(ctx, email)
	if err == nil && existing != nil {
		return existing, nil
	}
	if !isNotFoundError(err) {
		return nil, err
	}
	return nil, nil
}