package service

import (
	"context"
	"errors"
	"time"

	"git.threesix.ai/jordan/slate-v3-1770514618/pkg/logging"
	"git.threesix.ai/jordan/slate-v3-1770514618/services/preferences-api/internal/domain"
	"git.threesix.ai/jordan/slate-v3-1770514618/services/preferences-api/internal/port"
)

// PreferencesService handles preferences-related business logic.
type PreferencesService struct {
	repo   port.PreferencesRepository
	logger *logging.Logger
}

// NewPreferencesService creates a new preferences service.
func NewPreferencesService(repo port.PreferencesRepository, logger *logging.Logger) *PreferencesService {
	return &PreferencesService{
		repo:   repo,
		logger: logger.WithService("PreferencesService"),
	}
}

// Get returns preferences for a user.
// Returns domain.ErrPreferencesNotFound if not found.
func (s *PreferencesService) Get(ctx context.Context, userID domain.UserID) (*domain.Preferences, error) {
	return s.repo.Get(ctx, userID)
}

// Upsert creates or updates preferences for a user with merge semantics.
// If no preferences exist, creates defaults and merges the update.
// Validates the merged result before persisting.
func (s *PreferencesService) Upsert(ctx context.Context, userID domain.UserID, update *domain.PreferencesUpdate) (*domain.Preferences, error) {
	prefs, err := s.repo.Get(ctx, userID)
	if err != nil {
		if !errors.Is(err, domain.ErrPreferencesNotFound) {
			return nil, err
		}
		prefs = domain.NewDefaultPreferences(userID)
	}

	prefs.MergeFrom(update)

	if err := prefs.Validate(); err != nil {
		return nil, err
	}

	prefs.UpdatedAt = time.Now().UTC()

	if err := s.repo.Upsert(ctx, userID, prefs); err != nil {
		return nil, err
	}

	s.logger.Info("preferences upserted", "user_id", userID.String())
	return prefs, nil
}