// Package service provides business logic / use cases for the application.
// Services orchestrate domain operations using port interfaces.
package service

import (
	"context"
	"time"

	"git.threesix.ai/jordan/slack5-1770603014/pkg/logging"
	"git.threesix.ai/jordan/slack5-1770603014/services/preferences-api/internal/domain"
	"git.threesix.ai/jordan/slack5-1770603014/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"),
	}
}

// GetPreferences returns preferences for a user. Returns defaults if none are stored.
func (s *PreferencesService) GetPreferences(ctx context.Context, userID domain.UserID) (*domain.UserPreferences, error) {
	prefs, err := s.repo.Get(ctx, userID)
	if err != nil {
		return nil, err
	}

	if prefs != nil {
		return prefs, nil
	}

	// Return defaults for unknown users
	return &domain.UserPreferences{
		UserID:      userID,
		Preferences: domain.DefaultPreferences(),
		UpdatedAt:   time.Now().UTC(),
	}, nil
}

// UpdateInput contains the partial preference data for an update.
// Pointer fields distinguish "not provided" from zero values.
type UpdateInput struct {
	Theme         *string
	Language      *string
	Notifications *NotificationsInput
}

// NotificationsInput contains partial notification settings.
type NotificationsInput struct {
	Email  *bool
	Push   *bool
	Digest *string
}

// UpdatePreferences merges partial input with existing preferences and persists.
func (s *PreferencesService) UpdatePreferences(ctx context.Context, userID domain.UserID, input UpdateInput) (*domain.UserPreferences, error) {
	// Fetch existing or start from defaults
	existing, err := s.repo.Get(ctx, userID)
	if err != nil {
		return nil, err
	}

	var merged domain.Preferences
	if existing != nil {
		merged = existing.Preferences
	} else {
		merged = domain.DefaultPreferences()
	}

	// Deep merge incoming fields
	if input.Theme != nil {
		merged.Theme = *input.Theme
	}
	if input.Language != nil {
		merged.Language = *input.Language
	}
	if input.Notifications != nil {
		if input.Notifications.Email != nil {
			merged.Notifications.Email = *input.Notifications.Email
		}
		if input.Notifications.Push != nil {
			merged.Notifications.Push = *input.Notifications.Push
		}
		if input.Notifications.Digest != nil {
			merged.Notifications.Digest = *input.Notifications.Digest
		}
	}

	// Validate merged result
	if err := merged.Validate(); err != nil {
		return nil, err
	}

	now := time.Now().UTC()
	prefs := &domain.UserPreferences{
		UserID:      userID,
		Preferences: merged,
		UpdatedAt:   now,
	}

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

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