package memory

import (
	"context"
	"sync"

	"git.threesix.ai/jordan/slack5-1770574304/services/preferences-api/internal/domain"
	"git.threesix.ai/jordan/slack5-1770574304/services/preferences-api/internal/port"
)

// Compile-time verification that PreferenceRepository implements port.PreferenceRepository.
var _ port.PreferenceRepository = (*PreferenceRepository)(nil)

// PreferenceRepository is a thread-safe in-memory implementation of port.PreferenceRepository.
type PreferenceRepository struct {
	mu    sync.RWMutex
	prefs map[string]*domain.UserPreferences
}

// NewPreferenceRepository creates a new in-memory preference repository.
func NewPreferenceRepository() *PreferenceRepository {
	return &PreferenceRepository{
		prefs: make(map[string]*domain.UserPreferences),
	}
}

// Get returns the preferences for a user by ID.
// Returns nil, nil when no preferences exist.
func (r *PreferenceRepository) Get(_ context.Context, userID string) (*domain.UserPreferences, error) {
	r.mu.RLock()
	defer r.mu.RUnlock()

	p, ok := r.prefs[userID]
	if !ok {
		return nil, nil
	}
	// Return a defensive copy
	cp := *p
	return &cp, nil
}

// Upsert creates or replaces preferences for a user.
func (r *PreferenceRepository) Upsert(_ context.Context, prefs *domain.UserPreferences) error {
	r.mu.Lock()
	defer r.mu.Unlock()

	cp := *prefs
	r.prefs[prefs.UserID] = &cp
	return nil
}