import { Component, OnInit, signal, computed, ChangeDetectionStrategy } from '@angular/core';
import { CommonModule } from '@angular/common';
import { RouterLink } from '@angular/router';
import { ApiService } from '../../services';
import { Category } from '../../models';
import { environment } from '../../../environments/environment';
import { ItemsCarouselComponent } from '../../components/items-carousel/items-carousel.component';

@Component({
  selector: 'app-home',
  standalone: true,
  imports: [CommonModule, RouterLink, ItemsCarouselComponent],
  templateUrl: './home.component.html',
  styleUrls: ['./home.component.scss'],
  changeDetection: ChangeDetectionStrategy.OnPush
})
export class HomeComponent implements OnInit {
  brandName = environment.brandFullName;
  isnovo = environment.theme === 'novo';
  categories = signal<Category[]>([]);
  loading = signal(true);
  error = signal<string | null>(null);
  
  // Memoized computed values for performance
  topLevelCategories = computed(() => {
    return this.categories().filter(cat => cat.parentID === 0);
  });

  // Cache subcategories by parent ID
  private subcategoriesCache = computed(() => {
    const cache = new Map<number, Category[]>();
    this.categories().forEach(cat => {
      if (cat.parentID !== 0) {
        if (!cache.has(cat.parentID)) {
          cache.set(cat.parentID, []);
        }
        cache.get(cat.parentID)!.push(cat);
      }
    });
    return cache;
  });

  constructor(private apiService: ApiService) {}

  ngOnInit(): void {
    this.loadCategories();
  }

  loadCategories(): void {
    this.loading.set(true);
    this.apiService.getCategories().subscribe({
      next: (categories) => {
        this.categories.set(categories);
        this.loading.set(false);
      },
      error: (err) => {
        this.error.set('Failed to load categories');
        this.loading.set(false);
        console.error('Error loading categories:', err);
      }
    });
  }

  getTopLevelCategories(): Category[] {
    return this.topLevelCategories();
  }

  getSubCategories(parentID: number): Category[] {
    return this.subcategoriesCache().get(parentID) || [];
  }
}