import { Component, OnInit, signal, computed, ChangeDetectionStrategy } from '@angular/core';
import { CommonModule } from '@angular/common';
import { Router, RouterLink } from '@angular/router';
import { forkJoin } from 'rxjs';
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[]>([]);
  itemCounts = signal<Map<number, number>>(new Map());
  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, private router: Router) {}

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

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

  private loadItemCounts(): void {
    const topLevel = this.topLevelCategories();
    if (topLevel.length === 0) return;

    const requests: Record<string, ReturnType<ApiService['getCategoryItems']>> = {};
    topLevel.forEach(cat => {
      requests[cat.categoryID.toString()] = this.apiService.getCategoryItems(cat.categoryID, 1000);
    });

    forkJoin(requests).subscribe({
      next: (results) => {
        const counts = new Map<number, number>();
        Object.entries(results).forEach(([id, items]) => {
          counts.set(Number(id), items.length);
        });
        this.itemCounts.set(counts);
      },
      error: (err) => console.error('Error loading item counts:', err)
    });
  }

  getItemCount(categoryID: number): number {
    return this.itemCounts().get(categoryID) || 0;
  }

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

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

  navigateToSearch(): void {
    this.router.navigate(['/search']);
  }

  scrollToCatalog(): void {
    const target = document.getElementById('catalog');
    if (!target) return;
    
    const targetY = target.getBoundingClientRect().top + window.scrollY;
    const startY = window.scrollY;
    const distance = targetY - startY;
    const duration = 1200;
    let start: number | null = null;

    const easeInOutCubic = (t: number) =>
      t < 0.5 ? 4 * t * t * t : 1 - Math.pow(-2 * t + 2, 3) / 2;

    const step = (timestamp: number) => {
      if (!start) start = timestamp;
      const elapsed = timestamp - start;
      const progress = Math.min(elapsed / duration, 1);
      window.scrollTo(0, startY + distance * easeInOutCubic(progress));
      if (progress < 1) requestAnimationFrame(step);
    };

    requestAnimationFrame(step);
  }
}