import { Component, signal, HostListener, OnDestroy, ChangeDetectionStrategy } from '@angular/core';
import { DecimalPipe } from '@angular/common';
import { FormsModule } from '@angular/forms';
import { RouterLink } from '@angular/router';
import { ApiService, CartService } from '../../services';
import { Item } from '../../models';
import { Subject, Subscription } from 'rxjs';
import { debounceTime, distinctUntilChanged } from 'rxjs/operators';
import { getDiscountedPrice, getMainImage, trackByItemId } from '../../utils/item.utils';

@Component({
  selector: 'app-search',
  imports: [DecimalPipe, FormsModule, RouterLink],
  templateUrl: './search.component.html',
  styleUrls: ['./search.component.scss'],
  changeDetection: ChangeDetectionStrategy.OnPush
})
export class SearchComponent implements OnDestroy {
  searchQuery = '';
  items = signal<Item[]>([]);
  loading = signal(false);
  error = signal<string | null>(null);
  hasMore = signal(true);
  totalResults = signal<number>(0);
  
  private skip = 0;
  private readonly count = 20;
  private isLoadingMore = false;
  private searchSubject = new Subject<string>();
  private searchSubscription: Subscription;

  constructor(
    private apiService: ApiService,
    private cartService: CartService
  ) {
    this.searchSubscription = this.searchSubject
      .pipe(
        debounceTime(300),
        distinctUntilChanged()
      )
      .subscribe(query => {
        if (query.trim().length >= 3 || query.trim().length === 0) {
          this.performSearch(query);
        }
      });
  }

  ngOnDestroy(): void {
    this.searchSubscription.unsubscribe();
    this.searchSubject.complete();
  }

  onSearchInput(query: string): void {
    this.searchQuery = query;
    this.searchSubject.next(query);
  }

  performSearch(query: string): void {
    if (!query.trim()) {
      this.items.set([]);
      this.hasMore.set(true);
      this.totalResults.set(0);
      return;
    }

    this.items.set([]);
    this.skip = 0;
    this.hasMore.set(true);
    this.totalResults.set(0);
    this.loadResults();
  }

  loadResults(): void {
    if (this.isLoadingMore || !this.hasMore() || !this.searchQuery.trim()) return;

    this.loading.set(true);
    this.isLoadingMore = true;

    this.apiService.searchItems(this.searchQuery, this.count, this.skip).subscribe({
      next: (response) => {
        // Update total results (only on first load)
        if (this.skip === 0) {
          this.totalResults.set(response.total);
        }

        // Handle empty results
        if (!response.items || response.items.length === 0) {
          this.hasMore.set(false);
        } else {
          // Check if there are more items to load
          if (response.items.length < this.count || this.skip + response.items.length >= response.total) {
            this.hasMore.set(false);
          }
          this.items.update(current => [...current, ...response.items]);
          this.skip += response.items.length;
        }
        this.loading.set(false);
        this.isLoadingMore = false;
      },
      error: (err) => {
        this.error.set('Ошибка при поиске товаров');
        this.loading.set(false);
        this.isLoadingMore = false;
        console.error('Error searching items:', err);
      }
    });
  }

  private scrollTimeout: any;

  @HostListener('window:scroll')
  onScroll(): void {
    if (this.scrollTimeout) clearTimeout(this.scrollTimeout);
    
    this.scrollTimeout = setTimeout(() => {
      const scrollPosition = window.innerHeight + window.scrollY;
      const bottomPosition = document.documentElement.scrollHeight - 500;

      if (scrollPosition >= bottomPosition && !this.loading() && this.hasMore()) {
        this.loadResults();
      }
    }, 100);
  }

  addToCart(itemID: number, event: Event): void {
    event.preventDefault();
    event.stopPropagation();
    this.cartService.addItem(itemID);
  }

  readonly getDiscountedPrice = getDiscountedPrice;
  readonly getMainImage = getMainImage;
  readonly trackByItemId = trackByItemId;
}