DiunaBI/Frontend/src/app/modules/layers/layers-list/layers-list.component.ts

import { HttpClient } from '@angular/common/http';
import { Component, HostListener, OnInit, ViewChild } from '@angular/core';
import { MatSort, MatSortable, MatSortModule } from '@angular/material/sort';
import { MatTableDataSource, MatTableModule } from '@angular/material/table';
import { Layer } from 'src/app/models/layer.model';
import { MatInputModule } from '@angular/material/input';
import { MatFormFieldModule } from '@angular/material/form-field';
import { RouterLink } from '@angular/router';
import { MatButtonModule } from '@angular/material/button';
import { MatGridListModule } from '@angular/material/grid-list';

@Component({
    selector: 'app-layers-list',
    templateUrl: './layers-list.component.html',
    styleUrls: ['./layers-list.component.scss'],
    standalone: true,
    imports: [MatGridListModule, MatButtonModule, RouterLink, MatFormFieldModule, MatInputModule, MatTableModule, MatSortModule]
})
export class LayersListComponent implements OnInit {
  displayedColumns = ['number', 'name', 'source'];
  dataSource!: MatTableDataSource<Layer>;

  @ViewChild(MatSort) sort!: MatSort;

  start: number = 0;
  limit: number = 50;
  end: number = this.limit + this.start;
  loadingInProgress: boolean = false;

  constructor(
    private _http: HttpClient,
  ) { }

  @HostListener('document:scroll', ['$event'])
  public async  onScroll(event: any) {
    if (event.target.offsetHeight + event.target.scrollTop >= event.target.scrollHeight - 1 && !this.loadingInProgress) {
      this.loadingInProgress = true;
      let data: Layer[] = await Layer.getList(this._http, this.start, this.limit);
      this.dataSource.data = this.dataSource.data.concat(data);
      this.start = this.end;
      this.end = this.limit + this.start;
      setTimeout(() => {
        this.loadingInProgress = false;
      }, 500);
    }
  }
  async ngOnInit() {
    this.dataSource = new MatTableDataSource(await Layer.getList(this._http, this.start, this.limit));
    this.dataSource.sort = this.sort;
    this.dataSource.sort.sort({ id: 'number', start: 'desc' } as MatSortable);
    this.start = this.end;
    this.end = this.limit + this.start;
  }
  applyFilter(event: Event) {
    const filterValue = (event.target as HTMLInputElement).value;
    this.dataSource.filter =  filterValue.trim().toLowerCase();
  }
  trackByUid(index : number, item : Layer) {
    return item.id;
  }
}