brewman/overlord/src/app/recipe/recipe-list/recipe-list-datasource.ts

import { DataSource } from '@angular/cdk/collections';
import { EventEmitter } from '@angular/core';
import { MatPaginator, PageEvent } from '@angular/material/paginator';
import { MatSort, Sort } from '@angular/material/sort';
import { merge, Observable } from 'rxjs';
import { map, tap } from 'rxjs/operators';

import { Recipe } from '../recipe';

export class RecipeListDatasource extends DataSource<Recipe> {
  public data: Recipe[];
  public filteredData: Recipe[];
  public productGroup: string;

  constructor(
    private readonly productGroupFilter: Observable<string>,
    private readonly dataObs: Observable<Recipe[]>,

    private paginator?: MatPaginator,
    private sort?: MatSort,
  ) {
    super();
    this.data = [];
    this.filteredData = [];
    this.productGroup = '';
  }

  connect(): Observable<Recipe[]> {
    const dataMutations: (EventEmitter<PageEvent> | EventEmitter<Sort>)[] = [];
    const d = this.dataObs.pipe(
      tap((x) => {
        this.data = x;
      }),
    );
    const pg = this.productGroupFilter.pipe(
      tap((x) => {
        this.productGroup = x;
      }),
    );
    if (this.paginator) {
      dataMutations.push((this.paginator as MatPaginator).page);
    }
    if (this.sort) {
      dataMutations.push((this.sort as MatSort).sortChange);
    }

    return merge(d, pg, ...dataMutations).pipe(
      map(() => this.getFilteredData(this.data, this.productGroup)),
      tap((x: Recipe[]) => {
        if (this.paginator) {
          this.paginator.length = x.length;
        }
      }),
      tap((x) => {
        this.filteredData = x;
      }),
      map(() => this.getPagedData(this.getSortedData([...this.filteredData]))),
    );
  }

  disconnect() {}

  private getFilteredData(data: Recipe[], productGroup: string): Recipe[] {
    return data.filter((x: Recipe) => productGroup === '' || x.productGroupId === productGroup);
  }

  private getPagedData(data: Recipe[]) {
    if (this.paginator === undefined) {
      return data;
    }
    const startIndex = this.paginator.pageIndex * this.paginator.pageSize;
    return data.splice(startIndex, this.paginator.pageSize);
  }

  private getSortedData(data: Recipe[]) {
    if (this.sort === undefined) {
      return data;
    }
    if (!this.sort.active || this.sort.direction === '') {
      return data;
    }

    const sort = this.sort as MatSort;
    return data.sort((a, b) => {
      const isAsc = sort.direction === 'asc';
      switch (sort.active) {
        case 'name':
          return compare(a.sku.name, b.sku.name, isAsc);
        default:
          return 0;
      }
    });
  }
}
/** Simple sort comparator for example ID/Name columns (for client-side sorting). */
const compare = (a: string | number | Date, b: string | number | Date, isAsc: boolean) =>
  (a < b ? -1 : 1) * (isAsc ? 1 : -1);
// const compareDate = (a: string, b: string, isAsc: boolean) =>
//   (moment(a, 'DD-MMM-YYYY').toDate() < moment(b, 'DD-MMM-YYYY').toDate() ? -1 : 1) *
//   (isAsc ? 1 : -1);