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, of as observableOf } from 'rxjs';
import { map, tap } from 'rxjs/operators';

import { Account } from '../../core/account';

/** Simple sort comparator for example ID/Name columns (for client-side sorting). */
function compare(a: string | number | boolean, b: string | number | boolean, isAsc: boolean) {
  return (a < b ? -1 : 1) * (isAsc ? 1 : -1);
}
export class AccountListDataSource extends DataSource<Account> {
  private filterValue = '';

  constructor(
    public data: Account[],
    private filter: Observable<string>,
    private paginator?: MatPaginator,
    private sort?: MatSort,
  ) {
    super();
    this.filter = filter.pipe(
      tap((x) => {
        this.filterValue = x;
      }),
    );
  }

  connect(): Observable<Account[]> {
    const dataMutations: (
      | Observable<Account[]>
      | Observable<string>
      | EventEmitter<PageEvent>
      | EventEmitter<Sort>
    )[] = [observableOf(this.data), this.filter];
    if (this.paginator) dataMutations.push((this.paginator as MatPaginator).page);
    if (this.sort) dataMutations.push((this.sort as MatSort).sortChange);

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

  disconnect() {}

  private getFilteredData(data: Account[]): Account[] {
    return this.filterValue.split(' ').reduce(
      (p: Account[], c: string) =>
        p.filter((x) => {
          const accountString = `${x.name} ${x.type} ${x.costCentre}${
            x.isActive ? ' active' : ' inactive'
          }`.toLowerCase();
          return accountString.indexOf(c) !== -1;
        }),
      Object.assign([], data),
    );
  }

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

  private getSortedData(data: Account[]) {
    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.name, b.name, isAsc);
        case 'type':
          return compare(a.type.name, b.type.name, isAsc);
        case 'isActive':
          return compare(a.isActive, b.isActive, isAsc);
        case 'isReconcilable':
          return compare(a.isReconcilable, b.isReconcilable, isAsc);
        case 'costCentre':
          return compare(a.costCentre.name, b.costCentre.name, isAsc);
        default:
          return 0;
      }
    });
  }
}