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 { Employee } from '../employee';

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

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

  connect(): Observable<Employee[]> {
    const dataMutations: (
      | Observable<Employee[]>
      | 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: Employee[]) => {
          if (this.paginator) {
            this.paginator.length = x.length;
          }
        }),
      )
      .pipe(map((x: Employee[]) => this.getPagedData(this.getSortedData(x))));
  }

  disconnect() {}

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

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

  private getSortedData(data: Employee[]) {
    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 'code':
          return compare(+a.code, +b.code, isAsc);
        case 'name':
          return compare(a.name, b.name, isAsc);
        case 'designation':
          return compare(a.designation, b.designation, isAsc);
        case 'salary':
          return compare(a.salary, b.salary, isAsc);
        case 'points':
          return compare(a.points, b.points, isAsc);
        case 'department':
          return compare(a.costCentre.name, b.costCentre.name, isAsc);
        case 'joiningDate':
          return compare(a.joiningDate, b.joiningDate, isAsc);
        case 'leavingDate':
          return compare(a.leavingDate || '', b.leavingDate || '', isAsc);
        default:
          return 0;
      }
    });
  }
}