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

import { Case } from '../../core/case';

export class CaseListDataSource extends DataSource<Case> {
  private dataValues: Case[] = [];
  private searchValues = '';
  private data: Observable<Case[]>;
  private search: Observable<string>;
  constructor(
    public d: Observable<Case[]>,
    public s: Observable<string>,
    private paginator?: MatPaginator,
  ) {
    super();
    this.data = d.pipe(tap((x) => (this.dataValues = x)));
    this.search = s.pipe(tap((x) => (this.searchValues = x)));
  }

  connect(): Observable<Case[]> {
    const dataMutations: (Observable<Case[]> | Observable<string> | EventEmitter<PageEvent>)[] = [
      this.data,
      this.search,
    ];
    if (this.paginator) {
      dataMutations.push((this.paginator as MatPaginator).page);
    }

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

  disconnect() {}

  private getFilteredData(data: Case[]): Case[] {
    return this.searchValues.split(' ').reduce(
      (p: Case[], c: string) =>
        p.filter((x) => {
          const accountString =
            `${x.caseSource.prefix}-${x.officeFileNumber} ${x.courtCaseNumber} ${x.year} ${x.title}
           ${x.docketNumber} ${x.remarks}`.toLowerCase();
          return accountString.indexOf(c) !== -1;
        }),
      Object.assign([], data),
    );
  }

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