import { Injectable }             from '@angular/core';
import {
  Router, Resolve,
  RouterStateSnapshot,
  ActivatedRouteSnapshot
}                                 from '@angular/router';
import { Observable, of, EMPTY }  from 'rxjs';
import { mergeMap, take }         from 'rxjs/operators';
 
import { CrisisService }  from './crisis.service';
import { Crisis } from './crisis';
 
@Injectable({
  providedIn: 'root',
})
export class CrisisDetailResolverService implements Resolve {
  constructor(private cs: CrisisService, private router: Router) {}
 
  resolve(route: ActivatedRouteSnapshot, state: RouterStateSnapshot): Observable | Observable {
    let id = route.paramMap.get('id');
 
    return this.cs.getCrisis(id).pipe(
      take(1),
      mergeMap(crisis => {
        if (crisis) {
          return of(crisis);
        } else { // id not found
          this.router.navigate(['/crisis-center']);
          return EMPTY;
        }
      })
    );
  }
}