import { Injectable } from '@angular/core';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/of';
import 'rxjs/add/operator/do';
import 'rxjs/add/operator/share';

import { CacheService  } from '../cache.service';
import { ApiService  } from '../api.service';

export function hashCodeString(str: string): string {
  let hash = 0;
  if (str.length === 0) {
    return hash + '';
  }
  for (let i = 0; i < str.length; i++) {
    let char = str.charCodeAt(i);
    hash = ((hash << 5) - hash) + char;
    hash = hash & hash; // Convert to 32bit integer
  }
  return hash + '';
}

// domain/feature service
@Injectable()
export class ModelService {
   // This is only one example of one Model depending on your domain
  constructor(public _api: ApiService, public _cache: CacheService) {

  }

 /**
  * whatever domain/feature method name
  */
  get(url) {
    // you want to return the cache if there is a response in it.
    // This would cache the first response so if your API isn't idempotent
    // you probably want to remove the item from the cache after you use it. LRU of 10
    // you can use also hashCodeString here
    let key = url;

    if (this._cache.has(key)) {
      return Observable.of(this._cache.get(key));
    }
    // you probably shouldn't .share() and you should write the correct logic
    return this._api.get(url)
      .do(json => {
        this._cache.set(key, json);
      })
      .share();
  }
  // don't cache here since we're creating
  create() {
    // TODO
  }
}