in-memory-data.service.ts

/**
 * Hero-oriented InMemoryDbService with method overrides.
 */
import { Injectable } from '@angular/core';

import {
  RequestInfo,
  RequestInfoUtilities,
  ParsedRequestUrl,
  ResponseOptions,
  STATUS
} from 'angular-in-memory-web-api';

import { ChangeSet } from 'ngrx-data';

/** In-memory database data */
interface Db {
  [collectionName: string]: any[];
}

@Injectable()
export class InMemoryDataService {
  /** True if in-mem service is intercepting; all requests pass thru when false. */
  active = true;
  maxId = 0;

  /** In-memory database data */
  db: Db = {};

  /** Create the in-memory database on start or by command */
  createDb(reqInfo?: RequestInfo) {
    this.db = getDbData();

    if (reqInfo) {
      const body = reqInfo.utils.getJsonBody(reqInfo.req) || {};
      if (body.clear === true) {
        // tslint:disable-next-line:forin
        for (const coll in this.db) {
          this.db[coll].length = 0;
        }
      }

      this.active = !!body.active;
    }
    return this.db;
  }

  /**
   * Simulate generating new Id on the server
   * All collections in this db have numeric ids.
   * Seed grows by highest id seen in any of the collections.
   */
  genId(collection: { id: number }[], collectionName: string) {
    this.maxId = 1 + collection.reduce((prev, cur) => Math.max(prev, cur.id || 0), this.maxId);
    return this.maxId;
  }

  /**
   * Override `parseRequestUrl`
   * Manipulates the request URL or the parsed result.
   * If in-mem is inactive, clear collectionName so that service passes request thru.
   * If in-mem is active, after parsing with the default parser,
   * @param url from request URL
   * @param utils for manipulating parsed URL
   */
  parseRequestUrl(url: string, utils: RequestInfoUtilities): ParsedRequestUrl {
    const parsed = utils.parseRequestUrl(url);
    parsed.collectionName = this.active ? mapCollectionName(parsed.collectionName) : undefined;
    return parsed;
  }

  /**
   * Special-cases for POST methods
   */
  post(req: RequestInfo) {
    if (req.url.endsWith('/save/delete-villains')) {
      return this.mockDeleteVillains(req);
    }

    // Let all other POST requests through
    return null;
  }

  private mockDeleteVillains(requestInfo: RequestInfo) {
    const originalRequest = requestInfo.req as any;
    const changeSet: ChangeSet = originalRequest.body;

    const changes = changeSet.changes;
    changes.forEach(item => {
      // Only know how to delete villains
      if (item.entityName === 'Villain') {
        const deleteIds = item.entities as number[];
        this.db['villains'] = this.db['villains'].filter(v => !deleteIds.includes(v.id));
      }
    });

    // In this example, the server processes the request
    // w/o changing the data that it inserts or updates.
    // There's no reason to expect the server to return anything.
    // So this API responds with 204-No Content and no body.
    const options: ResponseOptions = {
      url: requestInfo.url,
      status: STATUS.NO_CONTENT,
      statusText: 'NO CONTENT',
      body: null
    };

    // But if it did return updated entities it might respond with this
    // const options: ResponseOptions = {
    //   url: requestInfo.url,
    //   status: STATUS.OK,
    //   statusText: 'OK',
    //   body: changeSet
    // };

    return requestInfo.utils.createResponse$(() => options);
  }
}

/**
 * Remap a known singular collection name ("hero")
 * to the plural collection name ("heroes"); else return the name
 * @param name - collection name from the parsed URL
 */
function mapCollectionName(name: string): string {
  return (
    ({
      hero: 'heroes',
      villain: 'villains'
    } as any)[name] || name
  );
}

/**
 * Development data
 */
function getDbData() {
  const heroes: any[] = [
    {
      id: 11,
      name: 'Maxwell Smart',
      saying: 'Missed it by that much.'
    },
    {
      id: 12,
      name: 'Bullwinkle J. Moose',
      saying: 'Watch me pull a rabbit out of a hat.'
    },
    {
      id: 13,
      name: 'Muhammad Ali',
      saying: 'Float like a butterfly, sting like a bee.'
    },
    {
      id: 14,
      name: 'Eleanor Roosevelt',
      saying: 'No one can make you feel inferior without your consent.'
    }
  ];

  const villains: any[] = [
    {
      id: 21,
      name: 'Dr. Evil',
      saying: 'One million dollars!'
    },
    {
      id: 22,
      name: 'Agent Smith',
      saying: 'Human beings are a disease.'
    },
    {
      id: 23,
      name: 'Natasha Fatale',
      saying: 'You can say that again, dahling.'
    },
    {
      id: 24,
      name: 'Goldfinger',
      saying: 'No, I expect you to die!'
    },
    {
      id: 25,
      name: 'West Witch',
      saying: `I'll get you, my pretty, and your little dog too!`
    },
    {
      id: 26,
      name: 'Tony Montana',
      saying: 'Say hello to my little friend.'
    }
  ];

  return { heroes, villains } as Db;
}