feat: implement configuration via forRoot (#21)

Adds the ability to provide configuration to the InMemoryDBModule via `forRoot` static method.

Implements #18

lib/in-memory-db.module.ts

@@ -1,8 +1,23 @@
-import { Module } from '@nestjs/common';
+import { DynamicModule, Module } from '@nestjs/common';
+
+import { InMemoryDBConfig } from './interfaces';
 import { InMemoryDBService } from './services';
 
 @Module({
   providers: [InMemoryDBService],
   exports: [InMemoryDBService],
 })
-export class InMemoryDBModule {}
+export class InMemoryDBModule {
+  static forRoot(config: Partial<InMemoryDBConfig> = {}): DynamicModule {
+    return {
+      module: InMemoryDBModule,
+      providers: [
+        {
+          provide: InMemoryDBService,
+          useValue: new InMemoryDBService(config),
+        },
+      ],
+      exports: [InMemoryDBService],
+    };
+  }
+}

lib/interfaces/in-memory-db-config.ts

@@ -0,0 +1 @@
+export interface InMemoryDBConfig {}

lib/interfaces/index.ts

@@ -1 +1,2 @@
+export * from './in-memory-db-config';
 export * from './in-memory-db-entity';

lib/services/in-memory-db.service.ts

@@ -1,10 +1,16 @@
-import { Injectable } from '@nestjs/common';
-import { InMemoryDBEntity } from '../interfaces';
+import { Injectable, Optional } from '@nestjs/common';
+
+import { InMemoryDBConfig, InMemoryDBEntity } from '../interfaces';
 
 @Injectable()
 export class InMemoryDBService<T extends InMemoryDBEntity> {
+  private readonly moduleConfig: Partial<InMemoryDBConfig>;
   private recordMap: { [id: number]: T } = {};
 
+  constructor(@Optional() config: Partial<InMemoryDBConfig> = {}) {
+    this.moduleConfig = config || {};
+  }
+
   /**
    * Given the array of records of type `T`, reduce the array into a dictionary object of
    * type `{ [id: number]: T }`. Set the value of the in-memory data store

package.json

@@ -7,6 +7,7 @@
   "repository": "https://github.com/nestjs-addons/in-memory-db",
   "scripts": {
     "build": "tsc -p tsconfig.json",
+    "build:dev": "tsc-watch -p tsconfig.json",
     "format": "prettier lib/**/*.ts --write",
     "test": "jest --config jest.json",
     "semantic-release": "semantic-release"
@@ -25,6 +26,7 @@
     "reflect-metadata": "0.1.13",
     "semantic-release": "^15.13.19",
     "ts-jest": "24.0.2",
+    "tsc-watch": "^2.4.0",
     "typescript": "3.5.3"
   },
   "peerDependencies": {