Typescript Essentials Capstone Project

index.ts

@@ -0,0 +1,154 @@
+enum HttpMethods {
+  GET = 'GET',
+  POST = 'POST'
+}
+
+const HttpStatusCodes = {
+  Ok: 200,
+  InternalServerError: 500
+} as const
+
+export interface ObserverHandlers<T> {
+  next?: (value: T) => void;
+  error?: (err: unknown) => void;
+  complete?: () => void;
+}
+type UserType = 'user' |'admin'
+
+export interface User {
+  name: string,
+  age: number,
+  roles: UserType[];
+  createdAt: Date,
+  isDeleted: boolean
+};
+
+type RequestMock = {
+  method: HttpMethods;
+  host: string;
+  path: string;
+  body?: User; 
+  params: Record<string, string>; 
+};
+
+type TeardownLogic = () => void;
+type subscribeFn<T>= (observer: Observer<T>) => TeardownLogic | void;
+
+// observer class
+export class Observer<T> {
+  public isUnsubscribed: boolean = false;
+  public _unsubscribe?: TeardownLogic;
+  constructor(private handlers: ObserverHandlers<T>) {}
+
+  public next(value: T): void {
+    if (this.handlers.next && !this.isUnsubscribed) {
+      this.handlers.next(value);
+    }
+  }
+
+  public error(error: unknown): void {
+    if(!this.isUnsubscribed){
+      this.handlers.error?.(error)
+    this.unsubscribe();
+  }
+}
+
+public complete(): void{
+  if(!this.isUnsubscribed){
+    this.handlers.complete?.();
+    this.unsubscribe();
+  }
+}
+
+public unsubscribe(): void{
+  this.isUnsubscribed = true;
+  if(this._unsubscribe){
+    this._unsubscribe();
+  }
+}
+}
+
+// Observable class
+export class Observable<T>{
+  private _subscribe: subscribeFn<T>;
+
+    constructor(subscribe: subscribeFn<T>) {
+        this._subscribe = subscribe;
+    }
+
+  static from<U>(values: U[]): Observable<U>{
+
+    return new Observable<U>((observer)=>{
+      values.forEach((value) => observer.next(value))
+      observer.complete();
+
+      return () =>{
+        console.log('unsubscrubed')
+      };
+    });
+  }
+
+  public subscribe(handlers: ObserverHandlers<T>){
+    const observer = new Observer<T>(handlers);
+
+    const tearDown = this._subscribe(observer); 
+
+    if(typeof tearDown === 'function'){
+      observer._unsubscribe = tearDown
+    }
+
+    return ({
+      unsubscribe(){
+        observer.unsubscribe();
+      }
+    })
+  }
+}
+
+const userMock: User ={
+  name: 'User Name',
+  age: 26,
+  roles: [ 'user', 'admin'
+  ],
+  createdAt: new Date(),
+  isDeleted: false,
+}
+
+const requestMock: RequestMock[] =[
+  {
+    method: HttpMethods.POST,
+    host: 'service.example',
+    path: 'user',
+    body: userMock,
+    params: {},
+  },
+  {
+    method: HttpMethods.GET,
+    host: 'service.example',
+    path: 'user',
+    params: {
+      id: '3f5h67s4s'
+    }
+  }
+]
+
+const handleRequest = (request: RequestMock) =>{
+  return {status: HttpStatusCodes.Ok}
+};
+
+const handleError = (error: unknown) =>{
+  return {status: HttpStatusCodes.InternalServerError}
+};
+
+const handleComplete = () => console.log('complete');
+
+const request$ = Observable.from(requestMock);
+
+const subscription = request$.subscribe({
+  next: handleRequest,
+  error: handleError,
+  complete: handleComplete,
+})
+
+subscription.unsubscribe();
+