Typescript Capstone Project

index.ts

@@ -0,0 +1,169 @@
+interface ObserverStatus {
+  status: HttpStatus;
+}
+
+interface ObserverError {
+  code: number;
+  text: string;
+}
+
+interface ObserverHandlers<T> {
+  next: (value: T) => ObserverStatus;
+  error: (value: ObserverError) => ObserverStatus;
+  complete: () => void;
+}
+
+type ObserverUnsubscriber = () => void;
+
+class Observer<T> {
+  private isUnsubscribed = false;
+  unsubscribeHolder: ObserverUnsubscriber | undefined;
+
+  constructor(private handlers: ObserverHandlers<T>) {}
+
+  next(value: T): void {
+    if (this.handlers.next && !this.isUnsubscribed) {
+      this.handlers.next(value);
+    }
+  }
+
+  error(error: ObserverError): void {
+    if (!this.isUnsubscribed) {
+      if (this.handlers.error) {
+        this.handlers.error(error);
+      }
+
+      this.unsubscribe();
+    }
+  }
+
+  complete(): void {
+    if (!this.isUnsubscribed) {
+      if (this.handlers.complete) {
+        this.handlers.complete();
+      }
+
+      this.unsubscribe();
+    }
+  }
+
+  unsubscribe(): void {
+    this.isUnsubscribed = true;
+
+    if (this.unsubscribeHolder) {
+      this.unsubscribeHolder();
+    }
+  }
+}
+
+type ObservableSubscriber<T> = (observer: Observer<T>) => ObserverUnsubscriber;
+
+class Observable<T> {
+  private subscribeHolder: ObservableSubscriber<T>;
+
+  constructor(subscribe: ObservableSubscriber<T>) {
+    this.subscribeHolder = subscribe;
+  }
+
+  static from<T>(values: T[]): Observable<T> {
+    return new Observable<T>((observer) => {
+      values.forEach((value) => observer.next(value));
+
+      observer.complete();
+
+      return () => {
+        console.log("unsubscribed");
+      };
+    });
+  }
+
+  subscribe(obs: ObserverHandlers<T>): { unsubscribe(): void } {
+    const observer = new Observer(obs);
+
+    observer.unsubscribeHolder = this.subscribeHolder(observer);
+
+    return {
+      unsubscribe(): void {
+        observer.unsubscribe();
+      },
+    };
+  }
+}
+
+const HTTP_METHOD = {
+  post: "POST",
+  get: "GET",
+} as const;
+
+type HttpMethod = (typeof HTTP_METHOD)[keyof typeof HTTP_METHOD];
+
+const HTTP_STATUS = {
+  ok: 200,
+  internalServerError: 500,
+} as const;
+
+type HttpStatus = (typeof HTTP_STATUS)[keyof typeof HTTP_STATUS];
+
+type User = {
+  name: string;
+  age: number;
+  roles: Array<"user" | "admin">;
+  createdAt: Date;
+  isDeleted: boolean;
+};
+
+type HTTPRequest<T> = {
+  method: HttpMethod;
+  host: string;
+  path: string;
+  body?: T;
+  params: Record<string, string>;
+};
+
+const userMock: User = {
+  name: "User Name",
+  age: 26,
+  roles: ["user", "admin"],
+  createdAt: new Date(),
+  isDeleted: false,
+};
+
+const requestsMock: HTTPRequest<User>[] = [
+  {
+    method: HTTP_METHOD.post,
+    host: "service.example",
+    path: "user",
+    body: userMock,
+    params: {},
+  },
+  {
+    method: HTTP_METHOD.get,
+    host: "service.example",
+    path: "user",
+    params: {
+      id: "3f5h67s4s",
+    },
+  },
+];
+
+const handleRequest = (request: HTTPRequest<User>): ObserverStatus => {
+  // handling of request
+  return { status: HTTP_STATUS.ok };
+};
+
+const handleError = (error: ObserverError): ObserverStatus => {
+  // handling of error
+  return { status: HTTP_STATUS.internalServerError };
+};
+
+const handleComplete = (): void => console.log("complete");
+
+const requests$ = Observable.from(requestsMock);
+
+const subscription = requests$.subscribe({
+  next: handleRequest,
+  error: handleError,
+  complete: handleComplete,
+});
+
+subscription.unsubscribe();