Update index.ts

index.ts

@@ -0,0 +1,200 @@
+/**
+ * Interface representing handlers passed to the Observer.
+ */
+interface ObserverHandlers<T> {
+  next?: (value: T) => void;
+  error?: (error: unknown) => void;
+  complete?: () => void;
+}
+
+/**
+ * Observer class that manages execution and handles stream states.
+ */
+class Observer<T> {
+  private handlers: ObserverHandlers<T>;
+  private isUnsubscribed: boolean;
+  _unsubscribe?: () => void;
+
+  constructor(handlers: ObserverHandlers<T>) {
+    this.handlers = handlers;
+    this.isUnsubscribed = false;
+  }
+
+  next(value: T): void {
+    if (this.handlers.next && !this.isUnsubscribed) {
+      this.handlers.next(value);
+    }
+  }
+
+  error(error: unknown): 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._unsubscribe) {
+      this._unsubscribe();
+    }
+  }
+}
+
+/**
+ * Type representing the subscription callback logic of the Observable.
+ */
+type SubscribeFunction<T> = (observer: Observer<T>) => (() => void) | void;
+
+/**
+ * Observable class representing a stream of values.
+ */
+class Observable<T> {
+  private _subscribe: SubscribeFunction<T>;
+
+  constructor(subscribe: SubscribeFunction<T>) {
+    this._subscribe = subscribe;
+  }
+
+  /**
+   * Creates an Observable stream from an array of values.
+   */
+  static from<T>(values: T[]): Observable<T> {
+    return new Observable<T>((observer) => {
+      values.forEach((value) => observer.next(value));
+      observer.complete();
+      return () => {
+        console.log('unsubscribed');
+      };
+    });
+  }
+
+  /**
+   * Subscribes to the stream with the provided observer handlers.
+   */
+  subscribe(obs: ObserverHandlers<T>): { unsubscribe: () => void } {
+    const observer = new Observer<T>(obs);
+    observer._unsubscribe = this._subscribe(observer) || undefined;
+    return {
+      unsubscribe() {
+        observer.unsubscribe();
+      }
+    };
+  }
+}
+
+// HTTP Methods Constants and Type
+const HTTP_POST_METHOD = 'POST' as const;
+const HTTP_GET_METHOD = 'GET' as const;
+
+type HttpMethod = typeof HTTP_POST_METHOD | typeof HTTP_GET_METHOD;
+
+// HTTP Status Constants
+const HTTP_STATUS_OK = 200;
+const HTTP_STATUS_INTERNAL_SERVER_ERROR = 500;
+
+/**
+ * Interface representing a User model.
+ */
+interface User {
+  name: string;
+  age: number;
+  roles: string[];
+  createdAt: Date;
+  isDeleated: boolean;
+}
+
+/**
+ * Interface representing a HTTP Request, parameterized by its payload/body type.
+ */
+interface HttpRequest<TBody = unknown> {
+  method: HttpMethod;
+  host: string;
+  path: string;
+  body?: TBody;
+  params: Record<string, string>;
+}
+
+/**
+ * Mock User data matching the interface.
+ */
+const userMock: User = {
+  name: 'User Name',
+  age: 26,
+  roles: [
+    'user',
+    'admin'
+  ],
+  createdAt: new Date(),
+  isDeleated: false,
+};
+
+/**
+ * Mock Request list matching HTTP request models.
+ */
+const requestsMock: HttpRequest<User>[] = [
+  {
+    method: HTTP_POST_METHOD,
+    host: 'service.example',
+    path: 'user',
+    body: userMock,
+    params: {},
+  },
+  {
+    method: HTTP_GET_METHOD,
+    host: 'service.example',
+    path: 'user',
+    params: {
+      id: '3f5h67s4s'
+    },
+  }
+];
+
+interface RequestResponse {
+  status: number;
+}
+
+/**
+ * Request success handler.
+ */
+const handleRequest = (request: HttpRequest<User>): RequestResponse => {
+  // handling of request
+  return { status: HTTP_STATUS_OK };
+};
+
+/**
+ * Request error handler.
+ */
+const handleError = (error: unknown): RequestResponse => {
+  // handling of error
+  return { status: HTTP_STATUS_INTERNAL_SERVER_ERROR };
+};
+
+/**
+ * Request completion handler.
+ */
+const handleComplete = (): void => console.log('complete');
+
+// Creating stream of HTTP Requests
+const requests$ = Observable.from(requestsMock);
+
+// Subscribing to the stream
+const subscription = requests$.subscribe({
+  next: handleRequest,
+  error: handleError,
+  complete: handleComplete
+});
+
+// Clean up/Unsubscribe
+subscription.unsubscribe();