Added app module and http error interceptor

src/app/app.module.ts

@@ -1,7 +1,7 @@
 import { BrowserModule } from '@angular/platform-browser';
 import { NgModule } from '@angular/core';
 import { RouterModule, Routes } from '@angular/router';
-import { HttpClientModule } from '@angular/common/http';
+import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';
 
 import { AppComponent } from './app.component';
 import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
@@ -14,6 +14,7 @@ import { FrontpageComponent } from './frontpage/frontpage.component';
 import { GeneratorSearchComponent } from './generator-search/generator-search.component';
 import { SignUpComponent } from './sign-up/sign-up.component';
 import { VisualizeAllComponent } from './visualize-all/visualize-all.component';
+import { HttpErrorInterceptor } from './http-error.interceptor';
 
 @NgModule({
   declarations: [
@@ -46,7 +47,13 @@ import { VisualizeAllComponent } from './visualize-all/visualize-all.component';
     ]),
 
   ],
-  providers: [],
+  providers: [
+     {
+       provide: HTTP_INTERCEPTORS,
+       useClass: HttpErrorInterceptor,
+       multi: true
+   }
+  ],
   bootstrap: [AppComponent]
 })
 export class AppModule { }

src/app/http-error.interceptor.ts

@@ -0,0 +1,32 @@
+import {
+ HttpEvent,
+ HttpInterceptor,
+ HttpHandler,
+ HttpRequest,
+ HttpResponse,
+ HttpErrorResponse
+} from '@angular/common/http';
+import { Observable, throwError } from 'rxjs';
+import { retry, catchError } from 'rxjs/operators';
+
+export class HttpErrorInterceptor implements HttpInterceptor {
+ intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
+   return next.handle(request)
+     .pipe(
+       retry(1),
+       catchError((error: HttpErrorResponse) => {
+         let errorMessage = '';
+         if (error.error instanceof ErrorEvent) {
+           // client-side error
+           errorMessage = `Error: ${error.error.message}`;
+         } else {
+           // server-side error
+           //console.log("poop");
+           errorMessage = `Error Code: ${error.status}\nMessage: ${error.message}`;
+         }
+
+         return throwError(errorMessage);
+       })
+     )
+ }
+}