Implement health check service and global exception handling

backend/src/common/filters/global-exception.filter.ts

@@ -0,0 +1,82 @@
+import {
+  ExceptionFilter,
+  Catch,
+  ArgumentsHost,
+  HttpException,
+  HttpStatus,
+  Logger,
+} from '@nestjs/common';
+import { Response } from 'express';
+
+interface ErrorResponse {
+  statusCode: number;
+  message: string;
+  timestamp: string;
+  path?: string;
+}
+
+/**
+ * Global exception filter som formaterar alla errors konsistent
+ * Returnerar tydliga, svenska felmeddelanden utan att läcka känslig info
+ */
+@Catch()
+export class GlobalExceptionFilter implements ExceptionFilter {
+  private readonly logger = new Logger(GlobalExceptionFilter.name);
+
+  catch(exception: any, host: ArgumentsHost) {
+    const ctx = host.switchToHttp();
+    const response = ctx.getResponse<Response>();
+    const request = ctx.getRequest();
+    const path = request.url;
+
+    let statusCode = HttpStatus.INTERNAL_SERVER_ERROR;
+    let message = 'Ett internt serverfel inträffade.';
+
+    // Hantera HTTP-exceptions (t.ex. NotFoundException)
+    if (exception instanceof HttpException) {
+      statusCode = exception.getStatus();
+      const exceptionResponse = exception.getResponse();
+
+      if (typeof exceptionResponse === 'object' && 'message' in exceptionResponse) {
+        message = (exceptionResponse as any).message || message;
+      } else if (typeof exceptionResponse === 'string') {
+        message = exceptionResponse;
+      }
+    } else if (exception instanceof Error) {
+      // Hantera vanliga Error-instanser
+      message = exception.message || message;
+      statusCode = HttpStatus.BAD_REQUEST;
+
+      // Log interna fel för debugging
+      this.logger.error(`Error: ${exception.message}`, exception.stack);
+    }
+
+    // Säkerställ att felmeddelanden är användarvänliga (på svenska)
+    if (message.includes('Unknown unit')) {
+      message = 'Okänd enhet. Kontrollera enheten och försök igen.';
+    } else if (message.includes('Cannot convert between incompatible unit types')) {
+      message = 'Kan inte konvertera mellan dessa enhetstyper.';
+    } else if (message.includes('Inventory item with id') && message.includes('not found')) {
+      message = 'Hemmavarorna hittades inte.';
+    } else if (message.includes('Product with id') && message.includes('not found')) {
+      message = 'Produkten hittades inte.';
+    } else if (message.includes('Recipe with id') && message.includes('not found')) {
+      message = 'Receptet hittades inte.';
+    } else if (message.includes('sourceProductId och targetProductId kan inte vara samma')) {
+      message = 'Du kan inte slå samman en produkt med sig själv.';
+    }
+
+    const errorResponse: ErrorResponse = {
+      statusCode,
+      message,
+      timestamp: new Date().toISOString(),
+      path,
+    };
+
+    this.logger.warn(
+      `${request.method} ${path} - Status: ${statusCode}, Message: ${message}`,
+    );
+
+    response.status(statusCode).json(errorResponse);
+  }
+}