Introduce caching in CustomerRepository and refactor API integration

- Add in-memory caching for customer data in `CustomerRepository` to reduce API calls.
- Replace direct API calls with methods from `CustomerRepository`.
- Update customer-related pages (`[id]/page.tsx`, `customers/page.tsx`) to use `CustomerRepository` for data fetching.
- Adjust breadcrumb resolver to leverage `CustomerRepository`.
- Remove `axios` dependency from customer-related components.

internal_frontend/app/customers/[id]/page.tsx

@@ -1,19 +1,17 @@
 "use client";
 
-import React, {useEffect, useState, useMemo} from "react";
+import React, {useEffect, useState} from "react";
 import {useParams, useRouter} from "next/navigation";
 import {ChevronLeft} from "lucide-react";
-import axios, {AxiosError} from "axios";
 import {Button} from "@/components/ui/button";
 import {Dialog} from "@/components/ui/dialog";
 import {Skeleton} from "@/components/ui/skeleton";
 import CustomerDetailContent from "@/components/customers/details/CustomerDetailContent";
-import {Customer} from "@/services/customers/entities/customer";
 import CustomerInformationContent from "@/components/customers/details/sub/ContactInformationContent";
 import CustomerPhoneNumberContent from "@/components/customers/details/sub/CustomerPhoneNumberContent";
 import CustomerNotesContent from "@/components/customers/details/sub/CustomerNotesContent";
-
-const API_BASE_URL = process.env.NEXT_PUBLIC_API_URL || '/api';
+import {Customer} from "@/services/customers/entities/customer";
+import {CustomerRepository} from "@/services/customers/repositories/customerRepository";
 
 export default function CustomerDetailPage() {
     const router = useRouter();
@@ -35,23 +33,22 @@ export default function CustomerDetailPage() {
         setLoading(true);
         setError(null);
 
-        axios
-            .get<Customer>(`${API_BASE_URL}/customers/${id}`)
-            .then((res) => {
-                if (isMounted) {
-                    setCustomer(res.data);
+        CustomerRepository.getById(id)
+            .then((result) => {
+                if (!isMounted) return;
+
+                if (!result) {
+                    setError("Kunde nicht gefunden");
+                    setCustomer(null);
+                } else {
+                    setCustomer(result);
                 }
             })
-            .catch((error: AxiosError) => {
-                if (isMounted) {
+            .catch((error) => {
+                if (!isMounted) return;
                 console.error('Error fetching customer:', error);
                 setCustomer(null);
-                    setError(
-                        error.response?.status === 404
-                            ? "Kunde nicht gefunden"
-                            : "Fehler beim Laden der Kundendaten"
-                    );
-                }
+                setError("Fehler beim Laden der Kundendaten");
             })
             .finally(() => {
                 if (isMounted) {
@@ -85,14 +82,14 @@ export default function CustomerDetailPage() {
         }
     };
 
-    const customerMetadata = useMemo(() => ({
+    const customerMetadata = {
         createdInfo: customer
             ? `Erstellt von ${customer.createdBy || "-"} am ${formatDate(customer.createdAt)}`
             : "Erstellt von - am -",
         lastActivityInfo: customer
             ? `Letzte Aktivität: ${customer.updatedBy || "-"} am ${formatDate(customer.updatedAt)}`
             : "Letzte Aktivität: - am -"
-    }), [customer]);
+    };
 
     const renderMetadata = () => {
         if (loading) {

internal_frontend/app/customers/page.tsx

@@ -22,9 +22,9 @@ import {
 import {motion} from "framer-motion";
 import {ArrowRight} from "lucide-react";
 import {NewCustomerModal} from "@/components/customers/modal/NewCustomerModal";
-import axios from "axios";
 import {Customer} from "@/services/customers/entities/customer";
 import Link from "next/link";
+import {CustomerRepository} from "@/services/customers/repositories/customerRepository";
 
 export default function CustomersPage() {
     const [customers, setCustomers] = useState<Customer[]>([]);
@@ -35,9 +35,9 @@ export default function CustomersPage() {
 
     useEffect(() => {
         setLoading(true);
-        axios.get("/api/customers")
-            .then((res) => {
-                setCustomers(res.data);
+        CustomerRepository.getAll()
+            .then((data) => {
+                setCustomers(data);
             })
             .catch((error) => {
                 console.error('Error fetching customers:', error);

internal_frontend/lib/navigation/breadcrumb-map.ts

@@ -1,4 +1,4 @@
-import {customerRoutes} from "@/app/api/customers/customerRoutes";
+import {CustomerRepository} from "@/services/customers/repositories/customerRepository";
 
 export const breadcrumbMap: Record<string, string> = {
     'dashboard': 'Dashboard',
@@ -10,8 +10,9 @@ export const breadcrumbMap: Record<string, string> = {
 
 export const breadcrumbResolvers: Record<string, (id: string) => Promise<string>> = {
     "customers": async (id: string) => {
-        const res = await fetch(`/api${customerRoutes.getById(id)}`, {cache: "no-store"});
-        const customer = await res.json();
+        const customer = await CustomerRepository.getById(id);
+        if (!customer) return `ID: ${id}`;
+
         if (customer.companyName) return `Firma: ${customer.companyName}`;
         if (customer.name) return `Name: ${customer.name}`;
         return `ID: ${id}`;

internal_frontend/services/customers/repositories/customerRepository.ts

@@ -1,13 +1,86 @@
 import {Customer} from "@/services/customers/entities/customer";
 import {CreateCustomerDto} from "@/services/customers/dtos/createCustomer.dto";
-import {callApi} from "@/lib/api/callApi";
 
 export class CustomerRepository {
+    private static readonly customerCache: Map<string, Customer> = new Map();
+    private static lastFetchAll: number | null = null;
+    private static readonly CACHE_DURATION = 10 * 1000; // seconds in milliseconds
+
     static async getAll(): Promise<Customer[]> {
-        return await callApi<Customer[]>("/customers", "GET");
+        const now = Date.now();
+        if (this.lastFetchAll && (now - this.lastFetchAll < this.CACHE_DURATION)) {
+            return Array.from(this.customerCache.values());
+        }
+
+        console.log('Cache expired or not initialized, fetching fresh data from API');
+
+        const response = await fetch('/api/customers');
+        if (!response.ok) {
+            console.error('Failed to fetch customers:', response.status, response.statusText);
+            return Promise.reject(new Error(`Failed to fetch customers: ${response.statusText}`));
+        }
+
+        const customers: Customer[] = await response.json();
+        this.customerCache.clear();
+        customers.forEach((customer: Customer) => this.customerCache.set(customer.id, customer));
+        this.lastFetchAll = now;
+        return customers;
+    }
+
+    static async getById(id: string): Promise<Customer | null> {
+        const cachedCustomer = this.customerCache.get(id);
+        if (cachedCustomer) {
+            return cachedCustomer;
+        }
+
+        console.log(`Cache miss for customer ${id}, fetching from API`);
+
+        try {
+            const response = await fetch(`/api/customers/${id}`);
+            if (!response.ok) {
+                if (response.status === 404) {
+                    console.log(`Customer ${id} not found`);
+                    return null;
+                }
+                console.error('Failed to fetch customer:', response.status, response.statusText);
+                return Promise.reject(new Error(`Failed to fetch customer: ${response.statusText}`));
+            }
+
+            const customer: Customer = await response.json();
+            this.customerCache.set(id, customer);
+            return customer;
+        } catch (error) {
+            console.error('Error fetching customer:', error);
+            return Promise.reject(error);
+        }
     }
 
     static async create(payload: CreateCustomerDto): Promise<void> {
-        await callApi<void, CreateCustomerDto>("/customers", "POST", payload);
+        const response = await fetch('/api/customers', {
+            method: 'POST',
+            headers: {
+                'Content-Type': 'application/json',
+            },
+            body: JSON.stringify(payload)
+        });
+
+        if (!response.ok) {
+            console.error('Failed to create customer:', response.status, response.statusText);
+            return Promise.reject(new Error(`Failed to create customer: ${response.statusText}`));
+        }
+
+        console.log('Cache invalidated after creating new customer');
+        this.lastFetchAll = null; // Invalidate the cache after creating new customer
+    }
+
+    static clearCache(): void {
+        console.log('Cache manually cleared');
+        this.customerCache.clear();
+        this.lastFetchAll = null;
+    }
+
+    static updateCache(customer: Customer): void {
+        console.log(`Cache updated for customer ${customer.id}`);
+        this.customerCache.set(customer.id, customer);
     }
 }