CLB 2nd PR: Add DiffTracker core types, state management, and sync operations

pkg/provider/difftracker/config.go

@@ -0,0 +1,65 @@
+/*
+Copyright 2026 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package difftracker
+
+import "fmt"
+
+// Config holds the configuration values needed by DiffTracker
+// to perform Azure operations without depending on the entire AzureCloud struct
+// This allows DiffTracker to be more modular and testable
+type Config struct {
+	// Azure subscription ID
+	SubscriptionID string
+
+	// Azure resource group name
+	ResourceGroup string
+
+	// Azure location/region
+	Location string
+
+	// Service Gateway resource name
+	ServiceGatewayResourceName string
+
+	// Full Service Gateway resource ID
+	ServiceGatewayID string
+
+	// Virtual Network name (required for backend pool configuration)
+	VNetName string
+}
+
+// Validate checks if the configuration has all required fields
+func (c *Config) Validate() error {
+	if c.SubscriptionID == "" {
+		return fmt.Errorf("config validation failed: SubscriptionID is required")
+	}
+	if c.ResourceGroup == "" {
+		return fmt.Errorf("config validation failed: ResourceGroup is required")
+	}
+	if c.Location == "" {
+		return fmt.Errorf("config validation failed: Location is required")
+	}
+	if c.ServiceGatewayResourceName == "" {
+		return fmt.Errorf("config validation failed: ServiceGatewayResourceName is required")
+	}
+	if c.ServiceGatewayID == "" {
+		return fmt.Errorf("config validation failed: ServiceGatewayID is required")
+	}
+	if c.VNetName == "" {
+		return fmt.Errorf("config validation failed: VNetName is required")
+	}
+	return nil
+}

pkg/provider/difftracker/difftracker.go

@@ -0,0 +1,78 @@
+/*
+Copyright 2026 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package difftracker
+
+import (
+	"fmt"
+
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/klog/v2"
+
+	"sigs.k8s.io/cloud-provider-azure/pkg/azclient"
+	utilsets "sigs.k8s.io/cloud-provider-azure/pkg/util/sets"
+)
+
+// InitializeDiffTracker creates and initializes a new DiffTracker with the given state and configuration.
+// It validates the configuration and ensures all required dependencies are present.
+// Returns an error if the configuration is invalid or if any required dependency is nil.
+func InitializeDiffTracker(K8s K8sState, NRP NRPState, config Config, networkClientFactory azclient.ClientFactory, kubeClient kubernetes.Interface) (*DiffTracker, error) {
+	if err := config.Validate(); err != nil {
+		return nil, fmt.Errorf("InitializeDiffTracker: %w", err)
+	}
+
+	if networkClientFactory == nil {
+		return nil, fmt.Errorf("InitializeDiffTracker: networkClientFactory must not be nil")
+	}
+	if kubeClient == nil {
+		return nil, fmt.Errorf("InitializeDiffTracker: kubeClient must not be nil")
+	}
+
+	klog.V(2).Infof("InitializeDiffTracker: initializing with config: subscription=%s, resourceGroup=%s, location=%s",
+		config.SubscriptionID, config.ResourceGroup, config.Location)
+
+	// If any field is nil, initialize it
+	if K8s.Services == nil {
+		K8s.Services = utilsets.NewString()
+	}
+	if K8s.Egresses == nil {
+		K8s.Egresses = utilsets.NewString()
+	}
+	if K8s.Nodes == nil {
+		K8s.Nodes = make(map[string]Node)
+	}
+	if NRP.LoadBalancers == nil {
+		NRP.LoadBalancers = utilsets.NewString()
+	}
+	if NRP.NATGateways == nil {
+		NRP.NATGateways = utilsets.NewString()
+	}
+	if NRP.Locations == nil {
+		NRP.Locations = make(map[string]NRPLocation)
+	}
+
+	diffTracker := &DiffTracker{
+		K8sResources: K8s,
+		NRPResources: NRP,
+
+		// Configuration and clients
+		config:               config,
+		networkClientFactory: networkClientFactory,
+		kubeClient:           kubeClient,
+	}
+
+	return diffTracker, nil
+}