feat: Implement configuration management and DNS provider integration

- Added configuration management using Viper in internal/config/config.go
- Implemented ClientConfig, ServerConfig, TLSConfig, HetznerConfig, UpstreamConfig, and main Config struct.
- Created LoadConfig function to read and validate configuration files.
- Developed Hetzner DNS provider in internal/provider/hetzner/hetzner.go with methods for updating DNS records.
- Added comprehensive unit tests for configuration loading and Hetzner provider functionality.
- Established HTTP server with metrics and update endpoint in internal/server/server.go.
- Implemented request handling, authorization, and error management in the server.
- Created integration tests for the Hetzner provider API interactions.
- Removed legacy dynamic DNS integration tests in favor of the new API-based approach.

internal/provider/hetzner/hetzner.go

@@ -0,0 +1,132 @@
+package hetzner
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+
+	pvd "git.cloonar.com/cloonar/updns/internal/provider"
+)
+
+const defaultAPIBase = "https://dns.hetzner.com"
+
+type provider struct {
+	token      string
+	client     *http.Client
+	apiBaseURL string
+}
+
+type zone struct {
+	ID   string `json:"id"`
+	Name string `json:"name"`
+}
+
+type zonesResponse struct {
+	Zones []zone `json:"zones"`
+}
+
+type record struct {
+	ID    string `json:"id"`
+	Name  string `json:"name"`
+	Value string `json:"value"`
+	Type  string `json:"type"`
+}
+
+type recordsResponse struct {
+	Records []record `json:"records"`
+}
+
+// NewProvider creates a Hetzner DNS provider using the official API.
+func NewProvider(token string) pvd.Provider {
+	return &provider{token: token, client: http.DefaultClient, apiBaseURL: defaultAPIBase}
+}
+
+// NewProviderWithURL creates a Hetzner provider with a custom API base URL (for testing).
+func NewProviderWithURL(token, apiBaseURL string) pvd.Provider {
+	return &provider{token: token, client: http.DefaultClient, apiBaseURL: apiBaseURL}
+}
+
+// UpdateRecord updates the DNS record for the given domain to the provided IP.
+func (p *provider) UpdateRecord(ctx context.Context, domain, ip string) error {
+	// Determine zone name (last two labels, or single label for two-part domains)
+	parts := strings.Split(domain, ".")
+	if len(parts) < 2 {
+		return fmt.Errorf("invalid domain: %s", domain)
+	}
+	var zoneName string
+	if len(parts) == 2 {
+		zoneName = parts[1]
+	} else {
+		zoneName = strings.Join(parts[len(parts)-2:], ".")
+	}
+	// Fetch zone ID
+	zonesURL := fmt.Sprintf("%s/zones?name=%s", p.apiBaseURL, zoneName)
+	req, _ := http.NewRequestWithContext(ctx, http.MethodGet, zonesURL, nil)
+	req.Header.Set("Authorization", "Bearer "+p.token)
+	resp, err := p.client.Do(req)
+	if err != nil {
+		return fmt.Errorf("fetch zones: %w", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("hetzner update failed with status: %s", resp.Status)
+	}
+	var zr zonesResponse
+	if err := json.NewDecoder(resp.Body).Decode(&zr); err != nil {
+		return fmt.Errorf("parsing zones response: %w", err)
+	}
+	if len(zr.Zones) == 0 {
+		return fmt.Errorf("zone %s not found", zoneName)
+	}
+	zoneID := zr.Zones[0].ID
+
+	// Fetch records in zone
+	recsURL := fmt.Sprintf("%s/records?zone_id=%s", p.apiBaseURL, zoneID)
+	req, _ = http.NewRequestWithContext(ctx, http.MethodGet, recsURL, nil)
+	req.Header.Set("Authorization", "Bearer "+p.token)
+	resp, err = p.client.Do(req)
+	if err != nil {
+		return fmt.Errorf("fetch records: %w", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("hetzner update failed with status: %s", resp.Status)
+	}
+	var rr recordsResponse
+	if err := json.NewDecoder(resp.Body).Decode(&rr); err != nil {
+		return fmt.Errorf("parsing records response: %w", err)
+	}
+	var recID string
+	for _, rec := range rr.Records {
+		if rec.Name == domain {
+			recID = rec.ID
+			break
+		}
+	}
+	if recID == "" {
+		return fmt.Errorf("record %s not found", domain)
+	}
+
+	// Update record value
+	updateURL := fmt.Sprintf("%s/records/%s", p.apiBaseURL, recID)
+	body := map[string]string{"value": ip}
+	buf := &bytes.Buffer{}
+	if err := json.NewEncoder(buf).Encode(body); err != nil {
+		return fmt.Errorf("encode update body: %w", err)
+	}
+	req, _ = http.NewRequestWithContext(ctx, http.MethodPut, updateURL, buf)
+	req.Header.Set("Authorization", "Bearer "+p.token)
+	req.Header.Set("Content-Type", "application/json")
+	resp, err = p.client.Do(req)
+	if err != nil {
+		return fmt.Errorf("update record: %w", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		return fmt.Errorf("update API status: %s", resp.Status)
+	}
+	return nil
+}

internal/provider/hetzner/hetzner_api_test.go

@@ -0,0 +1,91 @@
+package hetzner_test
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"git.cloonar.com/cloonar/updns/internal/provider/hetzner"
+)
+
+func TestUpdateRecordFullAPILifecycle(t *testing.T) {
+	domain := "test.example.com"
+	ip := "1.2.3.4"
+	zoneName := "example.com"
+	zoneID := "zone-123"
+	recID := "rec-456"
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch {
+		case r.Method == http.MethodGet && r.URL.Path == "/zones":
+			// Query zones by name
+			resp := map[string]interface{}{
+				"zones": []map[string]string{{"id": zoneID, "name": zoneName}},
+			}
+			json.NewEncoder(w).Encode(resp)
+		case r.Method == http.MethodGet && r.URL.Path == "/records":
+			// Query records by zone_id
+			resp := map[string]interface{}{
+				"records": []map[string]string{{"id": recID, "name": domain, "value": "0.0.0.0", "type": "A"}},
+			}
+			json.NewEncoder(w).Encode(resp)
+		case r.Method == http.MethodPut && r.URL.Path == "/records/"+recID:
+			// Validate update payload
+			body, _ := io.ReadAll(r.Body)
+			var payload map[string]string
+			json.Unmarshal(body, &payload)
+			if payload["value"] != ip {
+				t.Errorf("expected update value %s, got %s", ip, payload["value"])
+			}
+			w.WriteHeader(http.StatusOK)
+		default:
+			http.Error(w, "not found", http.StatusNotFound)
+		}
+	}))
+	defer ts.Close()
+
+	provider := hetzner.NewProviderWithURL("token", ts.URL)
+	if err := provider.UpdateRecord(context.Background(), domain, ip); err != nil {
+		t.Fatalf("full API lifecycle failed: %v", err)
+	}
+}
+
+func TestUpdateRecordZoneNotFound(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		json.NewEncoder(w).Encode(map[string]interface{}{"zones": []map[string]string{}})
+	}))
+	defer ts.Close()
+
+	provider := hetzner.NewProviderWithURL("token", ts.URL)
+	err := provider.UpdateRecord(context.Background(), "nozone.example", "1.1.1.1")
+	if err == nil || !strings.Contains(err.Error(), "zone example not found") {
+		t.Fatalf("expected zone not found error, got %v", err)
+	}
+}
+
+func TestUpdateRecordRecordNotFound(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.URL.Path {
+		case "/zones":
+			json.NewEncoder(w).Encode(map[string]interface{}{
+				"zones": []map[string]string{{"id": "z", "name": "example.com"}},
+			})
+		case "/records":
+			json.NewEncoder(w).Encode(map[string]interface{}{"records": []map[string]string{}})
+		default:
+			http.Error(w, "not found", http.StatusNotFound)
+		}
+	}))
+	defer ts.Close()
+
+	provider := hetzner.NewProviderWithURL("token", ts.URL)
+	err := provider.UpdateRecord(context.Background(), "missing.example.com", "1.1.1.1")
+	if err == nil || !strings.Contains(err.Error(), "record missing.example.com not found") {
+		t.Fatalf("expected record not found error, got %v", err)
+	}
+}

internal/provider/hetzner/hetzner_integration_test.go

@@ -0,0 +1,4 @@
+package hetzner_test
+
+// Legacy dynamic DNS integration tests have been removed.
+// The Hetzner provider now uses the official DNS API; see hetzner_api_test.go for coverage.

internal/provider/hetzner/hetzner_test.go

@@ -0,0 +1,12 @@
+package hetzner_test
+
+import (
+	"testing"
+
+	pvd "git.cloonar.com/cloonar/updns/internal/provider"
+	"git.cloonar.com/cloonar/updns/internal/provider/hetzner"
+)
+
+func TestNewProviderImplementsInterface(t *testing.T) {
+	var _ pvd.Provider = hetzner.NewProvider("token")
+}

internal/provider/provider.go

@@ -0,0 +1,8 @@
+package provider
+
+import "context"
+
+// Provider defines the interface for updating DNS records.
+type Provider interface {
+	UpdateRecord(ctx context.Context, domain, ip string) error
+}

internal/provider/provider_test.go

@@ -0,0 +1,22 @@
+package provider_test
+
+import (
+	"context"
+	"testing"
+
+	"git.cloonar.com/cloonar/updns/internal/provider"
+)
+
+// mockProvider is a dummy implementation for testing the Provider interface.
+type mockProvider struct{}
+
+func (m *mockProvider) UpdateRecord(ctx context.Context, domain, ip string) error {
+	return nil
+}
+
+func TestProviderInterfaceCompliance(t *testing.T) {
+	var p provider.Provider = &mockProvider{}
+	if err := p.UpdateRecord(context.Background(), "example.com", "1.2.3.4"); err != nil {
+		t.Errorf("expected no error, got %v", err)
+	}
+}