Refactor DNS resolution: create an interface to have multiple implementations

pkg/analyzer/dns.go

@@ -22,7 +22,6 @@
 package analyzer
 
 import (
-	"net"
 	"time"
 
 	"git.happydns.org/happyDeliver/internal/api"
@@ -31,19 +30,26 @@ import (
 // DNSAnalyzer analyzes DNS records for email domains
 type DNSAnalyzer struct {
 	Timeout  time.Duration
-	resolver *net.Resolver
+	resolver DNSResolver
 }
 
 // NewDNSAnalyzer creates a new DNS analyzer with configurable timeout
 func NewDNSAnalyzer(timeout time.Duration) *DNSAnalyzer {
+	return NewDNSAnalyzerWithResolver(timeout, NewStandardDNSResolver())
+}
+
+// NewDNSAnalyzerWithResolver creates a new DNS analyzer with a custom resolver.
+// If resolver is nil, a StandardDNSResolver will be used.
+func NewDNSAnalyzerWithResolver(timeout time.Duration, resolver DNSResolver) *DNSAnalyzer {
 	if timeout == 0 {
 		timeout = 10 * time.Second // Default timeout
 	}
+	if resolver == nil {
+		resolver = NewStandardDNSResolver()
+	}
 	return &DNSAnalyzer{
-		Timeout: timeout,
-		resolver: &net.Resolver{
-			PreferGo: true,
-		},
+		Timeout:  timeout,
+		resolver: resolver,
 	}
 }
 

pkg/analyzer/dns_resolver.go

@@ -0,0 +1,80 @@
+// This file is part of the happyDeliver (R) project.
+// Copyright (c) 2025 happyDomain
+// Authors: Pierre-Olivier Mercier, et al.
+//
+// This program is offered under a commercial and under the AGPL license.
+// For commercial licensing, contact us at <contact@happydomain.org>.
+//
+// For AGPL licensing:
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package analyzer
+
+import (
+	"context"
+	"net"
+)
+
+// DNSResolver defines the interface for DNS resolution operations.
+// This interface abstracts DNS lookups to allow for custom implementations,
+// such as mock resolvers for testing or caching resolvers for performance.
+type DNSResolver interface {
+	// LookupMX returns the DNS MX records for the given domain.
+	LookupMX(ctx context.Context, name string) ([]*net.MX, error)
+
+	// LookupTXT returns the DNS TXT records for the given domain.
+	LookupTXT(ctx context.Context, name string) ([]string, error)
+
+	// LookupAddr performs a reverse lookup for the given IP address,
+	// returning a list of hostnames mapping to that address.
+	LookupAddr(ctx context.Context, addr string) ([]string, error)
+
+	// LookupHost looks up the given hostname using the local resolver.
+	// It returns a slice of that host's addresses (IPv4 and IPv6).
+	LookupHost(ctx context.Context, host string) ([]string, error)
+}
+
+// StandardDNSResolver is the default DNS resolver implementation that uses net.Resolver.
+type StandardDNSResolver struct {
+	resolver *net.Resolver
+}
+
+// NewStandardDNSResolver creates a new StandardDNSResolver with default settings.
+func NewStandardDNSResolver() DNSResolver {
+	return &StandardDNSResolver{
+		resolver: &net.Resolver{
+			PreferGo: true,
+		},
+	}
+}
+
+// LookupMX implements DNSResolver.LookupMX using net.Resolver.
+func (r *StandardDNSResolver) LookupMX(ctx context.Context, name string) ([]*net.MX, error) {
+	return r.resolver.LookupMX(ctx, name)
+}
+
+// LookupTXT implements DNSResolver.LookupTXT using net.Resolver.
+func (r *StandardDNSResolver) LookupTXT(ctx context.Context, name string) ([]string, error) {
+	return r.resolver.LookupTXT(ctx, name)
+}
+
+// LookupAddr implements DNSResolver.LookupAddr using net.Resolver.
+func (r *StandardDNSResolver) LookupAddr(ctx context.Context, addr string) ([]string, error) {
+	return r.resolver.LookupAddr(ctx, addr)
+}
+
+// LookupHost implements DNSResolver.LookupHost using net.Resolver.
+func (r *StandardDNSResolver) LookupHost(ctx context.Context, host string) ([]string, error) {
+	return r.resolver.LookupHost(ctx, host)
+}