chore: Restructure

internal/dns/dns.go

@@ -0,0 +1,77 @@
+package dns
+
+import (
+	"errors"
+	"net"
+	"strings"
+	"time"
+
+	"github.com/patrickmn/go-cache"
+)
+
+const (
+	// TXT record name that lookupRepoTXT will try to lookup.
+	TxtRepoRecord = "_rio-pages."
+
+	// The key that the TXT record will have to start with, e.g.
+	// "repo=some-random-repo".
+	TxtRepoKey = "repo="
+)
+
+var (
+	// Cache for CNAME resolution results.
+	cnameCache = cache.New(1*time.Hour, 1*time.Hour)
+
+	// Cache for TXT resolution results.
+	txtRepoCache = cache.New(1*time.Hour, 1*time.Hour)
+)
+
+// Query the domain for the a repository redirect.
+// Returns the new repository name or "", if we could not
+// resolve a repository redirect.
+func LookupRepoTXT(domain string) (string, error) {
+	repoLookup, found := txtRepoCache.Get(domain)
+	if found {
+		return repoLookup.(string), nil
+	}
+
+	txts, err := net.LookupTXT("_rio-pages." + domain)
+	if err != nil {
+		return "", err
+	}
+
+	repo := ""
+	for _, txt := range txts {
+		if !strings.HasPrefix(txt, TxtRepoKey) {
+			continue
+		}
+
+		repo = strings.TrimPrefix(txt, TxtRepoKey)
+		break
+	}
+
+	txtRepoCache.Set(domain, repo, cache.DefaultExpiration)
+	return repo, nil
+}
+
+// Query the domain for a CNAME record. Returns the resolved
+// CNAME or "", if no CNAME could be queried.
+func LookupCNAME(domain string) (string, error) {
+	cname, found := cnameCache.Get(domain)
+	if found {
+		if cname == "" {
+			return "", errors.New("Previous request failure")
+		}
+
+		return cname.(string), nil
+	}
+
+	cname, err := net.LookupCNAME(domain)
+	if err == nil {
+		cnameCache.Set(domain, cname, cache.DefaultExpiration)
+		return cname.(string), nil
+	}
+
+	cnameCache.Set(domain, "", cache.DefaultExpiration)
+	return "", err
+}