Fix path for asset storage (#144)

Define locations for keys and secondary zones, 'n stuff.

Add a bunch of tests as well.

core/dns/storage.go

@@ -0,0 +1,28 @@
+package dns
+
+import (
+	"path/filepath"
+
+	"github.com/miekg/coredns/core/assets"
+)
+
+var storage = Storage(assets.Path())
+
+// Storage is a root directory and facilitates
+// forming file paths derived from it.
+type Storage string
+
+// Zones gets the directory that stores zones data.
+func (s Storage) Zones() string {
+	return filepath.Join(string(s), "zones")
+}
+
+// Zone returns the path to the folder containing assets for domain.
+func (s Storage) Zone(domain string) string {
+	return filepath.Join(s.Zones(), domain)
+}
+
+// SecondaryZoneFile returns the path to domain's secondary zone file (when fetched).
+func (s Storage) SecondaryZoneFile(domain string) string {
+	return filepath.Join(s.Zone(domain), "db."+domain)
+}

core/dns/storage_test.go

@@ -0,0 +1,20 @@
+package dns
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func TestStorage(t *testing.T) {
+	storage = Storage("./le_test")
+
+	if expected, actual := filepath.Join("le_test", "zones"), storage.Zones(); actual != expected {
+		t.Errorf("Expected Zones() to return '%s' but got '%s'", expected, actual)
+	}
+	if expected, actual := filepath.Join("le_test", "zones", "test.com"), storage.Zone("test.com"); actual != expected {
+		t.Errorf("Expected Site() to return '%s' but got '%s'", expected, actual)
+	}
+	if expected, actual := filepath.Join("le_test", "zones", "test.com", "db.test.com"), storage.SecondaryZoneFile("test.com"); actual != expected {
+		t.Errorf("Expected SecondaryZoneFile() to return '%s' but got '%s'", expected, actual)
+	}
+}