state/remote: add undocumented file backend for remote state

state/remote/file.go

@@ -0,0 +1,64 @@
+package remote
+
+import (
+	"bytes"
+	"crypto/md5"
+	"fmt"
+	"io"
+	"os"
+)
+
+func fileFactory(conf map[string]string) (Client, error) {
+	path, ok := conf["path"]
+	if !ok {
+		return nil, fmt.Errorf("missing 'path' configuration")
+	}
+
+	return &FileClient{
+		Path: path,
+	}, nil
+}
+
+// FileClient is a remote client that stores data locally on disk.
+// This is only used for development reasons to test remote state... locally.
+type FileClient struct {
+	Path string
+}
+
+func (c *FileClient) Get() (*Payload, error) {
+	var buf bytes.Buffer
+	f, err := os.Open(c.Path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil
+		}
+
+		return nil, err
+	}
+	defer f.Close()
+
+	if _, err := io.Copy(&buf, f); err != nil {
+		return nil, err
+	}
+
+	md5 := md5.Sum(buf.Bytes())
+	return &Payload{
+		Data: buf.Bytes(),
+		MD5:  md5[:],
+	}, nil
+}
+
+func (c *FileClient) Put(data []byte) error {
+	f, err := os.Create(c.Path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	_, err = f.Write(data)
+	return err
+}
+
+func (c *FileClient) Delete() error {
+	return os.Remove(c.Path)
+}

state/remote/file_test.go

@@ -0,0 +1,29 @@
+package remote
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+func TestFileClient_impl(t *testing.T) {
+	var _ Client = new(FileClient)
+}
+
+func TestFileClient(t *testing.T) {
+	tf, err := ioutil.TempFile("", "tf")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	tf.Close()
+	defer os.Remove(tf.Name())
+
+	client, err := fileFactory(map[string]string{
+		"path": tf.Name(),
+	})
+	if err != nil {
+		t.Fatalf("bad: %s", err)
+	}
+
+	testClient(t, client)
+}

state/remote/remote.go

@@ -39,4 +39,7 @@ var BuiltinClients = map[string]Factory{
 	"atlas":  atlasFactory,
 	"consul": consulFactory,
 	"http":   httpFactory,
+
+	// This is used for development purposes only.
+	"_local": fileFactory,
 }