feat(encoding): Add hcl codec

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

internal/encoding/hcl/codec.go

@@ -0,0 +1,40 @@
+package hcl
+
+import (
+	"bytes"
+	"encoding/json"
+
+	"github.com/hashicorp/hcl"
+	"github.com/hashicorp/hcl/hcl/printer"
+)
+
+// Codec implements the encoding.Encoder and encoding.Decoder interfaces for HCL encoding.
+// TODO: add printer config to the codec?
+type Codec struct{}
+
+func (Codec) Encode(v interface{}) ([]byte, error) {
+	b, err := json.Marshal(v)
+	if err != nil {
+		return nil, err
+	}
+
+	// TODO: use printer.Format? Is the trailing newline an issue?
+
+	ast, err := hcl.Parse(string(b))
+	if err != nil {
+		return nil, err
+	}
+
+	var buf bytes.Buffer
+
+	err = printer.Fprint(&buf, ast.Node)
+	if err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
+
+func (Codec) Decode(b []byte, v interface{}) error {
+	return hcl.Unmarshal(b, v)
+}