commands: start a new internal sub-package for working with json commands

This code was part of cephfs/admin but will be shared with a soon-to-be
rbd/admin package.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

internal/commands/commands.go

@@ -0,0 +1,71 @@
+package commands
+
+import (
+	"encoding/json"
+
+	"github.com/ceph/go-ceph/rados"
+)
+
+// MgrCommander in an interface for the API needed to execute JSON formatted
+// commands on the ceph mgr.
+type MgrCommander interface {
+	MgrCommand(buf [][]byte) ([]byte, string, error)
+}
+
+// MonCommander is an interface for the API needed to execute JSON formatted
+// commands on the ceph mon(s).
+type MonCommander interface {
+	MonCommand(buf []byte) ([]byte, string, error)
+}
+
+// RadosCommander provides an interface for APIs needed to execute JSON
+// formatted commands on the Ceph cluster.
+type RadosCommander interface {
+	MgrCommander
+	MonCommander
+}
+
+func validate(m interface{}) error {
+	if m == nil {
+		return rados.ErrNotConnected
+	}
+	return nil
+}
+
+// RawMgrCommand takes a byte buffer and sends it to the MGR as a command.
+// The buffer is expected to contain preformatted JSON.
+func RawMgrCommand(m MgrCommander, buf []byte) Response {
+	if err := validate(m); err != nil {
+		return Response{err: err}
+	}
+	return NewResponse(m.MgrCommand([][]byte{buf}))
+}
+
+// MarshalMgrCommand takes an generic interface{} value, converts it to JSON
+// and sends the json to the MGR as a command.
+func MarshalMgrCommand(m MgrCommander, v interface{}) Response {
+	b, err := json.Marshal(v)
+	if err != nil {
+		return Response{err: err}
+	}
+	return RawMgrCommand(m, b)
+}
+
+// RawMonCommand takes a byte buffer and sends it to the MON as a command.
+// The buffer is expected to contain preformatted JSON.
+func RawMonCommand(m MonCommander, buf []byte) Response {
+	if err := validate(m); err != nil {
+		return Response{err: err}
+	}
+	return NewResponse(m.MonCommand(buf))
+}
+
+// MarshalMonCommand takes an generic interface{} value, converts it to JSON
+// and sends the json to the MGR as a command.
+func MarshalMonCommand(m MonCommander, v interface{}) Response {
+	b, err := json.Marshal(v)
+	if err != nil {
+		return Response{err: err}
+	}
+	return RawMonCommand(m, b)
+}