move nodestate and role

Signed-off-by: Fabian Kammel <fk@edgeless.systems>

internal/nodestate/nodestate.go

@@ -0,0 +1,31 @@
+package nodestate
+
+import (
+	"fmt"
+
+	"github.com/edgelesssys/constellation/internal/file"
+	"github.com/edgelesssys/constellation/internal/role"
+)
+
+const nodeStatePath = "/run/state/constellation/node_state.json"
+
+// NodeState is the state of a constellation node that is required to recover from a reboot.
+// Can be persisted to disk and reloaded later.
+type NodeState struct {
+	Role            role.Role
+	MeasurementSalt []byte
+}
+
+// FromFile reads a NodeState from disk.
+func FromFile(fileHandler file.Handler) (*NodeState, error) {
+	nodeState := &NodeState{}
+	if err := fileHandler.ReadJSON(nodeStatePath, nodeState); err != nil {
+		return nil, fmt.Errorf("loading node state: %w", err)
+	}
+	return nodeState, nil
+}
+
+// ToFile writes a NodeState to disk.
+func (nodeState *NodeState) ToFile(fileHandler file.Handler) error {
+	return fileHandler.WriteJSON(nodeStatePath, nodeState, file.OptMkdirAll)
+}