Start refactor how qemu-system commands are built

qemucli/flag_arg.go

@@ -0,0 +1,45 @@
+package qemucli
+
+import (
+	"github.com/pkg/errors"
+)
+
+type FlagArg struct {
+	key string
+}
+
+func MustNewFlagArg(key string) *FlagArg {
+	a, err := NewFlagArg(key)
+	if err != nil {
+		panic(err)
+	}
+
+	return a
+}
+
+func NewFlagArg(key string) (*FlagArg, error) {
+	a := &FlagArg{
+		key: key,
+	}
+
+	// Preflight arg key/type check.
+	err := validateArgKey(a.key, a.ValueType())
+	if err != nil {
+		return nil, errors.Wrap(err, "validate arg key")
+	}
+
+	return a, nil
+}
+
+func (a *FlagArg) StringKey() string {
+	return a.key
+}
+
+func (a *FlagArg) StringValue() string {
+	// Boolean flags have no value.
+	return ""
+}
+
+func (a *FlagArg) ValueType() ArgAcceptedValue {
+	return ArgAcceptedValueNone
+}