// Copyright 2016 The Xorm Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package builder

// Cond defines an interface
type Cond interface {
	WriteTo(Writer) error
	And(...Cond) Cond
	Or(...Cond) Cond
	IsValid() bool
}

type condEmpty struct{}

var _ Cond = condEmpty{}

// NewCond creates an empty condition
func NewCond() Cond {
	return condEmpty{}
}

func (condEmpty) WriteTo(w Writer) error {
	return nil
}

func (condEmpty) And(conds ...Cond) Cond {
	return And(conds...)
}

func (condEmpty) Or(conds ...Cond) Cond {
	return Or(conds...)
}

func (condEmpty) IsValid() bool {
	return false
}