// Copyright 2015 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package flags

import "errors"

// NewStringsFlag creates a new string flag for which any one of the given
// strings is a valid value, and any other value is an error.
func NewStringsFlag(valids ...string) *StringsFlag {
	return &StringsFlag{Values: valids}
}

// StringsFlag implements the flag.Value interface.
type StringsFlag struct {
	Values []string
	val    string
}

// Set verifies the argument to be a valid member of the allowed values
// before setting the underlying flag value.
func (ss *StringsFlag) Set(s string) error {
	for _, v := range ss.Values {
		if s == v {
			ss.val = s
			return nil
		}
	}
	return errors.New("invalid value")
}

// String returns the set value (if any) of the StringsFlag
func (ss *StringsFlag) String() string {
	return ss.val
}