fields.go

/*
Copyright 2015 Google Inc. All rights reserved.

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 fields

import (
	"sort"
	"strings"
)

// Fields allows you to present fields independently from their storage.
type Fields interface {
	// Has returns whether the provided field exists.
	Has(field string) (exists bool)

	// Get returns the value for the provided field.
	Get(field string) (value string)
}

// Set is a map of field:value. It implements Fields.
type Set map[string]string

// String returns all fields listed as a human readable string.
// Conveniently, exactly the format that ParseSelector takes.
func (ls Set) String() string {
	selector := make([]string, 0, len(ls))
	for key, value := range ls {
		selector = append(selector, key+"="+value)
	}
	// Sort for determinism.
	sort.StringSlice(selector).Sort()
	return strings.Join(selector, ",")
}

// Has returns whether the provided field exists in the map.
func (ls Set) Has(field string) bool {
	_, exists := ls[field]
	return exists
}

// Get returns the value in the map for the provided field.
func (ls Set) Get(field string) string {
	return ls[field]
}

// AsSelector converts fields into a selectors.
func (ls Set) AsSelector() Selector {
	return SelectorFromSet(ls)
}