censoredstring.go

// SPDX-FileCopyrightText: 2022 Coop Norge SA
//
// SPDX-License-Identifier: MIT

// Package masker provides Go types which makes it easy to protect sensitive data from
// exposure by masking the data in situations that would result in exposure
// such as string formatting, logging and marshalling to JSON or YAML.
package masker

import (
	"encoding"
	"fmt"
	"log/slog"
)

// CensoredText is the text displayed instead of protected values when they are masked.
const CensoredText = "###CENSORED###"

// CensoredString masks a string value by censoring it when it printed or marshalled to JSON, YAML or Text. The protected value can be revealed by calling the UnmaskString() method on the CensoredString value.
type CensoredString string

// MarshalText marshals the CensoredString value into a textual form, which will invariably be the value of the CensoredText constant.
func (s CensoredString) MarshalText() ([]byte, error) {
	return []byte(s.String()), nil
}

// String returns the native format for a CensoredString value, which will invariably be the value of the CensoredText constant.
func (s CensoredString) String() string {
	return CensoredText
}

// GoString returns the Go syntax for a CensoredString value, which will invariably be the Go syntax for the CensoredText constant.
func (s CensoredString) GoString() string {
	return fmt.Sprintf("%#v", s.String())
}

// Format formats the CensoredString according to the verb, which will
// invariably be the CensoredString constant.
func (s CensoredString) Format(f fmt.State, verb rune) {
	var value string
	if verb == 'v' && f.Flag('#') {
		value = s.GoString()
	} else {
		value = s.String()
	}
	f.Write([]byte(value)) //nolint:errcheck
}

// LogValue converts the CensoredString into a slog.Value, which will
// invariably contain the value of the CensoredString constant.
func (s CensoredString) LogValue() slog.Value {
	return slog.StringValue(s.String())
}

// UnmaskString returns the underlying protected string of a CensoredString value.
func (s CensoredString) UnmaskString() string {
	return string(s)
}

var (
	_ encoding.TextMarshaler = (*CensoredString)(nil)
	_ fmt.Stringer           = (*CensoredString)(nil)
	_ fmt.GoStringer         = (*CensoredString)(nil)
	_ fmt.Formatter          = (*CensoredString)(nil)
	_ StringUnmasker         = (*CensoredString)(nil)
	_ slog.LogValuer         = (*CensoredString)(nil)
)