// Package ident is the reference implementation of system and member
// identifiers.
package ident

import (
	"encoding"
	"errors"
	"fmt"
	"strconv"
)

// ErrNewline is returned for identifiers found to contain newline characters.
var ErrNewline = errors.New("identifier contains newline characters")

// UnexpectedSizeError describes a malformed string representation of an
// identifier, with unexpected length.
type UnexpectedSizeError struct {
	Data []byte
	Want int
}

func (e *UnexpectedSizeError) Error() string {
	return "got " + strconv.Itoa(len(e.Data)) + " bytes for " +
		"a " + strconv.Itoa(e.Want) + "-byte identifier"
}

// MS is a system or member identifier.
type MS interface {
	encoding.TextMarshaler
	encoding.TextUnmarshaler
	fmt.Stringer

	// EncodedSize returns the number of bytes appended by Encode.
	EncodedSize() int
	// Encode appends the canonical string representation of MS to dst and
	// returns the extended buffer.
	Encode(dst []byte) []byte

	// ident is a no-op function but serves to distinguish types that are
	// identifiers from ordinary types with custom marshaler/unmarshaler
	// behaviour: a type is an identifier part if it has an ident method.
	ident()
}