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ergo/irc/strings_nickname.go

90 lines
2.5 KiB
Go

// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//NOTE(dan): I need this because the default PRECIS API does not allow a way to retrieve the casefolded version of strings.
// See also: https://github.com/golang/go/issues/17386
// the content of this file is taken wholesale from the proper PRECIS API:
// https://github.com/golang/text/tree/master/secure/precis
package irc
import (
"unicode"
"unicode/utf8"
"golang.org/x/text/secure/precis"
"golang.org/x/text/transform"
"golang.org/x/text/unicode/norm"
)
type nickAdditionalMapping struct {
// TODO: This transformer needs to be stateless somehow…
notStart bool
prevSpace bool
}
func (t *nickAdditionalMapping) Reset() {
t.prevSpace = false
t.notStart = false
}
func (t *nickAdditionalMapping) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
// RFC 7700 §2.1. Rules
//
// 2. Additional Mapping Rule: The additional mapping rule consists of
// the following sub-rules.
//
// 1. Any instances of non-ASCII space MUST be mapped to ASCII
// space (U+0020); a non-ASCII space is any Unicode code point
// having a general category of "Zs", naturally with the
// exception of U+0020.
//
// 2. Any instances of the ASCII space character at the beginning
// or end of a nickname MUST be removed (e.g., "stpeter " is
// mapped to "stpeter").
//
// 3. Interior sequences of more than one ASCII space character
// MUST be mapped to a single ASCII space character (e.g.,
// "St Peter" is mapped to "St Peter").
for nSrc < len(src) {
r, size := utf8.DecodeRune(src[nSrc:])
if size == 0 { // Incomplete UTF-8 encoding
if !atEOF {
return nDst, nSrc, transform.ErrShortSrc
}
size = 1
}
if unicode.Is(unicode.Zs, r) {
t.prevSpace = true
} else {
if t.prevSpace && t.notStart {
dst[nDst] = ' '
nDst += 1
}
if size != copy(dst[nDst:], src[nSrc:nSrc+size]) {
nDst += size
return nDst, nSrc, transform.ErrShortDst
}
nDst += size
t.prevSpace = false
t.notStart = true
}
nSrc += size
}
return nDst, nSrc, nil
}
var (
NicknameProfile = precis.NewFreeform(
precis.AdditionalMapping(func() transform.Transformer {
return &nickAdditionalMapping{}
}),
precis.LowerCase(),
precis.Norm(norm.NFKC),
precis.DisallowEmpty,
)
)