normalize.go

// Copyright 2023 Dolthub, 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.

// Copyright 2017 The Cockroach Authors.
//
// Use of this software is governed by the Business Source License
// included in the file licenses/BSL.txt.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0, included in the file
// licenses/APL.txt.

package lex

import (
	"strings"
	"unicode"

	"golang.org/x/text/unicode/norm"
)

// Special case normalization rules for Turkish/Azeri lowercase dotless-i and
// uppercase dotted-i. Fold both dotted and dotless 'i' into the ascii i/I, so
// our case-insensitive comparison functions can be locale-invariant. This
// mapping implements case-insensitivity for Turkish and other latin-derived
// languages simultaneously, with the additional quirk that it is also
// insensitive to the dottedness of the i's
var normalize = unicode.SpecialCase{
	unicode.CaseRange{
		Lo: 0x0130,
		Hi: 0x0130,
		Delta: [unicode.MaxCase]rune{
			0x49 - 0x130, // Upper
			0x69 - 0x130, // Lower
			0x49 - 0x130, // Title
		},
	},
	unicode.CaseRange{
		Lo: 0x0131,
		Hi: 0x0131,
		Delta: [unicode.MaxCase]rune{
			0x49 - 0x131, // Upper
			0x69 - 0x131, // Lower
			0x49 - 0x131, // Title
		},
	},
}

// NormalizeName normalizes to lowercase and Unicode Normalization
// Form C (NFC).
func NormalizeName(n string) string {
	lower := strings.Map(normalize.ToLower, n)
	if isASCII(lower) {
		return lower
	}
	return norm.NFC.String(lower)
}