1
// Copyright 2015 The Go Authors. All rights reserved.
2
// Use of this source code is governed by a BSD-style
3
// license that can be found in the LICENSE file.
4

5
package internal
6

7
// This file contains matchers that implement CLDR inheritance.
8
//
9
//     See https://unicode.org/reports/tr35/#Locale_Inheritance.
10
//
11
// Some of the inheritance described in this document is already handled by
12
// the cldr package.
13

14
import (
15
	"golang.org/x/text/language"
16
)
17

18
// TODO: consider if (some of the) matching algorithm needs to be public after
19
// getting some feel about what is generic and what is specific.
20

21
// NewInheritanceMatcher returns a matcher that matches based on the inheritance
22
// chain.
23
//
24
// The matcher uses canonicalization and the parent relationship to find a
25
// match. The resulting match will always be either Und or a language with the
26
// same language and script as the requested language. It will not match
27
// languages for which there is understood to be mutual or one-directional
28
// intelligibility.
29
//
30
// A Match will indicate an Exact match if the language matches after
31
// canonicalization and High if the matched tag is a parent.
32
func NewInheritanceMatcher(t []language.Tag) *InheritanceMatcher {
33
	tags := &InheritanceMatcher{make(map[language.Tag]int)}
34
	for i, tag := range t {
35
		ct, err := language.All.Canonicalize(tag)
36
		if err != nil {
37
			ct = tag
38
		}
39
		tags.index[ct] = i
40
	}
41
	return tags
42
}
43

44
type InheritanceMatcher struct {
45
	index map[language.Tag]int
46
}
47

48
func (m InheritanceMatcher) Match(want ...language.Tag) (language.Tag, int, language.Confidence) {
49
	for _, t := range want {
50
		ct, err := language.All.Canonicalize(t)
51
		if err != nil {
52
			ct = t
53
		}
54
		conf := language.Exact
55
		for {
56
			if index, ok := m.index[ct]; ok {
57
				return ct, index, conf
58
			}
59
			if ct == language.Und {
60
				break
61
			}
62
			ct = ct.Parent()
63
			conf = language.High
64
		}
65
	}
66
	return language.Und, 0, language.No
67
}
68

69