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
 5package 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
14import (
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.
32func 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
44type InheritanceMatcher struct {
45	index map[language.Tag]int
46}
47
48func (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}