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