Add better locale matching

nyaruka · Sep 1, 2023 · cecf580 · cecf580
1 parent d26cae2
commit cecf580
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Showing 2 changed files with 43 additions and 0 deletions.
diff --git a/envs/locale.go b/envs/locale.go
@@ -24,6 +24,10 @@ func NewLocale(l Language, c Country) Locale {
 	return Locale(fmt.Sprintf("%s-%s", l, c)) // e.g. "eng-US", "por-BR"
 }
 
+func (l Locale) ToTag() language.Tag {
+	return language.MustParse(string(l))
+}
+
 // ToBCP47 returns the BCP47 code, e.g. en-US, pt, pt-BR
 func (l Locale) ToBCP47() string {
 	if l == NilLocale {
@@ -71,3 +75,18 @@ func (l *Locale) Scan(value any) error         { return null.ScanString(value, l
 func (l Locale) Value() (driver.Value, error)  { return null.StringValue(l) }
 func (l Locale) MarshalJSON() ([]byte, error)  { return null.MarshalString(l) }
 func (l *Locale) UnmarshalJSON(b []byte) error { return null.UnmarshalString(b, l) }
+
+// LocaleBestMatch returns the best match between a list of preferred locales and a list of available BCP 47 language tags.
+// The provided tags don't necessarily use 3 char language codes like our locales do.
+func LocaleBestMatch(preferred []Locale, available []language.Tag) language.Tag {
+	prefTags := make([]language.Tag, len(preferred))
+	for i := range preferred {
+		prefTags[i] = preferred[i].ToTag()
+	}
+
+	m := language.NewMatcher(available)
+
+	// see https://github.com/golang/go/issues/24211
+	_, idx, _ := m.Match(prefTags...)
+	return available[idx]
+}
diff --git a/envs/locale_test.go b/envs/locale_test.go
@@ -5,6 +5,7 @@ import (
 
 	"github.com/nyaruka/goflow/envs"
 	"github.com/stretchr/testify/assert"
+	"golang.org/x/text/language"
 )
 
 func TestLocale(t *testing.T) {
@@ -70,3 +71,26 @@ func TestToBCP47(t *testing.T) {
 		assert.Equal(t, tc.bcp47, tc.locale.ToBCP47())
 	}
 }
+
+func TestLocaleBestMatch(t *testing.T) {
+	p := language.MustParse
+
+	tests := []struct {
+		preferred []envs.Locale
+		available []language.Tag
+		best      language.Tag
+	}{
+		{preferred: []envs.Locale{"eng-US"}, available: []language.Tag{p("es_EC"), p("en-US")}, best: p("en-US")},
+		{preferred: []envs.Locale{"eng-US"}, available: []language.Tag{p("es"), p("en")}, best: p("en")},
+		{preferred: []envs.Locale{"eng"}, available: []language.Tag{p("es-US"), p("en-UK")}, best: p("en-UK")},
+		{preferred: []envs.Locale{"eng", "fra"}, available: []language.Tag{p("fr-CA"), p("en-RW")}, best: p("en-RW")},
+		{preferred: []envs.Locale{"eng", "fra"}, available: []language.Tag{p("fra-CA"), p("eng-RW")}, best: p("eng-RW")},
+		{preferred: []envs.Locale{"fra", "eng"}, available: []language.Tag{p("fra-CA"), p("eng-RW")}, best: p("fra-CA")},
+		{preferred: []envs.Locale{"spa"}, available: []language.Tag{p("es-EC"), p("es-MX"), p("es-ES")}, best: p("es-ES")},
+		{preferred: []envs.Locale{}, available: []language.Tag{p("es_EC"), p("en-US")}, best: p("es_EC")},
+	}
+
+	for _, tc := range tests {
+		assert.Equal(t, tc.best, envs.LocaleBestMatch(tc.preferred, tc.available), "locale mismatch for preferred=%v available=%s", tc.preferred, tc.available)
+	}
+}