locale_test.go

package i18n

import (
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

func TestMatchAvailableLocale(t *testing.T) {
	t.Parallel()

	bundle := newTestBundle(t, "en",
		WithLocales("zh-Hans", "ja-JP", "ko-KR"),
	)

	require.NoError(t, bundle.LoadMessages(map[string]map[string]string{
		"en":      {"hello_world": "Hello, world"},
		"zh-Hans": {"hello_world": "你好，世界"},
		"ja-JP":   {"hello_world": "こんにちは世界"},
		"ko-KR":   {"hello_world": "안녕 세상"},
	}))

	tests := []struct {
		name       string
		accepts    []string
		wantLocale string
		wantText   string
	}{
		{
			name:       "Chinese simplified via zh-CN",
			accepts:    []string{"zh-CN,zh;q=0.9,en-US;q=0.8,en;q=0.7,ja;q=0.6"},
			wantLocale: "zh-Hans",
			wantText:   "你好，世界",
		},
		{
			name:       "English via en-us",
			accepts:    []string{"en-us;q=0.7,en;q=0.3"},
			wantLocale: "en",
			wantText:   "Hello, world",
		},
		{
			name:       "Japanese via ja-JP",
			accepts:    []string{"ja-JP,ja;q=0.9,en;q=0.8"},
			wantLocale: "ja-JP",
			wantText:   "こんにちは世界",
		},
		{
			name:       "unsupported language falls back to default",
			accepts:    []string{"de;q=0.9,de-DE;q=0.8"},
			wantLocale: "en",
			wantText:   "Hello, world",
		},
		{
			name:       "invalid header falls back to default",
			accepts:    []string{"not-a-valid-header!!!"},
			wantLocale: "en",
			wantText:   "Hello, world",
		},
		{
			name:       "empty header falls back to default",
			accepts:    []string{""},
			wantLocale: "en",
			wantText:   "Hello, world",
		},
		{
			name:       "multiple headers picks best match",
			accepts:    []string{"de;q=0.9", "ja-JP;q=0.8"},
			wantLocale: "ja-JP",
			wantText:   "こんにちは世界",
		},
		{
			name:       "multiple headers use global quality order",
			accepts:    []string{"zh;q=0.1", "ja;q=0.9"},
			wantLocale: "ja-JP",
			wantText:   "こんにちは世界",
		},
		{
			name:       "zero quality entry is ignored across headers",
			accepts:    []string{"zh;q=0", "ja;q=0.5"},
			wantLocale: "ja-JP",
			wantText:   "こんにちは世界",
		},
		{
			name:       "equal quality preserves first header order",
			accepts:    []string{"zh;q=0.8", "ja;q=0.8"},
			wantLocale: "zh-Hans",
			wantText:   "你好，世界",
		},
		{
			name:       "no arguments falls back to default",
			accepts:    nil,
			wantLocale: "en",
			wantText:   "Hello, world",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()
			locale := bundle.MatchAvailableLocale(tt.accepts...)
			loc := bundle.NewLocalizer(locale)

			assert.Equal(t, tt.wantLocale, loc.Locale())
			assert.Equal(t, tt.wantText, loc.Get("hello_world"))
		})
	}
}