feat: add language package with core types and helpers

internal/language/language_test.go

@@ -0,0 +1,119 @@
+package language
+
+import "testing"
+
+func TestFromCode(t *testing.T) {
+	tests := []struct {
+		code     string
+		wantCode string
+		wantName string
+	}{
+		{"en", "en", "English"},
+		{"es", "es", "Spanish"},
+		{"zh", "zh", "Chinese"},
+		{"invalid", "", "Auto-detect"},
+		{"", "", "Auto-detect"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.code, func(t *testing.T) {
+			got := FromCode(tt.code)
+			if got.Code != tt.wantCode {
+				t.Errorf("FromCode(%q).Code = %q, want %q", tt.code, got.Code, tt.wantCode)
+			}
+			if got.Name != tt.wantName {
+				t.Errorf("FromCode(%q).Name = %q, want %q", tt.code, got.Name, tt.wantName)
+			}
+		})
+	}
+}
+
+func TestFromCodeEnglish(t *testing.T) {
+	lang := FromCode("en")
+	if lang.Code != "en" {
+		t.Errorf("FromCode('en').Code = %q, want 'en'", lang.Code)
+	}
+	if lang.Name != "English" {
+		t.Errorf("FromCode('en').Name = %q, want 'English'", lang.Name)
+	}
+	if lang.NativeName != "English" {
+		t.Errorf("FromCode('en').NativeName = %q, want 'English'", lang.NativeName)
+	}
+}
+
+func TestIsValidCode(t *testing.T) {
+	tests := []struct {
+		code string
+		want bool
+	}{
+		{"en", true},
+		{"es", true},
+		{"zh", true},
+		{"invalid", false},
+		{"", true}, // auto is valid
+		{"xyz", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.code, func(t *testing.T) {
+			got := IsValidCode(tt.code)
+			if got != tt.want {
+				t.Errorf("IsValidCode(%q) = %v, want %v", tt.code, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestList(t *testing.T) {
+	list := List()
+	if len(list) != 57 {
+		t.Errorf("List() returned %d languages, want 57", len(list))
+	}
+
+	// verify English is in the list
+	found := false
+	for _, lang := range list {
+		if lang.Code == "en" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Error("List() does not contain English")
+	}
+}
+
+func TestCodes(t *testing.T) {
+	codes := Codes()
+	if len(codes) != 57 {
+		t.Errorf("Codes() returned %d codes, want 57", len(codes))
+	}
+
+	// verify 'en' is in the codes
+	found := false
+	for _, code := range codes {
+		if code == "en" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Error("Codes() does not contain 'en'")
+	}
+}
+
+func TestAllLanguageCodes(t *testing.T) {
+	codes := AllLanguageCodes()
+	if len(codes) != 57 {
+		t.Errorf("AllLanguageCodes() returned %d codes, want 57", len(codes))
+	}
+}
+
+func TestAuto(t *testing.T) {
+	if Auto.Code != "" {
+		t.Errorf("Auto.Code = %q, want empty string", Auto.Code)
+	}
+	if Auto.Name != "Auto-detect" {
+		t.Errorf("Auto.Name = %q, want 'Auto-detect'", Auto.Name)
+	}
+}