Refactor application structure and initialize core components

I decided to rewrite the program taking into account the experience gained.

internal/application/setting/lang.go

@@ -0,0 +1,66 @@
+package setting
+
+import (
+	"encoding/json"
+	"fyne.io/fyne/v2"
+	fyneLang "fyne.io/fyne/v2/lang"
+	"git.kor-elf.net/kor-elf/gui-for-ffmpeg/internal/resources"
+)
+
+var supportedLanguages = map[string]Lang{
+	"ru": {Code: "ru", Title: "Русский"},
+	"kk": {Code: "kk", Title: "Қазақ Тілі"},
+	"en": {Code: "en", Title: "English"},
+}
+
+type Lang struct {
+	Code  string
+	Title string
+}
+
+func ChangeLang(lang Lang) error {
+	translationsData, err := getTranslations(lang)
+	if err != nil {
+		return err
+	}
+
+	name := fyneLang.SystemLocale().LanguageString()
+	return fyneLang.AddTranslations(fyne.NewStaticResource(name+".json", translationsData))
+}
+
+func defaultLang() Lang {
+	return supportedLanguages["ru"]
+}
+
+func getTranslations(language Lang) ([]byte, error) {
+	translations := resources.GetTranslations()
+
+	baseJson, err := translations.ReadFile("translations/base." + language.Code + ".json")
+	if err != nil {
+		return nil, err
+	}
+	appJson, err := translations.ReadFile("translations/app." + language.Code + ".json")
+	if err != nil {
+		return nil, err
+	}
+
+	return mergeTranslations(baseJson, appJson)
+}
+
+func mergeTranslations(baseJson []byte, appJson []byte) ([]byte, error) {
+	base := map[string]interface{}{}
+	custom := map[string]interface{}{}
+	err := json.Unmarshal(baseJson, &base)
+	if err != nil {
+		return nil, err
+	}
+	err = json.Unmarshal(appJson, &custom)
+	if err != nil {
+		return nil, err
+	}
+
+	for k, v := range custom {
+		base[k] = v
+	}
+	return json.Marshal(base)
+}