🧹 move default locale logic from main file

This logic needs to be done in localization.rs.

Also expands usage of environment variables: `LC_ALL`,
`LC_MESSAGES`, `LANG`.

src/localization.rs

@@ -26,22 +26,22 @@ macro_rules! fl {
     }};
 }
 
-// Get the `Localizer` to be used for localizing this library.
+/// Get the `Localizer` to be used for localizing this library.
 pub fn localizer() -> Box<dyn Localizer> {
     Box::from(DefaultLocalizer::new(&*LANGUAGE_LOADER, &Localizations))
 }
 
-// Get translated text
+/// Get translated text
 pub fn get_locale_text(message_id: &str) -> String {
     LANGUAGE_LOADER.get(message_id)
 }
 
-// Get available languages
+/// Get available languages
 pub fn get_available_languages() -> Result<Vec<unic_langid::LanguageIdentifier>, I18nEmbedError> {
     LANGUAGE_LOADER.available_languages(&Localizations)
 }
 
-// Check if language is available
+/// Check if language is available
 pub fn check_language_valid(requested_language: &str) -> bool {
     let available_languages = get_available_languages().unwrap();
     available_languages.iter().any(|x| {
@@ -49,3 +49,17 @@ pub fn check_language_valid(requested_language: &str) -> bool {
         lang == requested_language
     })
 }
+
+/// Get system language or default language if system one is not supported
+///
+/// Checks env variables in following order:
+/// - `LC_ALL`
+/// - `LC_MESSAGES`
+/// - `LANG`
+pub fn get_default_lang() -> String {
+    std::env::var("LC_ALL").unwrap_or_else(|_| {
+        std::env::var("LC_MESSAGES").unwrap_or_else(|_| {
+            std::env::var("LANG").unwrap_or_else(|_| String::from("en_US.UTF-8"))
+        })
+    })
+}

src/main.rs

@@ -350,7 +350,7 @@ pub fn get_best_locale(
         return Ok(preferences["default_locale"].as_str().unwrap().to_owned());
     }
 
-    let locale_name = std::env::var("LC_MESSAGES").unwrap_or_else(|_| String::from("en_US.UTF-8"));
+    let locale_name = crate::localization::get_default_lang();
     let sys_locale =
         string_substr(locale_name.as_str(), 0, locale_name.find('.').unwrap_or(usize::MAX))?;
     let two_letters = string_substr(sys_locale, 0, 2)?;