app: make it multilingual, add i18n support

bin/app/src/util/i18n.rs

@@ -0,0 +1,65 @@
+/* This file is part of DarkFi (https://dark.fi)
+ *
+ * Copyright (C) 2020-2025 Dyne.org foundation
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+use fluent::{concurrent::FluentBundle, FluentResource};
+use parking_lot::RwLock;
+use std::sync::Arc;
+use unic_langid::langid;
+
+pub type I18nResource = Arc<FluentResource>;
+
+pub struct I18nBabelFish {
+    bundle: RwLock<Arc<FluentBundle<I18nResource>>>,
+}
+
+impl I18nBabelFish {
+    pub fn new(src: String, lang: &str) -> Self {
+        let mut langs = vec![lang.parse().unwrap()];
+        if lang != "en-US" {
+            langs.push(langid!("en-US"));
+        }
+
+        let res = Arc::new(FluentResource::try_new(src).unwrap());
+        let mut bundle = FluentBundle::new_concurrent(langs);
+        bundle.add_resource(res).unwrap();
+        Self { bundle: RwLock::new(Arc::new(bundle)) }
+    }
+
+    pub fn set(&self, other: Self) {
+        let bundle = other.bundle.read();
+        *self.bundle.write() = Arc::clone(&*bundle);
+    }
+
+    pub fn tr(&self, id: &str) -> Option<String> {
+        let bundle = self.bundle.read();
+        let msg = bundle.get_message(id)?;
+        let patt = msg.value()?;
+        // See FluentBundle::format_pattern()
+        // this is where we can also pass args into the ftl str
+        let mut errs = vec![];
+        let res = bundle.format_pattern(&patt, None, &mut errs);
+        Some(res.into_owned())
+    }
+}
+
+impl Clone for I18nBabelFish {
+    fn clone(&self) -> Self {
+        let bundle = self.bundle.read();
+        Self { bundle: RwLock::new(Arc::clone(&*bundle)) }
+    }
+}