l10n: add en, de, ja and fr

app.py

@@ -1,8 +1,62 @@
 from os import system as console
-from flask import Flask, render_template
+from configparser import ConfigParser
+from flask import (
+    Flask,
+    g,
+    request,
+    render_template,
+)
+
+
+translations_cache = {}
+
+def load_translations(lang):
+    if lang not in translations_cache:
+        translations_cache[lang] = {}
+
+        try:
+            config = ConfigParser()
+            config.read(f'locale/{lang}.ini')
+            for section in config.sections():
+                translations_cache[lang][section] = dict(config.items(section))
+        except:
+            pass
+
+    return translations_cache[lang]
+
+
+def get_locale():
+    return request.accept_languages.best_match(('en', 'ru', 'de', 'fr', 'ja'), 'en')
 
 app = Flask(__name__)
 
+
+@app.before_request
+def before_request():
+    g.locale = get_locale()
+    g.translations = load_translations(g.locale)
+
+
+@app.context_processor
+def inject_translations():
+    def translate(text, **kwargs):
+        if ":" in text:
+            section, key = text.split(":", 1)
+        else:
+            section, key = "common", text
+
+        template = g.translations \
+            .get(section, {}) \
+            .get(key, f"${section}: {key}$")
+
+        try:
+            return template.format(**kwargs)
+        except:
+            return template
+
+    return {'_': translate}
+
+
 if app.debug:
     console("sass static/style/main.scss static/style/main.css")