Add examples to better understand middleware handler

examples/middleware/i18n.py

@@ -0,0 +1,53 @@
+#!/usr/bin/python
+
+# This example shows how to implement i18n (internationalization) l10n (localization) to create
+# multi-language bots with middleware handler.
+#
+# Note: For the sake of simplicity of this example no extra library is used. However, it is recommended to use
+# better i18n systems (gettext and etc) for handling multilingual translations.
+# This is not a working, production-ready sample and it is highly recommended not to use it in production.
+#
+# In this example let's imagine we want to introduce localization or internationalization into our project and
+# we need some global function to activate the language once and to use that language in all other message
+# handler functions for not repeatedly activating it.
+# The middleware (i18n and l10n) is explained:
+
+import telebot
+from telebot import apihelper
+
+apihelper.ENABLE_MIDDLEWARE = True
+
+TRANSLATIONS = {
+    'hello': {
+        'en': 'hello',
+        'ru': 'привет',
+        'uz': 'salom'
+    }
+}
+
+_lang = 'en'
+
+
+def activate(lang):
+    global _lang
+    _lang = lang
+
+
+def _(string):
+    return TRANSLATIONS[string][_lang]
+
+
+bot = telebot.TeleBot('TOKEN')
+
+
+@bot.middleware_handler(update_types=['message'])
+def activate_language(bot_instance, message):
+    activate(message.from_user.language_code)
+
+
+@bot.message_handler(commands=['start'])
+def start(message):
+    bot.send_message(message.chat.id, _('hello'))
+
+
+bot.polling()

examples/middleware/session.py

@@ -0,0 +1,61 @@
+#!/usr/bin/python
+
+# This example shows how to implement session creation and retrieval based on user id with middleware handler.
+#
+# Note: For the sake of simplicity of this example no extra library is used. However, it is recommended to use
+# in-memory or on-disk storage implementations (redis, mysql, postgres and etc) for storing and retrieving structures.
+# This is not a working, production-ready sample and it is highly recommended not to use it in production.
+#
+# In this example let's imagine we want to create a session for each user who communicates with the bot to store
+# different kind of temporary data while session is active. As an example we want to track the state of the user
+# with the help of this session. So, we need a way to store this session data somewhere globally to enable other
+# message handler functions to be able to use it.
+# The middleware session is explained:
+
+import telebot
+from telebot import apihelper
+
+apihelper.ENABLE_MIDDLEWARE = True
+
+INFO_STATE = 'ON_INFO_MENU'
+MAIN_STATE = 'ON_MAIN_MENU'
+
+SESSIONS = {
+    -10000: {
+        'state': INFO_STATE
+    },
+    -11111: {
+        'state': MAIN_STATE
+    }
+}
+
+
+def get_or_create_session(user_id):
+    try:
+        return SESSIONS[user_id]
+    except KeyError:
+        SESSIONS[user_id] = {'state': MAIN_STATE}
+        return SESSIONS[user_id]
+
+
+bot = telebot.TeleBot('TOKEN')
+
+
+@bot.middleware_handler(update_types=['message'])
+def set_session(bot_instance, message):
+    bot_instance.session = get_or_create_session(message.from_user.id)
+
+
+@bot.message_handler(commands=['start'])
+def start(message):
+    bot.session['state'] = MAIN_STATE
+    bot.send_message(message.chat.id, bot.session['state'])
+
+
+@bot.message_handler(commands=['info'])
+def start(message):
+    bot.session['state'] = INFO_STATE
+    bot.send_message(message.chat.id, bot.session['state'])
+
+
+bot.polling()