1 files changed, 99 insertions, 0 deletions
diff --git a/vk/tracking/status_tracker.py b/vk/tracking/status_tracker.py
new file mode 100644
index 0000000..3d1f032
--- /dev/null
+++ b/vk/tracking/status_tracker.py
@@ -0,0 +1,99 @@
+# Copyright 2016 Egor Tensin <Egor.Tensin@gmail.com>
+# This file is licensed under the terms of the MIT License.
+# See LICENSE.txt for details.
+
+from collections import Callable
+import time
+
+import vk.error
+from vk.user import UserField
+
+class StatusTracker:
+    DEFAULT_TIMEOUT = 5
+
+    def __init__(self, api, timeout=DEFAULT_TIMEOUT):
+        self._api = api
+        self._timeout = timeout
+        self._on_initial_status = []
+        self._on_status_update = []
+        self._on_connection_error = []
+
+    def _wait_after_connection_error(self):
+        time.sleep(self._timeout)
+
+    def add_database_writer(self, writer):
+        self.add_initial_status_handler(lambda user: writer.on_initial_status(user))
+        self.add_status_update_handler(lambda user: writer.on_status_update(user))
+        self.add_connection_error_handler(lambda e: writer.on_connection_error(e))
+
+    def add_initial_status_handler(self, fn):
+        self._assert_is_callback(fn)
+        self._on_initial_status.append(fn)
+
+    def add_status_update_handler(self, fn):
+        self._assert_is_callback(fn)
+        self._on_status_update.append(fn)
+
+    def add_connection_error_handler(self, fn):
+        self._assert_is_callback(fn)
+        self._on_connection_error.append(fn)
+
+    @staticmethod
+    def _assert_is_callback(fn):
+        if not isinstance(fn, Callable):
+            raise TypeError()
+
+    _USER_FIELDS = UserField.SCREEN_NAME, UserField.ONLINE, UserField.LAST_SEEN
+
+    def _query_status(self, uids):
+        return {user.get_uid(): user for user in self._api.users_get(uids, self._USER_FIELDS)}
+
+    def _notify_status(self, user):
+        for fn in self._on_initial_status:
+            fn(user)
+
+    def _notify_status_update(self, user):
+        for fn in self._on_status_update:
+            fn(user)
+
+    def _notify_connection_error(self, e):
+        for fn in self._on_connection_error:
+            fn(e)
+
+    def _query_initial_status(self, uids):
+        while True:
+            try:
+                return self._query_status(uids)
+            except vk.error.ConnectionError as e:
+                self._notify_connection_error(e)
+                self._wait_after_connection_error()
+
+    def _query_status_updates(self, uids):
+        while True:
+            self._wait_after_connection_error()
+            try:
+                return self._query_status(uids)
+            except vk.error.ConnectionError as e:
+                self._notify_connection_error(e)
+
+    @staticmethod
+    def _filter_status_updates(old_users, new_users):
+        for uid, user in new_users.items():
+            if old_users[uid].is_online() != user.is_online():
+                old_users[uid] = user
+                yield user
+
+    def _do_loop(self, uids):
+        users = self._query_initial_status(uids)
+        for user in users.values():
+            self._notify_status(user)
+        while True:
+            updated_users = self._query_status_updates(uids)
+            for user in self._filter_status_updates(users, updated_users):
+                self._notify_status_update(user)
+
+    def loop(self, uids):
+        try:
+            self._do_loop(uids)
+        except KeyboardInterrupt:
+            pass