1 files changed, 139 insertions, 0 deletions
diff --git a/vk/tracking/status.py b/vk/tracking/status.py
new file mode 100644
index 0000000..a16a34e
--- /dev/null
+++ b/vk/tracking/status.py
@@ -0,0 +1,139 @@
+# Copyright (c) 2016 Egor Tensin <Egor.Tensin@gmail.com>
+# This file is part of the "VK scripts" project.
+# For details, see https://github.com/egor-tensin/vk-scripts.
+# Distributed under the MIT License.
+
+from collections.abc import Callable
+import contextlib
+import time
+import signal
+
+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(writer.on_initial_status)
+        self.add_status_update_handler(writer.on_status_update)
+        self.add_connection_error_handler(writer.on_connection_error)
+
+    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.DOMAIN, UserField.ONLINE, UserField.LAST_SEEN,
+
+    def _query_status(self, uids):
+        user_list = self._api.users_get(uids, self._USER_FIELDS,
+                                        deactivated_users=False)
+        return {user.get_uid(): user for user in user_list}
+
+    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.APIConnectionError 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.APIConnectionError 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 query_status(self, uids):
+        users = self._query_initial_status(uids)
+        for user in users.values():
+            self._notify_status(user)
+        return users
+
+    def _do_loop(self, uids):
+        users = self.query_status(uids)
+        while True:
+            updated_users = self._query_status_updates(uids)
+            for user in self._filter_status_updates(users, updated_users):
+                self._notify_status_update(user)
+
+    class StopLooping(RuntimeError):
+        pass
+
+    @staticmethod
+    def _stop_looping(signo, frame):
+        raise StatusTracker.StopLooping()
+
+    @staticmethod
+    @contextlib.contextmanager
+    def _handle_signal(signo, handler):
+        old_handler = signal.getsignal(signo)
+        signal.signal(signo, handler)
+        try:
+            yield
+        finally:
+            signal.signal(signal.SIGINT, old_handler)
+
+    @staticmethod
+    def _handle_sigint():
+        # Python doesn't raise KeyboardInterrupt in case a real SIGINT is sent
+        # from outside, surprisingly.
+        return StatusTracker._handle_signal(signal.SIGINT,
+                                            StatusTracker._stop_looping)
+
+    @staticmethod
+    def _handle_sigterm():
+        return StatusTracker._handle_signal(signal.SIGTERM,
+                                            StatusTracker._stop_looping)
+
+    def loop(self, uids):
+        with self._handle_sigint(), self._handle_sigterm():
+            try:
+                self._do_loop(uids)
+            except (KeyboardInterrupt, StatusTracker.StopLooping):
+                pass