Simplify package structure

tfw/components/fsm/__init__.py

@@ -0,0 +1 @@
+from .fsm_handler import FSMHandler

tfw/components/fsm/fsm_handler.py

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+import logging
+
+from tfw.internals.crypto import KeyManager, sign_message, verify_message
+from tfw.internals.networking import Scope
+
+from .fsm_updater import FSMUpdater
+
+
+LOG = logging.getLogger(__name__)
+
+
+class FSMHandler:
+    keys = ['fsm']
+    """
+    EventHandler responsible for managing the state machine of
+    the framework (TFW FSM).
+
+    tfw.networking.TFWServer instances automatically send 'trigger'
+    commands to the event handler listening on the 'fsm' key,
+    which should be an instance of this event handler.
+
+    This event handler accepts messages that have a
+    data['command'] key specifying a command to be executed.
+
+    An 'fsm_update' message is broadcasted after every successful
+    command.
+    """
+    def __init__(self, *, fsm_type, require_signature=False):
+        self.fsm = fsm_type()
+        self._fsm_updater = FSMUpdater(self.fsm)
+        self.auth_key = KeyManager().auth_key
+        self._require_signature = require_signature
+
+        self.command_handlers = {
+            'trigger': self.handle_trigger,
+            'update':  self.handle_update
+        }
+
+    def handle_event(self, message, server_connector):
+        try:
+            message = self.command_handlers[message['data']['command']](message)
+            if message:
+                fsm_update_message = self._fsm_updater.fsm_update
+                sign_message(self.auth_key, message)
+                sign_message(self.auth_key, fsm_update_message)
+                server_connector.send_message(fsm_update_message, Scope.BROADCAST)
+        except KeyError:
+            LOG.error('IGNORING MESSAGE: Invalid message received: %s', message)
+
+    def handle_trigger(self, message):
+        """
+        Attempts to step the FSM with the supplied trigger.
+
+        :param message: TFW message with a data field containing
+                        the action to try triggering in data['value']
+        """
+        trigger = message['data']['value']
+        if self._require_signature:
+            if not verify_message(self.auth_key, message):
+                LOG.error('Ignoring unsigned trigger command: %s', message)
+                return None
+        if self.fsm.step(trigger):
+            return message
+        return None
+
+    def handle_update(self, message):
+        """
+        Does nothing, but triggers an 'fsm_update' message.
+        """
+        # pylint: disable=no-self-use
+        return message

tfw/components/fsm/fsm_updater.py

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+class FSMUpdater:
+    def __init__(self, fsm):
+        self.fsm = fsm
+
+    @property
+    def fsm_update(self):
+        return {
+            'key': 'fsm_update',
+            **self.fsm_update_data
+        }
+
+    @property
+    def fsm_update_data(self):
+        valid_transitions = [
+            {'trigger': trigger}
+            for trigger in self.fsm.get_triggers(self.fsm.state)
+        ]
+        last_fsm_event = self.fsm.event_log[-1]
+        last_fsm_event['timestamp'] = last_fsm_event['timestamp'].isoformat()
+        return {
+            'current_state': self.fsm.state,
+            'valid_transitions': valid_transitions,
+            'in_accepted_state': self.fsm.in_accepted_state,
+            'last_event': last_fsm_event
+        }