Move FSM handling logic to an event handler

lib/tfw/components/__init__.py

@@ -8,3 +8,4 @@ from .ide_event_handler import IdeEventHandler
 from .history_monitor import HistoryMonitor, BashMonitor, GDBMonitor
 from .terminal_commands import TerminalCommands
 from .log_monitoring_event_handler import LogMonitoringEventHandler
+from .fsm_managing_event_handler import FSMManagingEventHandler

lib/tfw/components/fsm_managing_event_handler.py

@@ -0,0 +1,88 @@
+# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
+# All Rights Reserved. See LICENSE file for details.
+
+from collections import defaultdict
+
+from tfw import BroadcastingEventHandler
+from tfw.config.logs import logging
+
+LOG = logging.getLogger(__name__)
+
+
+class FSMManagingEventHandler(BroadcastingEventHandler):
+    def __init__(self, key, fsm_type):
+        super().__init__(key)
+        self.fsm = fsm_type()
+        self.fsm_manager = FSMManager(self.fsm)
+        self._fsm_updater = FSMUpdater(self.fsm)
+
+        self.command_handlers = {
+            'trigger': self.handle_trigger,
+            'update':  self.handle_update
+        }
+
+    def handle_event(self, message):
+        try:
+            data = message['data']
+            message['data'] = self.command_handlers[data['command']](data)
+            return message
+        except KeyError:
+            LOG.error('IGNORING MESSAGE: Invalid message received: %s', message)
+
+    def handle_trigger(self, data):
+        self.fsm_manager.trigger(data['value'])
+        return self.with_fsm_update(data)
+
+    def with_fsm_update(self, data):
+        return {
+            **data,
+            **self._fsm_updater.get_fsm_state_and_transitions()
+        }
+
+    def handle_update(self, data):
+        return self.with_fsm_update(data)
+
+
+class FSMManager:
+    def __init__(self, fsm):
+        self.fsm = fsm
+        self.trigger_predicates = defaultdict(list)
+
+    def trigger(self, trigger):
+        predicate_results = [
+            predicate()
+            for predicate in self.trigger_predicates[trigger]
+        ]
+
+        # TODO: think about what could we do when this prevents triggering
+        if all(predicate_results):
+            try:
+                self.fsm.trigger(trigger)
+            except AttributeError:
+                LOG.debug('FSM failed to execute nonexistent trigger: "%s"', trigger)
+
+    def subscribe_predicate(self, trigger, *predicates):
+        self.trigger_predicates[trigger].extend(predicates)
+
+    def unsubscribe_predicate(self, trigger, *predicates):
+        self.trigger_predicates[trigger] = [
+            predicate
+            for predicate in self.trigger_predicates[trigger]
+            not in predicates
+        ]
+
+
+class FSMUpdater:
+    def __init__(self, fsm):
+        self.fsm = fsm
+
+    def get_fsm_state_and_transitions(self):
+        state = self.fsm.state
+        valid_transitions = [
+            {'trigger': trigger}
+            for trigger in self.fsm.machine.get_triggers(self.fsm.state)
+        ]
+        return {
+            'current_state': state,
+            'valid_transitions': valid_transitions
+        }