Refactor of EventHandler boilerplate ¯\_(ツ)_/¯

src/event_handlers/event_handler.py

@@ -1,18 +0,0 @@
-import json
-
-from event_handler_base import EventHandlerBase
-
-
-class EventHandler(EventHandlerBase):
-    def __init__(self, anchor, event_handler_function, zmq_context=None):
-        super().__init__(anchor, zmq_context)
-        self.event_handler_function = event_handler_function
-
-        def event_handler_callback(msg_parts):
-            anchor, message = msg_parts
-            data_json = json.loads(message)
-            response = self.event_handler_function(data_json)
-            encoded_response = json.dumps(response).encode('utf-8')
-            self.zmq_push_socket.send_multipart([anchor, encoded_response])
-
-        self.zmq_sub_stream.on_recv(event_handler_callback)

src/event_handlers/event_handler_base.py

@@ -19,6 +19,18 @@ class EventHandlerBase:
         self.zmq_sub_stream = ZMQStream(self.zmq_sub_socket)
         self.zmq_push_socket = self.zmq_context.socket(zmq.PUSH)
         self.zmq_push_socket.connect('tcp://localhost:{}'.format(RECEIVER_PORT))
+        self.zmq_sub_stream.on_recv(self.event_handler_callback)
+
+    def event_handler_callback(self, msg_parts):
+        anchor, message = msg_parts
+        data_json = json.loads(message)
+        response = self.handle_event(anchor, data_json)
+        if response is None: return
+        encoded_response = json.dumps(response).encode('utf-8')
+        self.zmq_push_socket.send_multipart([anchor, encoded_response])
+
+    def handle_event(self, anchor, data_json):
+        raise NotImplementedError
 
     def message_other(self, anchor, data):
         encoded_anchor = anchor.encode('utf-8')

src/event_handlers/event_handler_main.py

@@ -3,7 +3,7 @@ import sqlite3
 from functools import partial
 
 import source_code
-from event_handler import EventHandler
+from event_handler_base import EventHandlerBase
 from source_code_event_handler import SourceCodeEventHandler
 from stateful_event_handler import StatefulEventHandler
 from tornado.ioloop import IOLoop
@@ -16,72 +16,76 @@ login_component_py_response = partial(
 )
 
 
-def echo_handler(data):
-    return data
+class EchoHandler(EventHandlerBase):
+    def handle_event(self, anchor, data_json):
+        return data_json
 
 
-def rot13_handler(data):
-    data['data'] = codecs.encode(data['data'], 'rot13')
-    return data
+class Rot13Handler(EventHandlerBase):
+    def handle_event(self, anchor, data_json):
+        data_json['data'] = codecs.encode(data_json['data'], 'rot13')
+        return data_json
 
 
-def change_case_handler(data):
-    data['data'] = data['data'].upper() if data['data'].islower() else data['data'].lower()
-    return data
+class ChangeCaseHandler(EventHandlerBase):
+    def handle_event(self, anchor, data_json):
+        data_json['data'] = data_json['data'].upper() if data_json['data'].islower() else data_json['data'].lower()
+        return data_json
 
 
-def reverse_handler(data):
-    data['data'] = data['data'][::-1]
-    return data
+class ReverseHandler(EventHandlerBase):
+    def handle_event(self, anchor, data_json):
+        data_json['data'] = data_json['data'][::-1]
+        return data_json
 
 
-def login_handler(data):
-    email, password = data['data']['email'], data['data']['password']
-    try:
-        sql_statement = source_code.find_local_variable_value(authorize_login, 'sql_statement')
-        yield (
-            'anchor_logger',
-            'The SQL statement executed by the server will look like this:\n `{}`'.format(sql_statement)
-        )
-
-        yield ('anchor_webide',
-               login_component_py_response(content=source_code.get_source_code(authorize_login, strip_comments=False)))
-
-        sql_statement_with_values = sql_statement.format(email, password)
-        yield (
-            'anchor_logger',
-            'After the submitted parameters are substituted it looks like this:\n `{}`'.format(
-                sql_statement_with_values
+class LoginHandler(EventHandlerBase):
+    def handle_event(self, anchor, data_json):
+        email, password = data_json['data']['email'], data_json['data']['password']
+        try:
+            sql_statement = source_code.find_local_variable_value(authorize_login, 'sql_statement')
+            yield (
+                'anchor_logger',
+                'The SQL statement executed by the server will look like this:\n `{}`'.format(sql_statement)
             )
-        )
 
-        logged_in_email, is_admin = authorize_login(email, password)
+            yield ('anchor_webide',
+                   login_component_py_response(content=source_code.get_source_code(authorize_login, strip_comments=False)))
 
-        yield (
-            'anchor_logger',
-            'After the query is executed, it returns _{}_ as email address, and _{}_ for is_admin'.format(
-                logged_in_email, is_admin
+            sql_statement_with_values = sql_statement.format(email, password)
+            yield (
+                'anchor_logger',
+                'After the submitted parameters are substituted it looks like this:\n `{}`'.format(
+                    sql_statement_with_values
+                )
             )
-        )
 
-        if logged_in_email is not None:
-            response = 'Logged in as _{}_. You __{}have__ admin privileges.'.format(
-                logged_in_email,
-                '' if is_admin else 'don\'t '
+            logged_in_email, is_admin = authorize_login(email, password)
+
+            yield (
+                'anchor_logger',
+                'After the query is executed, it returns _{}_ as email address, and _{}_ for is_admin'.format(
+                    logged_in_email, is_admin
+                )
             )
-        else:
-            response = 'Bad username/password!'
-    except sqlite3.Warning:
-        response = 'Invalid request!'
 
-    yield ('anchor_login', '# Login page\n' + response)
+            if logged_in_email is not None:
+                response = 'Logged in as _{}_. You __{}have__ admin privileges.'.format(
+                    logged_in_email,
+                    '' if is_admin else 'don\'t '
+                )
+            else:
+                response = 'Bad username/password!'
+        except sqlite3.Warning:
+            response = 'Invalid request!'
+
+        yield ('anchor_login', '# Login page\n' + response)
 
 
 if __name__ == '__main__':
-    anchor_a = EventHandler('anchor_a', change_case_handler)
-    anchor_b = EventHandler('anchor_b', rot13_handler)
-    anchor_c = EventHandler('anchor_c', reverse_handler)
-    anchor_login = StatefulEventHandler('anchor_login', login_handler)
+    anchor_a = ChangeCaseHandler('anchor_a')
+    anchor_b = Rot13Handler('anchor_b')
+    anchor_c = ReverseHandler('anchor_c')
     anchor_webide = SourceCodeEventHandler('anchor_webide', 'login_component.py', 'login')
     IOLoop.instance().start()
 

src/event_handlers/source_code_event_handler.py

@@ -20,29 +20,25 @@ class SourceCodeEventHandler(EventHandlerBase):
 
         self.file = self.create_initial_state()
 
-        def event_handler_callback(msg_parts):
-            anchor, message = msg_parts
-            message_json = json.loads(message)
-            data = message_json['data']
-            if anchor == b'reset':
-                self.file = self.create_initial_state(process_is_running=True)
-            if data['command'] == 'read':
-                with open(self.file, 'r') as ifile:
-                    content = ifile.read()
-                message_json['data'] = {
-                    'filename': self.filename,
-                    'content': content,
-                    'language': self.language
-                }
-                encoded_response = json.dumps(message_json).encode('utf-8')
-                self.zmq_push_socket.send_multipart([anchor, encoded_response])
-            elif data['command'] == 'write':
-                with open(self.file, 'w') as ofile:
-                    ofile.write(data['content'])
-                self.supervisor.stopProcess(self.process_name)
-                self.supervisor.startProcess(self.process_name)
-
-        self.zmq_sub_stream.on_recv(event_handler_callback)
+    def handle_event(self, anchor, data_json):
+        data = data_json['data']
+        if anchor == b'reset':
+            self.file = self.create_initial_state(process_is_running=True)
+        if data['command'] == 'read':
+            with open(self.file, 'r') as ifile:
+                content = ifile.read()
+            data_json['data'] = {
+                'filename': self.filename,
+                'content': content,
+                'language': self.language
+            }
+            return data_json
+        elif data['command'] == 'write':
+            with open(self.file, 'w') as ofile:
+                ofile.write(data['content'])
+            self.supervisor.stopProcess(self.process_name)
+            self.supervisor.startProcess(self.process_name)
+            return None
 
     def create_initial_state(self, process_is_running=False):
         if process_is_running: