Add support for transformation/translation modules that do arbitrary request processing to generate the message

Fixes #3

1 files changed, 54 insertions, 7 deletions

diff --git a/http2irc.py b/http2irc.py
index 1ead513..7a09642 100644
--- a/http2irc.py
+++ b/http2irc.py
@@ -4,6 +4,8 @@ import asyncio
 import base64
 import collections
 import concurrent.futures
+import importlib.util
+import inspect
 import logging
 import os.path
 import signal
@@ -114,9 +116,11 @@ class Config(dict):
 					raise InvalidConfig(f'Invalid map key {key!r}')
 				if not isinstance(map_, collections.abc.Mapping):
 					raise InvalidConfig(f'Invalid map for {key!r}')
-				if any(x not in ('webpath', 'ircchannel', 'auth') for x in map_):
+				if any(x not in ('webpath', 'ircchannel', 'auth', 'module') for x in map_):
 					raise InvalidConfig(f'Unknown key(s) found in map {key!r}')
 				#TODO: Check values
+				if 'module' in map_ and not os.path.isfile(map_['module']):
+					raise InvalidConfig(f'Module {map_["module"]!r} in map {key!r} is not a file')
 
 		# Default values
 		finalObj = {'logging': {'level': 'INFO', 'format': '{asctime} {levelname} {message}'}, 'irc': {'host': 'irc.hackint.org', 'port': 6697, 'ssl': 'yes', 'nick': 'h2ibot', 'real': 'I am an http2irc bot.', 'certfile': None, 'certkeyfile': None}, 'web': {'host': '127.0.0.1', 'port': 8080}, 'maps': {}}
@@ -129,6 +133,33 @@ class Config(dict):
 				map_['ircchannel'] = f'#{key}'
 			if 'auth' not in map_:
 				map_['auth'] = False
+			if 'module' not in map_:
+				map_['module'] = None
+
+		# Load modules
+		modulePaths = {map_['module'] for map_ in obj['maps'].values() if 'module' in map_ and map_['module'] is not None}
+		modules = {} # path: str -> module: module
+		for i, path in enumerate(modulePaths):
+			try:
+				# Build a name that is virtually guaranteed to be unique across a process.
+				# Although importlib does not seem to perform any caching as of CPython 3.8, this is not guaranteed by spec.
+				spec = importlib.util.spec_from_file_location(f'http2irc-module-{id(self)}-{i}', path)
+				module = importlib.util.module_from_spec(spec)
+				spec.loader.exec_module(module)
+			except Exception as e: # This is ugly, but exec_module can raise virtually any exception
+				raise InvalidConfig(f'Loading module {path!r} failed: {e!s}')
+			if not hasattr(module, 'process'):
+				raise InvalidConfig(f'Module {path!r} does not have a process function')
+			if not inspect.iscoroutinefunction(module.process):
+				raise InvalidConfig(f'Module {path!r} process attribute is not a coroutine function')
+			if len(inspect.signature(module.process).parameters) != 1:
+				raise InvalidConfig(f'Module {path!r} process function does not take exactly 1 parameter')
+			modules[path] = module
+
+		# Replace module value in maps
+		for map_ in obj['maps'].values():
+			if 'module' in map_ and map_['module'] is not None:
+				map_['module'] = modules[map_['module']]
 
 		# Merge in what was read from the config file and set keys on self
 		for key in ('logging', 'irc', 'web', 'maps'):
@@ -370,7 +401,7 @@ class WebServer:
 		self.messageQueue = messageQueue
 		self.config = config
 
-		self._paths = {} # '/path' => ('#channel', auth)  where auth is either False (no authentication) or the HTTP header value for basic auth
+		self._paths = {} # '/path' => ('#channel', auth, module)  where auth is either False (no authentication) or the HTTP header value for basic auth
 
 		self._app = aiohttp.web.Application()
 		self._app.add_routes([aiohttp.web.post('/{path:.+}', self.post)])
@@ -379,7 +410,7 @@ class WebServer:
 		self._configChanged = asyncio.Event()
 
 	def update_config(self, config):
-		self._paths = {map_['webpath']: (map_['ircchannel'], f'Basic {base64.b64encode(map_["auth"].encode("utf-8")).decode("utf-8")}' if map_['auth'] else False) for map_ in config['maps'].values()}
+		self._paths = {map_['webpath']: (map_['ircchannel'], f'Basic {base64.b64encode(map_["auth"].encode("utf-8")).decode("utf-8")}' if map_['auth'] else False, map_['module']) for map_ in config['maps'].values()}
 		needRebind = self.config['web'] != config['web']
 		self.config = config
 		if needRebind:
@@ -400,7 +431,7 @@ class WebServer:
 	async def post(self, request):
 		logging.info(f'Received request for {request.path!r}')
 		try:
-			channel, auth = self._paths[request.path]
+			channel, auth, module = self._paths[request.path]
 		except KeyError:
 			logging.info(f'Bad request: no path {request.path!r}')
 			raise aiohttp.web.HTTPNotFound()
@@ -409,6 +440,24 @@ class WebServer:
 			if not authHeader or authHeader != auth:
 				logging.info(f'Bad request: authentication failed: {authHeader!r} != {auth}')
 				raise aiohttp.web.HTTPForbidden()
+		if module is not None:
+			try:
+				message = await module.process(request)
+			except aiohttp.web.HTTPException as e:
+				raise e
+			except Exception as e:
+				logging.error(f'Bad request: exception in module process function: {e!s}')
+				raise aiohttp.web.HTTPBadRequest()
+			if '\r' in message or '\n' in message:
+				logging.error(f'Bad request: module process function returned message with linebreaks: {message!r}')
+				raise aiohttp.web.HTTPBadRequest()
+		else:
+			message = await self._default_process(request)
+		logging.debug(f'Putting message {message!r} for {channel} into message queue')
+		self.messageQueue.put_nowait((channel, message))
+		raise aiohttp.web.HTTPOk()
+
+	async def _default_process(self, request):
 		try:
 			message = await request.text()
 		except Exception as e:
@@ -423,9 +472,7 @@ class WebServer:
 		if '\r' in message or '\n' in message:
 			logging.info('Bad request: linebreaks in message')
 			raise aiohttp.web.HTTPBadRequest()
-		logging.debug(f'Putting message {message!r} for {channel} into message queue')
-		self.messageQueue.put_nowait((channel, message))
-		raise aiohttp.web.HTTPOk()
+		return message
 
 
 def configure_logging(config):