add listen command

config.py

@@ -3,19 +3,25 @@ import os
 from pathlib import Path
 import sys
 
-config_path = Path.cwd()
 
-for child in sorted(config_path.iterdir()):
+class ConfigurationManager:
+    def __init__(self):
+        config_path = Path.cwd()
+
+        for child in sorted(config_path.iterdir()):
             if child.is_file() and child.name.endswith('.py'):
                 mod_name = child.name.rsplit('.', 1)[0]
                 if mod_name == 'tzk_config':
                     sys.path.insert(0, str(config_path))
-            importlib.import_module(mod_name)
+                    self.conf_mod = importlib.import_module(mod_name)
                     del sys.path[0]
                     break
-else:
+        else:
             print(
                 f"Your TZK config file could not be found. "
                 f"Please ensure there is a file called tzk_config.py "
                 f"in the current directory.", file=sys.stderr)
             sys.exit(1)
+
+    def __getattr__(self, attr):
+        return getattr(self.conf_mod, attr, None)

tw.py

@@ -0,0 +1,12 @@
+import subprocess
+from typing import Sequence
+
+
+def exec(args: Sequence[Sequence[str]]) -> None:
+    bin_dir = subprocess.check_output(("npm", "bin"), text=True).strip()
+    call_args = [bin_dir + "/tiddlywiki"]
+    for tw_arg in args:
+        call_args.append(f"--{tw_arg[0]}")
+        for inner_arg in tw_arg[1:]:
+            call_args.append(inner_arg)
+    return subprocess.call(call_args)

tzk.py

@@ -2,7 +2,9 @@ from abc import ABC, abstractmethod, abstractclassmethod
 import argparse
 import os
 
+import config
 import git
+import tw
 
 
 class CliCommand(ABC):
@@ -40,7 +42,43 @@ class CommitCommand(CliCommand):
             git.exec("push", "backup")
 
 
-import config
+class ListenCommand(CliCommand):
+    cmd = "listen"
+    help = "Start a TiddlyWiki server in the current directory."
+
+    @classmethod
+    def setup_arguments(self, parser: argparse.ArgumentParser) -> None:
+        parser.add_argument(
+            "-p", "--port",
+            metavar="PORT",
+            help="Port to listen on.",
+            default=str(cm.listen_port or "8080"),
+        )
+        parser.add_argument(
+            "--username",
+            metavar="USERNAME",
+            default=cm.listen_username or "",
+            help="Username to use for basic authentication, if any.",
+        )
+        parser.add_argument(
+            "--password",
+            metavar="PASSWORD",
+            default=cm.listen_password or "",
+            help="Password to use for basic authentication, if any.",
+        )
+    
+    def execute(self, args: argparse.Namespace) -> None:
+        tw.exec(
+            [
+                ("listen",
+                 f"port={args.port}",
+                 f"username={args.username}",
+                 f"password={args.password}")
+            ]
+        )
+
+
+cm = config.ConfigurationManager()
 
 os.chdir("zk-wiki")
 # TODO: confirm we're in the right directory