refactor: extract CLI into separate package (#23)

### Summary of Changes

Move the CLI out of the `server` package.

docs/README.md

@@ -17,10 +17,10 @@ pip install safe-ds-runner
 
 ## Usage
 
-Launch the runner:
+Start the runner server:
 
 ```shell
-safe-ds-runner
+safe-ds-runner start
 ```
 
 ## Documentation

pyproject.toml

@@ -13,7 +13,7 @@ packages = [
 ]
 
 [tool.poetry.scripts]
-safe-ds-runner = "safeds_runner.server.main:main"
+safe-ds-runner = "safeds_runner.main:main"
 
 [tool.poetry.dependencies]
 python = "^3.11,<3.13"

src/safeds_runner/cli/__init__.py

@@ -0,0 +1,5 @@
+"""The command line interface of the application."""
+
+from ._cli import cli
+
+__all__ = ["cli"]

src/safeds_runner/cli/_cli.py

@@ -0,0 +1,47 @@
+import argparse
+import logging
+from importlib.metadata import version
+
+from safeds_runner.server.main import start_server
+
+
+class Commands:
+    START = "start"
+
+
+def cli() -> None:  # pragma: no cover
+    """Run the application via the command line."""
+    args = _get_args()
+
+    # Set logging level
+    if args.verbose:
+        logging.basicConfig(level=logging.DEBUG)
+    else:
+        logging.basicConfig(level=logging.INFO)
+
+    # Run command
+    match args.command:
+        case Commands.START:
+            start_server(args.port)
+
+
+def _get_args() -> argparse.Namespace:  # pragma: no cover
+    parser = argparse.ArgumentParser(description="Execute Safe-DS programs that were compiled to Python.")
+    parser.add_argument(
+        "-V",
+        "--version",
+        action="version",
+        version=f"%(prog)s {version('safe-ds-runner')}",
+    )
+    parser.add_argument("-v", "--verbose", help="increase logging verbosity", action="store_true")
+
+    # Commands
+    subparsers = parser.add_subparsers(dest="command")
+    _add_start_subparser(subparsers)
+
+    return parser.parse_args()
+
+
+def _add_start_subparser(subparsers: argparse._SubParsersAction) -> None:  # pragma: no cover
+    parser = subparsers.add_parser(Commands.START, help="start the Safe-DS Runner server")
+    parser.add_argument("-p", "--port", type=int, default=5000, help="the port to use")

src/safeds_runner/main.py

@@ -0,0 +1,8 @@
+"""The main entry point of the application."""
+
+from safeds_runner.cli import cli
+
+
+def main() -> None:  # pragma: no cover
+    """Run the application."""
+    cli()

src/safeds_runner/server/main.py

@@ -1,9 +1,7 @@
 """Module containing the main entry point, for starting the Safe-DS runner."""
 
-import argparse
 import json
 import logging
-from importlib.metadata import version
 
 import flask.app
 import flask_sock
@@ -162,12 +160,8 @@ def send_websocket_message(connection: simple_websocket.Server, message: Message
     connection.send(json.dumps(message.to_dict()))
 
 
-def main() -> None:  # pragma: no cover
-    """
-    Execute the runner application.
-
-    Main entry point of the runner application.
-    """
+def start_server(port: int) -> None:  # pragma: no cover
+    """Start the Safe-DS Runner server."""
     # Allow prints to be unbuffered by default
     import builtins
     import functools
@@ -177,19 +171,6 @@ def main() -> None:  # pragma: no cover
     logging.getLogger().setLevel(logging.DEBUG)
     from gevent.pywsgi import WSGIServer
 
-    parser = argparse.ArgumentParser(description="Start Safe-DS Runner on a specific port.")
-    parser.add_argument("--port", type=int, default=5000, help="Port on which to run the python server.")
-    parser.add_argument(
-        "-V",
-        "--version",
-        action="version",
-        version="%(prog)s {version}".format(version=version("safe-ds-runner")),
-    )
-    args = parser.parse_args()
-    logging.info("Starting Safe-DS Runner on port %s", str(args.port))
+    logging.info("Starting Safe-DS Runner on port %s", str(port))
     # Only bind to host=127.0.0.1. Connections from other devices should not be accepted
-    WSGIServer(("127.0.0.1", args.port), app).serve_forever()
-
-
-if __name__ == "__main__":
-    main()  # pragma: no cover
+    WSGIServer(("127.0.0.1", port), app).serve_forever()

tests/safeds_runner/server/test_runner_main.py

@@ -7,7 +7,7 @@
 
 
 def test_should_runner_start_successfully() -> None:
-    process = subprocess.Popen(["poetry", "run", "safe-ds-runner"], cwd=_project_root, stderr=subprocess.PIPE)
+    process = subprocess.Popen(["poetry", "run", "safe-ds-runner", "start"], cwd=_project_root, stderr=subprocess.PIPE)
     while process.poll() is None:
         process_line = str(typing.cast(IO[bytes], process.stderr).readline(), "utf-8").strip()
         # Wait for first line of log