Refactor scheduler launcher

The CLI is refactored to start schedulers based on the name they have
been registered under in the pybatsim.schedulers entry point.

pybatsim-core/pyproject.toml

@@ -55,7 +55,8 @@ Sphinx = "^4.3.1"
 tools = ["pandas"]
 
 [tool.poetry.scripts]
-pybatsim = "pybatsim.batsim.cmds.launcher:main"
+pybatsim = "pybatsim.cmdline:main"
+pybatsim-legacy = "pybatsim.batsim.cmds.launcher:main"
 pybatsim-experiment = "pybatsim.batsim.cmds.experiments:main"
 
 # definition of officialy maintained schedulers

pybatsim-core/src/pybatsim/cmdline.py

+"""
+    pybatsim.cmdline
+    ~~~~~~~~~~~~~~~~
+
+    Command line interface.
+"""
+
+import argparse
+import io
+import json
+
+from pybatsim import __version__
+from pybatsim.plugin import SCHEDULER_ENTRY_POINT, find_plugin_schedulers
+from pybatsim.batsim.tools.launcher import launch_scheduler as legacy_launch_scheduler
+
+
+# TODO: relocate under scheduler module?
+def find_scheduler_class(name):
+    """Lookup a scheduler by name. Return None if not found."""
+    for found_name, cls in find_plugin_schedulers():
+        if name == found_name:
+            return cls
+    return None
+
+
+# TODO: relocate under scheduler module?
+def get_scheduler_by_name(name, *, options):
+    """Return an instantiated scheduler.
+
+    Options are passed to the scheduler initializer.
+    Raises if not found.
+    """
+    cls = find_scheduler_class(name)
+    if cls is None:
+        raise ValueError(f'Unknown scheduler name: {name}')
+    return cls(options)
+
+
+# TODO: correct handling of error path
+def _scheduler_options(string):
+    """Convert JSON-encoded scheduler options into a dict."""
+    string = string.strip()
+    if string.startswith('@'):
+        # classic text stream of the file containing the options
+        json_file = open(string[1:], mode='rt', encoding='utf-8')
+    else:
+        # encapsulate the whole JSON string in a text stream
+        json_file = io.StringIO(string)
+
+    with json_file:
+        options = json.load(json_file)
+        return options
+
+
+def _build_parser():
+    parser = argparse.ArgumentParser(
+        description='Run a PyBatsim scheduler.',
+    )
+    parser.add_argument(
+        '--version',
+        action='version',
+        version=__version__,
+    )
+    parser.add_argument(
+        '-t', '--timeout',
+        default=2_000,
+        type=int,
+        help='the timeout (in milliseconds) to wait for a Batsim answer, '
+             'supply a negative value to disable '
+             '(default: 2000)',
+    )
+    parser.add_argument(
+        '-s', '--socket-endpoint',
+        default='tcp://*:28000',
+        help='address of Batsim socket, '
+             'formatted as \'protocol://interface:port\' '
+             '(default: tcp://*:28000)',
+        metavar='ADDRESS',
+    )
+    parser.add_argument(
+        '-e', '--event-socket-endpoint',
+        help='address of scheduler-published events socket, '
+             'formatted as \'protocol://interface:port\'',
+        metavar='ADDRESS',
+    )
+    parser.add_argument(
+        '-o', '--scheduler-options',
+        default={},
+        type=_scheduler_options,
+        help='options forwarded to the scheduler, '
+             'either a JSON string (e.g., \'{"option": "value"}\') '
+             'or an @-prefixed JSON file containing the options (e.g., \'@options.json\')',
+        metavar='OPTIONS',
+    )
+    parser.add_argument(
+        'scheduler',
+        help='name of the scheduler to run '
+             f'(as registered under \'{SCHEDULER_ENTRY_POINT}\' entry point)',
+    )
+
+    return parser
+
+
+def main(args=None):
+    parser = _build_parser()
+    arguments = parser.parse_args(args)
+    # instantiate scheduler
+    scheduler = get_scheduler_by_name(arguments.scheduler, options=arguments.scheduler_options)
+    # launch simulation
+    legacy_launch_scheduler(
+        scheduler=scheduler,
+        socket_endpoint=arguments.socket_endpoint,
+        event_socket_endpoint=arguments.event_socket_endpoint,
+        options=arguments.scheduler_options,
+        timeout=arguments.timeout,
+    )