Mini Shell

"""Command line tool for starting a Cheroot WSGI/HTTP server instance.

Basic usage:

.. code-block:: shell-session

    $ # Start a server on 127.0.0.1:8000 with the default settings
    $ # for the WSGI app myapp/wsgi.py:application()
    $ cheroot myapp.wsgi

    $ # Start a server on 0.0.0.0:9000 with 8 threads
    $ # for the WSGI app myapp/wsgi.py:main_app()
    $ cheroot myapp.wsgi:main_app --bind 0.0.0.0:9000 --threads 8

    $ # Start a server for the cheroot.server.Gateway subclass
    $ # myapp/gateway.py:HTTPGateway
    $ cheroot myapp.gateway:HTTPGateway

    $ # Start a server on the UNIX socket /var/spool/myapp.sock
    $ cheroot myapp.wsgi --bind /var/spool/myapp.sock

    $ # Start a server on the abstract UNIX socket CherootServer
    $ cheroot myapp.wsgi --bind @CherootServer

.. spelling::

   cli
"""

import argparse
import os
import sys
import urllib.parse  # noqa: WPS301
from importlib import import_module
from contextlib import suppress

from . import server
from . import wsgi


class BindLocation:
    """A class for storing the bind location for a Cheroot instance."""


class TCPSocket(BindLocation):
    """TCPSocket."""

    def __init__(self, address, port):
        """Initialize.

        Args:
            address (str): Host name or IP address
            port (int): TCP port number

        """
        self.bind_addr = address, port


class UnixSocket(BindLocation):
    """UnixSocket."""

    def __init__(self, path):
        """Initialize."""
        self.bind_addr = path


class AbstractSocket(BindLocation):
    """AbstractSocket."""

    def __init__(self, abstract_socket):
        """Initialize."""
        self.bind_addr = '\x00{sock_path}'.format(sock_path=abstract_socket)


class Application:
    """Application."""

    @classmethod
    def resolve(cls, full_path):
        """Read WSGI app/Gateway path string and import application module."""
        mod_path, _, app_path = full_path.partition(':')
        app = getattr(import_module(mod_path), app_path or 'application')
        # suppress the `TypeError` exception, just in case `app` is not a class
        with suppress(TypeError):
            if issubclass(app, server.Gateway):
                return GatewayYo(app)

        return cls(app)

    def __init__(self, wsgi_app):
        """Initialize."""
        if not callable(wsgi_app):
            raise TypeError(
                'Application must be a callable object or '
                'cheroot.server.Gateway subclass',
            )
        self.wsgi_app = wsgi_app

    def server_args(self, parsed_args):
        """Return keyword args for Server class."""
        args = {
            arg: value
            for arg, value in vars(parsed_args).items()
            if not arg.startswith('_') and value is not None
        }
        args.update(vars(self))
        return args

    def server(self, parsed_args):
        """Server."""
        return wsgi.Server(**self.server_args(parsed_args))


class GatewayYo:
    """Gateway."""

    def __init__(self, gateway):
        """Init."""
        self.gateway = gateway

    def server(self, parsed_args):
        """Server."""
        server_args = vars(self)
        server_args['bind_addr'] = parsed_args['bind_addr']
        if parsed_args.max is not None:
            server_args['maxthreads'] = parsed_args.max
        if parsed_args.numthreads is not None:
            server_args['minthreads'] = parsed_args.numthreads
        return server.HTTPServer(**server_args)


def parse_wsgi_bind_location(bind_addr_string):
    """Convert bind address string to a BindLocation."""
    # if the string begins with an @ symbol, use an abstract socket,
    # this is the first condition to verify, otherwise the urlparse
    # validation would detect //@<value> as a valid url with a hostname
    # with value: "<value>" and port: None
    if bind_addr_string.startswith('@'):
        return AbstractSocket(bind_addr_string[1:])

    # try and match for an IP/hostname and port
    match = urllib.parse.urlparse(
        '//{addr}'.format(addr=bind_addr_string),
    )
    try:
        addr = match.hostname
        port = match.port
        if addr is not None or port is not None:
            return TCPSocket(addr, port)
    except ValueError:
        pass

    # else, assume a UNIX socket path
    return UnixSocket(path=bind_addr_string)


def parse_wsgi_bind_addr(bind_addr_string):
    """Convert bind address string to bind address parameter."""
    return parse_wsgi_bind_location(bind_addr_string).bind_addr


_arg_spec = {
    '_wsgi_app': {
        'metavar': 'APP_MODULE',
        'type': Application.resolve,
        'help': 'WSGI application callable or cheroot.server.Gateway subclass',
    },
    '--bind': {
        'metavar': 'ADDRESS',
        'dest': 'bind_addr',
        'type': parse_wsgi_bind_addr,
        'default': '[::1]:8000',
        'help': 'Network interface to listen on (default: [::1]:8000)',
    },
    '--chdir': {
        'metavar': 'PATH',
        'type': os.chdir,
        'help': 'Set the working directory',
    },
    '--server-name': {
        'dest': 'server_name',
        'type': str,
        'help': 'Web server name to be advertised via Server HTTP header',
    },
    '--threads': {
        'metavar': 'INT',
        'dest': 'numthreads',
        'type': int,
        'help': 'Minimum number of worker threads',
    },
    '--max-threads': {
        'metavar': 'INT',
        'dest': 'max',
        'type': int,
        'help': 'Maximum number of worker threads',
    },
    '--timeout': {
        'metavar': 'INT',
        'dest': 'timeout',
        'type': int,
        'help': 'Timeout in seconds for accepted connections',
    },
    '--shutdown-timeout': {
        'metavar': 'INT',
        'dest': 'shutdown_timeout',
        'type': int,
        'help': 'Time in seconds to wait for worker threads to cleanly exit',
    },
    '--request-queue-size': {
        'metavar': 'INT',
        'dest': 'request_queue_size',
        'type': int,
        'help': 'Maximum number of queued connections',
    },
    '--accepted-queue-size': {
        'metavar': 'INT',
        'dest': 'accepted_queue_size',
        'type': int,
        'help': 'Maximum number of active requests in queue',
    },
    '--accepted-queue-timeout': {
        'metavar': 'INT',
        'dest': 'accepted_queue_timeout',
        'type': int,
        'help': 'Timeout in seconds for putting requests into queue',
    },
}


def main():
    """Create a new Cheroot instance with arguments from the command line."""
    parser = argparse.ArgumentParser(
        description='Start an instance of the Cheroot WSGI/HTTP server.',
    )
    for arg, spec in _arg_spec.items():
        parser.add_argument(arg, **spec)
    raw_args = parser.parse_args()

    # ensure cwd in sys.path
    '' in sys.path or sys.path.insert(0, '')

    # create a server based on the arguments provided
    raw_args._wsgi_app.server(raw_args).safe_start()