CN2021/client/command.py

import logging
from abc import ABC, abstractmethod
from typing import Dict, Tuple
from urllib.parse import urlparse

from client.httpclient import FORMAT, HTTPClient
from httplib import parser
from httplib.exceptions import InvalidResponse, InvalidStatusLine, UnsupportedEncoding
from httplib.message import ClientMessage as Message
from httplib.retriever import PreambleRetriever

sockets: Dict[str, HTTPClient] = {}


def create(command: str, url: str, port):
    """
    Create a corresponding Command instance of the specified HTTP `command` with the specified `url` and `port`.
    @param command: The command type to create
    @param url: The url for the command
    @param port: The port for the command
    """

    uri = parser.get_uri(url)
    if command == "GET":
        return GetCommand(uri, port)
    elif command == "HEAD":
        return HeadCommand(uri, port)
    elif command == "POST":
        return PostCommand(uri, port)
    elif command == "PUT":
        return PutCommand(uri, port)
    else:
        raise ValueError()


class AbstractCommand(ABC):
    """
    A class representing the command for sending an HTTP command.
    """
    uri: str
    host: str
    path: str
    port: int
    sub_request: bool

    def __init__(self, uri: str, port):
        self.uri = uri
        self.host, _, self.path = parser.parse_uri(uri)
        self.port = int(port)
        self.sub_request = False

    @property
    @abstractmethod
    def command(self):
        pass

    def execute(self, sub_request=False):
        self.sub_request = sub_request
        (host, path) = self.parse_uri()

        client = sockets.get(host)

        if client and client.is_closed():
            sockets.pop(self.host)
            client = None

        if not client:
            client = HTTPClient(host)
            client.conn.connect((host, self.port))
            sockets[host] = client

        message = f"{self.command} {path} HTTP/1.1\r\n"
        message += f"Host: {host}:{self.port}\r\n"
        message += "Accept: */*\r\nAccept-Encoding: identity\r\n"
        encoded_msg = self._build_message(message)

        logging.debug("---request begin---\r\n%s---request end---", encoded_msg.decode(FORMAT))

        client.conn.sendall(encoded_msg)

        logging.info("HTTP request sent, awaiting response...")

        try:
            retriever = PreambleRetriever(client)
            self._await_response(client, retriever)
        except InvalidResponse as e:
            logging.debug("Internal error: Response could not be parsed", exc_info=e)
            return
        except InvalidStatusLine as e:
            logging.debug("Internal error: Invalid status-line in response", exc_info=e)
            return
        except UnsupportedEncoding as e:
            logging.debug("Internal error: Unsupported encoding in response", exc_info=e)
        finally:
            if not sub_request:
                client.close()

    def _await_response(self, client, retriever):
        while True:
            line = client.read_line()
            print(line, end="")
            if line in ("\r\n", "\n", ""):
                break

    def _build_message(self, message: str) -> bytes:
        return (message + "\r\n").encode(FORMAT)

    def parse_uri(self):
        parsed = urlparse(self.uri)

        # If there is no netloc, the url is invalid, so prepend `//` and try again
        if parsed.netloc == "":
            parsed = urlparse("//" + self.uri)

        host = parsed.netloc
        path = parsed.path
        if len(path) == 0 or path[0] != '/':
            path = "/" + path

        port_pos = host.find(":")
        if port_pos >= 0:
            host = host[:port_pos]

        return host, path


class AbstractWithBodyCommand(AbstractCommand, ABC):
    """
    The building block for creating an HTTP message for an HTTP command with a body.
    """

    def _build_message(self, message: str) -> bytes:
        body = input(f"Enter {self.command} data: ").encode(FORMAT)
        print()

        message += "Content-Type: text/plain\r\n"
        message += f"Content-Length: {len(body)}\r\n"
        message += "\r\n"
        message = message.encode(FORMAT)
        message += body
        message += b"\r\n"

        return message


class HeadCommand(AbstractCommand):
    """
    A Command for sending a `HEAD` message.
    """

    @property
    def command(self):
        return "HEAD"


class GetCommand(AbstractCommand):
    """
    A Command for sending a `GET` message.
    """

    def __init__(self, uri: str, port, dir=None):
        super().__init__(uri, port)
        self.dir = dir
        self.filename = None

    @property
    def command(self):
        return "GET"

    def _get_preamble(self, retriever):
        lines = retriever.retrieve()
        (version, status, msg) = parser.parse_status_line(next(lines))
        headers = parser.parse_headers(lines)

        buffer = retriever.buffer
        logging.debug("---response begin---\r\n%s---response end---", "".join(buffer))

        return Message(version, status, msg, headers, buffer)

    def _await_response(self, client, retriever):
        msg = self._get_preamble(retriever)

        from client import response_handler
        self.filename = response_handler.handle(client, msg, self, self.dir)


class PostCommand(AbstractWithBodyCommand):
    """
    A command for sending a `POST` command.
    """

    @property
    def command(self):
        return "POST"


class PutCommand(AbstractWithBodyCommand):
    """
    A command for sending a `PUT` command.
    """

    @property
    def command(self):
        return "PUT"