# $Id$
# an asynchronous ftp client

# see: http://www.effbot.org/zone/asyncore-ftp-client.htm

import asyncore, asynchat
import re, socket, sys

# get port number from pasv response
pasv_pattern = re.compile("[-\d]+,[-\d]+,[-\d]+,[-\d]+,([-\d]+),([-\d]+)")

class anon_ftp(asynchat.async_chat):

    def __init__(self, host):
        asynchat.async_chat.__init__(self)

        self.host = host

        self.user = "anonymous"
        self.password = "anonymous@"

        self.set_terminator("\n")

        self.data = ""

        self.response = []

        self.commands = [
            "PASV", self.ftp_handle_pasv_response,
            "LIST",
            "QUIT"
        ]

        self.handler = self.ftp_handle_connect

        # connect to ftp server
        self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
        self.connect((host, 21))

    def handle_connect(self):
        # connection succeeded
        pass

    def handle_expt(self):
        # connection failed
        self.close()

    def collect_incoming_data(self, data):
        self.data = self.data + data

    def found_terminator(self):

        # collect response
        data = self.data
        if data.endswith("\r"):
            data = data[:-1]
        self.data = ""
        self.response.append(data)
        if not re.match("\d\d\d ", data):
            return

        response = self.response
        self.response = []

        for line in response:
            print "S:", line

        # process response
        if self.handler:
            # call the response handler
            handler = self.handler
            self.handler = None

            handler(response)

            if self.handler:
                return # follow-up command in progress

        # send next command from queue
        # send next command from queue
        try:
            command = self.commands.pop(0)
            if self.commands and callable(self.commands[0]):
                self.handler = self.commands.pop(0)
            print "C:", command
            self.push(command + "\r\n")
        except IndexError:
            pass

    def ftp_handle_connect(self, response):
        code = response[-1][:3] # get response code
        if code == "220":
            self.push("USER " + self.user + "\r\n")
            self.handler = self.ftp_handle_user_response
        else:
            raise Exception("ftp login failed")

    def ftp_handle_user_response(self, response):
        code = response[-1][:3]
        if code == "230":
            return # user accepted
        elif code == "331" or code == "332":
            self.push("PASS " + self.password + "\r\n")
            self.handler = self.ftp_handle_pass_response
        else:
            raise Exception("ftp login failed: user name not accepted")

    def ftp_handle_pass_response(self, response):
        code = response[-1][:3]
        if code == "230":
            return # user and password accepted
        else:
            raise Exception("ftp login failed: user/password not accepted")

    def ftp_handle_pasv_response(self, response):
        code = response[-1][:3]
        if code != "227":
            return # pasv failed
        match = pasv_pattern.search(response[-1])
        if not match:
            return # bad port
        p1, p2 = match.groups()
        try:
            port = (int(p1) & 255) * 256 + (int(p2) & 255)
        except ValueError:
            return # bad port
        # establish data connection
        async_ftp_download(self.host, port)

class async_ftp_download(asyncore.dispatcher):

    def __init__(self, host, port):
        asyncore.dispatcher.__init__(self)
        self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
        self.connect((host, port))

    def writable(self):
        return 0

    def handle_connect(self):
        pass

    def handle_expt(self):
        self.close()

    def handle_read(self):
        sys.stdout.write(self.recv(8192))

    def handle_close(self):
        self.close()

# anon_ftp("ftp.python.org")
anon_ftp("ftp.sunet.se")

asyncore.loop()