# -*- Mode: Python; tab-width: 4 -*-

#       Id: asynchat.py,v 2.26 2000/09/07 22:29:26 rushing Exp

#       Author: Sam Rushing <rushing@nightmare.com>

# ======================================================================

# Copyright 1996 by Sam Rushing

#

#                         All Rights Reserved

#

# Permission to use, copy, modify, and distribute this software and

# its documentation for any purpose and without fee is hereby

# granted, provided that the above copyright notice appear in all

# copies and that both that copyright notice and this permission

# notice appear in supporting documentation, and that the name of Sam

# Rushing not be used in advertising or publicity pertaining to

# distribution of the software without specific, written prior

# permission.

#

# SAM RUSHING DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,

# INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN

# NO EVENT SHALL SAM RUSHING BE LIABLE FOR ANY SPECIAL, INDIRECT OR

# CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS

# OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,

# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN

# CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

# ======================================================================

r"""A class supporting chat-style (command/response) protocols.

This class adds support for 'chat' style protocols - where one side

sends a 'command', and the other sends a response (examples would be

the common internet protocols - smtp, nntp, ftp, etc..).

The handle_read() method looks at the input stream for the current

'terminator' (usually '\r\n' for single-line responses, '\r\n.\r\n'

for multi-line output), calling self.found_terminator() on its

receipt.

for example:

Say you build an async nntp client using this class.  At the start

of the connection, you'll have self.terminator set to '\r\n', in

order to process the single-line greeting.  Just before issuing a

'LIST' command you'll set it to '\r\n.\r\n'.  The output of the LIST

command will be accumulated (using your own 'collect_incoming_data'

method) up to the terminator, and then control will be returned to

you - by calling your self.found_terminator() method.

"""

import socket

import asyncore

from collections import deque

class async_chat (asyncore.dispatcher):

    """This is an abstract class.  You must derive from this class, and add

    the two methods collect_incoming_data() and found_terminator()"""

    # these are overridable defaults

    ac_in_buffer_size       = 4096

    ac_out_buffer_size      = 4096

    def __init__ (self, conn=None):

        self.ac_in_buffer = ''

        self.ac_out_buffer = ''

        self.producer_fifo = fifo()

        asyncore.dispatcher.__init__ (self, conn)

    def collect_incoming_data(self, data):

        raise NotImplementedError, "must be implemented in subclass"

    def found_terminator(self):

        raise NotImplementedError, "must be implemented in subclass"

    def set_terminator (self, term):

        "Set the input delimiter.  Can be a fixed string of any length, an integer, or None"

        self.terminator = term

    def get_terminator (self):

        return self.terminator

    # grab some more data from the socket,

    # throw it to the collector method,

    # check for the terminator,

    # if found, transition to the next state.

    def handle_read (self):

        try:

            data = self.recv (self.ac_in_buffer_size)

        except socket.error, why:

            self.handle_error()

            return

        self.ac_in_buffer = self.ac_in_buffer + data

        # Continue to search for self.terminator in self.ac_in_buffer,

        # while calling self.collect_incoming_data.  The while loop

        # is necessary because we might read several data+terminator

        # combos with a single recv(1024).

        while self.ac_in_buffer:

            lb = len(self.ac_in_buffer)

            terminator = self.get_terminator()

            if not terminator:

                # no terminator, collect it all

                self.collect_incoming_data (self.ac_in_buffer)

                self.ac_in_buffer = ''

            elif isinstance(terminator, int) or isinstance(terminator, long):

                # numeric terminator

                n = terminator

                if lb < n:

                    self.collect_incoming_data (self.ac_in_buffer)

                    self.ac_in_buffer = ''

                    self.terminator = self.terminator - lb

                else:

                    self.collect_incoming_data (self.ac_in_buffer[:n])

                    self.ac_in_buffer = self.ac_in_buffer[n:]

                    self.terminator = 0

                    self.found_terminator()

            else:

                # 3 cases:

                # 1) end of buffer matches terminator exactly:

                #    collect data, transition

                # 2) end of buffer matches some prefix:

                #    collect data to the prefix

                # 3) end of buffer does not match any prefix:

                #    collect data

                terminator_len = len(terminator)

                index = self.ac_in_buffer.find(terminator)

                if index != -1:

                    # we found the terminator

                    if index > 0:

                        # don't bother reporting the empty string (source of subtle bugs)

                        self.collect_incoming_data (self.ac_in_buffer[:index])

                    self.ac_in_buffer = self.ac_in_buffer[index+terminator_len:]

                    # This does the Right Thing if the terminator is changed here.

                    self.found_terminator()

                else:

                    # check for a prefix of the terminator

                    index = find_prefix_at_end (self.ac_in_buffer, terminator)

                    if index:

                        if index != lb:

                            # we found a prefix, collect up to the prefix

                            self.collect_incoming_data (self.ac_in_buffer[:-index])

                            self.ac_in_buffer = self.ac_in_buffer[-index:]

                        break

                    else:

                        # no prefix, collect it all

                        self.collect_incoming_data (self.ac_in_buffer)

                        self.ac_in_buffer = ''

    def handle_write (self):

        self.initiate_send ()

    def handle_close (self):

        self.close()

    def push (self, data):

        self.producer_fifo.push (simple_producer (data))

        self.initiate_send()

    def push_with_producer (self, producer):

        self.producer_fifo.push (producer)

        self.initiate_send()

    def readable (self):

        "predicate for inclusion in the readable for select()"

        return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)

    def writable (self):

        "predicate for inclusion in the writable for select()"

        # return len(self.ac_out_buffer) or len(self.producer_fifo) or (not self.connected)

        # this is about twice as fast, though not as clear.

        return not (

                (self.ac_out_buffer == '') and

                self.producer_fifo.is_empty() and

                self.connected

                )

    def close_when_done (self):

        "automatically close this channel once the outgoing queue is empty"

        self.producer_fifo.push (None)

    # refill the outgoing buffer by calling the more() method

    # of the first producer in the queue

    def refill_buffer (self):

        while 1:

            if len(self.producer_fifo):

                p = self.producer_fifo.first()

                # a 'None' in the producer fifo is a sentinel,

                # telling us to close the channel.

                if p is None:

                    if not self.ac_out_buffer:

                        self.producer_fifo.pop()

                        self.close()

                    return

                elif isinstance(p, str):

                    self.producer_fifo.pop()

                    self.ac_out_buffer = self.ac_out_buffer + p

                    return

                data = p.more()

                if data:

                    self.ac_out_buffer = self.ac_out_buffer + data

                    return

                else:

                    self.producer_fifo.pop()

            else:

                return

    def initiate_send (self):

        obs = self.ac_out_buffer_size

        # try to refill the buffer

        if (len (self.ac_out_buffer) < obs):

            self.refill_buffer()

        if self.ac_out_buffer and self.connected:

            # try to send the buffer

            try:

                num_sent = self.send (self.ac_out_buffer[:obs])

                if num_sent:

                    self.ac_out_buffer = self.ac_out_buffer[num_sent:]

            except socket.error, why:

                self.handle_error()

                return

    def discard_buffers (self):

        # Emergencies only!

        self.ac_in_buffer = ''

        self.ac_out_buffer = ''

        while self.producer_fifo:

            self.producer_fifo.pop()

class simple_producer:

    def __init__ (self, data, buffer_size=512):

        self.data = data

        self.buffer_size = buffer_size

    def more (self):

        if len (self.data) > self.buffer_size:

            result = self.data[:self.buffer_size]

            self.data = self.data[self.buffer_size:]

            return result

        else:

            result = self.data

            self.data = ''

            return result

class fifo:

    def __init__ (self, list=None):

        if not list:

            self.list = deque()

        else:

            self.list = deque(list)

    def __len__ (self):

        return len(self.list)

    def is_empty (self):

        return not self.list

    def first (self):

        return self.list[0]

    def push (self, data):

        self.list.append(data)

    def pop (self):

        if self.list:

            return (1, self.list.popleft())

        else:

            return (0, None)

# Given 'haystack', see if any prefix of 'needle' is at its end.  This

# assumes an exact match has already been checked.  Return the number of

# characters matched.

# for example:

# f_p_a_e ("qwerty\r", "\r\n") => 1

# f_p_a_e ("qwertydkjf", "\r\n") => 0

# f_p_a_e ("qwerty\r\n", "\r\n") => <undefined>

# this could maybe be made faster with a computed regex?

# [answer: no; circa Python-2.0, Jan 2001]

# new python:   28961/s

# old python:   18307/s

# re:        12820/s

# regex:     14035/s

def find_prefix_at_end (haystack, needle):

    l = len(needle) - 1

    while l and not haystack.endswith(needle[:l]):

        l -= 1

    return l