# -*- Mode: Python; tab-width: 4 -*-
# Id: asynchat.py,v 2.26 2000年09月07日 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 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 = 65536
 ac_out_buffer_size = 65536

 # we don't want to enable the use of encoding by default, because that is a
 # sign of an application bug that we don't want to pass silently

 use_encoding = 0
 encoding = 'latin-1'

 def __init__(self, sock=None, map=None):
 # for string terminator matching
 self.ac_in_buffer = b''

 # we use a list here rather than io.BytesIO for a few reasons...
 # del lst[:] is faster than bio.truncate(0)
 # lst = [] is faster than bio.truncate(0)
 self.incoming = []

 # we toss the use of the "simple producer" and replace it with
 # a pure deque, which the original fifo was a wrapping of
 self.producer_fifo = deque()
 asyncore.dispatcher.__init__(self, sock, map)

 def collect_incoming_data(self, data):
 raise NotImplementedError("must be implemented in subclass")

 def _collect_incoming_data(self, data):
 self.incoming.append(data)

 def _get_data(self):
 d = b''.join(self.incoming)
 del self.incoming[:]
 return d

 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.
 """
 if isinstance(term, str) and self.use_encoding:
 term = bytes(term, self.encoding)
 elif isinstance(term, int) and term < 0:
 raise ValueError('the number of received bytes must be positive')
 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 BlockingIOError:
 return
 except OSError as why:
 self.handle_error()
 return

 if isinstance(data, str) and self.use_encoding:
 data = bytes(str, self.encoding)
 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(4096).

 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 = b''
 elif isinstance(terminator, int):
 # numeric terminator
 n = terminator
 if lb < n:
 self.collect_incoming_data(self.ac_in_buffer)
 self.ac_in_buffer = b''
 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 = b''

 def handle_write(self):
 self.initiate_send()

 def handle_close(self):
 self.close()

 def push(self, data):
 if not isinstance(data, (bytes, bytearray, memoryview)):
 raise TypeError('data argument must be byte-ish (%r)',
 type(data))
 sabs = self.ac_out_buffer_size
 if len(data) > sabs:
 for i in range(0, len(data), sabs):
 self.producer_fifo.append(data[i:i+sabs])
 else:
 self.producer_fifo.append(data)
 self.initiate_send()

 def push_with_producer(self, producer):
 self.producer_fifo.append(producer)
 self.initiate_send()

 def readable(self):
 "predicate for inclusion in the readable for select()"
 # cannot use the old predicate, it violates the claim of the
 # set_terminator method.

 # return (len(self.ac_in_buffer) <= self.ac_in_buffer_size)
 return 1

 def writable(self):
 "predicate for inclusion in the writable for select()"
 return self.producer_fifo or (not self.connected)

 def close_when_done(self):
 "automatically close this channel once the outgoing queue is empty"
 self.producer_fifo.append(None)

 def initiate_send(self):
 while self.producer_fifo and self.connected:
 first = self.producer_fifo[0]
 # handle empty string/buffer or None entry
 if not first:
 del self.producer_fifo[0]
 if first is None:
 self.handle_close()
 return

 # handle classic producer behavior
 obs = self.ac_out_buffer_size
 try:
 data = first[:obs]
 except TypeError:
 data = first.more()
 if data:
 self.producer_fifo.appendleft(data)
 else:
 del self.producer_fifo[0]
 continue

 if isinstance(data, str) and self.use_encoding:
 data = bytes(data, self.encoding)

 # send the data
 try:
 num_sent = self.send(data)
 except OSError:
 self.handle_error()
 return

 if num_sent:
 if num_sent < len(data) or obs < len(first):
 self.producer_fifo[0] = first[num_sent:]
 else:
 del self.producer_fifo[0]
 # we tried to send some actual data
 return

 def discard_buffers(self):
 # Emergencies only!
 self.ac_in_buffer = b''
 del self.incoming[:]
 self.producer_fifo.clear()


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 = b''
 return result


# 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