#!/usr/bin/env python

#
# Copyright (c) 2006 The Apache Software Foundation
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

"""
Utility code to translate between python objects and AMQP encoded data
fields.
"""

from cStringIO import StringIO
from struct import *

class EOF(Exception):
  pass

class Codec:

  def __init__(self, stream):
    self.stream = stream
    self.nwrote = 0
    self.nread = 0
    self.incoming_bits = []
    self.outgoing_bits = []

  def read(self, n):
    data = self.stream.read(n)
    if n > 0 and len(data) == 0:
      raise EOF()
    self.nread += len(data)
    return data

  def write(self, s):
    self.flushbits()
    self.stream.write(s)
    self.nwrote += len(s)

  def flush(self):
    self.flushbits()
    self.stream.flush()

  def flushbits(self):
    if len(self.outgoing_bits) > 0:
      bytes = []
      index = 0
      for b in self.outgoing_bits:
        if index == 0: bytes.append(0)
        if b: bytes[-1] |= 1 << index
        index = (index + 1) % 8
      del self.outgoing_bits[:]
      for byte in bytes:
        self.encode_octet(byte)

  def pack(self, fmt, *args):
    self.write(pack(fmt, *args))

  def unpack(self, fmt):
    size = calcsize(fmt)
    data = self.read(size)
    values = unpack(fmt, data)
    if len(values) == 1:
      return values[0]
    else:
      return values

  def encode(self, type, value):
    getattr(self, "encode_" + type)(value)

  def decode(self, type):
    return getattr(self, "decode_" + type)()

  # bit
  def encode_bit(self, o):
    if o:
      self.outgoing_bits.append(True)
    else:
      self.outgoing_bits.append(False)

  def decode_bit(self):
    if len(self.incoming_bits) == 0:
      bits = self.decode_octet()
      for i in range(8):
        self.incoming_bits.append(bits >> i & 1 != 0)
    return self.incoming_bits.pop(0)

  # octet
  def encode_octet(self, o):
    self.pack("!B", o)

  def decode_octet(self):
    return self.unpack("!B")

  # short
  def encode_short(self, o):
    self.pack("!H", o)

  def decode_short(self):
    return self.unpack("!H")

  # long
  def encode_long(self, o):
    self.pack("!L", o)

  def decode_long(self):
    return self.unpack("!L")

  # longlong
  def encode_longlong(self, o):
    self.pack("!Q", o)

  def decode_longlong(self):
    return self.unpack("!Q")

  def enc_str(self, fmt, s):
    size = len(s)
    self.pack(fmt, size)
    self.write(s)

  def dec_str(self, fmt):
    size = self.unpack(fmt)
    return self.read(size)

  # shortstr
  def encode_shortstr(self, s):
    self.enc_str("!B", s)

  def decode_shortstr(self):
    return self.dec_str("!B")

  # longstr
  def encode_longstr(self, s):
    if isinstance(s, dict):
      self.encode_table(s)
    else:
      self.enc_str("!L", s)

  def decode_longstr(self):
    return self.dec_str("!L")

  # table
  def encode_table(self, tbl):
    enc = StringIO()
    codec = Codec(enc)
    for key, value in tbl.items():
      codec.encode_shortstr(key)
      if isinstance(value, basestring):
        codec.write("S")
        codec.encode_longstr(value)
      else:
        codec.write("I")
        codec.encode_long(value)
    s = enc.getvalue()
    self.encode_long(len(s))
    self.write(s)

  def decode_table(self):
    size = self.decode_long()
    start = self.nread
    result = {}
    while self.nread - start < size:
      key = self.decode_shortstr()
      type = self.read(1)
      if type == "S":
        value = self.decode_longstr()
      elif type == "I":
        value = self.decode_long()
      else:
        raise ValueError(repr(type))
      result[key] = value
    return result

def test(type, value):
  if isinstance(value, (list, tuple)):
    values = value
  else:
    values = [value]
  stream = StringIO()
  codec = Codec(stream)
  for v in values:
    codec.encode(type, v)
  codec.flush()
  enc = stream.getvalue()
  stream.reset()
  dup = []
  for i in xrange(len(values)):
    dup.append(codec.decode(type))
  if values != dup:
    raise AssertionError("%r --> %r --> %r" % (values, enc, dup))

if __name__ == "__main__":
  def dotest(type, value):
    args = (type, value)
    test(*args)

  for value in ("1", "0", "110", "011", "11001", "10101", "10011"):
    for i in range(10):
      dotest("bit", map(lambda x: x == "1", value*i))

  for value in ({}, {"asdf": "fdsa", "fdsa": 1, "three": 3}, {"one": 1}):
    dotest("table", value)

  for type in ("octet", "short", "long", "longlong"):
    for value in range(0, 256):
      dotest(type, value)

  for type in ("shortstr", "longstr"):
    for value in ("", "a", "asdf"):
      dotest(type, value)
