#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements.  See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership.  The ASF licenses this file
# to you 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.
#

from threading import Event
from invoker import Invoker
from datatypes import RangeSet, Struct, Future
from codec010 import StringCodec
from assembler import Segment

class SessionDetached(Exception): pass

def client(*args):
  return Client(*args)

def server(*args):
  return Server(*args)

class Session(Invoker):

  def __init__(self, name, spec, sync=True, timeout=10, delegate=client):
    self.name = name
    self.spec = spec
    self.sync = sync
    self.timeout = timeout
    self.channel = None
    self.opened = Event()
    self.closed = Event()
    self.receiver = Receiver(self)
    self.sender = Sender(self)
    self.delegate = delegate(self)
    self.send_id = True
    self.results = {}

  def close(self, timeout=None):
    self.channel.session_detach(self.name)
    self.closed.wait(timeout=timeout)

  def resolve_method(self, name):
    cmd = self.spec.instructions.get(name)
    if cmd is not None and cmd.track == self.spec["track.command"].value:
      return cmd
    else:
      return None

  def invoke(self, type, args, kwargs):
    if self.channel == None:
      raise SessionDetached()

    if type.segments:
      if len(args) == len(type.fields) + 1:
        message = args[-1]
        args = args[:-1]
      else:
        message = kwargs.pop("message", None)
    else:
      message = None

    cmd = type.new(args, kwargs)
    sc = StringCodec(self.spec)
    sc.write_command(type, cmd)

    seg = Segment(True, (message == None or
                         (message.headers == None and message.body == None)),
                  type.segment_type, type.track, self.channel.id, sc.encoded)

    if type.result:
      result = Future()
      self.results[self.sender.next_id] = result

    self.send(seg)

    if message != None:
      if message.headers != None:
        sc = StringCodec(self.spec)
        for st in message.headers:
          sc.write_struct32(st.type, st)
        seg = Segment(False, message.body == None, self.spec["segment_type.header"].value,
                      type.track, self.channel.id, sc.encoded)
        self.send(seg)
      if message.body != None:
        seg = Segment(False, True, self.spec["segment_type.body"].value,
                      type.track, self.channel.id, message.body)
        self.send(seg)

    if type.result:
      if self.sync:
        return result.get(self.timeout)
      else:
        return result

  def received(self, seg):
    self.receiver.received(seg)
    if seg.type == self.spec["segment_type.command"].value:
      cmd = seg.decode(self.spec)
      attr = cmd.type.qname.replace(".", "_")
      result = getattr(self.delegate, attr)(cmd)
      if cmd.type.result:
        self.execution_result(seg.id, result)
    elif seg.type == self.spec["segment_type.header"].value:
      self.delegate.header(seg.decode(self.spec))
    elif seg.type == self.spec["segment_type.body"].value:
      self.delegate.body(seg.decode(self.spec))
    else:
      raise ValueError("unknown segment type: %s" % seg.type)
    self.receiver.completed(seg)

  def send(self, seg):
    self.sender.send(seg)

  def __str__(self):
    return '<Session: %s, %s>' % (self.name, self.channel)

  def __repr__(self):
    return str(self)

class Receiver:

  def __init__(self, session):
    self.session = session
    self.next_id = None
    self.next_offset = None
    self._completed = RangeSet()

  def received(self, seg):
    if self.next_id == None or self.next_offset == None:
      raise Exception("todo")
    seg.id = self.next_id
    seg.offset = self.next_offset
    if seg.last:
      self.next_id += 1
      self.next_offset = 0
    else:
      self.next_offset += len(seg.payload)

  def completed(self, seg):
    if seg.id == None:
      raise ValueError("cannot complete unidentified segment")
    if seg.last:
      self._completed.add(seg.id)

class Sender:

  def __init__(self, session):
    self.session = session
    self.next_id = 0
    self.next_offset = 0
    self.segments = []

  def send(self, seg):
    seg.id = self.next_id
    seg.offset = self.next_offset
    if seg.last:
      self.next_id += 1
      self.next_offset = 0
    else:
      self.next_offset += len(seg.payload)
    self.segments.append(seg)
    if self.session.send_id:
      self.session.send_id = False
      self.session.channel.session_command_point(seg.id, seg.offset)
    self.session.channel.connection.write_segment(seg)

  def completed(self, commands):
    idx = 0
    while idx < len(self.segments):
      seg = self.segments[idx]
      if seg.id in commands:
        del self.segments[idx]
      else:
        idx += 1

from queue import Queue, Closed, Empty

class Delegate:

  def __init__(self, session):
    self.session = session

  def execution_result(self, er):
    future = self.session.results[er.command_id]
    future.set(er.value)

class Client(Delegate):

  def message_transfer(self, cmd):
    print "TRANSFER:", cmd

  def header(self, hdr):
    print "HEADER:", hdr

  def body(self, seg):
    print "BODY:", seg