Talk to a job from python

Very very basic inital checkin to show a way to talk to/from a Vim job
using python (mainly), and to parse the sort of messages that LSP and
VSCode debugger protocol speak (i.e. similar to http messages).

Very hacky, sort of holds together for what it is.

python3/vimspector/channel.py

@@ -0,0 +1,93 @@
+# vimspector - A multi-language debugging system for Vim
+# Copyright 2018 Ben Jackson
+#
+# 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.
+
+import logging
+import vim
+import json
+
+_logger = logging.getLogger( __name__ )
+
+
+class Channel( object ):
+  def __init__( self, send_func ):
+    self._Write = send_func
+    self._SetState( 'AWAIT_HEADER' )
+    self._buffer = ''
+
+  def _SetState( self, state ):
+    self._state = state
+    if state == 'AWAIT_HEADER':
+      self._headers = {}
+
+  def Write( self, data ):
+    self._Write( data )
+
+  def OnData( self, data ):
+    self._buffer = self._buffer + data
+
+    while True:
+      if self._state == 'AWAIT_HEADER':
+        vim.command( 'echom "reading headers"' )
+        data = self._ReadHeaders()
+
+      if self._state == 'READ_BODY':
+        vim.command( 'echom "got headers"' )
+        self._ReadBody()
+      else:
+        break
+
+      if self._state != 'AWAIT_HEADER':
+        break
+
+
+  def _ReadHeaders( self ):
+    vim.command( "echom 'Reading from: {0}'".format( json.dumps( str(
+      self._buffer ) ) ) )
+    headers = self._buffer.split( '\n\n', 1 )
+
+    vim.command( "echom 'Headers: {0}'".format( json.dumps( headers ) ) )
+
+    if len( headers ) > 1:
+      for header_line in headers[ 0 ].split( '\n' ):
+        if header_line.strip():
+          key, value = header_line.split( ':', 1 )
+          self._headers[ key ] = value
+
+      # Chomp
+      self._buffer = self._buffer[ len( headers[ 0 ] ) + 2 : ]
+      self._SetState( 'READ_BODY' )
+      return
+
+    # otherwise waiting for more data
+
+  def _ReadBody( self ):
+    content_length = int( self._headers[ 'Content-Length' ] )
+
+    vim.command( "echom 'Reading body of len {0} from: {1}'".format(
+      content_length,
+      json.dumps( str( self._buffer ) ) ) )
+
+    if len( self._buffer ) < content_length:
+      # Need more data
+      return
+
+    payload = self._buffer[ : content_length  ]
+    self._buffer = self._buffer[ content_length : ] # Off by one?
+
+    vim.command( 'echom {0}'.format( json.dumps( str( payload ) ) ) )
+
+    # TODO Handle message
+
+    self._SetState( 'AWAIT_HEADER' )