RefactoringRope/JsonClient.py

# -*- coding: utf-8 -*-

# Copyright (c) 2017 Detlev Offenbach <detlev@die-offenbachs.de>
#

"""
Module implementing the JSON based client base class.
"""

from __future__ import unicode_literals
try:
    bytes = unicode
    import StringIO as io   # __IGNORE_EXCEPTION__
except NameError:
    import io       # __IGNORE_WARNING__

import sys
import socket
import select
import traceback
import json


class JsonClient(object):
    """
    Class implementing the JSON based client base class.
    """
    def __init__(self, host, port, idString=""):
        """
        Constructor
        
        @param host ip address the background service is listening
        @type str
        @param port port of the background service
        @type int
        @param idString assigned client id to be sent back to the server in
            order to identify the connection
        @type str
        """
        self.__exitClient = False
        self.__connection = socket.create_connection((host, port))
        if idString:
            reply = idString + '\n'
            self.__connection.sendall(reply.encode('utf8', 'backslashreplace'))
    
    def sendJson(self, command, params):
        """
        Public method to send a single refactoring command to the server.
        
        @param command command name to be sent
        @type str
        @param params dictionary of named parameters for the command
        @type dict
        """
        commandDict = {
            "jsonrpc": "2.0",
            "method": command,
            "params": params,
        }
        cmd = json.dumps(commandDict) + '\n'
        self.__connection.sendall(cmd.encode('utf8', 'backslashreplace'))
    
    def __receiveJson(self):
        """
        Private method to receive a JSON encode command and data from the
        server.
        
        @return tuple containing the received command and a dictionary
            containing the associated data
        @rtype tuple of (str, dict)
        """
        # step 1: receive the data
        # The JSON RPC string is prefixed by a 9 character long length field.
        length = self.__connection.recv(9)
        length = int(length)
        data = b''
        while len(data) < length:
            newData = self.__connection.recv(length - len(data))
            if not newData:
                return None, None
            data += newData
        
        # step 2: decode and convert the data
        line = data.decode(
            'utf8', 'backslashreplace')
        try:
            commandDict = json.loads(line.strip())
        except (TypeError, ValueError) as err:
            self.sendJson("ClientException", {
                "ExceptionType": "ProtocolError",
                "ExceptionValue": str(err),
                "ProtocolData": line.strip(),
            })
            return None, None
        
        method = commandDict["method"]
        params = commandDict["params"]
        
        return method, params
    
    def handleCall(self, method, params):
        """
        Public method to handle a method call from the server.
        
        Note: This is an empty implementation that must be overridden in
        derived classes.
        
        @param method requested method name
        @type str
        @param params dictionary with method specific parameters
        @type dict
        """
        pass
    
    def run(self):
        """
        Public method implementing the main loop of the client.
        """
        try:
            while True:
                try:
                    rrdy, wrdy, xrdy = select.select(
                        [self.__connection], [], [])
                except (select.error, KeyboardInterrupt, socket.error):
                    # just carry on
                    continue
                
                if self.__connection in rrdy:
                    method, params = self.__receiveJson()
                    if method is not None:
                        if method == "Exit":
                            self.__exitClient = True
                        else:
                            self.handleCall(method, params)
                
                if self.__exitClient:
                    break
        
        except Exception:
            exctype, excval, exctb = sys.exc_info()
            tbinfofile = io.StringIO()
            traceback.print_tb(exctb, None, tbinfofile)
            tbinfofile.seek(0)
            tbinfo = tbinfofile.read()
            del exctb
            self.sendJson("ClientException", {
                "ExceptionType": str(exctype),
                "ExceptionValue": str(excval),
                "Traceback": tbinfo,
            })

        # Give time to process latest response on server side
        try:
            self.__connection.shutdown(socket.SHUT_RDWR)
            self.__connection.close()
        except (socket.error, OSError):
            # ignore these; socket might be closed already
            pass
    
    def poll(self, waitMethod=""):
        """
        Public method to check and receive one message (if available).
        
        @param waitMethod name of a method to wait for
        @type str
        @return dictionary containing the data of the waited for method
        @rtype dict
        """
        try:
            if waitMethod:
                rrdy, wrdy, xrdy = select.select(
                    [self.__connection], [], [])
            else:
                rrdy, wrdy, xrdy = select.select(
                    [self.__connection], [], [], 0)
            
            if self.__connection in rrdy:
                method, params = self.__receiveJson()
                if method is not None:
                    if method == "Exit":
                        self.__exitClient = True
                    elif method == waitMethod:
                        return params
                    else:
                        self.handleCall(method, params)
        
        except (select.error, KeyboardInterrupt, socket.error):
            # just ignore these
            pass
        
        except Exception:
            exctype, excval, exctb = sys.exc_info()
            tbinfofile = io.StringIO()
            traceback.print_tb(exctb, None, tbinfofile)
            tbinfofile.seek(0)
            tbinfo = tbinfofile.read()
            del exctb
            self.sendJson("ClientException", {
                "ExceptionType": str(exctype),
                "ExceptionValue": str(excval),
                "Traceback": tbinfo,
            })
        
        return None