#!/usr/bin/env python

import os
import unittest
import inspect
from multiprocessing import Process, Pipe
from pickle import dumps, PicklingError
from framework import VppTestCase


class SerializableClassCopy(object):
    """
    Empty class used as a basis for a serializable copy of another class.
    """
    pass


class RemoteClassAttr(object):
    """
    Wrapper around attribute of a remotely executed class.
    """

    def __init__(self, remote, attr):
        self._path = [attr] if attr else []
        self._remote = remote

    def path_to_str(self):
        return '.'.join(self._path)

    def get_remote_value(self):
        return self._remote._remote_exec(RemoteClass.GET, self.path_to_str())

    def __repr__(self):
        return self._remote._remote_exec(RemoteClass.REPR, self.path_to_str())

    def __str__(self):
        return self._remote._remote_exec(RemoteClass.STR, self.path_to_str())

    def __getattr__(self, attr):
        if attr[0] == '_':
            raise AttributeError
        self._path.append(attr)
        return self

    def __setattr__(self, attr, val):
        if attr[0] == '_':
            super(RemoteClassAttr, self).__setattr__(attr, val)
            return
        self._path.append(attr)
        self._remote._remote_exec(RemoteClass.SETATTR, self.path_to_str(),
                                  True, value=val)

    def __call__(self, *args, **kwargs):
        return self._remote._remote_exec(RemoteClass.CALL, self.path_to_str(),
                                         True, *args, **kwargs)


class RemoteClass(Process):
    """
    This class can wrap around and adapt the interface of another class,
    and then delegate its execution to a newly forked child process.
    Usage:
        # Create a remotely executed instance of MyClass
        object = RemoteClass(MyClass, arg1='foo', arg2='bar')
        object.start_remote()
        # Access the object normally as if it was an instance of your class.
        object.my_attribute = 20
        print object.my_attribute
        print object.my_method(object.my_attribute)
        object.my_attribute.nested_attribute = 'test'
        # If you need the value of a remote attribute, use .get_remote_value
        method. This method is automatically called when needed in the context
        of a remotely executed class. E.g.:
        if (object.my_attribute.get_remote_value() > 20):
            object.my_attribute2 = object.my_attribute
        # Destroy the instance
        object.quit_remote()
        object.terminate()
    """

    GET = 0       # Get attribute remotely
    CALL = 1      # Call method remotely
    SETATTR = 2   # Set attribute remotely
    REPR = 3      # Get representation of a remote object
    STR = 4       # Get string representation of a remote object
    QUIT = 5      # Quit remote execution

    PIPE_PARENT = 0  # Parent end of the pipe
    PIPE_CHILD = 1  # Child end of the pipe

    DEFAULT_TIMEOUT = 2  # default timeout for an operation to execute

    def __init__(self, cls, *args, **kwargs):
        super(RemoteClass, self).__init__()
        self._cls = cls
        self._args = args
        self._kwargs = kwargs
        self._timeout = RemoteClass.DEFAULT_TIMEOUT
        self._pipe = Pipe()  # pipe for input/output arguments

    def __repr__(self):
        return repr(RemoteClassAttr(self, None))

    def __str__(self):
        return str(RemoteClassAttr(self, None))

    def __call__(self, *args, **kwargs):
        return self.RemoteClassAttr(self, None)()

    def __getattr__(self, attr):
        if attr[0] == '_' or not self.is_alive():
            if hasattr(super(RemoteClass, self), '__getattr__'):
                return super(RemoteClass, self).__getattr__(attr)
            raise AttributeError
        return RemoteClassAttr(self, attr)

    def __setattr__(self, attr, val):
        if attr[0] == '_' or not self.is_alive():
            super(RemoteClass, self).__setattr__(attr, val)
            return
        setattr(RemoteClassAttr(self, None), attr, val)

    def _remote_exec(self, op, path=None, ret=True, *args, **kwargs):
        """
        Execute given operation on a given, possibly nested, member remotely.
        """
        # automatically resolve remote objects in the arguments
        mutable_args = list(args)
        for i, val in enumerate(mutable_args):
            if isinstance(val, RemoteClass) or \
               isinstance(val, RemoteClassAttr):
                mutable_args[i] = val.get_remote_value()
        args = tuple(mutable_args)
        for key, val in kwargs.iteritems():
            if isinstance(val, RemoteClass) or \
               isinstance(val, RemoteClassAttr):
                kwargs[key] = val.get_remote_value()
        # send request
        args = self._make_serializable(args)
        kwargs = self._make_serializable(kwargs)
        self._pipe[RemoteClass.PIPE_PARENT].send((op, path, args, kwargs))
        if not ret:
            # no return value expected
            return None
        timeout = self._timeout
        # adjust timeout specifically for the .sleep method
        if path.split('.')[-1] == 'sleep':
            if args and isinstance(args[0], (long, int)):
                timeout += args[0]
            elif 'timeout' in kwargs:
                timeout += kwargs['timeout']
        if not self._pipe[RemoteClass.PIPE_PARENT].poll(timeout):
            return None
        try:
            rv = self._pipe[RemoteClass.PIPE_PARENT].recv()
            rv = self._deserialize(rv)
            return rv
        except EOFError:
            return None

    def _get_local_object(self, path):
        """
        Follow the path to obtain a reference on the addressed nested attribute
        """
        obj = self._instance
        for attr in path:
            obj = getattr(obj, attr)
        return obj

    def _get_local_value(self, path):
        try:
            return self._get_local_object(path)
        except AttributeError:
            return None

    def _call_local_method(self, path, *args, **kwargs):
        try:
            method = self._get_local_object(path)
            return method(*args, **kwargs)
        except AttributeError:
            return None

    def _set_local_attr(self, path, value):
        try:
            obj = self._get_local_object(path[:-1])
            setattr(obj, path[-1], value)
        except AttributeError:
            pass
        return None

    def _get_local_repr(self, path):
        try:
            obj = self._get_local_object(path)
            return repr(obj)
        except AttributeError:
            return None

    def _get_local_str(self, path):
        try:
            obj = self._get_local_object(path)
            return str(obj)
        except AttributeError:
            return None

    def _serializable(self, obj):
        """ Test if the given object is serializable """
        try:
            dumps(obj)
            return True
        except:
            return False

    def _make_obj_serializable(self, obj):
        """
        Make a serializable copy of an object.
        Members which are difficult/impossible to serialize are stripped.
        """
        if self._serializable(obj):
            return obj  # already serializable
        copy = SerializableClassCopy()
        # copy at least serializable attributes and properties
        for name, member in inspect.getmembers(obj):
            if name[0] == '_':  # skip private members
                continue
            if callable(member) and not isinstance(member, property):
                continue
            if not self._serializable(member):
                continue
            setattr(copy, name, member)
        return copy

    def _make_serializable(self, obj):
        """
        Make a serializable copy of an object or a list/tuple of objects.
        Members which are difficult/impossible to serialize are stripped.
        """
        if (type(obj) is list) or (type(obj) is tuple):
            rv = []
            for item in obj:
                rv.append(self._make_serializable(item))
            if type(obj) is tuple:
                rv = tuple(rv)
            return rv
        else:
            return self._make_obj_serializable(obj)

    def _deserialize_obj(self, obj):
        return obj

    def _deserialize(self, obj):
        if (type(obj) is list) or (type(obj) is tuple):
            rv = []
            for item in obj:
                rv.append(self._deserialize(item))
            if type(obj) is tuple:
                rv = tuple(rv)
            return rv
        else:
            return self._deserialize_obj(obj)

    def start_remote(self):
        """ Start remote execution """
        self.start()

    def quit_remote(self):
        """ Quit remote execution """
        self._remote_exec(RemoteClass.QUIT, None, False)

    def get_remote_value(self):
        """ Get value of a remotely held object """
        return RemoteClassAttr(self, None).get_remote_value()

    def set_request_timeout(self, timeout):
        """ Change request timeout """
        self._timeout = timeout

    def run(self):
        """
        Create instance of the wrapped class and execute operations
        on it as requested by the parent process.
        """
        self._instance = self._cls(*self._args, **self._kwargs)
        while True:
            try:
                rv = None
                # get request from the parent process
                (op, path, args,
                 kwargs) = self._pipe[RemoteClass.PIPE_CHILD].recv()
                args = self._deserialize(args)
                kwargs = self._deserialize(kwargs)
                path = path.split('.') if path else []
                if op == RemoteClass.GET:
                    rv = self._get_local_value(path)
                elif op == RemoteClass.CALL:
                    rv = self._call_local_method(path, *args, **kwargs)
                elif op == RemoteClass.SETATTR and 'value' in kwargs:
                    self._set_local_attr(path, kwargs['value'])
                elif op == RemoteClass.REPR:
                    rv = self._get_local_repr(path)
                elif op == RemoteClass.STR:
                    rv = self._get_local_str(path)
                elif op == RemoteClass.QUIT:
                    break
                else:
                    continue
                # send return value
                if not self._serializable(rv):
                    rv = self._make_serializable(rv)
                self._pipe[RemoteClass.PIPE_CHILD].send(rv)
            except EOFError:
                break
        self._instance = None  # destroy the instance


@unittest.skip("Remote Vpp Test Case Class")
class RemoteVppTestCase(VppTestCase):
    """ Re-use VppTestCase to create remote VPP segment

        In your test case:

        @classmethod
        def setUpClass(cls):
            # fork new process before clinet connects to VPP
            cls.remote_test = RemoteClass(RemoteVppTestCase)

            # start remote process
            cls.remote_test.start_remote()

            # set up your test case
            super(MyTestCase, cls).setUpClass()

            # set up remote test
            cls.remote_test.setUpClass(cls.tempdir)

        @classmethod
        def tearDownClass(cls):
            # tear down remote test
            cls.remote_test.tearDownClass()

            # stop remote process
            cls.remote_test.quit_remote()

            # tear down your test case
            super(MyTestCase, cls).tearDownClass()
    """

    def __init__(self):
        super(RemoteVppTestCase, self).__init__("emptyTest")

    def __del__(self):
        if hasattr(self, "vpp"):
            cls.vpp.poll()
            if cls.vpp.returncode is None:
                cls.vpp.terminate()
                cls.vpp.communicate()

    @classmethod
    def setUpClass(cls, tempdir):
        # disable features unsupported in remote VPP
        orig_env = dict(os.environ)
        if 'STEP' in os.environ:
            del os.environ['STEP']
        if 'DEBUG' in os.environ:
            del os.environ['DEBUG']
        cls.tempdir_prefix = os.path.basename(tempdir) + "/"
        super(RemoteVppTestCase, cls).setUpClass()
        os.environ = orig_env

    @unittest.skip("Empty test")
    def emptyTest(self):
        """ Do nothing """
        pass

    def setTestFunctionInfo(self, name, doc):
        """
        Store the name and documentation string of currently executed test
        in the main VPP for logging purposes.
        """
        self._testMethodName = name
        self._testMethodDoc = doc