""" General Server side utilities 
"""
import pythoncom
from . import policy
import winerror
from .exception import COMException

def wrap(ob, iid=None, usePolicy=None, useDispatcher=None):
  """Wraps an object in a PyGDispatch gateway.

     Returns a client side PyI{iid} interface.

     Interface and gateway support must exist for the specified IID, as
     the QueryInterface() method is used.

  """
  if usePolicy is None:
    usePolicy = policy.DefaultPolicy
  if useDispatcher == 1: # True will also work here.
    import win32com.server.dispatcher
    useDispatcher = win32com.server.dispatcher.DefaultDebugDispatcher
  if useDispatcher is None or useDispatcher==0:
    ob = usePolicy(ob)
  else:
    ob = useDispatcher(usePolicy, ob)

  # get a PyIDispatch, which interfaces to PyGDispatch
  ob = pythoncom.WrapObject(ob)
  if iid is not None:
    ob = ob.QueryInterface(iid)       # Ask the PyIDispatch if it supports it?
  return ob

def unwrap(ob):
  """Unwraps an interface.

  Given an interface which wraps up a Gateway, return the object behind
  the gateway.
  """
  ob = pythoncom.UnwrapObject(ob)
  # see if the object is a dispatcher
  if hasattr(ob, 'policy'):
    ob = ob.policy
  return ob._obj_


class ListEnumerator:
  """A class to expose a Python sequence as an EnumVARIANT.

     Create an instance of this class passing a sequence (list, tuple, or
     any sequence protocol supporting object) and it will automatically
     support the EnumVARIANT interface for the object.

     See also the @NewEnum@ function, which can be used to turn the
     instance into an actual COM server.
  """
  _public_methods_ = [ 'Next', 'Skip', 'Reset', 'Clone' ]

  def __init__(self, data, index=0, iid = pythoncom.IID_IEnumVARIANT):
    self._list_ = data
    self.index = index
    self._iid_ = iid

  def _query_interface_(self, iid):
      if iid == self._iid_:
          return 1
  def Next(self, count):
    result = self._list_[self.index:self.index+count]
    self.Skip(count)
    return result

  def Skip(self, count):
    end = self.index + count
    if end > len(self._list_):
      end = len(self._list_)
    self.index = end

  def Reset(self):
    self.index = 0

  def Clone(self):
    return self._wrap(self.__class__(self._list_, self.index))

  def _wrap(self, ob):
    return wrap(ob)


class ListEnumeratorGateway(ListEnumerator):
  """A List Enumerator which wraps a sequence's items in gateways.

  If a sequence contains items (objects) that have not been wrapped for
  return through the COM layers, then a ListEnumeratorGateway can be
  used to wrap those items before returning them (from the Next() method).

  See also the @ListEnumerator@ class and the @NewEnum@ function.
  """

  def Next(self, count):
    result = self._list_[self.index:self.index+count]
    self.Skip(count)
    return map(self._wrap, result) 


def NewEnum(seq,
            cls=ListEnumerator,
            iid=pythoncom.IID_IEnumVARIANT,
            usePolicy=None,
            useDispatcher=None):
  """Creates a new enumerator COM server.

  This function creates a new COM Server that implements the 
  IID_IEnumVARIANT interface.

  A COM server that can enumerate the passed in sequence will be
  created, then wrapped up for return through the COM framework.
  Optionally, a custom COM server for enumeration can be passed
  (the default is @ListEnumerator@), and the specific IEnum
  interface can be specified.
  """
  ob = cls(seq, iid=iid)
  return wrap(ob, iid, usePolicy=usePolicy, useDispatcher=useDispatcher)


class Collection:
  "A collection of VARIANT values."

  _public_methods_ = [ 'Item', 'Count', 'Add', 'Remove', 'Insert' ]

  def __init__(self, data=None, readOnly=0):
    if data is None:
      data = [ ]
    self.data = data

    # disable Add/Remove if read-only. note that we adjust _public_methods_
    # on this instance only.
    if readOnly:
      self._public_methods_ = [ 'Item', 'Count' ]

  # This method is also used as the "default" method.
  # Thus "print ob" will cause this to be called with zero
  # params.  Handle this slightly more elegantly here.
  # Ideally the  policy should handle this.
  def Item(self, *args):
    if len(args) != 1:
      raise COMException(scode=winerror.DISP_E_BADPARAMCOUNT)

    try:
      return self.data[args[0]]
    except IndexError as desc:
      raise COMException(scode=winerror.DISP_E_BADINDEX, desc=str(desc))

    
  _value_ = Item
  
  def Count(self):
    return len(self.data)

  def Add(self, value):
    self.data.append(value)

  def Remove(self, index):
    try:
      del self.data[index]
    except IndexError as desc:
      raise COMException(scode=winerror.DISP_E_BADINDEX, desc=str(desc))

  def Insert(self, index, value):
    try:
      index = int(index)
    except (ValueError, TypeError):
      raise COMException(scode=winerror.DISP_E_TYPEMISMATCH)
    self.data.insert(index, value)

  def _NewEnum(self):
    return NewEnum(self.data)

def NewCollection(seq, cls=Collection):
  """Creates a new COM collection object

  This function creates a new COM Server that implements the 
  common collection protocols, including enumeration. (_NewEnum)

  A COM server that can enumerate the passed in sequence will be
  created, then wrapped up for return through the COM framework.
  Optionally, a custom COM server for enumeration can be passed
  (the default is @Collection@).
  """
  return pythoncom.WrapObject(policy.DefaultPolicy(cls(seq)),
                              pythoncom.IID_IDispatch,
                              pythoncom.IID_IDispatch)

class FileStream:
  _public_methods_ = [ 'Read', 'Write', 'Clone', 'CopyTo', 'Seek' ]
  _com_interfaces_ = [ pythoncom.IID_IStream ]

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

  def Read(self, amount):
    return self.file.read(amount)

  def Write(self, data):
    self.file.write(data)
    return len(data)

  def Clone(self):
    return self._wrap(self.__class__(self.file))

  def CopyTo(self, dest, cb):
    data=self.file.read(cb)
    cbread=len(data)
    dest.Write(data)    ## ??? Write does not currently return the length ???
    return cbread, cbread

  def Seek(self, offset, origin):
    # how convient that the 'origin' values are the same as the CRT :)
    self.file.seek(offset, origin)
    return self.file.tell()

  def _wrap(self, ob):
    return wrap(ob)