import os
from collections import namedtuple
import FreeCAD, FreeCADGui, Part
from PySide import QtCore, QtGui
from . import utils, gui
from .utils import logger, objName
from .constraint import Constraint, cstrName
from .system import System

def isTypeOf(obj,tp,resolve=False):
    if not obj:
        return False
    if not tp:
        return True
    if resolve:
        obj = obj.getLinkedObject(True)
    return isinstance(getattr(obj,'Proxy',None),tp)

def checkType(obj,tp,resolve=False):
    if not isTypeOf(obj,tp,resolve):
        raise TypeError('Expect object {} to be of type "{}"'.format(
                objName(obj),tp.__name__))

def getProxy(obj,tp):
    checkType(obj,tp)
    return obj.Proxy

def resolveAssembly(obj):
    '''Try various ways to obtain an assembly from the input object

    obj can be a link, a proxy, a child group of an assembly, or simply an
    assembly
    '''
    func = getattr(obj,'getLinkedObject',None)
    if func:
        obj = func(True)
    proxy = getattr(obj,'Proxy',None)
    if proxy:
        obj = proxy
    if isinstance(obj,Assembly):
        return obj
    func = getattr(obj,'getAssembly',None)
    if func:
        return func()
    raise TypeError('cannot resolve assembly from {}'.format(obj))


# For faking selection obtained from Gui.getSelectionEx()
Selection = namedtuple('AsmSelection',('Object','SubElementNames'))

_IgnoredProperties = set(['VisibilityList','Visibility',
    'Label','_LinkRecomputed'])

class AsmBase(object):
    def __init__(self):
        self.Object = None

    def __getstate__(self):
        return

    def __setstate__(self,_state):
        return

    def attach(self,obj):
        obj.addExtension('App::LinkBaseExtensionPython', None)
        self.linkSetup(obj)

    def linkSetup(self,obj):
        assert getattr(obj,'Proxy',None)==self
        self.Object = obj
        return

    def getViewProviderName(self,_obj):
        return 'Gui::ViewProviderLinkPython'

    def onDocumentRestored(self, obj):
        self.linkSetup(obj)


class ViewProviderAsmBase(object):
    def __init__(self,vobj):
        vobj.Visibility = False
        vobj.Proxy = self
        self.attach(vobj)

    def attach(self,vobj):
        self.ViewObject = vobj
        vobj.signalChangeIcon()
        vobj.setPropertyStatus('Visibility','Hidden')

    def __getstate__(self):
        return None

    def __setstate__(self, _state):
        return None

    _iconName = None

    @classmethod
    def getIcon(cls):
        if cls._iconName:
            return utils.getIcon(cls)

    def canDropObjects(self):
        return True

    def canDragObjects(self):
        return False

    def canDragAndDropObject(self,_obj):
        return False


class ViewProviderAsmOnTop(ViewProviderAsmBase):
    def __init__(self,vobj):
        vobj.OnTopWhenSelected = 2
        super(ViewProviderAsmOnTop,self).__init__(vobj)


class AsmGroup(AsmBase):
    def linkSetup(self,obj):
        super(AsmGroup,self).linkSetup(obj)
        obj.configLinkProperty(
                'VisibilityList',LinkMode='GroupMode',ElementList='Group')
        self.groupSetup()

    def groupSetup(self):
        self.Object.GroupMode = 1 # auto delete children
        self.Object.setPropertyStatus('GroupMode','Hidden')
        self.Object.setPropertyStatus('GroupMode','Immutable')
        self.Object.setPropertyStatus('GroupMode','Transient')
        self.Object.setPropertyStatus('Group','Hidden')
        self.Object.setPropertyStatus('Group','Immutable')
        self.Object.setPropertyStatus('VisibilityList','Output')

    def attach(self,obj):
        obj.addProperty("App::PropertyLinkList","Group","Base",'')
        obj.addProperty("App::PropertyBoolList","VisibilityList","Base",'')
        obj.addProperty("App::PropertyEnumeration","GroupMode","Base",'')
        super(AsmGroup,self).attach(obj)


class ViewProviderAsmGroup(ViewProviderAsmBase):
    def claimChildren(self):
        return self.ViewObject.Object.Group

    def doubleClicked(self, _vobj):
        return False

    def canDropObject(self,_child):
        return False


class ViewProviderAsmGroupOnTop(ViewProviderAsmGroup):
    def __init__(self,vobj):
        vobj.OnTopWhenSelected = 2
        super(ViewProviderAsmGroupOnTop,self).__init__(vobj)

class AsmPartGroup(AsmGroup):
    def __init__(self,parent):
        self.parent = getProxy(parent,Assembly)
        super(AsmPartGroup,self).__init__()

    def getAssembly(self):
        return self.parent

    def groupSetup(self):
        pass

    @staticmethod
    def make(parent,name='Parts'):
        obj = parent.Document.addObject("App::FeaturePython",name,
                    AsmPartGroup(parent),None,True)
        ViewProviderAsmPartGroup(obj.ViewObject)
        obj.purgeTouched()
        return obj


class ViewProviderAsmPartGroup(ViewProviderAsmGroup):
    _iconName = 'Assembly_Assembly_Part_Tree.svg'

    def onDelete(self,_obj,_subs):
        return False

    def canDropObjectEx(self,obj,_owner,_subname):
        return isTypeOf(obj,Assembly, True) or not isTypeOf(obj,AsmBase)

    def canDragObject(self,_obj):
        return True

    def canDragObjects(self):
        return True

    def canDragAndDropObject(self,_obj):
        return True


class AsmElement(AsmBase):
    def __init__(self,parent):
        self._initializing = True
        self.shape = None
        self.parent = getProxy(parent,AsmElementGroup)
        super(AsmElement,self).__init__()

    def linkSetup(self,obj):
        super(AsmElement,self).linkSetup(obj)
        obj.configLinkProperty('LinkedObject')
        #  obj.setPropertyStatus('LinkedObject','Immutable')
        obj.setPropertyStatus('LinkedObject','ReadOnly')

    def attach(self,obj):
        obj.addProperty("App::PropertyXLink","LinkedObject"," Link",'')
        super(AsmElement,self).attach(obj)

    def canLinkProperties(self,_obj):
        return False

    def allowDuplicateLabel(self,_obj):
        return True

    def onBeforeChangeLabel(self,obj,label):
        parent = getattr(self,'parent',None)
        if parent and not getattr(self,'_initializing',False):
            return parent.onChildLabelChange(obj,label)

    def onChanged(self,_obj,prop):
        parent = getattr(self,'parent',None)
        if parent and \
           not getattr(self,'_initializing',False) and \
           prop=='Label':
            parent.Object.cacheChildLabel()

    def execute(self,_obj):
        #  self.getShape(True)
        return False

    def getShape(self,refresh=False):
        if not refresh:
            ret = getattr(self,'shape',None)
            if ret:
                return ret
        self.shape = None
        self.shape = self.Object.getSubObject('')
        return self.shape

    def getAssembly(self):
        return self.parent.parent

    def getSubElement(self):
        link = self.Object.LinkedObject
        if isinstance(link,tuple):
            return link[1].split('.')[-1]
        return ''

    def getSubName(self):
        link = self.Object.LinkedObject
        if not isinstance(link,tuple):
            raise RuntimeError('Invalid element link "{}"'.format(
                objName(self.Object)))
        return link[1]

    def getElementSubname(self):
        '''
        Resolve the geometry element link relative to the parent assembly's part
        group
        '''

        subname = self.getSubName()
        obj = self.Object.getLinkedObject(False)
        if not obj or obj == self.Object:
            raise RuntimeError('Borken element link')
        if not isTypeOf(obj,AsmElement):
            # If not pointing to another element, then assume we are directly
            # pointing to the geometry element, just return as it is, which is a
            # subname relative to the parent assembly part group
            return subname

        childElement = obj.Proxy

        # If pointing to another element in the child assembly, first pop two
        # names in the subname reference, i.e. element label and element group
        # name
        idx = subname.rfind('.',0,subname.rfind('.',0,-1))
        subname = subname[:idx+1]

        # append the child assembly part group name, and recursively call into
        # child element
        return subname+childElement.getAssembly().getPartGroup().Name+'.'+\
                childElement.getElementSubname()

    # Element: optional, if none, then a new element will be created if no
    #          pre-existing. Or else, it shall be the element to be amended
    # Group: the immediate child object of an assembly (i.e. ConstraintGroup,
    #        ElementGroup, or PartGroup)
    # Subname: the subname reference realtive to 'Group'
    Selection = namedtuple('AsmElementSelection',('Element','Group','Subname'))

    @staticmethod
    def getSelection():
        '''
        Parse Gui.Selection for making an element

        If there is only one selection, then the selection must refer to a sub
        element of some part object of an assembly. We shall create a new
        element beloning to the top-level assembly

        If there are two selections, then first one shall be either the
        element group or an individual element. The second selection shall
        be a sub element belong to a child assembly of the parent assembly of
        the first selected element/element group
        '''
        sels = FreeCADGui.Selection.getSelectionEx('',False)
        if not sels:
            return
        if len(sels)>1:
            raise RuntimeError(
                    'The selections must have a common (grand)parent assembly')

        sel = sels[0]
        subs = list(sel.SubElementNames)
        if not subs:
            raise RuntimeError('no sub object in selection')
        if len(subs)>2:
            raise RuntimeError('At most two selection is allowed.\n'
                'The first selection must be a sub element belonging to some '
                'assembly. The optional second selection must be an element '
                'belonging to the same assembly of the first selection')
        if len(subs)==2:
            if len(subs[0])<len(subs[1]):
                subs = [subs[1],subs[2]]

        if subs[0][-1] == '.':
            if not utils.isElement((sel.Object,subs[0])):
                raise RuntimeError('no sub element (face, edge, vertex) in '
                        '{}.{}'.format(sel.Object.Name,subs[0]))
            subElement = utils.deduceSelectedElement(sel.Object,subs[0])
            if subElement:
                subs[0] += subElement

        link = Assembly.findPartGroup(sel.Object,subs[0])
        if not link:
            raise RuntimeError(
                    'Selected sub element does not belong to an assembly')

        element = None
        if len(subs)>1:
            ret = Assembly.findElementGroup(sel.Object,subs[1])
            if not ret:
                raise RuntimeError('The second selection must be an element')

            if ret.Assembly != link.Assembly:
                raise RuntimeError(
                        'The two selections must belong to the same assembly')

            element = ret.Object.getSubObject(ret.Subname,1)
            if not isTypeOf(element,AsmElement):
                raise RuntimeError('The second selection must be an element')

        return AsmElement.Selection(Element=element, Group=link.Object,
                                    Subname=link.Subname+subElement)

    @staticmethod
    def make(selection=None,name='Element',undo=False):
        '''Add/get/modify an element with the given selected object'''
        if not selection:
            selection = AsmElement.getSelection()

        group = selection.Group
        subname = selection.Subname

        if isTypeOf(group,AsmElementGroup):
            # if the selected object is an element of the owner assembly, simply
            # return that element
            element = group.getSubObject(subname,1)
            if not isTypeOf(element,AsmElement):
                raise RuntimeError('Invalid element reference {}.{}'.format(
                    group.Name,subname))
            return element

        if isTypeOf(group,AsmConstraintGroup):
            # if the selected object is an element link of a constraint of the
            # current assembly, then try to import its linked element if it is
            # not already imported
            link = group.getSubObject(subname,1)
            if not isTypeOf(link,AsmElementLink):
                raise RuntimeError('Invalid element link {}.{}'.format(
                    group.Name,subname))
            ref = link.LinkedObject
            if not isinstance(ref,tuple):
                raise RuntimeError('Invalid link reference {}.{}'.format(
                    group.Name,subname))
            if ref[1][0]=='$':
                # this means the element is in the current assembly already
                element = link.getLinkedObject(False)
                if not isTypeOf(element,AsmElement):
                    raise RuntimeError('broken element link {}.{}'.format(
                        group.Name,subname))
                return element

            subname = ref[1]
            group = group.getAssembly().getPartGroup()

        elif isTypeOf(group,AsmPartGroup):
            # If the selection come from the part group, first check for any
            # intermediate child assembly
            ret = Assembly.find(group,subname)
            if not ret:
                # If no child assembly in 'subname', simply assign the link as
                # it is, after making sure it is referencing an sub-element
                if not utils.isElement((group,subname)):
                    raise RuntimeError(
                            'Element must reference a geometry element')
            else:
                # In case there are intermediate assembly inside subname, we'll
                # recursively export the element in child assemblies first, and
                # then import that element to the current assembly.
                sel = AsmElement.Selection(
                        Element=None, Group=ret.Object, Subname=ret.Subname)
                element = AsmElement.make(sel)

                # now generate the subname reference

                # This give us reference to child assembly's immediate child
                # without trailing dot.
                prefix = subname[:len(subname)-len(ret.Subname)-1]

                # Pop the immediate child name, and replace it with child
                # assembly's element group name
                prefix = prefix[:prefix.rfind('.')+1] + \
                    resolveAssembly(ret.Assembly).getElementGroup().Name

                subname = '{}.${}.'.format(prefix,element.Label)

        else:
            raise RuntimeError('Invalid selection {}.{}'.format(
                group.Name,subname))

        element = selection.Element

        try:
            if undo:
                FreeCAD.setActiveTransaction('Assembly change element' \
                        if element else 'Assembly create element')
            if not element:
                elements = group.Proxy.getAssembly().getElementGroup()
                # try to search the element group for an existing element
                for e in elements.Group:
                    sub = logger.catch('',e.Proxy.getSubName)
                    if sub == subname:
                        return e
                element = elements.Document.addObject("App::FeaturePython",
                        name,AsmElement(elements),None,True)
                ViewProviderAsmElement(element.ViewObject)
                elements.setLink({-1:element})
                elements.setElementVisible(element.Name,False)
                element.Proxy._initializing = False
                elements.cacheChildLabel()
            element.setLink(group,subname)
            if undo:
                FreeCAD.closeActiveTransaction()
        except Exception:
            if undo:
                FreeCAD.closeActiveTransaction(True)
            raise
        return element


class ViewProviderAsmElement(ViewProviderAsmOnTop):
    def __init__(self,vobj):
        vobj.OverrideMaterial = True
        vobj.ShapeMaterial.DiffuseColor = self.getDefaultColor()
        vobj.ShapeMaterial.EmissiveColor = self.getDefaultColor()
        vobj.DrawStyle = 1
        vobj.LineWidth = 4
        vobj.PointSize = 8
        super(ViewProviderAsmElement,self).__init__(vobj)

    def attach(self,vobj):
        super(ViewProviderAsmElement,self).attach(vobj)
        if gui.AsmCmdManager.AutoElementVis:
            vobj.OnTopWhenSelected = 2

    def getDefaultColor(self):
        return (60.0/255.0,1.0,1.0)

    def canDropObjectEx(self,_obj,owner,subname):
        if not subname:
            return False
        proxy = self.ViewObject.Object.Proxy
        return proxy.getAssembly().getPartGroup()==owner

    def dropObjectEx(self,vobj,_obj,owner,subname):
        AsmElement.make(AsmElement.Selection(Element=vobj.Object,
            Group=owner, Subname=subname),undo=True)

ElementInfo = namedtuple('AsmElementInfo', ('Parent','SubnameRef','Part',
    'PartName','Placement','Object','Subname','Shape'))

def getElementInfo(parent, subname):
    '''Return a named tuple containing the part object element information

    Parameters:

        parent: the parent document object, either an assembly, or a part group

        subname: subname reference to the part element (i.e. edge, face, vertex)

    Return a named tuple with the following fields:

    Parent: set to the input parent object

    SubnameRef: set to the input subname reference

    Part: either the part object, or a tuple(obj, idx) to refer to an element in
    an link array,

    PartName: a string name for the part

    Placement: the placement of the part

    Object: the object that owns the element. In case 'Part' is an assembly, the
    element owner will always be some (grand)child of the 'Part'

    Subname: the subname reference to the element owner object. The reference is
    realtive to the 'Part', i.e. Object = Part.getSubObject(subname), or if
    'Part' is a tuple, Object = Part[0].getSubObject(str(Part[1]) + '.' +
    subname)

    Shape: Part.Shape of the linked element. The shape's placement is relative
    to the owner Part.
    '''

    subnameRef = subname

    names = subname.split('.')
    if isTypeOf(parent,Assembly,True):
        partGroup = None
        child = parent.getSubObject(names[0]+'.',1)
        if isTypeOf(child,(AsmElementGroup,AsmConstraintGroup)):
            child = parent.getSubObject(subname,1)
            if not child:
                raise RuntimeError('Invalid sub object {}, {}'.format(
                    objName(parent), subname))
            if not isTypeOf(child,(AsmElement,AsmElementLink)):
                raise RuntimeError('{} cannot be moved'.format(objName(child)))
            subname = child.Proxy.getElementSubname()
            names = subname.split('.')
            partGroup = parent.Proxy.getPartGroup()

        elif isTypeOf(child,AsmPartGroup):
            partGroup = child
            names = names[1:]
            subname = '.'.join(names)

        if not partGroup:
            raise RuntimeError('Invalid sub object {}, {}'.format(
                objName(parent), subname))

    elif isTypeOf(parent,AsmPartGroup):
        partGroup = parent
    else:
        raise RuntimeError('{} is not Assembly or PartGroup'.format(
            objName(parent)))

    part = partGroup.getSubObject(names[0]+'.',1)
    if not part:
        raise RuntimeError('Invalid sub object {}, {}'.format(
            objName(parent), subnameRef))

    # For storing the shape of the element with proper transformation
    shape = None
    # For storing the placement of the movable part
    pla = None
    # For storing the actual geometry object of the part, in case 'part' is
    # a link
    obj = None

    if not isTypeOf(part,Assembly,True):
        getter = getattr(part.getLinkedObject(True),
                'getLinkExtProperty',None)

        # special treatment of link array (i.e. when ElementCount!=0), we
        # allow the array element to be moveable by the solver
        if getter and getter('ElementCount'):

            # store both the part (i.e. the link array), and the array
            # element object
            part = (part,part.getSubObject(names[1]+'.',1))

            # trim the subname to be after the array element
            sub = '.'.join(names[2:])

            # There are two states of an link array. 
            if getter('ElementList'):
                # a) The elements are expanded as individual objects, i.e
                # when ElementList has members, then the moveable Placement
                # is a property of the array element. So we obtain the shape
                # before 'Placement' by setting 'transform' set to False.
                shape=part[1].getSubObject(sub,transform=False)
                pla = part[1].Placement
                obj = part[0].getLinkedObject(False)
                partName = part[1].Name
                part = part[1]
            else:
                # b) The elements are collapsed. Then the moveable Placement
                # is stored inside link object's PlacementList property. So,
                # the shape obtained below is already before 'Placement',
                # i.e. no need to set 'transform' to False.
                shape=part[1].getSubObject(sub)
                obj = part[1]
                try:
                    idx = names[1].split('_i')[-1]
                    # we store the array index instead, in order to modified
                    # Placement later when the solver is done. Also because
                    # that when the elements are collapsed, there is really
                    # no element object here.
                    part = (part[0],int(idx),part[1])
                    pla = part[0].PlacementList[idx]
                except ValueError:
                    raise RuntimeError('invalid array subname of element {}: '
                        '{}'.format(objName(parent),subnameRef))

                partName = '{}.{}.'.format(part[0].Name,idx)

            subname = sub

    if not shape:
        # Here means, either the 'part' is an assembly or it is a non array
        # object. We trim the subname reference to be relative to the part
        # object.  And obtain the shape before part's Placement by setting
        # 'transform' to False
        subname = '.'.join(names[1:])
        shape = utils.getElementShape((part,subname),Part.Shape)
        if not shape:
            raise RuntimeError('cannot get geometry element from {}.{}'.format(
                part.Name,subname))
        pla = part.Placement
        obj = part.getLinkedObject(False)
        partName = part.Name

    return ElementInfo(Parent = parent,
                    SubnameRef = subnameRef,
                    Part = part,
                    PartName = partName,
                    Placement = pla.copy(),
                    Object = obj,
                    Subname = subname,
                    Shape = shape.copy())


class AsmElementLink(AsmBase):
    def __init__(self,parent):
        super(AsmElementLink,self).__init__()
        self.info = None
        self.parent = getProxy(parent,AsmConstraint)

    def linkSetup(self,obj):
        super(AsmElementLink,self).linkSetup(obj)
        obj.configLinkProperty('LinkedObject')
        #  obj.setPropertyStatus('LinkedObject','Immutable')
        obj.setPropertyStatus('LinkedObject','ReadOnly')

    def attach(self,obj):
        obj.addProperty("App::PropertyXLink","LinkedObject"," Link",'')
        super(AsmElementLink,self).attach(obj)

    def canLinkProperties(self,_obj):
        return False

    def execute(self,_obj):
        self.getInfo(True)
        return False

    def onChanged(self,_obj,prop):
        if prop=='LinkedObject' and \
           getattr(self,'parent',None) and \
           not Constraint.isDisabled(self.parent.Object):
           Assembly.autoSolve()

    def getAssembly(self):
        return self.parent.parent.parent

    def getElementSubname(self):
        'Resolve element link subname'

        #  AsmElementLink is used by constraint to link to a geometry link. It
        #  does so by indirectly linking to an AsmElement object belonging to
        #  the same parent assembly. AsmElement is also a link, which again
        #  links to another AsmElement of a child assembly or the actual
        #  geometry element of a child feature. This function is for resolving
        #  the AsmElementLink's subname reference to the actual part object
        #  subname reference relative to the parent assembly's part group

        linked = self.Object.getLinkedObject(False)
        if not linked or linked == self.Object:
            raise RuntimeError('Element link broken')
        element = getProxy(linked,AsmElement)
        assembly = element.getAssembly()
        if assembly == self.getAssembly():
            return element.getElementSubname()

        # The reference stored inside this ElementLink. We need the sub assembly
        # name, which is the name before the first dot. This name may be
        # different from the actual assembly object's name, in case where the
        # assembly is accessed through a link. And the sub assembly may be
        # inside a link array, which we don't know for sure. But we do know that
        # the last two names are element group and element label. So just pop
        # two names.
        ref = self.Object.LinkedObject[1]
        prefix = ref[0:ref.rfind('.',0,ref.rfind('.',0,-1))]
        return '{}.{}.{}'.format(prefix, assembly.getPartGroup().Name,
                element.getElementSubname())

    def setLink(self,owner,subname,checkOnly=False):
        # check if there is any sub assembly in the reference
        ret = Assembly.find(owner,subname)
        if not ret:
            # if not, add/get an element in our own element group
            sel = AsmElement.Selection(Element=None, Group=owner,
                                       Subname=subname)
            element = AsmElement.make(sel)
            owner = element.Proxy.parent.Object
            subname = '${}.'.format(element.Label)
        else:
            # if so, add/get an element from the sub assembly
            sel = AsmElement.Selection(Element=None, Group=ret.Object,
                                       Subname=ret.Subname)
            element = AsmElement.make(sel)
            owner = owner.Proxy.getAssembly().getPartGroup()

            # This give us reference to child assembly's immediate child
            # without trailing dot.
            prefix = subname[:len(subname)-len(ret.Subname)-1]

            # Pop the immediate child name, and replace it with child
            # assembly's element group name
            prefix = prefix[:prefix.rfind('.')+1] + \
                resolveAssembly(ret.Assembly).getElementGroup().Name

            subname = '{}.${}.'.format(prefix, element.Label)

        for sibling in self.parent.Object.Group:
            if sibling == self.Object:
                continue
            linked = sibling.LinkedObject
            if isinstance(linked,tuple) and \
               linked[0]==owner and linked[1]==subname:
                raise RuntimeError('duplicate element link {} in constraint '
                    '{}'.format(objName(sibling),objName(self.parent.Object)))
        if not checkOnly:
            self.Object.setLink(owner,subname)

    def getInfo(self,refresh=False):
        if not refresh:
            ret = getattr(self,'info',None)
            if ret:
                return ret
        self.info = None
        if not getattr(self,'Object',None):
            return
        self.info = getElementInfo(self.getAssembly().getPartGroup(),
                self.getElementSubname())
        return self.info

    @staticmethod
    def setPlacement(part,pla):
        '''
        called by solver after solving to adjust the placement.
        
        part: obtained by AsmConstraint.getInfo().Part
        pla: the new placement
        '''
        if isinstance(part,tuple):
            if isinstance(part[1],int):
                part[0].PlacementList = {part[1]:pla}
            else:
                part[1].Placement = pla
        else:
            part.Placement = pla

    MakeInfo = namedtuple('AsmElementLinkMakeInfo',
            ('Constraint','Owner','Subname'))

    @staticmethod
    def make(info,name='ElementLink'):
        link = info.Constraint.Document.addObject("App::FeaturePython",
                    name,AsmElementLink(info.Constraint),None,True)
        ViewProviderAsmElementLink(link.ViewObject)
        info.Constraint.setLink({-1:link})
        link.Proxy.setLink(info.Owner,info.Subname)
        if not gui.AsmCmdManager.AutoElementVis:
            info.Constraint.setElementVisible(link.Name,False)
        return link


def setPlacement(part,pla):
    AsmElementLink.setPlacement(part,pla)


class ViewProviderAsmElementLink(ViewProviderAsmOnTop):
    def __init__(self,vobj):
        vobj.OverrideMaterial = True
        vobj.ShapeMaterial.DiffuseColor = self.getDefaultColor()
        vobj.ShapeMaterial.EmissiveColor = self.getDefaultColor()
        super(ViewProviderAsmElementLink,self).__init__(vobj)

    def attach(self,vobj):
        super(ViewProviderAsmElementLink,self).attach(vobj)
        if gui.AsmCmdManager.AutoElementVis:
            vobj.OnTopWhenSelected = 2

    def getDefaultColor(self):
        return (1.0,60.0/255.0,60.0/255.0)

    def doubleClicked(self,_vobj):
        from . import mover
        return mover.movePart()

    def canDropObjectEx(self,_obj,owner,subname):
        if logger.catchTrace('Cannot drop to AsmLink {}'.format(
            objName(self.ViewObject.Object)),
            self.ViewObject.Object.Proxy.setLink,
            owner, subname, True):
            return True
        return False

    def dropObjectEx(self,vobj,_obj,owner,subname):
        vobj.Object.Proxy.setLink(owner,subname)


class AsmConstraint(AsmGroup):

    def __init__(self,parent):
        self._initializing = True
        self.elements = None
        self.parent = getProxy(parent,AsmConstraintGroup)
        super(AsmConstraint,self).__init__()

    def getAssembly(self):
        return self.parent.parent

    def checkSupport(self):
        # this function maybe called during document restore, hence the
        # extensive check below
        obj = getattr(self,'Object',None)
        if not obj:
            return
        if Constraint.isDisabled(obj):
           return
        parent = getattr(self,'parent',None)
        if not parent:
            return
        parent = getattr(parent,'parent',None)
        if not parent:
            return
        assembly = getattr(parent,'Object',None)
        if not assembly or \
           System.isConstraintSupported(assembly,Constraint.getTypeName(obj)):
            return
        raise RuntimeError('Constraint type "{}" is not supported by '
                'solver "{}"'.format(Constraint.getTypeName(obj),
                    System.getTypeName(assembly)))

    def onChanged(self,obj,prop):
        if prop not in _IgnoredProperties:
           Constraint.onChanged(obj,prop)
           Assembly.autoSolve()

    def linkSetup(self,obj):
        self.elements = None
        super(AsmConstraint,self).linkSetup(obj)
        group = obj.Group
        for o in group:
            getProxy(o,AsmElementLink).parent = self
        if gui.AsmCmdManager.AutoElementVis:
            obj.setPropertyStatus('VisibilityList','-Immutable')
            obj.VisibilityList = [False]*len(group)
            obj.setPropertyStatus('VisibilityList','Immutable')
        Constraint.attach(obj)
        obj.recompute()

    def execute(self,_obj):
        if not getattr(self,'_initializing',False) and\
           getattr(self,'parent',None):
            self.checkSupport()
            self.getElements(True)
        return False

    def getElements(self,refresh=False):
        if refresh:
            self.elements = None
        obj = getattr(self,'Object',None)
        if not obj:
            return
        ret = getattr(self,'elements',None)
        if ret or Constraint.isDisabled(obj):
            return ret
        elementInfo = []
        elements = []
        for o in obj.Group:
            checkType(o,AsmElementLink)
            info = o.Proxy.getInfo()
            if not info:
                return
            elementInfo.append(info)
            elements.append(o)
        Constraint.check(obj,elementInfo,True)
        self.elements = elements
        return self.elements

    Selection = namedtuple('AsmConstraintSelection',
                ('SelObject','SelSubname','Assembly','Constraint','Elements'))

    @staticmethod
    def getSelection(typeid=0,sels=None):
        '''
        Parse Gui.Selection for making a constraint

        The selected elements must all belong to the same immediate parent
        assembly. 
        '''
        if not sels:
            sels = FreeCADGui.Selection.getSelectionEx('',False)
        if not sels:
            raise RuntimeError('no selection')
        if len(sels)>1:
            raise RuntimeError(
                    'The selections must have a common (grand)parent assembly')
        sel = sels[0]
        subs = sel.SubElementNames
        if not subs:
            subs = ['']

        cstr = None
        elements = []
        elementInfo = []
        assembly = None
        selSubname = None
        for sub in subs:
            sobj = sel.Object.getSubObject(sub,1)
            if not sobj:
                raise RuntimeError('Cannot find sub-object {}.{}'.format(
                    sel.Object.Name,sub))
            ret = Assembly.find(sel.Object,sub,
                    recursive=True,relativeToChild=False,keepEmptyChild=True)
            if not ret:
                raise RuntimeError('Selection {}.{} is not from an '
                    'assembly'.format(sel.Object.Name,sub))

            if not assembly:
                assembly = ret[0].Assembly
                selSubname = sub[:-len(ret[0].Subname)]
                found = ret[0]
            else:
                found = None
                for r in ret:
                    if r.Assembly == assembly:
                        found = r
                        break
                if not found:
                    raise RuntimeError('Selection {}.{} is not from the target '
                        'assembly {}'.format(
                            sel.Object.Name,sub,objName(assembly)))

            if isTypeOf(sobj,Assembly,True):
                continue

            # check if the selection is a constraint group or a constraint
            if isTypeOf(sobj,Assembly,True) or \
               isTypeOf(sobj,(AsmConstraintGroup,AsmConstraint)):
                if isTypeOf(sobj,AsmConstraint):
                    if cstr:
                        raise RuntimeError('more than one constraint selected')
                    assembly = ret[-1].Assembly
                    selSubname = sub[:-len(ret[-1].Subname)]
                    cstr = sobj
                continue


            # because we call Assembly.find() above with relativeToChild=False,
            # we shall adjust the element subname by popping the first '.'
            sub = found.Subname
            sub = sub[sub.index('.')+1:]
            if sub[-1] == '.' and \
               not isTypeOf(sobj,(AsmElement,AsmElementLink)):
                # Too bad, its a full selection, let's guess the sub element
                if not utils.isElement((found.Object,sub)):
                    raise RuntimeError('no sub element (face, edge, vertex) in '
                        '{}.{}'.format(found.Object.Name,sub))
                subElement = utils.deduceSelectedElement(found.Object,sub)
                if subElement:
                    sub += subElement

            elements.append((found.Object,sub))

            elementInfo.append(getElementInfo(
                assembly,found.Object.Name+'.'+sub))

        if not Constraint.isDisabled(cstr):
            if cstr:
                typeid = Constraint.getTypeID(cstr)
                check = []
                for o in cstr.Group:
                    check.append(o.Proxy.getInfo())
                elementInfo = check + elementInfo

            Constraint.check(typeid,elementInfo)

        return AsmConstraint.Selection(SelObject=sel.Object,
                                       SelSubname=selSubname,
                                       Assembly = assembly,
                                       Constraint = cstr,
                                       Elements = elements)

    @staticmethod
    def make(typeid,sel=None,name='Constraint',undo=True):
        if not sel:
            sel = AsmConstraint.getSelection(typeid)
        if sel.Constraint:
            if undo:
                FreeCAD.setActiveTransaction('Assembly change constraint')
            cstr = sel.Constraint
        else:
            if undo:
                FreeCAD.setActiveTransaction('Assembly create constraint')
            constraints = sel.Assembly.Proxy.getConstraintGroup()
            cstr = constraints.Document.addObject("App::FeaturePython",
                    name,AsmConstraint(constraints),None,True)
            proxy = ViewProviderAsmConstraint(cstr.ViewObject)
            logger.debug('cstr viewobject {},{},{},{}'.format(
                id(proxy),id(cstr.ViewObject.Proxy),
                id(proxy.ViewObject),id(cstr.ViewObject)))
            constraints.setLink({-1:cstr})
            Constraint.setTypeID(cstr,typeid)

        try:
            for e in sel.Elements:
                AsmElementLink.make(AsmElementLink.MakeInfo(cstr,*e))
            cstr.Proxy._initializing = False
            if undo:
                FreeCAD.closeActiveTransaction()

            if sel.SelObject:
                FreeCADGui.Selection.clearSelection()
                subname = sel.SelSubname
                if subname:
                    subname += '.'
                subname += sel.Assembly.Proxy.getConstraintGroup().Name + \
                        '.' + cstr.Name + '.'
                FreeCADGui.Selection.addSelection(sel.SelObject,subname)
                FreeCADGui.runCommand('Std_TreeSelection')
            return cstr

        except Exception:
            if undo:
                FreeCAD.closeActiveTransaction(True)
            raise


class ViewProviderAsmConstraint(ViewProviderAsmGroup):
    def attach(self,vobj):
        super(ViewProviderAsmConstraint,self).attach(vobj)
        if gui.AsmCmdManager.AutoElementVis:
            vobj.OnTopWhenSelected = 2

    def getIcon(self):
        return Constraint.getIcon(self.ViewObject.Object)

    def _getSelection(self,owner,subname):
        if not owner:
            raise RuntimeError('no owner')
        parent = getattr(owner.Proxy,'parent',None)
        if isinstance(parent,AsmConstraintGroup):
            # This can happen when we are dropping another element link from the
            # same constraint group, in which case, 'owner' here will be the
            # parent constraint of the dropping element link
            subname = owner.Name + '.' + subname
            owner = parent.Object
            parent = parent.parent # ascend to the parent assembly
        if not isinstance(parent,Assembly):
            raise RuntimeError('not from the same assembly')
        subname = owner.Name + '.' + subname
        obj = self.ViewObject.Object
        mysub = parent.getConstraintGroup().Name + '.' + obj.Name + '.'
        sel = [Selection(Object=parent.Object,SubElementNames=[subname,mysub])]
        typeid = Constraint.getTypeID(obj)
        return AsmConstraint.getSelection(typeid,sel)

    def canDropObjectEx(self,_obj,owner,subname):
        cstr = self.ViewObject.Object
        if logger.catchTrace('Cannot drop to AsmConstraint {}'.format(cstr),
                self._getSelection,owner,subname):
            return True
        return False

    def dropObjectEx(self,_vobj,_obj,owner,subname):
        sel = self._getSelection(owner,subname)
        cstr = self.ViewObject.Object
        typeid = Constraint.getTypeID(cstr)
        sel = AsmConstraint.Selection(SelObject=None,
                                      SelSubname=None,
                                      Assembly=sel.Assembly,
                                      Constraint=cstr,
                                      Elements=sel.Elements)
        AsmConstraint.make(typeid,sel,undo=False)


class AsmConstraintGroup(AsmGroup):
    def __init__(self,parent):
        self.parent = getProxy(parent,Assembly)
        super(AsmConstraintGroup,self).__init__()

    def getAssembly(self):
        return self.parent

    def linkSetup(self,obj):
        super(AsmConstraintGroup,self).linkSetup(obj)
        for o in obj.Group:
            cstr = getProxy(o,AsmConstraint)
            if cstr:
                cstr.parent = self
                obj.recompute()

    @staticmethod
    def make(parent,name='Constraints'):
        obj = parent.Document.addObject("App::FeaturePython",name,
                AsmConstraintGroup(parent),None,True)
        ViewProviderAsmConstraintGroup(obj.ViewObject)
        obj.purgeTouched()
        return obj


class ViewProviderAsmConstraintGroup(ViewProviderAsmGroup):
    _iconName = 'Assembly_Assembly_Constraints_Tree.svg'

    def canDropObjects(self):
        return False


class AsmElementGroup(AsmGroup):
    def __init__(self,parent):
        self.parent = getProxy(parent,Assembly)
        super(AsmElementGroup,self).__init__()

    def linkSetup(self,obj):
        super(AsmElementGroup,self).linkSetup(obj)
        for o in obj.Group:
            getProxy(o,AsmElement).parent = self
        obj.cacheChildLabel()

    def getAssembly(self):
        return self.parent

    def onChildLabelChange(self,obj,label):
        names = set()
        for o in self.Object.Group:
            if o != obj:
                names.add(o.Name)
        if label not in names:
            return
        for i,c in enumerate(reversed(label)):
            if not c.isdigit():
                if i:
                    label = label[:-i]
                break;
        i=0
        while True:
            i=i+1;
            newLabel = '{}{03d}'.format(label,i);
            if newLabel!=obj.Label and newLabel not in names:
                return newLabel

    @staticmethod
    def make(parent,name='Elements'):
        obj = parent.Document.addObject("App::FeaturePython",name,
                        AsmElementGroup(parent),None,True)
        ViewProviderAsmElementGroup(obj.ViewObject)
        obj.purgeTouched()
        return obj


class ViewProviderAsmElementGroup(ViewProviderAsmGroup):
    _iconName = 'Assembly_Assembly_Element_Tree.svg'

    def onDelete(self,_obj,_subs):
        return False

    def canDropObjectEx(self,_obj,owner,subname):
        if not subname:
            return False
        proxy = self.ViewObject.Object.Proxy
        return proxy.getAssembly().getPartGroup()==owner

    def dropObjectEx(self,_vobj,_obj,owner,subname):
        AsmElement.make(AsmElement.Selection(
            Element=None, Group=owner, Subname=subname))


BuildShapeNone = 'None'
BuildShapeCompound = 'Compound'
BuildShapeFuse = 'Fuse'
BuildShapeCut = 'Cut'
BuildShapeNames = (BuildShapeNone,BuildShapeCompound,
        BuildShapeFuse,BuildShapeCut)

class Assembly(AsmGroup):
    _Timer = QtCore.QTimer()
    _PartMap = {} # maps part to assembly
    _PartArrayMap = {} # maps array part to assembly

    def __init__(self):
        self.parts = set()
        self.partArrays = set()
        self.constraints = None
        super(Assembly,self).__init__()

    def _collectParts(self,oldParts,newParts,partMap):
        for part in newParts:
            try:
                oldParts.remove(part)
            except KeyError:
                partMap[part] = self
        for part in oldParts:
            del partMap[part]
        return newParts

    def execute(self,obj):
        self.constraints = None
        self.buildShape()
        System.touch(obj)
        obj.ViewObject.Proxy.onExecute()

        parts = set()
        partArrays = set()
        for cstr in self.getConstraints():
            for element in cstr.Proxy.getElements():
                info = element.Proxy.getInfo()
                if isinstance(info.Part,tuple):
                    partArrays.add(info.Part[0])
                else:
                    parts.add(info.Part)
        parts = self._collectParts(self.parts,parts,Assembly._PartMap)
        partArrays = self._collectParts(
                self.partArrays,partArrays,Assembly._PartArrayMap)

        return False # return False to call LinkBaseExtension::execute()

    @classmethod
    def canAutoSolve(cls):
        from . import solver
        return gui.AsmCmdManager.AutoRecompute and \
               not FreeCADGui.ActiveDocument.Transacting and \
               not FreeCAD.isRestoring() and \
               not solver.isBusy() and \
               not ViewProviderAssembly.isBusy()

    @classmethod
    def checkPartChange(cls, obj, prop):
        if not cls.canAutoSolve() or prop in _IgnoredProperties:
            return
        assembly = None
        if prop == 'Placement':
            partMap = cls._PartMap
            assembly = partMap.get(obj,None)
        elif prop == 'PlacementList':
            partMap = cls._PartArrayMap
            assembly = partMap.get(obj,None)
        if assembly:
            try:
                # This will fail if assembly got deleted
                assembly.Object.Name
            except Exception:
                del partMap[obj]
            else:
                cls.autoSolve(True)

    @classmethod
    def autoSolve(cls,force=False):
        if force or cls.canAutoSolve():
            if not cls._Timer.isSingleShot():
                cls._Timer.setSingleShot(True)
                cls._Timer.timeout.connect(Assembly.onSolverTimer)
            logger.debug('auto solve scheduled',frame=1)
            cls._Timer.start(300)

    @classmethod
    def cancelAutoSolve(cls):
        cls._Timer.stop()

    @classmethod
    def onSolverTimer(cls):
        if cls.canAutoSolve():
            from . import solver
            logger.catch('solver exception when auto recompute',
                    solver.solve, FreeCAD.ActiveDocument.Objects, True)

    def onSolverChanged(self,setup=False):
        for obj in self.getConstraintGroup().Group:
            # setup==True usually means we are restoring, so try to restore the
            # non-touched state if possible, since recompute() below will touch
            # the constraint object
            touched = not setup or 'Touched' in obj.State
            obj.recompute()
            if not touched:
                obj.purgeTouched()

    def buildShape(self):
        obj = self.Object
        if obj.BuildShape == BuildShapeNone:
            if not obj.Shape.isNull():
                obj.Shape = Part.Shape()
            return

        shape = []
        partGroup = self.getPartGroup(obj)
        group = partGroup.Group
        if not group:
            raise RuntimeError('no parts')
        if obj.BuildShape == BuildShapeCut:
            shape = Part.getShape(group[0]).Solids
            if not shape:
                raise RuntimeError('First part has no solid')
            if len(shape)>1:
                shape = [shape[0].fuse(shape[1:])]
            group = group[1:]

        for o in group:
            if obj.isElementVisible(o.Name):
                shape += Part.getShape(o).Solids
        if not shape:
            raise RuntimeError('No solids found in parts')
        if len(shape) == 1:
            obj.Shape = shape[0]
        elif obj.BuildShape == BuildShapeFuse:
            obj.Shape = shape[0].fuse(shape[1:])
        elif obj.BuildShape == BuildShapeCut:
            if len(shape)>2:
                obj.Shape = shape[0].cut(shape[1].fuse(shape[2:]))
            else:
                obj.Shape = shape[0].cut(shape[1])
        else:
            obj.Shape = Part.makeCompound(shape)

    def attach(self, obj):
        obj.addProperty("App::PropertyEnumeration","BuildShape","Base",'')
        obj.BuildShape = BuildShapeNames
        super(Assembly,self).attach(obj)

    def linkSetup(self,obj):
        self.parts = set()
        self.partArrays = set()
        obj.configLinkProperty('Placement')
        super(Assembly,self).linkSetup(obj)
        System.attach(obj)
        self.onChanged(obj,'BuildShape')

        # make sure all children are there, first constraint group, then element
        # group, and finally part group. Call getPartGroup below will make sure
        # all groups exist. The order of the group is important to make sure
        # correct rendering and picking behavior
        self.getPartGroup(True)

        self.onSolverChanged(True)

    def onChanged(self, obj, prop):
        if prop == 'BuildShape':
            if not obj.BuildShape or obj.BuildShape == BuildShapeCompound:
                obj.setPropertyStatus('Shape','-Transient')
            else:
                obj.setPropertyStatus('Shape','Transient')
            return
        if prop not in _IgnoredProperties:
            System.onChanged(obj,prop)
            Assembly.autoSolve()

    def getConstraintGroup(self, create=False):
        obj = self.Object
        try:
            ret = obj.Group[0]
            checkType(ret,AsmConstraintGroup)
            parent = getattr(ret.Proxy,'parent',None)
            if not parent:
                ret.Proxy.parent = self
            elif parent!=self:
                raise RuntimeError('invalid parent of constraint group '
                    '{}'.format(objName(ret)))
            return ret
        except IndexError:
            if not create or obj.Group:
                raise RuntimeError('Invalid assembly')
            ret = AsmConstraintGroup.make(obj)
            obj.setLink({0:ret})
            return ret

    def getConstraints(self,refresh=False):
        if not refresh:
            ret = getattr(self,'constraints',None)
            if ret:
                return ret
        self.constraints = None
        cstrGroup = self.getConstraintGroup()
        if not cstrGroup:
            return
        ret = []
        for o in cstrGroup.Group:
            checkType(o,AsmConstraint)
            if Constraint.isDisabled(o):
                logger.debug('skip constraint {}'.format(cstrName(o)))
                continue
            if not System.isConstraintSupported(self.Object,
                       Constraint.getTypeName(o)):
                logger.debug('skip unsupported constraint '
                    '{}'.format(cstrName(o)))
                continue
            ret.append(o)
        self.constraints = ret
        return self.constraints

    def getElementGroup(self,create=False):
        obj = self.Object
        if create:
            # make sure previous group exists
            self.getConstraintGroup(True)
        try:
            ret = obj.Group[1]
            checkType(ret,AsmElementGroup)
            parent = getattr(ret.Proxy,'parent',None)
            if not parent:
                ret.Proxy.parent = self
            elif parent!=self:
                raise RuntimeError('invalid parent of element group '
                    '{}'.format(objName(ret)))
            return ret
        except IndexError:
            if not create:
                raise RuntimeError('Missing element group')
            ret = AsmElementGroup.make(obj)
            obj.setLink({1:ret})
            return ret

    def getPartGroup(self,create=False):
        obj = self.Object
        if create:
            # make sure previous group exists
            self.getElementGroup(True)
        try:
            ret = obj.Group[2]
            checkType(ret,AsmPartGroup)
            parent = getattr(ret.Proxy,'parent',None)
            if not parent:
                ret.Proxy.parent = self
            elif parent!=self:
                raise RuntimeError(
                        'invalid parent of part group {}'.format(objName(ret)))
            return ret
        except IndexError:
            if not create:
                raise RuntimeError('Missing part group')
            ret = AsmPartGroup.make(obj)
            obj.setLink({2:ret})
            return ret

    @staticmethod
    def make(doc=None,name='Assembly',undo=True):
        if not doc:
            doc = FreeCAD.ActiveDocument
            if not doc:
                raise RuntimeError('No active document')
        if undo:
            FreeCAD.setActiveTransaction('Create assembly')
        try:
            obj = doc.addObject(
                    "Part::FeaturePython",name,Assembly(),None,True)
            ViewProviderAssembly(obj.ViewObject)
            obj.Visibility = True
            obj.purgeTouched()
            if undo:
                FreeCAD.closeActiveTransaction()
        except Exception:
            if undo:
                FreeCAD.closeActiveTransaction(True)
            raise
        return obj

    Info = namedtuple('AssemblyInfo',('Assembly','Object','Subname'))

    @staticmethod
    def getSelection(sels=None):
        'Find all assembly objects among the current selection'
        objs = set()
        if sels is None:
            sels = FreeCADGui.Selection.getSelectionEx('',False)
        for sel in sels:
            if not sel.SubElementNames:
                if isTypeOf(sel.Object,Assembly,True):
                    objs.add(sel.Object)
                continue
            for subname in sel.SubElementNames:
                ret = Assembly.find(sel.Object,subname,keepEmptyChild=True)
                if ret:
                    objs.add(ret.Assembly)
        return tuple(objs)

    @staticmethod
    def find(obj,subname,childType=None,
            recursive=False,relativeToChild=True,keepEmptyChild=False):
        '''
        Find the immediate child of the first Assembly referenced in 'subs'

        obj: the parent object

        subname: '.' separted sub-object reference, or string list of sub-object
                 names. Must contain no sub element name.

        childType: optional checking of the child type.

        recursive: If True, continue finding the child of the next assembly.

        relativeToChild: If True, the returned subname is realtive to the child
        object found, or else, it is relative to the assembly, i.e., including
        the child's name

        Return None if not found, or (assembly,child,sub), where 'sub' is the
        remaining sub name list. If recursive is True, then return a list of
        tuples
        '''
        assembly = None
        child = None
        if isTypeOf(obj,Assembly,True):
            assembly = obj
        subs = subname if isinstance(subname,list) else subname.split('.')
        i= 0
        for i,name in enumerate(subs[:-1]):
            sobj = obj.getSubObject(name+'.',1)
            if not sobj:
                raise RuntimeError('Cannot find sub object {}, '
                    '{}'.format(objName(obj),name))
            obj = sobj
            if assembly and isTypeOf(obj,childType):
                child = obj
                break
            assembly = obj if isTypeOf(obj,Assembly,True) else None

        if not child:
            if keepEmptyChild and assembly:
                ret = Assembly.Info(Assembly=assembly,Object=None,Subname='')
                return [ret] if recursive else ret
            return

        ret = Assembly.Info(Assembly = assembly, Object = child,
            Subname = '.'.join(subs[i+1:] if relativeToChild else subs[i:]))

        if not recursive:
            return ret

        nret = Assembly.find(child, subs[i+1:], childType, recursive,
                relativeToChild, keepEmptyChild)
        if nret:
            return [ret] + nret
        return [ret]

    @staticmethod
    def findChildren(obj,subname,tp=None):
        return Assembly.find(obj,subname,tp,True,False,True)

    @staticmethod
    def findPartGroup(obj,subname='2.',recursive=False,relativeToChild=True):
        return Assembly.find(
                obj,subname,AsmPartGroup,recursive,relativeToChild)

    @staticmethod
    def findElementGroup(obj,subname='1.',relativeToChild=True):
        return Assembly.find(
                obj,subname,AsmElementGroup,False,relativeToChild)

    @staticmethod
    def findConstraintGroup(obj,subname='0.',relativeToChild=True):
        return Assembly.find(
                obj,subname,AsmConstraintGroup,False,relativeToChild)


class ViewProviderAssembly(ViewProviderAsmGroup):
    def __init__(self,vobj):
        self._movingPart = None
        super(ViewProviderAssembly,self).__init__(vobj)

    def _convertSubname(self,owner,subname):
        sub = subname.split('.')
        if not sub:
            return
        me = self.ViewObject.Object
        partGroup = me.Proxy.getPartGroup().ViewObject
        if sub == me.Name:
            return partGroup,partGroup,subname[len[sub]+1:]
        return partGroup,owner,subname

    def canDropObjectEx(self,obj,owner,subname):
        info = self._convertSubname(owner,subname)
        if not info:
            return False
        partGroup,owner,subname = info
        return partGroup.canDropObject(obj,owner,subname)

    def canDragAndDropObject(self,_obj):
        return True

    def dropObjectEx(self,_vobj,obj,owner,subname):
        info = self._convertSubname(owner,subname)
        if not info:
            return False
        partGroup,owner,subname = info
        partGroup.dropObject(obj,owner,subname)

    def getIcon(self):
        return System.getIcon(self.ViewObject.Object)

    def doubleClicked(self, _vobj):
        from . import mover
        return mover.movePart()

    def onExecute(self):
        if not getattr(self,'_movingPart',None):
            return

        pla = logger.catch('exception when update moving part',
                self._movingPart.update)
        if pla:
            self.ViewObject.DraggingPlacement = pla
            return

        # Must NOT call resetEdit() here. Because we are called through dragger
        # callback, meaning that we are called during coin node traversal.
        # resetEdit() will cause View3DInventorView to reset editing root node.
        # And disaster will happen when modifying coin node tree while
        # traversing.
        #
        #  doc = FreeCADGui.editDocument()
        #  if doc:
        #      doc.resetEdit()

    def initDraggingPlacement(self):
        if not getattr(self,'_movingPart',None):
            return
        return (FreeCADGui.editDocument().EditingTransform,
                self._movingPart.draggerPlacement,
                self._movingPart.bbox)

    _Busy = False

    def onDragStart(self):
        Assembly.cancelAutoSolve();
        FreeCADGui.Selection.clearSelection()
        self.__class__._Busy = True
        FreeCAD.setActiveTransaction('Assembly move')

    def onDragMotion(self):
        return self._movingPart.move()

    def onDragEnd(self):
        self.__class__._Busy = False
        FreeCAD.closeActiveTransaction()

    def unsetEdit(self,_vobj,_mode):
        self._movingPart = None
        return False

    @classmethod
    def isBusy(cls):
        return cls._Busy


class AsmWorkPlane(object):
    def __init__(self,obj):
        obj.addProperty("App::PropertyLength","Length","Base")
        obj.addProperty("App::PropertyLength","Width","Base")
        obj.Length = 10
        obj.Width = 10
        obj.Proxy = self

    def execute(self,obj):
        if not obj.Length or not obj.Width:
            raise RuntimeError('invalid workplane size')
        obj.Shape = Part.makePlane(obj.Length,obj.Width)

    def __getstate__(self):
        return

    def __setstate__(self,_state):
        return

    Info = namedtuple('AsmWorkPlaneSelectionInfo',
            ('SelObj','SelSubname','PartGroup'))

    @staticmethod
    def getSelection(sels=None):
        if not sels:
            sels = FreeCADGui.Selection.getSelectionEx('',False)
        if not sels:
            raise RuntimeError('no selection')
        if len(sels)!=1 or len(sels[0].SubElementNames)>1:
            raise RuntimeError('too many selections')
        if sels[0].SubElementNames:
            sub = sels[0].SubElementNames[0]
        else:
            sub = ''
        ret = Assembly.find(sels[0].Object,sub,
                relativeToChild=False,keepEmptyChild=True)
        if not ret:
            raise RuntimeError('invalid selection')
        if ret.Subname:
            sub = sub[:-len(ret.Subname)]
        return AsmWorkPlane.Info(
                SelObj = sels[0].Object,
                SelSubname = sub,
                PartGroup = ret.Assembly.Proxy.getPartGroup())

    @staticmethod
    def make(sels=None,name='Workplane', undo=True):
        info = AsmWorkPlane.getSelection(sels)
        doc = info.PartGroup.Document
        if undo:
            FreeCAD.setActiveTransaction('Assembly create workplane')
        try:
            obj = doc.addObject('Part::FeaturePython',name)
            AsmWorkPlane(obj)
            ViewProviderAsmWorkPlane(obj.ViewObject)
            bbox = info.PartGroup.ViewObject.getBoundingBox()
            if bbox.isValid():
                obj.Length = bbox.DiagonalLength*0.5
                obj.Width = obj.Length
            obj.recompute(True)
            info.PartGroup.setLink({-1:obj})
            if undo:
                FreeCAD.closeActiveTransaction()

            FreeCADGui.Selection.clearSelection()
            FreeCADGui.Selection.addSelection(info.SelObj,
                info.SelSubname + info.PartGroup.Name + '.' + obj.Name + '.')
            FreeCADGui.runCommand('Std_TreeSelection')
            return obj
        except Exception:
            if undo:
                FreeCAD.closeActiveTransaction(True)
            raise


class ViewProviderAsmWorkPlane(ViewProviderAsmBase):
    _iconName = 'Assembly_Workplane.svg'

    def __init__(self,vobj):
        vobj.Transparency = 50
        vobj.LineColor = (0.0,0.33,1.0,1.0)
        super(ViewProviderAsmWorkPlane,self).__init__(vobj)

    def canDropObjects(self):
        return False

    def getDisplayModes(self, _vobj):
        modes=[]
        return modes

    def setDisplayMode(self, mode):
        return mode