#!/usr/bin/env python2
# -*- coding: utf-8 -*-

# SAT: a jabber client
# Copyright (C) 2009-2018 Jérôme Poisson (goffi@goffi.org)

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from sat.core.i18n import _
from sat.core.constants import Const as C
from sat.core.log import getLogger
log = getLogger(__name__)

from xml.dom import minidom, NotFoundErr
from wokkel import data_form
from twisted.words.xish import domish
from twisted.words.protocols.jabber import jid
from twisted.internet import defer
from sat.core import exceptions
from collections import OrderedDict
from copy import deepcopy
import htmlentitydefs
import re

"""This library help manage XML used in SàT (parameters, registration, etc)"""

SAT_FORM_PREFIX = "SAT_FORM_"
SAT_PARAM_SEPARATOR = "_XMLUI_PARAM_"  # used to have unique elements names
html_entity_re = re.compile(r'&([a-zA-Z]+?);')
XML_ENTITIES = ('quot', 'amp', 'apos', 'lt', 'gt')

# TODO: move XMLUI stuff in a separate module
# TODO: rewrite this with lxml or ElementTree or domish.Element: it's complicated and difficult to maintain with current minidom implementation

# Helper functions

def _dataFormField2XMLUIData(field, read_only=False):
    """Get data needed to create an XMLUI's Widget from Wokkel's data_form's Field.

    The attribute field can be modified (if it's fixed and it has no value).
    @param field (data_form.Field): a field with attributes "value", "fieldType", "label" and "var"
    @param read_only (bool): if True and it makes sense, create a read only input widget
    @return: a tuple (widget_type, widget_args, widget_kwargs)
    """
    widget_args = [field.value]
    widget_kwargs = {}
    if field.fieldType == 'fixed' or field.fieldType is None:
        widget_type = 'text'
        if field.value is None:
            if field.label is None:
                log.warning(_("Fixed field has neither value nor label, ignoring it"))
                field.value = ""
            else:
                field.value = field.label
                field.label = None
            widget_args[0] = field.value
    elif field.fieldType == 'text-single':
        widget_type = "string"
        widget_kwargs['read_only'] = read_only
    elif field.fieldType == 'jid-single':
        widget_type = "jid_input"
        widget_kwargs['read_only'] = read_only
    elif field.fieldType == 'text-multi':
        widget_type = "textbox"
        widget_args[0] = u'\n'.join(field.values)
        widget_kwargs['read_only'] = read_only
    elif field.fieldType == 'text-private':
        widget_type = "password"
        widget_kwargs['read_only'] = read_only
    elif field.fieldType == 'boolean':
        widget_type = "bool"
        if widget_args[0] is None:
            widget_args[0] = 'false'
        widget_kwargs['read_only'] = read_only
    elif field.fieldType == 'integer':
        widget_type = "integer"
        widget_kwargs['read_only'] = read_only
    elif field.fieldType == 'list-single':
        widget_type = "list"
        widget_kwargs["options"] = [(option.value, option.label or option.value) for option in field.options]
        widget_kwargs["selected"] = widget_args
        widget_args = []
    else:
        log.error(u"FIXME FIXME FIXME: Type [%s] is not managed yet by SàT" % field.fieldType)
        widget_type = "string"
        widget_kwargs['read_only'] = read_only

    if field.var:
        widget_kwargs["name"] = field.var

    return widget_type, widget_args, widget_kwargs


def dataForm2Widgets(form_ui, form, read_only=False, prepend=None, filters=None):
    """Complete an existing XMLUI with widget converted from XEP-0004 data forms.

    @param form_ui (XMLUI): XMLUI instance
    @param form (data_form.Form): Wokkel's implementation of data form
    @param read_only (bool): if True and it makes sense, create a read only input widget
    @param prepend(iterable, None): widgets to prepend to main LabelContainer
        if not None, must be an iterable of *args for addWidget. Those widgets will
        be added first to the container.
    @param filters(dict, None): if not None, a dictionary of callable:
        key is the name of the widget to filter
        the value is a callable, it will get form's XMLUI, widget's type, args and kwargs
            and must return widget's type, args and kwargs (which can be modified)
        This is especially useful to modify well known fields
    @return: the completed XMLUI instance
    """
    if filters is None:
        filters = {}
    if form.instructions:
        form_ui.addText('\n'.join(form.instructions), 'instructions')

    form_ui.changeContainer("label")

    if prepend is not None:
        for widget_args in prepend:
            form_ui.addWidget(*widget_args)

    for field in form.fieldList:
        widget_type, widget_args, widget_kwargs = _dataFormField2XMLUIData(field, read_only)
        try:
            widget_filter = filters[widget_kwargs['name']]
        except KeyError:
            pass
        else:
            widget_type, widget_args, widget_kwargs = widget_filter(form_ui, widget_type, widget_args, widget_kwargs)
        label = field.label or field.var
        if label:
            form_ui.addLabel(label)
        else:
            form_ui.addEmpty()

        form_ui.addWidget(widget_type, *widget_args, **widget_kwargs)

    return form_ui


def dataForm2XMLUI(form, submit_id, session_id=None, read_only=False):
    """Take a data form (Wokkel's XEP-0004 implementation) and convert it to a SàT XMLUI.

    @param form (data_form.Form): a Form instance
    @param submit_id (unicode): callback id to call when submitting form
    @param session_id (unicode): session id to return with the data
    @param read_only (bool): if True and it makes sense, create a read only input widget
    @return: XMLUI instance
    """
    form_ui = XMLUI("form", "vertical", submit_id=submit_id, session_id=session_id)
    return dataForm2Widgets(form_ui, form, read_only=read_only)


def dataFormEltResult2XMLUIData(form_xml):
    """Parse a data form result (not parsed by Wokkel's XEP-0004 implementation).

    The raw data form is used because Wokkel doesn't manage result items parsing yet.
    @param form_xml (domish.Element): element of the data form
    @return: a couple (headers, result_list):
        - headers (dict{unicode: unicode}): form headers (field labels and types)
        - xmlui_data (list[tuple]): list of (widget_type, widget_args, widget_kwargs)
    """
    headers = OrderedDict()
    try:
        reported_elt = form_xml.elements('jabber:x:data', 'reported').next()
    except StopIteration:
        raise exceptions.DataError("Couldn't find expected <reported> tag in %s" % form_xml.toXml())

    for elt in reported_elt.elements():
        if elt.name != "field":
            raise exceptions.DataError("Unexpected tag")
        name = elt["var"]
        label = elt.attributes.get('label', '')
        type_ = elt.attributes.get('type')
        headers[name] = (label, type_)

    if not headers:
        raise exceptions.DataError("No reported fields (see XEP-0004 §3.4)")

    xmlui_data = []
    item_elts = form_xml.elements('jabber:x:data', 'item')

    for item_elt in item_elts:
        for elt in item_elt.elements():
            if elt.name != 'field':
                log.warning(u"Unexpected tag (%s)" % elt.name)
                continue
            field = data_form.Field.fromElement(elt)

            xmlui_data.append(_dataFormField2XMLUIData(field))

    return headers, xmlui_data


def XMLUIData2AdvancedList(xmlui, headers, xmlui_data):
    """Take a raw data form result (not parsed by Wokkel's XEP-0004 implementation) and convert it to an advanced list.

    The raw data form is used because Wokkel doesn't manage result items parsing yet.
    @param xmlui (XMLUI): the XMLUI where the AdvancedList will be added
    @param headers (dict{unicode: unicode}): form headers (field labels and types)
    @param xmlui_data (list[tuple]): list of (widget_type, widget_args, widget_kwargs)
    @return: the completed XMLUI instance
    """
    adv_list = AdvancedListContainer(xmlui, headers=headers, columns=len(headers), parent=xmlui.current_container)
    xmlui.changeContainer(adv_list)

    for widget_type, widget_args, widget_kwargs in xmlui_data:
        xmlui.addWidget(widget_type, *widget_args, **widget_kwargs)

    return xmlui


def dataFormResult2AdvancedList(xmlui, form_xml):
    """Take a raw data form result (not parsed by Wokkel's XEP-0004 implementation) and convert it to an advanced list.

    The raw data form is used because Wokkel doesn't manage result items parsing yet.
    @param xmlui (XMLUI): the XMLUI where the AdvancedList will be added
    @param form_xml (domish.Element): element of the data form
    @return: the completed XMLUI instance
    """
    headers, xmlui_data = dataFormEltResult2XMLUIData(form_xml)
    XMLUIData2AdvancedList(xmlui, headers, xmlui_data)


def dataFormEltResult2XMLUI(form_elt, session_id=None):
    """Take a raw data form (not parsed by XEP-0004) and convert it to a SàT XMLUI.

    The raw data form is used because Wokkel doesn't manage result items parsing yet.
    @param form_elt (domish.Element): element of the data form
    @param session_id (unicode): session id to return with the data
    @return: XMLUI instance
    """
    xml_ui = XMLUI("window", "vertical", session_id=session_id)
    try:
        dataFormResult2AdvancedList(xml_ui, form_elt)
    except exceptions.DataError:
        parsed_form = data_form.Form.fromElement(form_elt)
        dataForm2Widgets(xml_ui, parsed_form, read_only=True)
    return xml_ui

def dataFormResult2XMLUI(result_form, base_form, session_id=None, prepend=None, filters=None):
    """Convert data form result to SàT XMLUI.

    @param result_form (data_form.Form): result form to convert
    @param base_form (data_form.Form): initial form (i.e. of form type "form")
        this one is necessary to reconstruct options when needed (e.g. list elements)
    @param session_id (unicode): session id to return with the data
    @param prepend: same as for [dataForm2Widgets]
    @param filters: same as for [dataForm2Widgets]
    @return: XMLUI instance
    """
    form = deepcopy(result_form)
    for name, field in form.fields.iteritems():
        try:
            base_field = base_form.fields[name]
        except KeyError:
            continue
        field.options = base_field.options[:]
    xml_ui = XMLUI("window", "vertical", session_id=session_id)
    dataForm2Widgets(xml_ui, form, read_only=True, prepend=prepend, filters=filters)
    return xml_ui


def _cleanValue(value):
    """Workaround method to avoid DBus types with D-Bus bridge.

    @param value: value to clean
    @return: value in a non DBus type (only clean string yet)
    """
    # XXX: must be removed when DBus types will no cause problems anymore
    # FIXME: should be cleaned inside D-Bus bridge itself
    if isinstance(value, basestring):
        return unicode(value)
    return value


def XMLUIResult2DataFormResult(xmlui_data):
    """ Extract form data from a XMLUI return.

    @param xmlui_data (dict): data returned by frontends for XMLUI form
    @return: dict of data usable by Wokkel's data form
    """
    return {key[len(SAT_FORM_PREFIX):]: _cleanValue(value) for key, value in xmlui_data.iteritems() if key.startswith(SAT_FORM_PREFIX)}


def formEscape(name):
    """Return escaped name for forms.

    @param name (unicode): form name
    @return: unicode
    """
    return u"%s%s" % (SAT_FORM_PREFIX, name)


def XMLUIResultToElt(xmlui_data):
    """Construct result domish.Element from XMLUI result.

    @param xmlui_data (dict): data returned by frontends for XMLUI form
    @return: domish.Element
    """
    form = data_form.Form('submit')
    form.makeFields(XMLUIResult2DataFormResult(xmlui_data))
    return form.toElement()


def tupleList2dataForm(values):
    """Convert a list of tuples (name, value) to a wokkel submit data form.

    @param values (list): list of tuples
    @return: data_form.Form
    """
    form = data_form.Form('submit')
    for value in values:
        field = data_form.Field(var=value[0], value=value[1])
        form.addField(field)

    return form


def paramsXML2XMLUI(xml):
    """Convert the XML for parameter to a SàT XML User Interface.

    @param xml (unicode)
    @return: XMLUI
    """
    # TODO: refactor params and use Twisted directly to parse XML
    params_doc = minidom.parseString(xml.encode('utf-8'))
    top = params_doc.documentElement
    if top.nodeName != 'params':
        raise exceptions.DataError(_('INTERNAL ERROR: parameters xml not valid'))

    param_ui = XMLUI("param", "tabs")
    tabs_cont = param_ui.current_container

    for category in top.getElementsByTagName("category"):
        category_name = category.getAttribute('name')
        label = category.getAttribute('label')
        if not category_name:
            raise exceptions.DataError(_('INTERNAL ERROR: params categories must have a name'))
        tabs_cont.addTab(category_name, label=label, container=LabelContainer)
        for param in category.getElementsByTagName("param"):
            widget_kwargs = {}

            param_name = param.getAttribute('name')
            param_label = param.getAttribute('label')
            type_ = param.getAttribute('type')
            if not param_name and type_ != 'text':
                raise exceptions.DataError(_('INTERNAL ERROR: params must have a name'))

            value = param.getAttribute('value') or None
            callback_id = param.getAttribute('callback_id') or None

            if type_ == 'list':
                options, selected = _paramsGetListOptions(param)
                widget_kwargs['options'] = options
                widget_kwargs['selected'] = selected
                widget_kwargs['styles'] = ['extensible']
            elif type_ == 'jids_list':
                widget_kwargs['jids'] = _paramsGetListJids(param)

            if type_ in ("button", "text"):
                param_ui.addEmpty()
                value = param_label
            else:
                param_ui.addLabel(param_label or param_name)

            if value:
                widget_kwargs["value"] = value

            if callback_id:
                widget_kwargs['callback_id'] = callback_id
                others = ["%s%s%s" % (category_name, SAT_PARAM_SEPARATOR, other.getAttribute('name'))
                          for other in category.getElementsByTagName('param')
                          if other.getAttribute('type') != 'button']
                widget_kwargs['fields_back'] = others

            widget_kwargs['name'] = "%s%s%s" % (category_name, SAT_PARAM_SEPARATOR, param_name)

            param_ui.addWidget(type_, **widget_kwargs)

    return param_ui.toXml()


def _paramsGetListOptions(param):
    """Retrieve the options for list element.

    The <option/> tags must be direct children of <param/>.
    @param param (domish.Element): element
    @return: a tuple (options, selected_value)
    """
    if len(param.getElementsByTagName("options")) > 0:
        raise exceptions.DataError(_("The 'options' tag is not allowed in parameter of type 'list'!"))
    elems = param.getElementsByTagName("option")
    if len(elems) == 0:
        return []
    options = [elem.getAttribute("value") for elem in elems]
    selected = [elem.getAttribute("value") for elem in elems if elem.getAttribute("selected") == 'true']
    return (options, selected)

def _paramsGetListJids(param):
    """Retrive jids from a jids_list element.

    the <jid/> tags must be direct children of <param/>
    @param param (domish.Element): element
    @return: a list of jids
    """
    elems = param.getElementsByTagName("jid")
    jids = [elem.firstChild.data for elem in elems
            if elem.firstChild is not None
            and elem.firstChild.nodeType == elem.TEXT_NODE]
    return jids


### XMLUI Elements ###


class Element(object):
    """ Base XMLUI element """
    type = None

    def __init__(self, xmlui, parent=None):
        """Create a container element

        @param xmlui: XMLUI instance
        @parent: parent element
        """
        assert self.type is not None
        self.children = []
        if not hasattr(self, 'elem'):
            self.elem = parent.xmlui.doc.createElement(self.type)
        self.xmlui = xmlui
        if parent is not None:
            parent.append(self)
        self.parent = parent

    def append(self, child):
        """Append a child to this element.

        @param child (Element): child element
        @return: the added child Element
        """
        self.elem.appendChild(child.elem)
        child.parent = self
        self.children.append(child)
        return child


class TopElement(Element):
    """ Main XML Element """
    type = 'top'

    def __init__(self, xmlui):
        self.elem = xmlui.doc.documentElement
        super(TopElement, self).__init__(xmlui)


class TabElement(Element):
    """ Used by TabsContainer to give name and label to tabs."""
    type = 'tab'

    def __init__(self, parent, name, label, selected=False):
        """

        @param parent (TabsContainer): parent container
        @param name (unicode): tab name
        @param label (unicode): tab label
        @param selected (bool): set to True to select this tab
        """
        if not isinstance(parent, TabsContainer):
            raise exceptions.DataError(_("TabElement must be a child of TabsContainer"))
        super(TabElement, self).__init__(parent.xmlui, parent)
        self.elem.setAttribute('name', name)
        self.elem.setAttribute('label', label)
        if selected:
            self.setSelected(selected)

    def setSelected(self, selected=False):
        """Set the tab selected.

        @param selected (bool): set to True to select this tab
        """
        self.elem.setAttribute('selected', 'true' if selected else 'false')


class FieldBackElement(Element):
    """ Used by ButtonWidget to indicate which field have to be sent back """
    type = 'field_back'

    def __init__(self, parent, name):
        assert isinstance(parent, ButtonWidget)
        super(FieldBackElement, self).__init__(parent.xmlui, parent)
        self.elem.setAttribute('name', name)


class InternalFieldElement(Element):
    """ Used by internal callbacks to indicate which fields are manipulated """
    type = 'internal_field'

    def __init__(self, parent, name):
        super(InternalFieldElement, self).__init__(parent.xmlui, parent)
        self.elem.setAttribute('name', name)


class InternalDataElement(Element):
    """ Used by internal callbacks to retrieve extra data """
    type = 'internal_data'

    def __init__(self, parent, children):
        super(InternalDataElement, self).__init__(parent.xmlui, parent)
        assert isinstance(children, list)
        for child in children:
            self.elem.childNodes.append(child)


class OptionElement(Element):
    """" Used by ListWidget to specify options """
    type = 'option'

    def __init__(self, parent, option, selected=False):
        """

        @param parent
        @param option (string, tuple)
        @param selected (boolean)
        """
        assert isinstance(parent, ListWidget)
        super(OptionElement, self).__init__(parent.xmlui, parent)
        if isinstance(option, basestring):
            value, label = option, option
        elif isinstance(option, tuple):
            value, label = option
        else:
            raise NotImplementedError
        self.elem.setAttribute('value', value)
        self.elem.setAttribute('label', label)
        if selected:
            self.elem.setAttribute('selected', 'true')


class JidElement(Element):
    """" Used by JidsListWidget to specify jids"""
    type = 'jid'

    def __init__(self, parent, jid_):
        """
        @param jid_(jid.JID, unicode): jid to append
        """
        assert isinstance(parent, JidsListWidget)
        super(JidElement, self).__init__(parent.xmlui, parent)
        if isinstance(jid_, jid.JID):
            value = jid_.full()
        elif isinstance(jid_, basestring):
            value = unicode(jid_)
        else:
            raise NotImplementedError
        jid_txt = self.xmlui.doc.createTextNode(value)
        self.elem.appendChild(jid_txt)


class RowElement(Element):
    """" Used by AdvancedListContainer """
    type = 'row'

    def __init__(self, parent):
        assert isinstance(parent, AdvancedListContainer)
        super(RowElement, self).__init__(parent.xmlui, parent)
        if parent.next_row_idx is not None:
            if parent.auto_index:
                raise exceptions.DataError(_("Can't set row index if auto_index is True"))
            self.elem.setAttribute('index', parent.next_row_idx)
            parent.next_row_idx = None


class HeaderElement(Element):
    """" Used by AdvancedListContainer """
    type = 'header'

    def __init__(self, parent, name=None, label=None, description=None):
        """
        @param parent: AdvancedListContainer instance
        @param name: name of the container
        @param label: label to be displayed in columns
        @param description: long descriptive text
        """
        assert isinstance(parent, AdvancedListContainer)
        super(HeaderElement, self).__init__(parent.xmlui, parent)
        if name:
            self.elem.setAttribute('name', name)
        if label:
            self.elem.setAttribute('label', label)
        if description:
            self.elem.setAttribute('description', description)


## Containers ##


class Container(Element):
    """ And Element which contains other ones and has a layout """
    type = None

    def __init__(self, xmlui, parent=None):
        """Create a container element

        @param xmlui: XMLUI instance
        @parent: parent element or None
        """
        self.elem = xmlui.doc.createElement('container')
        super(Container, self).__init__(xmlui, parent)
        self.elem.setAttribute('type', self.type)

    def getParentContainer(self):
        """ Return first parent container

        @return: parent container or None
        """
        current = self.parent
        while(not isinstance(current, (Container)) and
              current is not None):
            current = current.parent
        return current


class VerticalContainer(Container):
    type = "vertical"


class HorizontalContainer(Container):
    type = "horizontal"


class PairsContainer(Container):
    type = "pairs"


class LabelContainer(Container):
    type = "label"


class TabsContainer(Container):
    type = "tabs"

    def addTab(self, name, label=None, selected=None, container=VerticalContainer):
        """Add a tab.

        @param name (unicode): tab name
        @param label (unicode): tab label
        @param selected (bool): set to True to select this tab
        @param container (class): container class, inheriting from Container
        @return: the container for the new tab
        """
        if not label:
            label = name
        tab_elt = TabElement(self, name, label, selected)
        new_container = container(self.xmlui, tab_elt)
        return self.xmlui.changeContainer(new_container)

    def end(self):
        """ Called when we have finished tabs

        change current container to first container parent
        """
        parent_container = self.getParentContainer()
        self.xmlui.changeContainer(parent_container)


class AdvancedListContainer(Container):
    """A list which can contain other widgets, headers, etc"""
    type = "advanced_list"

    def __init__(self, xmlui, callback_id=None, name=None, headers=None, items=None, columns=None, selectable='no', auto_index=False, parent=None):
        """Create an advanced list

        @param headers: optional headers information
        @param callback_id: id of the method to call when selection is done
        @param items: list of widgets to add (just the first row)
        @param columns: number of columns in this table, or None to autodetect
        @param selectable: one of:
            'no': nothing is done
            'single': one row can be selected
        @param auto_index: if True, indexes will be generated by frontends, starting from 0
        @return: created element
        """
        assert selectable in ('no', 'single')
        if not items and columns is None:
            raise exceptions.DataError(_("either items or columns need do be filled"))
        if headers is None:
            headers = []
        if items is None:
            items = []
        super(AdvancedListContainer, self).__init__(xmlui, parent)
        if columns is None:
            columns = len(items[0])
        self._columns = columns
        self._item_idx = 0
        self.current_row = None
        if headers:
            if len(headers) != self._columns:
                raise exceptions.DataError(_("Headers lenght doesn't correspond to columns"))
            self.addHeaders(headers)
        if items:
            self.addItems(items)
        self.elem.setAttribute('columns', str(self._columns))
        if callback_id is not None:
            self.elem.setAttribute('callback', callback_id)
        self.elem.setAttribute('selectable', selectable)
        self.auto_index = auto_index
        if auto_index:
            self.elem.setAttribute('auto_index', 'true')
        self.next_row_idx = None

    def addHeaders(self, headers):
        for header in headers:
            self.addHeader(header)

    def addHeader(self, header):
        pass  # TODO

    def addItems(self, items):
        for item in items:
            self.append(item)

    def setRowIndex(self, idx):
        """ Set index for next row

        index are returned when a row is selected, in data's "index" key
        @param idx: string index to associate to the next row
        """
        self.next_row_idx = idx

    def append(self, child):
        if isinstance(child, RowElement):
            return super(AdvancedListContainer, self).append(child)
        if self._item_idx % self._columns == 0:
            self.current_row = RowElement(self)
        self.current_row.append(child)
        self._item_idx += 1

    def end(self):
        """ Called when we have finished list

        change current container to first container parent
        """
        if self._item_idx % self._columns != 0:
            raise exceptions.DataError(_("Incorrect number of items in list"))
        parent_container = self.getParentContainer()
        self.xmlui.changeContainer(parent_container)


## Widgets ##


class Widget(Element):
    type = None

    def __init__(self, xmlui, name=None, parent=None):
        """Create an element

        @param xmlui: XMLUI instance
        @param name: name of the element or None
        @param parent: parent element or None
        """
        self.elem = xmlui.doc.createElement('widget')
        super(Widget, self).__init__(xmlui, parent)
        if name:
            self.elem.setAttribute('name', name)
            if name in xmlui.named_widgets:
                raise exceptions.ConflictError(_(u'A widget with the name "{name}" already exists.').format(name=name))
            xmlui.named_widgets[name] = self
        self.elem.setAttribute('type', self.type)

    def setInternalCallback(self, callback, fields, data_elts=None):
        """Set an internal UI callback when the widget value is changed.

        The internal callbacks are NO callback ids, they are strings from
        a predefined set of actions that are running in the scope of XMLUI.
        @param callback (string): a value from:
            - 'copy': process the widgets given in 'fields' two by two, by
                copying the values of one widget to the other. Target widgets
                of type List do not accept the empty value.
            - 'move': same than copy but moves the values if the source widget
                is not a List.
            - 'groups_of_contact': process the widgets two by two, assume A is
                is a list of JID and B a list of groups, select in B the groups
                to which the JID selected in A belongs.
            - more operation to be added when necessary...
        @param fields (list): a list of widget names (string)
        @param data_elts (list[Element]): extra data elements
        """
        self.elem.setAttribute('internal_callback', callback)
        if fields:
            for field in fields:
                InternalFieldElement(self, field)
        if data_elts:
            InternalDataElement(self, data_elts)


class EmptyWidget(Widget):
    """Place holder widget"""
    type = 'empty'


class TextWidget(Widget):
    """Used for blob of text"""
    type = 'text'

    def __init__(self, xmlui, value, name=None, parent=None):
        super(TextWidget, self).__init__(xmlui, name, parent)
        value_elt = self.xmlui.doc.createElement('value')
        text = self.xmlui.doc.createTextNode(value)
        value_elt.appendChild(text)
        self.elem.appendChild(value_elt)

    @property
    def value(self):
        return self.elem.firstChild.firstChild.wholeText


class LabelWidget(Widget):
    """One line blob of text

    used most of time to display the desciption or name of the next widget
    """
    type = 'label'

    def __init__(self, xmlui, label, name=None, parent=None):
        super(LabelWidget, self).__init__(xmlui, name, parent)
        self.elem.setAttribute('value', label)


class JidWidget(Widget):
    """Used to display a Jabber ID, some specific methods can be added"""
    type = 'jid'

    def __init__(self, xmlui, jid, name=None, parent=None):
        super(JidWidget, self).__init__(xmlui, name, parent)
        try:
            self.elem.setAttribute('value', jid.full())
        except AttributeError:
            self.elem.setAttribute('value', unicode(jid))


class DividerWidget(Widget):
    type = 'divider'

    def __init__(self, xmlui, style='line', name=None, parent=None):
        """ Create a divider

        @param xmlui: XMLUI instance
        @param style: one of:
            - line: a simple line
            - dot: a line of dots
            - dash: a line of dashes
            - plain: a full thick line
            - blank: a blank line/space
        @param name: name of the widget
        @param parent: parent container

        """
        super(DividerWidget, self).__init__(xmlui, name, parent)
        self.elem.setAttribute('style', style)


### Inputs ###


class InputWidget(Widget):
    """Widget which can accept user inputs

    used mainly in forms
    """
    def __init__(self, xmlui, name=None, parent=None, read_only=False):
        super(InputWidget, self).__init__(xmlui, name, parent)
        if read_only:
            self.elem.setAttribute('read_only', 'true')


class StringWidget(InputWidget):
    type = 'string'

    def __init__(self, xmlui, value=None, name=None, parent=None, read_only=False):
        super(StringWidget, self).__init__(xmlui, name, parent, read_only=read_only)
        if value:
            value_elt = self.xmlui.doc.createElement('value')
            text = self.xmlui.doc.createTextNode(value)
            value_elt.appendChild(text)
            self.elem.appendChild(value_elt)

    @property
    def value(self):
        return self.elem.firstChild.firstChild.wholeText


class PasswordWidget(StringWidget):
    type = 'password'


class TextBoxWidget(StringWidget):
    type = 'textbox'


class JidInputWidget(StringWidget):
    type = 'jid_input'


# TODO handle min and max values
class IntWidget(StringWidget):
    type = 'int'

    def __init__(self, xmlui, value=0, name=None, parent=None, read_only=False):
        try:
            int(value)
        except ValueError:
            raise exceptions.DataError(_("Value must be an integer"))
        super(IntWidget, self).__init__(xmlui, value, name, parent, read_only=read_only)


class BoolWidget(InputWidget):
    type = 'bool'

    def __init__(self, xmlui, value='false', name=None, parent=None, read_only=False):
        if isinstance(value, bool):
            value = 'true' if value else 'false'
        elif value == '0':
            value = 'false'
        elif value == '1':
            value = 'true'
        if value not in ('true', 'false'):
            raise exceptions.DataError(_("Value must be 0, 1, false or true"))
        super(BoolWidget, self).__init__(xmlui, name, parent, read_only=read_only)
        self.elem.setAttribute('value', value)


class ButtonWidget(Widget):
    type = 'button'

    def __init__(self, xmlui, callback_id, value=None, fields_back=None, name=None, parent=None):
        """Add a button

        @param callback_id: callback which will be called if button is pressed
        @param value: label of the button
        @param fields_back: list of names of field to give back when pushing the button
        @param name: name
        @param parent: parent container
        """
        if fields_back is None:
            fields_back = []
        super(ButtonWidget, self).__init__(xmlui, name, parent)
        self.elem.setAttribute('callback', callback_id)
        if value:
            self.elem.setAttribute('value', value)
        for field in fields_back:
            FieldBackElement(self, field)


class ListWidget(InputWidget):
    type = 'list'
    STYLES = (u'multi', u'noselect', u'extensible', u'reducible', u'inline')

    def __init__(self, xmlui, options, selected=None, styles=None, name=None, parent=None):
        """

        @param xmlui
        @param options (list[option]): each option can be given as:
            - a single string if the label and the value are the same
            - a tuple with a couple of string (value,label) if the label and the value differ
        @param selected (list[string]): list of the selected values
        @param styles (iterable[string]): flags to set the behaviour of the list
            can be:
                - multi: multiple selection is allowed
                - noselect: no selection is allowed
                    useful when only the list itself is needed
                - extensible: can be extended by user (i.e. new options can be added)
                - reducible: can be reduced by user (i.e. options can be removed)
                - inline: hint that this list should be displayed on a single line (e.g. list of labels)
        @param name (string)
        @param parent
        """
        styles = set() if styles is None else set(styles)
        if styles is None:
            styles = set()
        else:
            styles = set(styles)
        if u'noselect' in styles and (u'multi' in styles or selected):
                raise exceptions.DataError(_(u'"multi" flag and "selected" option are not compatible with "noselect" flag'))
        if not options:
            # we can have no options if we get a submitted data form
            # but we can't use submitted values directly,
            # because we would not have the labels
            log.warning(_('empty "options" list'))
        super(ListWidget, self).__init__(xmlui, name, parent)
        self.addOptions(options, selected)
        self.setStyles(styles)

    def addOptions(self, options, selected=None):
        """Add options to a multi-values element (e.g. list) """
        if selected:
            if isinstance(selected, basestring):
                selected = [selected]
        else:
            selected = []
        for option in options:
            assert isinstance(option, basestring) or isinstance(option, tuple)
            value = option if isinstance(option, basestring) else option[0]
            OptionElement(self, option, value in selected)

    def setStyles(self, styles):
        if not styles.issubset(self.STYLES):
            raise exceptions.DataError(_(u"invalid styles"))
        for style in styles:
            self.elem.setAttribute(style, 'yes')
        # TODO: check flags incompatibily (noselect and multi) like in __init__

    def setStyle(self, style):
        self.setStyles([style])

    @property
    def value(self):
        """Return the value of first selected option"""
        for child in self.elem.childNodes:
            if child.tagName == u'option' and child.getAttribute(u'selected') == u'true':
                return child.getAttribute(u'value')
        return u''

class JidsListWidget(InputWidget):
    """A list of text or jids where elements can be added/removed or modified"""
    type = 'jids_list'

    def __init__(self, xmlui, jids, styles=None, name=None, parent=None):
        """

        @param xmlui
        @param jids (list[jid.JID]): base jids
        @param styles (iterable[string]): flags to set the behaviour of the list
        @param name (string)
        @param parent
        """
        super(JidsListWidget, self).__init__(xmlui, name, parent)
        styles = set() if styles is None else set(styles)
        if not styles.issubset([]): # TODO
            raise exceptions.DataError(_("invalid styles"))
        for style in styles:
            self.elem.setAttribute(style, 'yes')
        if not jids:
            log.debug('empty jids list')
        else:
            self.addJids(jids)

    def addJids(self, jids):
        for jid_ in jids:
            JidElement(self, jid_)


## Dialog Elements ##


class DialogElement(Element):
    """Main dialog element """
    type = 'dialog'

    def __init__(self, parent, type_, level=None):
        if not isinstance(parent, TopElement):
            raise exceptions.DataError(_("DialogElement must be a direct child of TopElement"))
        super(DialogElement, self).__init__(parent.xmlui, parent)
        self.elem.setAttribute(C.XMLUI_DATA_TYPE, type_)
        self.elem.setAttribute(C.XMLUI_DATA_LVL, level or C.XMLUI_DATA_LVL_DEFAULT)


class MessageElement(Element):
    """Element with the instruction message"""
    type = C.XMLUI_DATA_MESS

    def __init__(self, parent, message):
        if not isinstance(parent, DialogElement):
            raise exceptions.DataError(_("MessageElement must be a direct child of DialogElement"))
        super(MessageElement, self).__init__(parent.xmlui, parent)
        message_txt = self.xmlui.doc.createTextNode(message)
        self.elem.appendChild(message_txt)


class ButtonsElement(Element):
    """Buttons element which indicate which set to use"""
    type = 'buttons'

    def __init__(self, parent, set_):
        if not isinstance(parent, DialogElement):
            raise exceptions.DataError(_("ButtonsElement must be a direct child of DialogElement"))
        super(ButtonsElement, self).__init__(parent.xmlui, parent)
        self.elem.setAttribute('set', set_)


class FileElement(Element):
    """File element used for FileDialog"""
    type = 'file'

    def __init__(self, parent, type_):
        if not isinstance(parent, DialogElement):
            raise exceptions.DataError(_("FileElement must be a direct child of DialogElement"))
        super(FileElement, self).__init__(parent.xmlui, parent)
        self.elem.setAttribute('type', type_)


## XMLUI main class


class XMLUI(object):
    """This class is used to create a user interface (form/window/parameters/etc) using SàT XML"""

    def __init__(self, panel_type="window", container="vertical", dialog_opt=None, title=None, submit_id=None, session_id=None):
        """Init SàT XML Panel

        @param panel_type: one of
            - C.XMLUI_WINDOW (new window)
            - C.XMLUI_POPUP
            - C.XMLUI_FORM (form, depend of the frontend, usually a panel with cancel/submit buttons)
            - C.XMLUI_PARAM (parameters, presentation depend of the frontend)
            - C.XMLUI_DIALOG (one common dialog, presentation depend of frontend)
        @param container: disposition of elements, one of:
            - vertical: elements are disposed up to bottom
            - horizontal: elements are disposed left to right
            - pairs: elements come on two aligned columns
              (usually one for a label, the next for the element)
            - label: associations of one LabelWidget or EmptyWidget with an other widget
                similar to pairs but specialized in LabelWidget, and not necessarily arranged in 2 columns
            - tabs: elemens are in categories with tabs (notebook)
        @param dialog_opt: only used if panel_type == C.XMLUI_DIALOG. Dictionnary (string/string) where key can be:
            - C.XMLUI_DATA_TYPE: type of dialog, value can be:
                - C.XMLUI_DIALOG_MESSAGE (default): an information/error message. Action of user is necessary to close the dialog. Usually the frontend display a classic popup
                - C.XMLUI_DIALOG_NOTE: like a C.XMLUI_DIALOG_MESSAGE, but action of user is not necessary to close, at frontend choice (it can be closed after a timeout). Usually the frontend display as a timed out notification
                - C.XMLUI_DIALOG_CONFIRM: dialog with 2 choices (usualy "Ok"/"Cancel").
                    returned data can contain:
                        - "answer": "true" if answer is "ok", "yes" or equivalent, "false" else
                - C.XLMUI_DIALOG_FILE: a file selection dialog
                    returned data can contain:
                        - "cancelled": "true" if dialog has been cancelled, not present or "false" else
                        - "path": path of the choosed file/dir
            - C.XMLUI_DATA_MESS: message shown in dialog
            - C.XMLUI_DATA_LVL: one of:
                - C.XMLUI_DATA_LVL_INFO (default): normal message
                - C.XMLUI_DATA_LVL_WARNING: attention of user is important
                - C.XMLUI_DATA_LVL_ERROR: something went wrong
            - C.XMLUI_DATA_BTNS_SET: one of:
                - C.XMLUI_DATA_BTNS_SET_OKCANCEL (default): classical "OK" and "Cancel" set
                - C.XMLUI_DATA_BTNS_SET_YESNO: a translated "yes" for OK, and "no" for Cancel
            - C.XMLUI_DATA_FILETYPE: only used for file dialogs, one of:
                - C.XMLUI_DATA_FILETYPE_FILE: a file path is requested
                - C.XMLUI_DATA_FILETYPE_DIR: a dir path is requested
                - C.XMLUI_DATA_FILETYPE_DEFAULT: same as C.XMLUI_DATA_FILETYPE_FILE

        @param title: title or default if None
        @param submit_id: callback id to call for panel_type we can submit (form, param, dialog)
        @param session_id: use to keep a session attached to the dialog, must be returned by frontends
        @attribute named_widgets(dict): map from name to widget
        """
        self._introspect() # FIXME: why doing that on each XMLUI ? should be done once
        if panel_type not in [C.XMLUI_WINDOW, C.XMLUI_FORM, C.XMLUI_PARAM, C.XMLUI_POPUP, C.XMLUI_DIALOG]:
            raise exceptions.DataError(_("Unknown panel type [%s]") % panel_type)
        if panel_type == C.XMLUI_FORM and submit_id is None:
            raise exceptions.DataError(_("form XMLUI need a submit_id"))
        if not isinstance(container, basestring):
            raise exceptions.DataError(_("container argument must be a string"))
        if dialog_opt is not None and panel_type != C.XMLUI_DIALOG:
            raise exceptions.DataError(_("dialog_opt can only be used with dialog panels"))
        self.type = panel_type
        impl = minidom.getDOMImplementation()

        self.doc = impl.createDocument(None, "sat_xmlui", None)
        top_element = self.doc.documentElement
        top_element.setAttribute("type", panel_type)
        if title:
            top_element.setAttribute("title", title)
        self.submit_id = submit_id
        self.session_id = session_id
        if panel_type == C.XMLUI_DIALOG:
            if dialog_opt is None:
                dialog_opt = {}
            self._createDialog(dialog_opt)
            return
        self.main_container = self._createContainer(container, TopElement(self))
        self.current_container = self.main_container
        self.named_widgets = {}

    def _introspect(self):
        """ Introspect module to find Widgets and Containers """
        self._containers = {}
        self._widgets = {}
        for obj in globals().values():
            try:
                if issubclass(obj, Widget):
                    if obj.__name__ == 'Widget':
                        continue
                    self._widgets[obj.type] = obj
                elif issubclass(obj, Container):
                    if obj.__name__ == 'Container':
                        continue
                    self._containers[obj.type] = obj
            except TypeError:
                pass

    def __del__(self):
        self.doc.unlink()

    def __getattr__(self, name):
        if name.startswith("add") and name not in ('addWidget',):  # addWidgetName(...) create an instance of WidgetName
            if self.type == C.XMLUI_DIALOG:
                raise exceptions.InternalError(_("addXXX can't be used with dialogs"))
            class_name = name[3:] + "Widget"
            if class_name in globals():
                cls = globals()[class_name]
                if issubclass(cls, Widget):
                    def createWidget(*args, **kwargs):
                        if "parent" not in kwargs:
                            kwargs["parent"] = self.current_container
                        if "name" not in kwargs and issubclass(cls, InputWidget):  # name can be given as first argument or in keyword arguments for InputWidgets
                            args = list(args)
                            kwargs["name"] = args.pop(0)
                        return cls(self, *args, **kwargs)
                    return createWidget
        return object.__getattribute__(self, name)

    @property
    def submit_id(self):
        top_element = self.doc.documentElement
        if not top_element.hasAttribute("submit"):
            # getAttribute never return None (it return empty string it attribute doesn't exists)
            # so we have to manage None here
            return None
        value = top_element.getAttribute("submit")
        return value

    @submit_id.setter
    def submit_id(self, value):
        top_element = self.doc.documentElement
        if value is None:
            try:
                top_element.removeAttribute("submit")
            except NotFoundErr:
                pass
        else:  # submit_id can be the empty string to bypass form restriction
            top_element.setAttribute("submit", value)

    @property
    def session_id(self):
        top_element = self.doc.documentElement
        value = top_element.getAttribute("session_id")
        return value or None

    @session_id.setter
    def session_id(self, value):
        top_element = self.doc.documentElement
        if value is None:
            try:
                top_element.removeAttribute("session_id")
            except NotFoundErr:
                pass
        elif value:
            top_element.setAttribute("session_id", value)
        else:
            raise exceptions.DataError("session_id can't be empty")

    def _createDialog(self, dialog_opt):
        dialog_type = dialog_opt.setdefault(C.XMLUI_DATA_TYPE, C.XMLUI_DIALOG_MESSAGE)
        if dialog_type in [C.XMLUI_DIALOG_CONFIRM, C.XMLUI_DIALOG_FILE] and self.submit_id is None:
            raise exceptions.InternalError(_("Submit ID must be filled for this kind of dialog"))
        top_element = TopElement(self)
        level = dialog_opt.get(C.XMLUI_DATA_LVL)
        dialog_elt = DialogElement(top_element, dialog_type, level)

        try:
            MessageElement(dialog_elt, dialog_opt[C.XMLUI_DATA_MESS])
        except KeyError:
            pass

        try:
            ButtonsElement(dialog_elt, dialog_opt[C.XMLUI_DATA_BTNS_SET])
        except KeyError:
            pass

        try:
            FileElement(dialog_elt, dialog_opt[C.XMLUI_DATA_FILETYPE])
        except KeyError:
            pass

    def _createContainer(self, container, parent=None, **kwargs):
        """Create a container element

        @param type: container type (cf init doc)
        @parent: parent element or None
        """
        if container not in self._containers:
            raise exceptions.DataError(_("Unknown container type [%s]") % container)
        cls = self._containers[container]
        new_container = cls(self, parent=parent, **kwargs)
        return new_container

    def changeContainer(self, container, **kwargs):
        """Change the current container

        @param container: either container type (container it then created),
                          or an Container instance"""
        if isinstance(container, basestring):
            self.current_container = self._createContainer(container, self.current_container.getParentContainer() or self.main_container, **kwargs)
        else:
            self.current_container = self.main_container if container is None else container
        assert isinstance(self.current_container, Container)
        return self.current_container

    def addWidget(self, type_, *args, **kwargs):
        """Convenience method to add an element"""
        if type_ not in self._widgets:
            raise exceptions.DataError(_("Invalid type [%s]") % type_)
        if "parent" not in kwargs:
            kwargs["parent"] = self.current_container
        cls = self._widgets[type_]
        return cls(self, *args, **kwargs)

    def toXml(self):
        """return the XML representation of the panel"""
        return self.doc.toxml()


# Some sugar for XMLUI dialogs

def note(message, title='', level=C.XMLUI_DATA_LVL_INFO):
    """sugar to easily create a Note Dialog

    @param message(unicode): body of the note
    @param title(unicode): title of the note
    @param level(unicode): one of C.XMLUI_DATA_LVL_*
    @return(XMLUI): instance of XMLUI
    """
    note_xmlui = XMLUI(C.XMLUI_DIALOG, dialog_opt={
                       C.XMLUI_DATA_TYPE: C.XMLUI_DIALOG_NOTE,
                       C.XMLUI_DATA_MESS: message,
                       C.XMLUI_DATA_LVL: level},
                       title=title
                       )
    return note_xmlui


def quickNote(host, client, message, title='', level=C.XMLUI_DATA_LVL_INFO):
    """more sugar to do the whole note process"""
    note_ui = note(message, title, level)
    host.actionNew({'xmlui': note_ui.toXml()}, profile=client.profile)


def deferredUI(host, xmlui, chained=False):
    """create a deferred linked to XMLUI

    @param xmlui(XMLUI): instance of the XMLUI
        Must be an XMLUI that you can submit, with submit_id set to ''
    @param chained(bool): True if the Deferred result must be returned to the frontend
        useful when backend is in a series of dialogs with an ui
    @return (D(data)): a deferred which fire the data
    """
    assert xmlui.submit_id == ''
    xmlui_d = defer.Deferred()

    def onSubmit(data, profile):
        xmlui_d.callback(data)
        return xmlui_d if chained else {}

    xmlui.submit_id = host.registerCallback(onSubmit, with_data=True, one_shot=True)
    return xmlui_d

def deferXMLUI(host, xmlui, action_extra=None, security_limit=C.NO_SECURITY_LIMIT, chained=False, profile=C.PROF_KEY_NONE):
    """Create a deferred linked to XMLUI

    @param xmlui(XMLUI): instance of the XMLUI
        Must be an XMLUI that you can submit, with submit_id set to ''
    @param profile: %(doc_profile)s
    @param action_extra(None, dict): extra action to merge with xmlui
        mainly used to add meta informations (see actionNew doc)
    @param security_limit: %(doc_security_limit)s
    @param chained(bool): True if the Deferred result must be returned to the frontend
        useful when backend is in a series of dialogs with an ui
    @return (data): a deferred which fire the data
    """
    xmlui_d = deferredUI(host, xmlui, chained)
    action_data = {'xmlui': xmlui.toXml()}
    if action_extra is not None:
        action_data.update(action_extra)
    host.actionNew(action_data, security_limit=security_limit, keep_id=xmlui.submit_id, profile=profile)
    return xmlui_d

def deferDialog(host, message, title=u'Please confirm', type_=C.XMLUI_DIALOG_CONFIRM, options=None,
        action_extra=None, security_limit=C.NO_SECURITY_LIMIT, chained=False, profile=C.PROF_KEY_NONE):
    """Create a submitable dialog and manage it with a deferred

    @param message(unicode): message to display
    @param title(unicode): title of the dialog
    @param type(unicode): dialog type (C.XMLUI_DIALOG_*)
    @param options(None, dict): if not None, will be used to update (extend) dialog_opt arguments of XMLUI
    @param action_extra(None, dict): extra action to merge with xmlui
        mainly used to add meta informations (see actionNew doc)
    @param security_limit: %(doc_security_limit)s
    @param chained(bool): True if the Deferred result must be returned to the frontend
        useful when backend is in a series of dialogs with an ui
    @param profile: %(doc_profile)s
    @return (dict): Deferred dict
    """
    assert profile is not None
    dialog_opt = {'type': type_, 'message': message}
    if options is not None:
        dialog_opt.update(options)
    dialog = XMLUI(C.XMLUI_DIALOG, title=title, dialog_opt=dialog_opt, submit_id='')
    return deferXMLUI(host, dialog, action_extra, security_limit, chained, profile)

def deferConfirm(*args, **kwargs):
    """call deferDialog and return a boolean instead of the whole data dict"""
    d = deferDialog(*args, **kwargs)
    d.addCallback(lambda data: C.bool(data['answer']))
    return d

# Misc other funtions

class ElementParser(object):
    """callable class to parse XML string into Element"""
    # XXX: Found at http://stackoverflow.com/questions/2093400/how-to-create-twisted-words-xish-domish-element-entirely-from-raw-xml/2095942#2095942

    def _escapeHTML(self, matchobj):
        entity = matchobj.group(1)
        if entity in XML_ENTITIES:
            # we don't escape XML entities
            return matchobj.group(0)
        else:
            try:
                return unichr(htmlentitydefs.name2codepoint[entity])
            except KeyError:
                log.warning(u"removing unknown entity {}".format(entity))
                return u''

    def __call__(self, raw_xml, force_spaces=False, namespace=None):
        """
        @param raw_xml(unicode): the raw XML
        @param force_spaces (bool): if True, replace occurrences of '\n' and '\t' with ' '.
        @param namespace(unicode, None): if set, use this namespace for the wrapping element
        """
        # we need to wrap element in case
        # there is not a unique one on the top
        if namespace is not None:
            raw_xml = u"<div xmlns='{}'>{}</div>".format(namespace, raw_xml)
        else:
            raw_xml = u"<div>{}</div>".format(raw_xml)

        # avoid ParserError on HTML escaped chars
        raw_xml = html_entity_re.sub(self._escapeHTML, raw_xml)

        self.result = None

        def onStart(elem):
            self.result = elem

        def onEnd():
            pass

        def onElement(elem):
            self.result.addChild(elem)

        parser = domish.elementStream()
        parser.DocumentStartEvent = onStart
        parser.ElementEvent = onElement
        parser.DocumentEndEvent = onEnd
        tmp = domish.Element((None, "s"))
        if force_spaces:
            raw_xml = raw_xml.replace('\n', ' ').replace('\t', ' ')
        tmp.addRawXml(raw_xml)
        parser.parse(tmp.toXml().encode('utf-8'))
        top_elt = self.result.firstChildElement()
        # we now can check if there was a unique element on the top
        # and remove our wrapping <div/> is this was the case
        if len(top_elt.children) == 1 and domish.IElement.providedBy(top_elt.children[0]):
            top_elt = top_elt.firstChildElement()
        return top_elt


# FIXME: this method is duplicated from frontends.tools.xmlui.getText
def getText(node):
    """Get child text nodes of a domish.Element.

    @param node (domish.Element)
    @return: joined unicode text of all nodes
    """
    data = []
    for child in node.childNodes:
        if child.nodeType == child.TEXT_NODE:
            data.append(child.wholeText)
    return u"".join(data)

def findAll(elt, namespaces=None, names=None, ):
    """Find child element at any depth matching criteria

    @param elt(domish.Element): top parent of the elements to find
    @param names(iterable[unicode], basestring, None): names to match
        None to accept every names
    @param namespace(iterable[unicode], basestring, None): URIs to match
        None to accept every namespaces
    @return ((G)domish.Element): found elements
    """
    if isinstance(namespaces, basestring):
        namespaces=tuple((namespaces,))
    if isinstance(names, basestring):
        names=tuple((names,))

    for child in elt.elements():
        if (domish.IElement.providedBy(child) and
            (not names or child.name in names) and
            (not namespaces or child.uri in namespaces)):
            yield child
        for found in findAll(child, namespaces, names):
            yield found