#!/usr/bin/env python2
# -*- coding: utf-8 -*-
#
# Copyright 2006-2009 Zuza Software Foundation
#
# This file is part of the Translate Toolkit.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, see <http://www.gnu.org/licenses/>.

"""Helper functions for working with XML."""

import re

from lxml import etree


# some useful xpath expressions
xml_preserve_ancestors = etree.XPath("ancestor-or-self::*[attribute::xml:space='preserve']")
"""All ancestors with xml:space='preserve'"""

xml_space_ancestors = etree.XPath("ancestor-or-self::*/attribute::xml:space")
"""All xml:space attributes in the ancestors"""

string_xpath = etree.XPath("string()")
"""Return a non-normalized string in the node subtree"""

string_xpath_normalized = etree.XPath("normalize-space()")
"""Return a (space) normalized string in the node subtree"""


def getText(node, xml_space="preserve"):
    """Extracts the plain text content out of the given node.

    This method checks the xml:space attribute of the given node, and takes
    an optional default to use in case nothing is specified in this node."""
    xml_space = getXMLspace(node, xml_space)
    if xml_space == "default":
        return unicode(string_xpath_normalized(node))  # specific to lxml.etree
    else:
        return unicode(string_xpath(node))  # specific to lxml.etree

    # If we want to normalise space and only preserve it when the directive
    # xml:space="preserve" is given in node or in parents, consider this code:
    #xml_preserves = xml_preserve_ancestors(node)
    #if xml_preserves and xml_preserves[-1] == "preserve":
    #    return unicode(string_xpath(node)) # specific to lxml.etree
    #else:
    #    return unicode(string_xpath_normalized(node)) # specific to lxml.etree


XML_NS = 'http://www.w3.org/XML/1998/namespace'


def getXMLlang(node):
    """Gets the xml:lang attribute on node"""
    return node.get("{%s}lang" % XML_NS)


def setXMLlang(node, lang):
    """Sets the xml:lang attribute on node"""
    node.set("{%s}lang" % XML_NS, lang)


def getXMLspace(node, default=None):
    """Gets the xml:space attribute on node"""
    value = node.get("{%s}space" % XML_NS)
    if value is None:
        value = default
    return value


def setXMLspace(node, value):
    """Sets the xml:space attribute on node"""
    node.set("{%s}space" % XML_NS, value)


def namespaced(namespace, name):
    """Returns name in Clark notation within the given namespace.

       For example namespaced("source") in an XLIFF document might return::
           {urn:oasis:names:tc:xliff:document:1.1}source

       This is needed throughout lxml.
    """
    if namespace:
        return "{%s}%s" % (namespace, name)
    else:
        return name

MULTIWHITESPACE_PATTERN = r"[\n\r\t ]+"
MULTIWHITESPACE_RE = re.compile(MULTIWHITESPACE_PATTERN, re.MULTILINE)


def normalize_space(text):
    """Normalize the given text for implementation of
    ``xml:space="default"``."""
    text = MULTIWHITESPACE_RE.sub(u" ", text)
    return text


def normalize_xml_space(node, xml_space, remove_start=False):
    """normalize spaces following the nodes xml:space, or alternatively the
    given xml_space parameter."""
    xml_space = getXMLspace(node) or xml_space
    if xml_space == 'preserve':
        return
    if node.text:
        node.text = normalize_space(node.text)
        if remove_start and node.text[0] == u" ":
            node.text = node.text.lstrip()
            remove_start = False
        if len(node.text) > 0 and node.text.endswith(u" "):
            remove_start = True
        if len(node) == 0:
            node.text = node.text.rstrip()
    if node.tail:
        node.tail = normalize_space(node.tail)

    for child in node:
        normalize_xml_space(child, remove_start)
