"""
Copyright 2008 Free Software Foundation, Inc.
This file is part of GNU Radio

GNU Radio Companion 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.

GNU Radio Companion 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, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
"""

from lxml import etree
from . import odict

class XMLSyntaxError(Exception):
    def __init__(self, error_log):
        self._error_log = error_log
    def __str__(self):
        return '\n'.join(map(str, self._error_log.filter_from_errors()))

def validate_dtd(xml_file, dtd_file=None):
    """
    Validate an xml file against its dtd.
    
    Args:
        xml_file: the xml file
        dtd_file: the optional dtd file
    @throws Exception validation fails
    """
    #perform parsing, use dtd validation if dtd file is not specified
    parser = etree.XMLParser(dtd_validation=not dtd_file)
    xml = etree.parse(xml_file, parser=parser)
    if parser.error_log: raise XMLSyntaxError(parser.error_log)
    #perform dtd validation if the dtd file is specified
    if not dtd_file: return
    dtd = etree.DTD(dtd_file)
    if not dtd.validate(xml.getroot()): raise XMLSyntaxError(dtd.error_log)

def from_file(xml_file):
    """
    Create nested data from an xml file using the from xml helper.
    
    Args:
        xml_file: the xml file path
    
    Returns:
        the nested data
    """
    xml = etree.parse(xml_file).getroot()
    return _from_file(xml)

def _from_file(xml):
    """
    Recursivly parse the xml tree into nested data format.
    
    Args:
        xml: the xml tree
    
    Returns:
        the nested data
    """
    tag = xml.tag
    if not len(xml):
        return odict({tag: xml.text or ''}) #store empty tags (text is None) as empty string
    nested_data = odict()
    for elem in xml:
        key, value = _from_file(elem).items()[0]
        if nested_data.has_key(key): nested_data[key].append(value)
        else: nested_data[key] = [value]
    #delistify if the length of values is 1
    for key, values in nested_data.iteritems():
        if len(values) == 1: nested_data[key] = values[0]

    return odict({tag: nested_data})

def to_file(nested_data, xml_file):
    """
    Write an xml file and use the to xml helper method to load it.
    
    Args:
        nested_data: the nested data
        xml_file: the xml file path
    """
    xml = _to_file(nested_data)[0]
    open(xml_file, 'w').write(etree.tostring(xml, xml_declaration=True, pretty_print=True))

def _to_file(nested_data):
    """
    Recursivly parse the nested data into xml tree format.
    
    Args:
        nested_data: the nested data
    
    Returns:
        the xml tree filled with child nodes
    """
    nodes = list()
    for key, values in nested_data.iteritems():
        #listify the values if not a list
        if not isinstance(values, (list, set, tuple)):
            values = [values]
        for value in values:
            node = etree.Element(key)
            if isinstance(value, (str, unicode)): node.text = value
            else: node.extend(_to_file(value))
            nodes.append(node)
    return nodes

if __name__ == '__main__':
    """Use the main method to test parse xml's functions."""
    pass
