import re

RE_XML_ENCODING = re.compile("encoding[ \t]*=[ \t]*\"([^\"]+)\"")
RE_XML_POSITION = re.compile("(\w+)\[(\d+)\]")

def getXMLEncoding(data):
    head = data[:100]
    headline = head.splitlines()[0]
    mo = RE_XML_ENCODING.search(headline)
    return mo.group(1) if mo else None

def decodeXML(data):
    head = data[:100]
    headline = head.splitlines()[0]
    mo = RE_XML_ENCODING.search(headline)
    if mo:
        encoding = mo.group(1)
        return data[len(headline):].decode(encoding)
    else:
        return data

def xml_dom_Document_getElementByPath(doc, path):
    positions = path.split("/")[1:] if path[0] == "/" else path.split("/")
    for index, position in enumerate(positions):
        mo = RE_XML_POSITION.search(position)
        name = mo.group(1)
        index = int(mo.group(2))-1
        docs = doc.getElementsByTagName(name)
        if docs:
            doc = docs[index]
        else:
            raise IndexError, "UNKNOWN_POSITION: %s" % ".".join(positions[:index])
    return doc

def xml_dom_Document_newNode(doc, tagName, attrs):
    newNode = doc.createElement(tagName)

    if type(attrs) is list:
        for key, value in attrs:
            newNode.setAttribute(key, value)
    else:
        key, value = attrs
        newNode.setAttribute(key, value)

    return newNode

def xml_dom_Document_appendElement(doc, path, tagName, attrs):
    targetNode = xml_dom_Document_getElementByPath(doc, path) if path else doc
    targetNode.appendChild(xml_dom_Document_newNode(doc, tagName, attrs))

def xml_dom_Document_removeElement(doc, path):
    targetNode = xml_dom_Document_getElementByPath(doc, path)
    targetNode.parentNode.removeChild(targetNode)

def xml_dom_Document_getElementByAttr(doc, path, tagName, attr):
    key, value = attr
    targetNode = xml_dom_Document_getElementByPath(doc,  path) if path else doc
    for childNode in targetNode.getElementsByTagName(tagName):
        if childNode.getAttribute(key) == value:
            return childNode

def xml_dom_Document_removeElementByAttr(doc, path, tagName, attr):
    delNode = xml_dom_Document_getElementByAttr(doc, path, tagName, attr)
    if delNode:
        delNode.parentNode.removeChild(delNode)

def xml_dom_Document_setElementAttr(doc, path, key, value):
    targetNode = xml_dom_Document_getElementByPath(doc, path) if path else None
    targetNode.setAttribute(key, value)

def xml_dom_Document_replaceElementByAttr(doc, path, tagName, key, oldValue, newValue=None):
    newValue = newValue if newValue else oldValue

    targetNode = xml_dom_Document_getElementByPath(doc,  path) if path else doc
    for childNode in targetNode.getElementsByTagName(tagName):
        curValue = childNode.getAttribute(key)
        if curValue == oldValue:
            childNode.setAttribute(key, newValue)
            return childNode
        elif curValue == newValue:
            return childNode
    else:
        newNode = xml_dom_Document_newNode(doc, tagName, [(key, newValue)])
        targetNode.appendChild(newNode)
        return newNode