# -*- coding: utf-8 -*-
"""
Transfomer: handles the Dublin Core recommendation for XHTML for adding DC values. What this means is that:

 - DC namespaces are defined via C{<link rel="schema.XX" value="...."/>}
 - The 'XX.term' is used much like QNames in C{<link>} and C{<meta>} elements. For the latter, the namespaced names are added to a C{@property} attribute.

This transformer adds "real" namespaces and changes the DC references in link and meta elements to abide to the
RDFa namespace syntax.

@summary: Dublin Core transformer
@requires: U{RDFLib package<http://rdflib.net>}
@organization: U{World Wide Web Consortium<http://www.w3.org>}
@author: U{Ivan Herman<a href="http://www.w3.org/People/Ivan/">}
@license: This software is available for use under the
U{W3C® SOFTWARE NOTICE AND LICENSE<href="http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231">}
@contact: Ivan Herman, ivan@w3.org
"""

"""
@version: $Id: DublinCore.py,v 1.4 2012-01-18 14:16:44 ivan Exp $
$Date: 2012-01-18 14:16:44 $
"""

def DC_transform(html, options, state):
    """
    @param html: a DOM node for the top level html element
    @param options: invocation options
    @type options: L{Options<pyRdfa.options>}
    @param state: top level execution state
    @type state: L{State<pyRdfa.state>}
    """
    from ..host import HostLanguage
    if not( options.host_language in [ HostLanguage.xhtml, HostLanguage.html5, HostLanguage.xhtml5 ] ):
        return
    
    # the head element is necessary; to be sure, the namespaces are set
    # on that level only
    head = None
    try:
        head = html.getElementsByTagName("head")[0]
    except:
        # no head....
        return

    # At first, the DC namespaces must be found
    dcprefixes = {}
    for link in html.getElementsByTagName("link"):
        if link.hasAttribute("rel"):
            rel = link.getAttribute("rel")
            uri = link.getAttribute("href")
            if uri != None and rel != None and rel.startswith("schema."):
                # bingo...
                try:
                    localname = rel.split(".")[1]
                    head.setAttributeNS("", "xmlns:"+localname,uri)
                    dcprefixes[localname] = uri
                except:
                    # problem with the split; just ignore
                    pass

    # get the link elements now to find the dc elements
    for link in html.getElementsByTagName("link"):
        if link.hasAttribute("rel"):
            newProp = ""
            for rel in link.getAttribute("rel").strip().split():
                # see if there is '.' to separate the attributes
                if rel.find(".") != -1:
                    key   = rel.split(".",1)[0]
                    lname = rel.split(".",1)[1]
                    if key in dcprefixes and lname != "":
                        # yep, this is one of those...
                        newProp += " " + key + ":" + lname
                    else:
                        newProp += " " + rel
                else:
                    newProp += " " + rel
            link.setAttribute("rel",newProp.strip())

    # do almost the same with the meta elements...
    for meta in html.getElementsByTagName("meta"):
        if meta.hasAttribute("name"):
            newProp = ""
            for name in meta.getAttribute("name").strip().split():
                # see if there is '.' to separate the attributes
                if name.find(".") != -1:
                    key   = name.split(".",1)[0]
                    lname = name.split(".",1)[1]
                    if key in dcprefixes and lname != "":
                        # yep, this is one of those...
                        newProp += " " + key + ":" + lname
                    else:
                        newProp += " " + name
                else:
                    newProp += " " + name
            meta.setAttribute("property", newProp.strip())