cwm_xml.py

"""XML built-ins for cwm
"""

from diag import progress, verbosity
from term import LightBuiltIn, Function, ReverseFunction, MultipleFunction, \
     HeavyBuiltIn

from llyn import loadToStore # for caching in store's experience
from sax2rdf import XMLtoDOM # for fn:doc

#from Ft.Xml.XPath import Evaluate as evalXPath
# http://packages.debian.org/unstable/python/python-xml
# see also for a review:
# http://www.oreillynet.com/onlamp/blog/2005/01/code_respecting_xpath_xml_pyth.html
##
## The following code allows for the lazy importing of the
## evalXPath function. It is a hack
def evalXPath(*args, **keywords):
    try:
        from xml.xpath import Evaluate as localEvalXPath 
    except ImportError:
        progress("Try getting python-xml from http://downloads.sourceforge.net/pyxml/PyXML-0.8.4.tar.gz")
        localEvalXPath = progress
    globals()['evalXPath'] = localEvalXPath
    return localEvalXPath(*args, **keywords)


XMLBI_NS_URI = "http://www.w3.org/2007/ont/xml#"


__version__ = "0.1"


# Node properties
# see http://www.python.org/doc/current/lib/dom-node-objects.html


class BI_nodeType(LightBuiltIn, Function):
    """An integer representing the node type
    """
    def evaluateObject(self, subj_py):
        return subj_py.nodeType

class BI_parentNode(LightBuiltIn, Function):
    """The parent of the current node, or None for the document node.
     The value is always a Node object or None. For Element nodes,
      this will be the parent element, except for the root element,
     in which case it will be the Document object. For Attr nodes, this is always None.
    """
    def evaluateObject(self, subj_py):
        return subj_py.parentNode

class BI_attributes(LightBuiltIn, Function):
    """A NamedNodeMap of attribute objects. Only elements have
     actual values for this.
    """
    def evaluateObject(self, subj_py):
        return subj_py.attributes

class BI_previousSibling(LightBuiltIn, Function):
    """The node that immediately precedes this one with the same parent.
    For instance the element with an end-tag that comes just before the
     self element's start-tag. Of course, XML documents are made up of
      more than just elements so the previous sibling could be text, 
    a comment, or something else.
     If this node is the first child of the parent, this property will not exist.
    """
    def evaluateObject(self, subj_py):
        return subj_py.previousSibling

class BI_nextSibling(LightBuiltIn, Function):
    """The node that immediately follows this one with the same parent. See also previousSibling.
    If this is the last child of the parent, this property will not exist.
    """
    def evaluateObject(self, subj_py):
        return subj_py.nextSibling

class BI_childNodes(LightBuiltIn, Function):
    """A list of nodes contained within this node.
    """
    def evaluateObject(self, subj_py):
        return subj_py.childNodes

class BI_firstChild(LightBuiltIn, Function):
    """The first child of the node, if there are any.
    """
    def evaluateObject(self, subj_py):
        return subj_py.firstChild

class BI_lastChild(LightBuiltIn, Function):
    """The last child of the node, if there are any.
    """
    def evaluateObject(self, subj_py):
        return subj_py.lastChild

class BI_localName(LightBuiltIn, Function):
    """The part of the tagName following the colon if there is one, else the entire tagName
    """
    def evaluateObject(self, subj_py):
        return subj_py.localName

class BI_prefix(LightBuiltIn, Function):
    """The part of the tagName preceding the colon if there is one, else the empty string
    """
    def evaluateObject(self, subj_py):
        return subj_py.prefix

class BI_namespaceURI(LightBuiltIn, Function):
    """The namespace associated with the element name.
    """
    def evaluateObject(self, subj_py):
        return subj_py.namespaceURI

class BI_nodeName(LightBuiltIn, Function):
    """This has a different meaning for each node type; see the DOM 
    specification for details. You can always get the information you would
     get here from another
     property such as the tagName property for elements or 
     the name property for attributes.
    """
    def evaluateObject(self, subj_py):
        return subj_py.nodeName

class BI_nodeValue(LightBuiltIn, Function):
    """This has a different meaning for each node type;
     see the DOM specification for details. 
     The situation is similar to that with nodeName
    """
    def evaluateObject(self, subj_py):
        return subj_py.nodeValue

class BI_hasAttributes(LightBuiltIn, Function):
    """True if the node has any attributes.
    """
    def evaluateObject(self, subj_py):
        return subj_py.hasAttributes()

class BI_hasChildNodes(LightBuiltIn, Function):
    """True if the node has any child nodes
    """
    def evaluateObject(self, subj_py):
        return subj_py.hasChildNodes()

class BI_isSameNode(LightBuiltIn):
    """Returns true if other refers to the same node as this node.
     This is especially useful for DOM implementations which use
     any sort of proxy architecture (because more than one object can refer to the same node).
    """
    def evaluate(self, subj_py, obj_py):
        return subj_py.sSameNode(obj_py)


class BI_xpath(LightBuiltIn, MultipleFunction):
    """Evaluate XPath expression and bind to each resulting node."""
    def evaluateObject(self, subj_py):
        node, expr = subj_py
        out = evalXPath(expr, node)
        return [self.store.newXMLLiteral(n) for n in out]

class BI_doc(HeavyBuiltIn, Function):
    """Load XML document from the web. subject is a string, per XQuery.

    see test/xml-syntax/fn_doc1.n3
    
    see also llyn.BI_xmlTree, which seems to be dead code
    """
    def evalObj(self, subj, queue, bindings, proof, query):
        progress("@@fn:doc", subj)

        # fn:doc takes a string, but the llyn cache keys of symbols
        sym = subj.store.newSymbol(subj.value())

        try:
            lit = loadToStore(sym, ["application/xml", "text/xml"])
        except IOError, e:
            progress("@@ioerror", e)
            return None # hmm... is built-in API evolving to support exceptions?

        dom = XMLtoDOM(lit.value())
        # odd... why does BI_xmlTree use the pair API rather than newXMLLiteral?
        progress("@@fn:doc returning")
        return lit.store.newXMLLiteral(dom)

#  Register the string built-ins with the store
def register(store):
    str = store.symbol(XMLBI_NS_URI[:-1])
    str.internFrag("nodeType", BI_nodeType)
    str.internFrag("parentNode", BI_parentNode)
    str.internFrag("attributes", BI_attributes)
    str.internFrag("previousSibling", BI_previousSibling)
    str.internFrag("nextSibling", BI_nextSibling)
    str.internFrag("childNodes", BI_childNodes)
    str.internFrag("firstChild", BI_firstChild)
    str.internFrag("lastChild", BI_lastChild)
    str.internFrag("localName", BI_localName)
    str.internFrag("prefix", BI_prefix)
    str.internFrag("namespaceURI", BI_namespaceURI)
    str.internFrag("nodeName", BI_nodeName)
    str.internFrag("nodeValue", BI_nodeValue)
    str.internFrag("hasAttributes", BI_hasAttributes)
    str.internFrag("hasChildNodes", BI_hasChildNodes)
    str.internFrag("isSameNode", BI_isSameNode)

    str.internFrag("xpath", BI_xpath) # needs test, docs

    fn = store.symbol("http://www.w3.org/2006/xpath-functions")
    fn.internFrag("string", BI_nodeValue) # probably not an exact match
    fn.internFrag("doc", BI_doc)
# ends