# XSLT extension elements

cdef class XSLTExtension:
    u"""Base class of an XSLT extension element.
    """
    def execute(self, context, self_node, input_node, output_parent):
        u"""execute(self, context, self_node, input_node, output_parent)
        Execute this extension element.

        Subclasses must override this method.  They may append
        elements to the `output_parent` element here, or set its text
        content.  To this end, the `input_node` provides read-only
        access to the current node in the input document, and the
        `self_node` points to the extension element in the stylesheet.

        Note that the `output_parent` parameter may be `None` if there
        is no parent element in the current context (e.g. no content
        was added to the output tree yet).
        """
        pass

    def apply_templates(self, _XSLTContext context not None, node, output_parent=None):
        u"""apply_templates(self, context, node, output_parent=None)

        Call this method to retrieve the result of applying templates
        to an element.

        The return value is a list of elements or text strings that
        were generated by the XSLT processor.

        If you pass an Element as `output_parent` parameter, the result
        will instead be appended to the element (including attributes
        etc.) and the return value will be `None`.  This is a safe way
        to generate content into the output document directly, without
        having to take care of special values like text or attributes.
        """
        cdef xmlNode* c_parent
        cdef xmlNode* c_node
        cdef xmlNode* c_context_node
        assert context._xsltCtxt is not NULL, "XSLT context not initialised"
        c_context_node = _roNodeOf(node)
        #assert c_context_node.doc is context._xsltContext.node.doc, \
        #    "switching input documents during transformation is not currently supported"

        if output_parent is not None:
            c_parent = _nonRoNodeOf(output_parent)
        else:
            c_parent = tree.xmlNewDocNode(
                context._xsltCtxt.output, NULL, "fake-parent", NULL)

        c_node = context._xsltCtxt.insert
        context._xsltCtxt.insert = c_parent
        xslt.xsltProcessOneNode(
            context._xsltCtxt, c_context_node, NULL)
        context._xsltCtxt.insert = c_node

        if output_parent is not None:
            return None

        try:
            return self._collectXSLTResultContent(context, c_parent)
        finally:
            # free all intermediate nodes that will not be freed by proxies
            tree.xmlFreeNode(c_parent)

    def process_children(self, _XSLTContext context not None, output_parent=None):
        u"""process_children(self, context, output_parent=None)

        Call this method to process the XSLT content of the extension
        element itself.

        The return value is a list of elements or text strings that
        were generated by the XSLT processor.

        If you pass an Element as `output_parent` parameter, the result
        will instead be appended to the element (including attributes
        etc.) and the return value will be `None`.  This is a safe way
        to generate content into the output document directly, without
        having to take care of special values like text or attributes.
        """
        cdef xmlNode* c_parent
        cdef xslt.xsltTransformContext* c_ctxt = context._xsltCtxt
        cdef xmlNode* c_old_output_parent = c_ctxt.insert
        assert context._xsltCtxt is not NULL, "XSLT context not initialised"

        # output_parent node is used for adding results instead of
        # elements list used in apply_templates, that's easier and allows to
        # use attributes added to extension element with <xsl:attribute>.

        if output_parent is not None:
            c_parent = _nonRoNodeOf(output_parent)
        else:
            c_parent = tree.xmlNewDocNode(
                context._xsltCtxt.output, NULL, "fake-parent", NULL)

        c_ctxt.insert = _nonRoNodeOf(output_parent)
        xslt.xsltApplyOneTemplate(c_ctxt,
            c_ctxt.node, c_ctxt.inst.children, NULL, NULL)
        c_ctxt.insert = c_old_output_parent

        if output_parent is not None:
            return None

        try:
            return self._collectXSLTResultContent(context, c_parent)
        finally:
            # free all intermediate nodes that will not be freed by proxies
            tree.xmlFreeNode(c_parent)

    cdef _collectXSLTResultContent(self, _XSLTContext context, xmlNode* c_parent):
        cdef xmlNode* c_node
        cdef xmlNode* c_next
        cdef _ReadOnlyProxy proxy
        cdef list results = [] # or maybe _collectAttributes(c_parent, 2) ?
        c_node = c_parent.children
        while c_node is not NULL:
            c_next = c_node.next
            if c_node.type == tree.XML_TEXT_NODE:
                results.append(funicode(c_node.content))
            elif c_node.type == tree.XML_ELEMENT_NODE:
                proxy = _newReadOnlyProxy(
                    context._extension_element_proxy, c_node)
                results.append(proxy)
                # unlink node and make sure it will be freed later on
                tree.xmlUnlinkNode(c_node)
                proxy.free_after_use()
            else:
                raise TypeError, \
                    u"unsupported XSLT result type: %d" % c_node.type
            c_node = c_next
        return results


cdef _registerXSLTExtensions(xslt.xsltTransformContext* c_ctxt,
                             extension_dict):
    for ns_utf, name_utf in extension_dict:
        xslt.xsltRegisterExtElement(
            c_ctxt, _cstr(name_utf), _cstr(ns_utf), _callExtensionElement)

cdef void _callExtensionElement(xslt.xsltTransformContext* c_ctxt,
                                xmlNode* c_context_node,
                                xmlNode* c_inst_node,
                                void* dummy) with gil:
    cdef _XSLTContext context
    cdef XSLTExtension extension
    cdef python.PyObject* dict_result
    cdef char* c_uri
    cdef xmlNode* c_node
    cdef _ReadOnlyProxy context_node = None, self_node = None
    cdef object output_parent # not restricted to ro-nodes
    c_uri = _getNs(c_inst_node)
    if c_uri is NULL:
        # not allowed, and should never happen
        return
    if c_ctxt.xpathCtxt.userData is NULL:
        # just for safety, should never happen
        return
    context = <_XSLTContext>c_ctxt.xpathCtxt.userData
    try:
        try:
            dict_result = python.PyDict_GetItem(
                context._extension_elements, (c_uri, c_inst_node.name))
            if dict_result is NULL:
                raise KeyError, \
                    u"extension element %s not found" % funicode(c_inst_node.name)
            extension = <object>dict_result

            try:
                # build the context proxy nodes
                self_node = _newReadOnlyProxy(None, c_inst_node)
                if _isElement(c_ctxt.insert):
                    output_parent = _newAppendOnlyProxy(self_node, c_ctxt.insert)
                else:
                    # may be the document node or other stuff
                    output_parent = _newOpaqueAppendOnlyNodeWrapper(c_ctxt.insert)
                if c_context_node.type in (tree.XML_DOCUMENT_NODE,
                                           tree.XML_HTML_DOCUMENT_NODE):
                    c_node = tree.xmlDocGetRootElement(<xmlDoc*>c_context_node)
                    if c_node is not NULL:
                        context_node = _newReadOnlyProxy(self_node, c_node)
                    else:
                        context_node = None
                elif c_context_node.type in (tree.XML_ATTRIBUTE_NODE,
                                             tree.XML_TEXT_NODE,
                                             tree.XML_CDATA_SECTION_NODE):
                    # this isn't easy to support using read-only
                    # nodes, as the smart-string factory must
                    # instantiate the parent proxy somehow...
                    raise TypeError("Unsupported element type: %d" % c_context_node.type)
                else:
                    context_node  = _newReadOnlyProxy(self_node, c_context_node)

                # run the XSLT extension
                context._extension_element_proxy = self_node
                extension.execute(context, self_node, context_node, output_parent)
            finally:
                context._extension_element_proxy = None
                if self_node is not None:
                    _freeReadOnlyProxies(self_node)
        except Exception, e:
            try:
                e = unicode(e).encode(u"UTF-8")
            except:
                e = repr(e).encode(u"UTF-8")
            message = python.PyBytes_FromFormat(
                "Error executing extension element '%s': %s",
                c_inst_node.name, _cstr(e))
            xslt.xsltTransformError(c_ctxt, NULL, c_inst_node, message)
            context._exc._store_raised()
        except:
            # just in case
            message = python.PyBytes_FromFormat(
                "Error executing extension element '%s'", c_inst_node.name)
            xslt.xsltTransformError(c_ctxt, NULL, c_inst_node, message)
            context._exc._store_raised()
    except:
        # no Python functions here - everything can fail...
        xslt.xsltTransformError(c_ctxt, NULL, c_inst_node,
                                "Error during XSLT extension element evaluation")
        context._exc._store_raised()
