'''
Event-driven, almost-SAXish, grove builder.


'''

from xml.dom.core import *
import string

_LEGAL_DOCUMENT_CHILDREN = (ELEMENT_NODE, PROCESSING_INSTRUCTION_NODE,
			    COMMENT_NODE)


class Builder:

	def __init__(self):
		self.document = createDocument()
		self.current_element = None


	def push(self, node):
		"Add node to current node and move to new node."

		nodetype = node.get_nodeType()

		if self.current_element:
			self.current_element.insertBefore(node, None)
		elif nodetype in _LEGAL_DOCUMENT_CHILDREN:
			if nodetype == TEXT_NODE:
				if string.strip(node.get_nodeValue()) != "":
					self.document.appendChild(node)
			else:
				self.document.appendChild(node)

		if nodetype == ELEMENT_NODE:
			self.current_element = node

	def pop(self):
		"Move to current node's parent."

		self.current_element = self.current_element.get_parentNode()
		

	def startElement(self, name, attrs = {}):
		if hasattr(self, 'start_' + name):
			getattr(self, 'start_' + name)(elm)
		else:
			element = self.document.createElement(name)
			for key, value in attrs.items():
				element.setAttribute(key, value)
			self.push(element)
	
	def endElement(self, name):
		assert name == self.current_element.get_nodeName()
		self.pop()


	def processingInstruction(self, target, data):
		node = self.document.createProcessingInstruction(target, data)
		self.push(node)


	def text(self, s):
		if self.current_element:
			text_node = self.document.createTextNode(s)
			if (self.current_element == self.document and
			    string.strip(s) == ""):
				return

			self.current_element.insertBefore(text_node, None)