#!/usr/bin/env python

from lxml import etree
import re

NSMAP = {'atom':	'http://www.w3.org/2005/Atom',
	'atom03':	'http://purl.org/atom/ns#',
	'media':	'http://search.yahoo.com/mrss/',
	'rdf':		'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
	'slash':	'http://purl.org/rss/1.0/modules/slash/',
	'dc':		'http://purl.org/dc/elements/1.1/',
	'content':	'http://purl.org/rss/1.0/modules/content/',
	'rssfake':	'http://purl.org/rss/1.0/'}

def load(url):
	import urllib2
	d = urllib2.urlopen(url).read()
	return parse(d)

def tagNS(tag, nsmap=NSMAP):
	match = re.search(r'^\{([^\}]+)\}(.*)$', tag)
	if match:
		match = match.groups()
		for (key, url) in nsmap.iteritems():
			if url == match[0]:
				return "%s:%s" % (key, match[1].lower())
	else:
		match = re.search(r'^([^:]+):([^:]+)$', tag)
		if match:
			match = match.groups()
			if match[0] in nsmap:
				return "{%s}%s" % (nsmap[match[0]], match[1].lower())
	return tag

def innerHTML(xml):
	return (xml.text or '') + ''.join([etree.tostring(child) for child in xml.iterchildren()])

def cleanNode(xml):
	[xml.remove(child) for child in xml.iterchildren()]

class FeedException(Exception):
	pass

def parse(data):
	doc = etree.fromstring(data)
	match = doc.xpath("//atom03:feed|//atom:feed|//channel|//rdf:rdf|//rdf:RDF", namespaces=NSMAP)
	if len(match):
		mtable = {	'rdf:rdf': FeedParserRSS, 'channel': FeedParserRSS,
					'atom03:feed': FeedParserAtom, 'atom:feed': FeedParserAtom }
		match = match[0]
		tag = tagNS(match.tag)
		if tag in mtable:
			return mtable[tag](doc, tag)

	raise FeedException('unknow feed type')

class FeedBase(object):
	"""
	Base for xml-related classes, which provides simple wrappers around xpath
	selection and item creation
	"""
	def xpath(self, path):
		""" Test xpath rule on xml tree """
		return self.root.xpath(path, namespaces=NSMAP)

	def xget(self, path):
		""" Returns the 1st xpath match """
		match = self.xpath(path)
		if len(match):
			return match[0]
		else:
			return None

	def xval(self, path):
		""" Returns the .text of the 1st match """
		match = self.xget(path)
		if match is not None:
			return match.text
		else:
			return ""

	def xgetCreate(self, table):
		""" Returns an element, and creates it when not present """
		tag = table[self.tag]
		match = self.xget(tag)
		if match is not None:
			return match
		else:
			element = etree.Element(tagNS(tag))
			self.root.append(element)
			return element

	def tostring(self, **k):
		""" Returns string using lxml. Arguments passed to tostring """
		return etree.tostring(self.xml, pretty_print=True, **k)

class FeedDescriptor(object):
	"""
	Descriptor which gives off elements based on "self.getName" and
	"self.setName" as getter/setters. Looks far better, and avoids duplicates
	"""
	def __init__(self, name):
		self.name = name

	def __get__(self, instance, owner):
		getter = getattr(instance, 'get%s' % self.name.title())
		return getter()

	def __set__(self, instance, value):
		setter = getattr(instance, 'set%s' % self.name.title())
		return setter(value)

class FeedList(object):
	"""
	Class to map a list of xml elements against a list of matching objects,
	while avoiding to recreate the same matching object over and over again. So
	as to avoid extra confusion, list's elements are called "children" here, so
	as not to use "items", which is already in use in RSS/Atom related code.

	Comes with its very own descriptor.
	"""
	def __init__(self, getter, tag, childClass):
		self.getter = getter
		self.childClass = childClass
		self.tag = tag
		self._children = {} # id(xml) => FeedItem

	def getChildren(self):
		children = self.getter()
		out = []
		for child in children:
			if id(child) in self._children:
				out.append(self._children[id(child)])
			else:
				new = self.childClass(child, self.tag)
				self._children[id(child)] = new
				out.append(new)
		return out

	def __getitem__(self, key):
		return self.getChildren()[key]

	def __delitem__(self, key):
		child = self.getter()[key]
		if id(child) in self._children:
			self._children[id(child)].remove()
			del self._children[id(child)]
		else:
			child.getparent().remove(child)

	def __len__(self):
		return len(self.getter())

class FeedListDescriptor(object):
	"""
	Descriptor for FeedList
	"""
	def __init__(self, name):
		self.name = name
		self.items = {} # id(instance) => FeedList

	def __get__(self, instance, owner):
		key = id(instance)
		if key in self.items:
			return self.items[key]
		else:
			getter = getattr(instance, 'get%s' % self.name.title())
			self.items[key] = FeedList(getter, instance.tag, eval(instance.itemClass))
			return self.items[key]

class FeedParser(FeedBase):
	itemClass = 'FeedItem'
	mimetype = 'application/xml'

	def __init__(self, xml, tag):
		self.xml = xml
		self.root = self.xml.xpath("//atom03:feed|//atom:feed|//channel|//rssfake:channel", namespaces=NSMAP)[0]
		self.tag = tag

	def getTitle(self):
		return ""

	def setTitle(self, value):
		pass


	def getDesc(self):
		pass

	def setDesc(self, value):
		pass


	def getItems(self):
		return []

	def setItems(self, value):
		pass

	title = FeedDescriptor('title')
	description = desc = FeedDescriptor('desc')
	items = FeedListDescriptor('items')

class FeedParserRSS(FeedParser):
	"""
	RSS Parser
	"""
	itemClass = 'FeedItemRSS'
	mimetype = 'application/rss+xml'

	def getTitle(self):
		return self.xval('rssfake:title|title')

	def setTitle(self, value):
		table = {	'rdf:rdf':	'rssfake:title',
					'channel':	'title'}
		element = self.xgetCreate(table)
		element.text = value


	def getDesc(self):
		return self.xval('rssfake:description|description')

	def setDesc(self, value):
		table = {	'rdf:rdf':	'rssfake:description',
					'channel':	'description'}
		element = self.xgetCreate(table)
		element.text = value


	def getItems(self):
		return self.xpath('rssfake:item|item')

class FeedParserAtom(FeedParser):
	"""
	Atom Parser
	"""
	itemClass = 'FeedItemAtom'
	mimetype = 'application/atom+xml'

	def getTitle(self):
		return self.xval('atom:title|atom03:title')

	def setTitle(self, value):
		table = {	'atom:feed':	'atom:title',
					'atom03:feed':	'atom03:title'}
		element = self.xgetCreate(table)
		element.text = value


	def getDesc(self):
		return self.xval('atom:subtitle|atom03:subtitle')

	def setDesc(self, value):
		table = {	'atom:feed':	'atom:subtitle',
					'atom03:feed':	'atom03:subtitle'}
		element = self.xgetCreate(table)
		element.text = value


	def getItems(self):
		return self.xpath('atom:entry|atom03:entry')

class FeedItem(FeedBase):
	def __init__(self, xml, tag):
		self.root = self.xml = xml
		self.tag = tag

	def getTitle(self):
		return ""

	def setTitle(self):
		pass


	def getDesc(self):
		return ""

	def setDesc(self, value):
		pass


	def getContent(self):
		return ""

	def setContent(self, value):
		pass


	title = FeedDescriptor('title')
	link = FeedDescriptor('link')
	description = desc = FeedDescriptor('desc')
	content = FeedDescriptor('content')

	def remove(self):
		self.xml.getparent().remove(self.xml)

class FeedItemRSS(FeedItem):
	def getTitle(self):
		return self.xval('rssfake:title|title')

	def setTitle(self, value):
		table = {	'rdf:rdf':	'rssfake:title',
					'channel':	'title'}
		element = self.xgetCreate(table)
		element.text = value


	def getLink(self):
		return self.xval('rssfake:link|link')

	def setLink(self, value):
		table = {	'rdf:rdf':	'rssfake:link',
					'channel':	'link'}
		element = self.xgetCreate(table)
		element.text = value


	def getDesc(self):
		return self.xval('rssfake:description|description')

	def setDesc(self, value):
		table = {	'rdf:rdf':	'rssfake:description',
					'channel':	'description'}
		element = self.xgetCreate(table)
		element.text = value


	def getContent(self):
		return self.xval('content:encoded')

	def setContent(self, value):
		table = {	'rdf:rdf':	'content:encoded',
					'channel':	'content:encoded'}
		element = self.xgetCreate(table)
		element.text = value

class FeedItemAtom(FeedItem):
	def getTitle(self):
		return self.xval('atom:title|atom03:title')

	def setTitle(self, value):
		table = {	'atom:feed':	'atom:title',
					'atom03:feed':	'atom03:title'}
		element = self.xgetCreate(table)
		element.text = value


	def getLink(self):
		return self.xget('atom:link|atom03:link').get('href', '')

	def setLink(self, value):
		table = {	'atom:feed':	'atom:link',
					'atom03:feed':	'atom03:link'}
		element = self.xgetCreate(table)
		element.attrib['href'] = value


	def getDesc(self):
		# default "type" is "text"
		element = self.xget('atom:summary|atom03:summary')
		if element is not None:
			return innerHTML(element)
		else:
			return ""

	def setDesc(self, value):
		table = {	'atom:feed':	'atom:summary',
					'atom03:feed':	'atom03:summary'}
		element = self.xgetCreate(table)
		if element.attrib.get('type', '') == 'xhtml':
			cleanNode(element)
		element.attrib['type'] = 'html'
		element.text = value


	def getContent(self):
		element = self.xget('atom:content|atom03:content')
		if element is not None:
			return innerHTML(element)
		else:
			return ""

	def setContent(self, value):
		table = {	'atom:feed':	'atom:content',
					'atom03:feed':	'atom03:content'}
		element = self.xgetCreate(table)
		if element.attrib.get('type', '') == 'xhtml':
			cleanNode(element)
		element.attrib['type'] = 'html'
		element.text = value