Django snippets

import re

from django.conf import settings


DEFAULT_JS_TAG = '<script type="text/javascript" src="%s"></script>'
DEFAULT_CSS_TAG = '<link rel="stylesheet" type="text/css" href="%s" />'
DEFAULT_JS_DIR = 'js'
DEFAULT_CSS_DIR = 'css'

HEAD_BASE = getattr(settings, 'HEAD_INCLUDE_BASE', settings.MEDIA_URL)
PREFIX_RE = getattr(settings, 'HEAD_INCLUDE_PREFIX_RE', '<!-- *HEAD_')
SUFFIX_RE = getattr(settings, 'HEAD_INCLUDE_SUFFIX_RE', ' *-->')
TAGS = {'js': getattr(settings, 'HEAD_INCLUDE_JS_TAG', DEFAULT_JS_TAG),
		'css': getattr(settings, 'HEAD_INCLUDE_CSS_TAG', DEFAULT_CSS_TAG)}
PATHS = {'js':'js/', 'css':'css/'}

HEAD_RE = re.compile(
	r'%s(include|version|include_js|include_css|render) +([\s\S]*?)%s' % (PREFIX_RE, SUFFIX_RE))
HEAD_INIT_RE = re.compile(
	'%sinit%s' % (PREFIX_RE, SUFFIX_RE))

class HeadLoader:

	def __init__(self):
		self._components = []
		self._js_components = []
		self._css_components = []

	def add_component(self, new_component_name, component_type = ''):
		if component_type == 'js' and not new_component_name in self._js_components:
			self._js_components.append(new_component_name)
		elif component_type == 'css' and not new_component_name in self._css_components:
			self._css_components.append(new_component_name)
		elif component_type == '' and not new_component_name in self._components:
			self._components.append(new_component_name)

	def render(self):
		#self._components.reverse()
		head = ''
		head += '\n' + '\n'.join(self._render_component(component, 'css') for component in self._css_components)
		head += '\n' + '\n'.join(self._render_component(component, 'js') for component in self._js_components)
		head += '\n' + '\n'.join(self._render_component(component) for component in self._components)
		
		return head
		

	def _has_component(self, component_name):
		return component_name in self._components

	def _render_component(self, component_name, component_type = ''):
		
		if component_type == '':
			# check what sort of component this is - based on the file name either ending with .js or .css
			last_three = component_name[-3:]
			if last_three == '.js':
				component_type = 'js'
			elif last_three == 'css':
				component_type = 'css'
			else:
				# we don't know what to do with anything else!
				return '<!-- HEAD - unknown compoent type : %s -->' % component_name
			
		# check if we've got an absolute or external js or css file
		if component_name[:7] == 'http://' or component_name[:1] == '/': 
			return TAGS[component_type] % (component_name,)
		else:
			return TAGS[component_type] % (HEAD_BASE + PATHS[component_type] + component_name,)


class HeadIncludeMiddleware(object):
	def process_response(self, request, response):
		components = []
		js_components = []
		css_components = []
		extra_head = []
		node = HeadLoader()
		def collect(match):
			cmd, data = match.groups()
			if cmd == 'include':
				components.extend(data.split())
			elif cmd == 'include_js':
				js_components.extend(data.split())
			elif cmd == 'include_css':
				css_components.extend(data.split())
			elif cmd == 'render':
				extra_head.append(data)
			else:
				return '<!-- UNKNOWN COMMAND HEAD_%s -->' % cmd
			return ''
		
		content = HEAD_RE.sub(collect, response.content)
		
		for component in components:
			node.add_component(component)
		
		for component in js_components:
			node.add_component(component, 'js')
			
		for component in css_components:
			node.add_component(component, 'css')
	
			
		rendered = node.render() + '\n'.join(extra_head)
		content = HEAD_INIT_RE.sub(rendered, content, 1)
		response.content = HEAD_INIT_RE.sub(
			'<!-- WARNING: MULTIPLE HEAD_init STATEMENTS -->', content)
			
		return response