Cheetah-style comments

"""
Custom template loader, enables Cheetah-like comments, saves the pain
of {%comment%} .. {%endcomment%}

This is a template loader, see http://www.djangoproject.com/documentation/templates_python/#loading-templates

Suppose you saved this in :
    myproject/utils/loaders.py

In settings.py, you should enable it, by adding it at the top of TEMPLATE_LOADERS, like :
    TEMPLATE_LOADERS = (
        'myproject.utils.loaders.load_template_source',
        'django.template.loaders.filesystem.load_template_source',
        ...
"""
import os

from django.conf import settings
from django.template import TemplateDoesNotExist
from django.template.loaders.filesystem import get_template_sources


#################################
def _handle_cheetah_comments(filepath):
    """
    Returns a string with cheetah-style comments stripped.
    This takes care of :
    1) ## blah blah
    2) #*
       blah blah
       *#
    3) display this ## not this
    
    Please note that the whole lines starting with #* or *# are removed.
    This code doesn't handle :
    1) *# display this
    """
    output = []
    multiline_comment = False
    for line in open(filepath):
        sline = line.strip()
        if sline.startswith("##"):
            continue
        elif sline.startswith("#*"):
            multiline_comment = True
            continue
        elif sline.startswith("*#"):
            multiline_comment = False
            continue
        else:
            if multiline_comment:
                continue
            else:
                output.append(line.split("##")[0])
    # Multiline comments should be closed at the end of the template
    if multiline_comment:
        raise Exception, "Multiline comment (#* .. *# syntax) not closed in %s" % filepath
    return "\n".join(output)



############################################################
def load_template_source(template_name, template_dirs=None):
    """
    Enables Cheetah-style comments.
    Almost like http://code.djangoproject.com/browser/django/trunk/django/template/loaders/filesystem.py
    """
    tried = []
    for filepath in get_template_sources(template_name, template_dirs):
        try:
            # return (open(filepath).read().decode(settings.FILE_CHARSET), filepath)
            input = _handle_cheetah_comments(filepath).decode(settings.FILE_CHARSET)
            return (input, filepath)
        except IOError:
            tried.append(filepath)
    if tried:
        error_msg = "Tried %s" % tried
    else:
        error_msg = "Your TEMPLATE_DIRS setting is empty. Change it to point to at least one template directory."
    raise TemplateDoesNotExist, error_msg

load_template_source.is_usable = True