# $Id$
# simple django-style templating.
#
# see: http://effbot.org/zone/django-simple-template.htm

import re
import cgi, string

TEMPLATE_STRING_IF_INVALID = ""

FILTERS = {
    "escape": cgi.escape,
    "upper": string.upper,
    "lower": string.lower,
    }

##
# Renders a Django-style template, using variables from the given
# context object.
#
# @param template A Django-style template.  Only variables are currently
#    supported.
# @param context A context object.  This can be any object that provides
#    the attributes, methods, or members that are used by the template.
# @return A list of string fragments.

def render(template, context):
    next = iter(re.split("({{|}})", template)).next
    data = []
    try:
        token = next()
        while 1:
            if token == "{{": # variable
                data.append(variable(next(), context))
                if next() != "}}":
                    raise SyntaxError("missing variable terminator")
            else:
                data.append(token) # literal
            token = next()
    except StopIteration:
        pass
    return data

def variable(name, context):
    name = name.strip()
    if "|" in name:
        name, filters = name.split("|", 1)
    else:
        filters = None
    obj = context
    for item in name.split("."):
        try:
            obj = obj[item] # dictionary member
        except (KeyError, AttributeError, TypeError):
            try:
                obj = getattr(obj, item) # or attribute
            except AttributeError:
                obj = TEMPLATE_STRING_IF_INVALID
                break
            else:
                if callable(obj): # or method
                    obj = obj()
    if filters:
        try:
            obj = FILTERS[filters](obj)
        except KeyError:
            pass
    return obj