from django.http import HttpResponse
from django.template import loader, Context, RequestContext

class ContentNotRenderedError(Exception):
    pass

class SimpleTemplateResponse(HttpResponse):

    def __init__(self, template, context=None, mimetype=None, status=None,
            content_type=None):
        # It would seem obvious to call these next two members 'template' and
        # 'context', but those names are reserved as part of the test Client API.
        # To avoid the name collision, we use
        # tricky-to-debug problems
        self.template_name = template
        self.context_data = context

        # _is_rendered tracks whether the template and context has been baked into
        # a final response.
        self._is_rendered = False

        # content argument doesn't make sense here because it will be replaced
        # with rendered template so we always pass empty string in order to
        # prevent errors and provide shorter signature.
        super(SimpleTemplateResponse, self).__init__('', mimetype, status,
                                                     content_type)

    def resolve_template(self, template):
        "Accepts a template object, path-to-template or list of paths"
        if isinstance(template, (list, tuple)):
            return loader.select_template(template)
        elif isinstance(template, basestring):
            return loader.get_template(template)
        else:
            return template

    def resolve_context(self, context):
        """Convert context data into a full Context object
        (assuming it isn't already a Context object).
        """
        if isinstance(context, Context):
            return context
        else:
            return Context(context)

    @property
    def rendered_content(self):
        """Returns the freshly rendered content for the template and context
        described by the TemplateResponse.

        This *does not* set the final content of the response. To set the
        response content, you must either call render(), or set the
        content explicitly using the value of this property.
        """
        template = self.resolve_template(self.template_name)
        context = self.resolve_context(self.context_data)
        content = template.render(context)
        return content

    def render(self):
        """Render (thereby finalizing) the content of the response.

        If the content has already been rendered, this is a no-op.

        Returns the baked response instance.
        """
        if not self._is_rendered:
            self._set_content(self.rendered_content)
        return self

    is_rendered = property(lambda self: self._is_rendered)

    def __iter__(self):
        if not self._is_rendered:
            raise ContentNotRenderedError('The response content must be rendered before it can be iterated over.')
        return super(SimpleTemplateResponse, self).__iter__()

    def _get_content(self):
        if not self._is_rendered:
            raise ContentNotRenderedError('The response content must be rendered before it can be accessed.')
        return super(SimpleTemplateResponse, self)._get_content()

    def _set_content(self, value):
        "Overrides rendered content, unless you later call render()"
        super(SimpleTemplateResponse, self)._set_content(value)
        self._is_rendered = True

    content = property(_get_content, _set_content)


class TemplateResponse(SimpleTemplateResponse):
    def __init__(self, request, template, context=None, mimetype=None,
            status=None, content_type=None):
        # self.request gets over-written by django.test.client.Client - and
        # unlike context_data and template_name the _request should not
        # be considered part of the public API.
        self._request = request
        super(TemplateResponse, self).__init__(
            template, context, mimetype, status, content_type)

    def resolve_context(self, context):
        """Convert context data into a full RequestContext object
        (assuming it isn't already a Context object).
        """
        if isinstance(context, Context):
            return context
        else:
            return RequestContext(self._request, context)
