from django import http
from django.template import Context, Engine, TemplateDoesNotExist, loader
from django.views.decorators.csrf import requires_csrf_token


# This can be called when CsrfViewMiddleware.process_view has not run,
# therefore need @requires_csrf_token in case the template needs
# {% csrf_token %}.
@requires_csrf_token
def page_not_found(request, template_name='404.html'):
    """
    Default 404 handler.

    Templates: :template:`404.html`
    Context:
        request_path
            The path of the requested URL (e.g., '/app/pages/bad_page/')
    """
    context = {'request_path': request.path}
    try:
        template = loader.get_template(template_name)
        body = template.render(context, request)
        content_type = None             # Django will use DEFAULT_CONTENT_TYPE
    except TemplateDoesNotExist:
        template = Engine().from_string(
            '<h1>Not Found</h1>'
            '<p>The requested URL {{ request_path }} was not found on this server.</p>')
        body = template.render(Context(context))
        content_type = 'text/html'
    return http.HttpResponseNotFound(body, content_type=content_type)


@requires_csrf_token
def server_error(request, template_name='500.html'):
    """
    500 error handler.

    Templates: :template:`500.html`
    Context: None
    """
    try:
        template = loader.get_template(template_name)
    except TemplateDoesNotExist:
        return http.HttpResponseServerError('<h1>Server Error (500)</h1>', content_type='text/html')
    return http.HttpResponseServerError(template.render())


@requires_csrf_token
def bad_request(request, template_name='400.html'):
    """
    400 error handler.

    Templates: :template:`400.html`
    Context: None
    """
    try:
        template = loader.get_template(template_name)
    except TemplateDoesNotExist:
        return http.HttpResponseBadRequest('<h1>Bad Request (400)</h1>', content_type='text/html')
    return http.HttpResponseBadRequest(template.render())


# This can be called when CsrfViewMiddleware.process_view has not run,
# therefore need @requires_csrf_token in case the template needs
# {% csrf_token %}.
@requires_csrf_token
def permission_denied(request, template_name='403.html'):
    """
    Permission denied (403) handler.

    Templates: :template:`403.html`
    Context: None

    If the template does not exist, an Http403 response containing the text
    "403 Forbidden" (as per RFC 2616) will be returned.
    """
    try:
        template = loader.get_template(template_name)
    except TemplateDoesNotExist:
        return http.HttpResponseForbidden('<h1>403 Forbidden</h1>', content_type='text/html')
    return http.HttpResponseForbidden(template.render(request=request))
