from django.http import HttpResponseForbidden
from django.template import Context, Template
from django.conf import settings

# We include the template inline since we need to be able to reliably display
# this error message, especially for the sake of developers, and there isn't any
# other way of making it available independent of what is in the settings file.

CSRF_FAILURE_TEMPLATE = """
<!DOCTYPE html>
<html lang="en">
<head>
  <meta http-equiv="content-type" content="text/html; charset=utf-8">
  <meta name="robots" content="NONE,NOARCHIVE">
  <title>403 Forbidden</title>
  <style type="text/css">
    html * { padding:0; margin:0; }
    body * { padding:10px 20px; }
    body * * { padding:0; }
    body { font:small sans-serif; background:#eee; }
    body>div { border-bottom:1px solid #ddd; }
    h1 { font-weight:normal; margin-bottom:.4em; }
    h1 span { font-size:60%; color:#666; font-weight:normal; }
    #info { background:#f6f6f6; }
    #info ul { margin: 0.5em 4em; }
    #info p, #summary p { padding-top:10px; }
    #summary { background: #ffc; }
    #explanation { background:#eee; border-bottom: 0px none; }
  </style>
</head>
<body>
<div id="summary">
  <h1>Forbidden <span>(403)</span></h1>
  <p>CSRF verification failed. Request aborted.</p>
{% if no_referer %}
  <p>You are seeing this message because this HTTPS site requires a 'Referer
   header' to be sent by your Web browser, but none was sent. This header is
   required for security reasons, to ensure that your browser is not being
   hijacked by third parties.</p>

  <p>If you have configured your browser to disable 'Referer' headers, please
   re-enable them, at least for this site, or for HTTPS connections, or for
   'same-origin' requests.</p>
{% endif %}
</div>
{% if DEBUG %}
<div id="info">
  <h2>Help</h2>
    {% if reason %}
    <p>Reason given for failure:</p>
    <pre>
    {{ reason }}
    </pre>
    {% endif %}

  <p>In general, this can occur when there is a genuine Cross Site Request Forgery, or when
  <a
  href='http://docs.djangoproject.com/en/dev/ref/contrib/csrf/#ref-contrib-csrf'>Django's
  CSRF mechanism</a> has not been used correctly.  For POST forms, you need to
  ensure:</p>

  <ul>
    <li>The view function uses <a
    href='http://docs.djangoproject.com/en/dev/ref/templates/api/#subclassing-context-requestcontext'><code>RequestContext</code></a>
    for the template, instead of <code>Context</code>.</li>

    <li>In the template, there is a <code>{% templatetag openblock %} csrf_token
    {% templatetag closeblock %}</code> template tag inside each POST form that
    targets an internal URL.</li>

    <li>If you are not using <code>CsrfViewMiddleware</code>, then you must use
    <code>csrf_protect</code> on any views that use the <code>csrf_token</code>
    template tag, as well as those that accept the POST data.</li>

  </ul>

  <p>You're seeing the help section of this page because you have <code>DEBUG =
  True</code> in your Django settings file. Change that to <code>False</code>,
  and only the initial error message will be displayed.  </p>

  <p>You can customize this page using the CSRF_FAILURE_VIEW setting.</p>
</div>
{% else %}
<div id="explanation">
  <p><small>More information is available with DEBUG=True.</small></p>
</div>
{% endif %}
</body>
</html>
"""

def csrf_failure(request, reason=""):
    """
    Default view used when request fails CSRF protection
    """
    from django.middleware.csrf import REASON_NO_REFERER
    t = Template(CSRF_FAILURE_TEMPLATE)
    c = Context({'DEBUG': settings.DEBUG,
                 'reason': reason,
                 'no_referer': reason == REASON_NO_REFERER
                 })
    return HttpResponseForbidden(t.render(c), mimetype='text/html')
