"""
Views and functions for serving static files. These are only to be used
during development, and SHOULD NOT be used in a production setting.
"""
import mimetypes
import posixpath
import re
from pathlib import Path

from django.http import (
    FileResponse, Http404, HttpResponse, HttpResponseNotModified,
)
from django.template import Context, Engine, TemplateDoesNotExist, loader
from django.utils._os import safe_join
from django.utils.http import http_date, parse_http_date
from django.utils.translation import gettext as _, gettext_lazy


def serve(request, path, document_root=None, show_indexes=False):
    """
    Serve static files below a given point in the directory structure.

    To use, put a URL pattern such as::

        from django.views.static import serve

        url(r'^(?P<path>.*)$', serve, {'document_root': '/path/to/my/files/'})

    in your URLconf. You must provide the ``document_root`` param. You may
    also set ``show_indexes`` to ``True`` if you'd like to serve a basic index
    of the directory.  This index view will use the template hardcoded below,
    but if you'd like to override it, you can create a template called
    ``static/directory_index.html``.
    """
    path = posixpath.normpath(path).lstrip('/')
    fullpath = Path(safe_join(document_root, path))
    if fullpath.is_dir():
        if show_indexes:
            return directory_index(path, fullpath)
        raise Http404(_("Directory indexes are not allowed here."))
    if not fullpath.exists():
        raise Http404(_('"%(path)s" does not exist') % {'path': fullpath})
    # Respect the If-Modified-Since header.
    statobj = fullpath.stat()
    if not was_modified_since(request.META.get('HTTP_IF_MODIFIED_SINCE'),
                              statobj.st_mtime, statobj.st_size):
        return HttpResponseNotModified()
    content_type, encoding = mimetypes.guess_type(str(fullpath))
    content_type = content_type or 'application/octet-stream'
    response = FileResponse(fullpath.open('rb'), content_type=content_type)
    response["Last-Modified"] = http_date(statobj.st_mtime)
    if encoding:
        response["Content-Encoding"] = encoding
    return response


DEFAULT_DIRECTORY_INDEX_TEMPLATE = """
{% load i18n %}
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta http-equiv="Content-type" content="text/html; charset=utf-8">
    <meta http-equiv="Content-Language" content="en-us">
    <meta name="robots" content="NONE,NOARCHIVE">
    <title>{% blocktrans %}Index of {{ directory }}{% endblocktrans %}</title>
  </head>
  <body>
    <h1>{% blocktrans %}Index of {{ directory }}{% endblocktrans %}</h1>
    <ul>
      {% if directory != "/" %}
      <li><a href="../">../</a></li>
      {% endif %}
      {% for f in file_list %}
      <li><a href="{{ f|urlencode }}">{{ f }}</a></li>
      {% endfor %}
    </ul>
  </body>
</html>
"""
template_translatable = gettext_lazy("Index of %(directory)s")


def directory_index(path, fullpath):
    try:
        t = loader.select_template([
            'static/directory_index.html',
            'static/directory_index',
        ])
    except TemplateDoesNotExist:
        t = Engine(libraries={'i18n': 'django.templatetags.i18n'}).from_string(DEFAULT_DIRECTORY_INDEX_TEMPLATE)
        c = Context()
    else:
        c = {}
    files = []
    for f in fullpath.iterdir():
        if not f.name.startswith('.'):
            url = str(f.relative_to(fullpath))
            if f.is_dir():
                url += '/'
            files.append(url)
    c.update({
        'directory': path + '/',
        'file_list': files,
    })
    return HttpResponse(t.render(c))


def was_modified_since(header=None, mtime=0, size=0):
    """
    Was something modified since the user last downloaded it?

    header
      This is the value of the If-Modified-Since header.  If this is None,
      I'll just return True.

    mtime
      This is the modification time of the item we're talking about.

    size
      This is the size of the item we're talking about.
    """
    try:
        if header is None:
            raise ValueError
        matches = re.match(r"^([^;]+)(; length=([0-9]+))?$", header,
                           re.IGNORECASE)
        header_mtime = parse_http_date(matches.group(1))
        header_len = matches.group(3)
        if header_len and int(header_len) != size:
            raise ValueError
        if int(mtime) > header_mtime:
            raise ValueError
    except (AttributeError, ValueError, OverflowError):
        return True
    return False
