# Copied from django-sendfile 0.3.6 and tweaked to allow a backend to be passed
# to sendfile()
# See: https://github.com/johnsensible/django-sendfile/pull/33
import os.path

from mimetypes import guess_type


VERSION = (0, 3, 6)
__version__ = '.'.join(map(str, VERSION))


def _lazy_load(fn):
    _cached = []

    def _decorated():
        if not _cached:
            _cached.append(fn())
        return _cached[0]

    def clear():
        while _cached:
            _cached.pop()
    _decorated.clear = clear
    return _decorated


@_lazy_load
def _get_sendfile():
    from importlib import import_module

    from django.conf import settings
    from django.core.exceptions import ImproperlyConfigured

    backend = getattr(settings, 'SENDFILE_BACKEND', None)
    if not backend:
        raise ImproperlyConfigured('You must specify a value for SENDFILE_BACKEND')
    module = import_module(backend)
    return module.sendfile


def sendfile(request, filename, attachment=False, attachment_filename=None, mimetype=None, encoding=None, backend=None):
    '''
    create a response to send file using backend configured in SENDFILE_BACKEND

    If attachment is True the content-disposition header will be set.
    This will typically prompt the user to download the file, rather
    than view it.  The content-disposition filename depends on the
    value of attachment_filename:

        None (default): Same as filename
        False: No content-disposition filename
        String: Value used as filename

    If no mimetype or encoding are specified, then they will be guessed via the
    filename (using the standard python mimetypes module)
    '''
    _sendfile = backend or _get_sendfile()

    if not os.path.exists(filename):
        from django.http import Http404
        raise Http404('"%s" does not exist' % filename)

    guessed_mimetype, guessed_encoding = guess_type(filename)
    if mimetype is None:
        if guessed_mimetype:
            mimetype = guessed_mimetype
        else:
            mimetype = 'application/octet-stream'

    response = _sendfile(request, filename, mimetype=mimetype)
    if attachment:
        if attachment_filename is None:
            attachment_filename = os.path.basename(filename)
        parts = ['attachment']
        if attachment_filename:
            from django.utils.encoding import force_str

            from wagtail.core.utils import string_to_ascii

            attachment_filename = force_str(attachment_filename)
            ascii_filename = string_to_ascii(attachment_filename)
            parts.append('filename="%s"' % ascii_filename)

            if ascii_filename != attachment_filename:
                from django.utils.http import urlquote

                quoted_filename = urlquote(attachment_filename)
                parts.append('filename*=UTF-8\'\'%s' % quoted_filename)

        response['Content-Disposition'] = '; '.join(parts)
    else:
        response['Content-Disposition'] = 'inline'

    response['Content-length'] = os.path.getsize(filename)
    response['Content-Type'] = mimetype
    response['Content-Encoding'] = encoding or guessed_encoding

    return response
