from mimetypes import guess_type
from typing import Union

from django.conf import settings
from django.contrib.auth.models import AnonymousUser
from django.core.files.uploadedfile import UploadedFile
from django.http import HttpRequest, HttpResponse, HttpResponseForbidden, HttpResponseNotFound
from django.shortcuts import redirect
from django.utils.cache import patch_cache_control
from django.utils.translation import gettext as _
from django_sendfile import sendfile

from zerver.context_processors import get_valid_realm_from_request
from zerver.lib.exceptions import JsonableError
from zerver.lib.response import json_success
from zerver.lib.upload import check_upload_within_quota, upload_message_image_from_request
from zerver.lib.upload.base import INLINE_MIME_TYPES
from zerver.lib.upload.local import (
    generate_unauthed_file_access_url,
    get_local_file_path,
    get_local_file_path_id_from_token,
)
from zerver.lib.upload.s3 import get_signed_upload_url
from zerver.models import UserProfile, validate_attachment_request


def serve_s3(
    request: HttpRequest, url_path: str, url_only: bool, download: bool = False
) -> HttpResponse:
    url = get_signed_upload_url(url_path, download=download)
    if url_only:
        return json_success(request, data=dict(url=url))

    return redirect(url)


def serve_local(
    request: HttpRequest, path_id: str, url_only: bool, download: bool = False
) -> HttpResponse:
    local_path = get_local_file_path(path_id)
    if local_path is None:
        return HttpResponseNotFound("<p>File not found</p>")

    if url_only:
        url = generate_unauthed_file_access_url(path_id)
        return json_success(request, data=dict(url=url))

    # Here we determine whether a browser should treat the file like
    # an attachment (and thus clicking a link to it should download)
    # or like a link (and thus clicking a link to it should display it
    # in a browser tab).  This is controlled by the
    # Content-Disposition header; `django-sendfile2` sends the
    # attachment-style version of that header if and only if the
    # attachment argument is passed to it.  For attachments,
    # django-sendfile2 sets the response['Content-disposition'] like
    # this: `attachment; filename="zulip.txt"; filename*=UTF-8''zulip.txt`.
    # The filename* parameter is omitted for ASCII filenames like this one.
    #
    # The "filename" field (used to name the file when downloaded) is
    # unreliable because it doesn't have a well-defined encoding; the
    # newer filename* field takes precedence, since it uses a
    # consistent format (urlquoted).  For more details on filename*
    # and filename, see the below docs:
    # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Disposition
    mimetype, encoding = guess_type(local_path)
    attachment = download or mimetype not in INLINE_MIME_TYPES

    response = sendfile(
        request, local_path, attachment=attachment, mimetype=mimetype, encoding=encoding
    )
    patch_cache_control(response, private=True, immutable=True)
    return response


def serve_file_download_backend(
    request: HttpRequest, user_profile: UserProfile, realm_id_str: str, filename: str
) -> HttpResponse:
    return serve_file(request, user_profile, realm_id_str, filename, url_only=False, download=True)


def serve_file_backend(
    request: HttpRequest,
    maybe_user_profile: Union[UserProfile, AnonymousUser],
    realm_id_str: str,
    filename: str,
) -> HttpResponse:
    return serve_file(request, maybe_user_profile, realm_id_str, filename, url_only=False)


def serve_file_url_backend(
    request: HttpRequest, user_profile: UserProfile, realm_id_str: str, filename: str
) -> HttpResponse:
    """
    We should return a signed, short-lived URL
    that the client can use for native mobile download, rather than serving a redirect.
    """

    return serve_file(request, user_profile, realm_id_str, filename, url_only=True)


def serve_file(
    request: HttpRequest,
    maybe_user_profile: Union[UserProfile, AnonymousUser],
    realm_id_str: str,
    filename: str,
    url_only: bool = False,
    download: bool = False,
) -> HttpResponse:
    path_id = f"{realm_id_str}/{filename}"
    realm = get_valid_realm_from_request(request)
    is_authorized = validate_attachment_request(maybe_user_profile, path_id, realm)

    if is_authorized is None:
        return HttpResponseNotFound(_("<p>File not found.</p>"))
    if not is_authorized:
        return HttpResponseForbidden(_("<p>You are not authorized to view this file.</p>"))
    if settings.LOCAL_UPLOADS_DIR is not None:
        return serve_local(request, path_id, url_only, download=download)

    return serve_s3(request, path_id, url_only, download=download)


def serve_local_file_unauthed(request: HttpRequest, token: str, filename: str) -> HttpResponse:
    path_id = get_local_file_path_id_from_token(token)
    if path_id is None:
        raise JsonableError(_("Invalid token"))
    if path_id.split("/")[-1] != filename:
        raise JsonableError(_("Invalid filename"))

    return serve_local(request, path_id, url_only=False)


def upload_file_backend(request: HttpRequest, user_profile: UserProfile) -> HttpResponse:
    if len(request.FILES) == 0:
        raise JsonableError(_("You must specify a file to upload"))
    if len(request.FILES) != 1:
        raise JsonableError(_("You may only upload one file at a time"))

    user_file = list(request.FILES.values())[0]
    assert isinstance(user_file, UploadedFile)
    file_size = user_file.size
    assert file_size is not None
    if settings.MAX_FILE_UPLOAD_SIZE * 1024 * 1024 < file_size:
        raise JsonableError(
            _("Uploaded file is larger than the allowed limit of {} MiB").format(
                settings.MAX_FILE_UPLOAD_SIZE,
            )
        )
    check_upload_within_quota(user_profile.realm, file_size)

    uri = upload_message_image_from_request(user_file, user_profile, file_size)
    return json_success(request, data={"uri": uri})