# Copyright (C) 2015-2019  The Software Heritage developers
# See the AUTHORS file at the top-level directory of this distribution
# License: GNU Affero General Public License version 3, or any later version
# See top-level LICENSE file for more information

import logging
import traceback

import sentry_sdk

from django.core import exceptions
from django.shortcuts import render
from django.utils.html import escape
from django.utils.safestring import mark_safe
from rest_framework.exceptions import AuthenticationFailed

from swh.web.config import get_config

logger = logging.getLogger("django")


class BadInputExc(ValueError):
    """Wrong request to the api.

    Example: Asking a content with the wrong identifier format.

    """

    pass


class NotFoundExc(exceptions.ObjectDoesNotExist):
    """Good request to the api but no result were found.

    Example: Asking a content with the right identifier format but
    that content does not exist.

    """

    pass


class ForbiddenExc(exceptions.PermissionDenied):
    """Good request to the api, forbidden result to return due to enforce
       policy.

    Example: Asking for a raw content which exists but whose mimetype
    is not text.

    """

    pass


class LargePayloadExc(Exception):
    """The input size is too large.

    Example: Asking to resolve 10000 SWHIDs when the limit is 1000.
    """

    pass


http_status_code_message = {
    400: "Bad Request",
    401: "Unauthorized",
    403: "Access Denied",
    404: "Resource not found",
    413: "Payload Too Large",
    500: "Internal Server Error",
    501: "Not Implemented",
    502: "Bad Gateway",
    503: "Service unavailable",
}


def _generate_error_page(request, error_code, error_description):
    return render(
        request,
        "error.html",
        {
            "error_code": error_code,
            "error_message": http_status_code_message[error_code],
            "error_description": mark_safe(error_description),
        },
        status=error_code,
    )


def swh_handle400(request, exception=None):
    """
    Custom Django HTTP error 400 handler for swh-web.
    """
    error_description = (
        "The server cannot process the request to %s due to "
        "something that is perceived to be a client error."
        % escape(request.META["PATH_INFO"])
    )
    return _generate_error_page(request, 400, error_description)


def swh_handle403(request, exception=None):
    """
    Custom Django HTTP error 403 handler for swh-web.
    """
    error_description = "The resource %s requires an authentication." % escape(
        request.META["PATH_INFO"]
    )
    return _generate_error_page(request, 403, error_description)


def swh_handle404(request, exception=None):
    """
    Custom Django HTTP error 404 handler for swh-web.
    """
    error_description = "The resource %s could not be found on the server." % escape(
        request.META["PATH_INFO"]
    )
    return _generate_error_page(request, 404, error_description)


def swh_handle500(request):
    """
    Custom Django HTTP error 500 handler for swh-web.
    """
    error_description = (
        "An unexpected condition was encountered when "
        "requesting resource %s." % escape(request.META["PATH_INFO"])
    )
    return _generate_error_page(request, 500, error_description)


def sentry_capture_exception(exc):
    if not isinstance(
        exc,
        (
            exceptions.ObjectDoesNotExist,
            exceptions.DisallowedHost,
            exceptions.PermissionDenied,
            BadInputExc,
            NotFoundExc,
            AuthenticationFailed,
        ),
    ):
        sentry_sdk.capture_exception(exc)


def handle_view_exception(request, exc):
    """
    Function used to generate an error page when an exception
    was raised inside a swh-web browse view.
    """
    sentry_capture_exception(exc)
    error_code = 500
    error_description = "%s: %s" % (type(exc).__name__, str(exc))
    if get_config()["debug"]:
        error_description = traceback.format_exc()
        logger.debug(error_description)
    if isinstance(exc, BadInputExc):
        error_code = 400
    if isinstance(exc, ForbiddenExc):
        error_code = 403
    if isinstance(exc, NotFoundExc):
        error_code = 404

    resp = _generate_error_page(request, error_code, error_description)
    if get_config()["debug"]:
        resp.traceback = error_description
    return resp