from typing import Union
from urllib.parse import urlparse

from django.contrib.sites.models import Site
from django.http import HttpResponse
from django.urls import resolve, Resolver404
from micropub.views import error

from .models import Entry


def from_url(url: str) -> Union[Entry, HttpResponse]:
    domain = Site.objects.get_current().domain
    if not url:
        return error.bad_req('url parameter required')
    if '//' not in url:
        url = '//' + url
    parts = urlparse(url, scheme='https')
    if parts.scheme not in ('http', 'https') or parts.netloc != domain:
        return error.bad_req('url does not point to this site')

    try:
        match = resolve(parts.path)
    except Resolver404:
        return error.bad_req('url does not point to a valid page on this site')

    if match.view_name != 'entries:entry':
        return error.bad_req('url does not point to an entry on this site')

    try:
        entry = Entry.objects.get(pk=match.kwargs['id'])
    except Entry.DoesNotExist:
        return error.bad_req('url does not point to an existing entry')

    return entry