# Tests for the HTTP server
# Copyright (C) 2025  Nguyễn Gia Phong
#
# This file is part of scadere.
#
# Scadere is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Scadere is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with scadere.  If not, see <https://www.gnu.org/licenses/>.

from asyncio import TaskGroup, open_connection, start_server
from base64 import (urlsafe_b64decode as from_base64,
                    urlsafe_b64encode as base64)
from contextlib import asynccontextmanager, contextmanager
from copy import deepcopy
from email.parser import BytesHeaderParser
from functools import partial
from pathlib import Path
from string import ascii_letters
from tempfile import mkstemp
from urllib.parse import urljoin, urlsplit
from xml.etree.ElementTree import (XML, XMLParser, indent,
                                   tostring as str_from_xml)
from xml.sax.saxutils import escape

from hypothesis import HealthCheck, given, settings
from hypothesis.strategies import (builds, composite, data,
                                   datetimes, integers, lists, text)
from hypothesis.provisional import domains, urls

from scadere.listen import (body, entry, handle, is_subdomain,
                            path, with_trailing_slash, xml)

ATOM_NAMESPACES = {'': 'http://www.w3.org/2005/Atom'}
XHTML_NAMESPACES = {'': 'http://www.w3.org/1999/xhtml'}


def ports():
    """Return a Hypothesis strategy for TCP ports."""
    return integers(1, 65535)


def serials():
    """Return a Hypothesis strategy for TLS serial number."""
    return builds(lambda n: hex(n).removeprefix('0x'), integers(0, 256**20-1))


def ca_names():
    """Return a Hypothesis strategy for CA names."""
    return text().map(lambda name: base64(name.encode()).decode())


@given(domains(), ports(), ca_names(), serials())
def test_path(hostname, port, issuer, serial):
    r = path(hostname, port, issuer, serial).split('/')
    assert r[0] == hostname
    assert int(r[1]) == port
    assert r[2] == issuer
    assert r[3] == serial


@given(domains(), ports(), ca_names(), serials(), datetimes(), datetimes())
def test_body(hostname, port, issuer, serial, not_before, not_after):
    r = body(not_before, not_after, hostname, port, serial, issuer)
    assert r[-1][0] == 'dl'
    d = dict(zip((v for k, v in r[-1][1:] if k == 'dt'),
                 (v for k, v in r[-1][1:] if k == 'dd')))
    assert d['Domain'] == hostname
    assert d['Port'] == port
    assert d['Issuer'] == from_base64(issuer.encode()).decode()
    assert d['Serial number'] == serial
    assert d['Valid from'] == not_before
    assert d['Valid until'] == not_after


@given(urls(), domains(), ports(),
       ca_names(), serials(), datetimes(), datetimes())
def test_atom_entry(base_url, hostname, port,
                    issuer, serial, not_before, not_after):
    cert = not_before, not_after, hostname, port, serial, issuer
    r = str_from_xml(xml(entry(base_url, cert)),
                     'unicode', short_empty_elements=False)
    issuer_str = from_base64(issuer.encode()).decode()
    url = urljoin(base_url, path(hostname, port, issuer, serial))
    assert r == f'''<entry>
  <author>
    <name>{escape(issuer_str)}</name>
  </author>
  <content type="xhtml">
    <div xmlns="http://www.w3.org/1999/xhtml">
      <h1>TLS certificate information</h1>
      <dl>
        <dt>Domain</dt>
        <dd>{hostname}</dd>
        <dt>Port</dt>
        <dd>{port}</dd>
        <dt>Issuer</dt>
        <dd>{escape(issuer_str)}</dd>
        <dt>Serial number</dt>
        <dd>{serial}</dd>
        <dt>Valid from</dt>
        <dd>{not_before.isoformat()}</dd>
        <dt>Valid until</dt>
        <dd>{not_after.isoformat()}</dd>
      </dl>
    </div>
  </content>
  <id>{url}</id>
  <link rel="alternate" type="application/xhtml+xml" href="{url}"></link>
  <title>TLS cert for {hostname} will expire at {not_after}</title>
  <updated>{not_before.isoformat()}</updated>
</entry>'''


@given(domains(), lists(domains()))
def test_is_subdomain(subject, objects):
    if not objects:
        assert is_subdomain(subject, objects)
    elif is_subdomain(subject, objects):
        assert any(child == '' or child.endswith('.')
                   for child in map(subject.removesuffix, objects))
    else:
        for obj in objects:
            assert (not subject.endswith(obj)
                    or not subject.removesuffix(obj).endswith('.'))


@composite
def certificates(draw):
    """Return a Hypothesis strategy for certificate summaries."""
    not_before = draw(datetimes()).isoformat()
    not_after = draw(datetimes()).isoformat()
    hostname = draw(domains())
    port = draw(ports())
    serial = draw(serials())
    # Free-formed UTF-8 could easily creates malformed XML.
    issuer = base64(draw(text(ascii_letters)).encode()).decode()
    return f'{not_before} {not_after} {hostname} {port} {serial} {issuer}'


@contextmanager
def tmp_cert_file(lines):
    cert_file = Path(mkstemp(text=True)[1])
    cert_file.write_text('\n'.join(lines))
    try:
        yield cert_file
    finally:
        cert_file.unlink()


def is_base_url(url):
    """Check if the given URL has a trailing slash.

    The parser for command-line arguments
    enforces this property for base URLs.
    """
    return url.endswith('/')


@given(urls())
def test_with_trailing_slash(url):
    if is_base_url(url):
        assert with_trailing_slash(url) == url
    else:
        assert with_trailing_slash(url) == f'{url}/'


def is_root(base_url, url):
    """Check if the given URL points to the same base URL.

    Paths starting with // are excluded because urljoin
    sometimes confuse them with URL scheme.
    """
    base_path = urlsplit(base_url).path
    url_path = urlsplit(url).path
    return urlsplit(urljoin(base_url, url_path)).path == base_path


def has_usual_path(url):
    """Check if the given URL path tends to mess with urljoin."""
    return is_root(url, url)


@asynccontextmanager
async def connect(socket):
    """Return a read-write stream for an asyncio TCP connection."""
    reader, writer = await open_connection(*socket.getsockname()[:2])
    try:
        yield reader, writer
    finally:
        writer.close()
        await writer.wait_closed()


async def fetch_xml(socket, url, content_type):
    """Fetch the content at the URL from the socket."""
    header_parser = BytesHeaderParser()
    xml_parser = XMLParser(encoding='utf-8')
    async with connect(socket) as (reader, writer):
        writer.write(f'GET {url}\r\n'.encode())
        await writer.drain()
        status = await reader.readuntil(b'\r\n')
        assert status == b'HTTP/1.1 200 OK\r\n'
        headers_bytes = await reader.readuntil(b'\r\n\r\n')
        headers = header_parser.parsebytes(headers_bytes)
        assert headers['Content-Type'] == content_type
        content = await reader.read()
        assert len(content) == int(headers['Content-Length'])
        return XML(content.decode(), xml_parser)


def equal_xml(a, b):
    """Check if the two XML elements are equal."""
    a_copy, b_copy = deepcopy(a), deepcopy(b)
    indent(a_copy)
    indent(b_copy)
    return str_from_xml(a_copy).rstrip() == str_from_xml(b_copy).rstrip()


async def check_feed(socket, base_url):
    """Check the Atom feed at the given path and its entry pages."""
    feed = await fetch_xml(socket, base_url, 'application/atom+xml')
    for feed_entry in feed.findall('entry', ATOM_NAMESPACES):
        link = feed_entry.find('link', ATOM_NAMESPACES).attrib
        assert link['rel'] == 'alternate'
        page = await fetch_xml(socket, link['href'], link['type'])
        assert equal_xml(feed_entry.find('.//dl', XHTML_NAMESPACES),
                         page.find('.//dl', XHTML_NAMESPACES))


async def check_server(sockets, func, *args):
    """Test server listening for connections on sockets using func."""
    async with TaskGroup() as group:
        for socket in sockets:
            group.create_task(func(socket, *args))


@given(urls().filter(is_base_url).filter(has_usual_path),
       lists(certificates(), min_size=1))
@settings(deadline=None)
async def test_http_200(base_url, certs):
    base_path = urlsplit(base_url).path
    with tmp_cert_file(certs) as cert_file:
        handler = partial(handle, cert_file, base_url)
        async with await start_server(handler, 'localhost') as server:
            await check_server(server.sockets, check_feed, base_path)


async def not_found(socket, url):
    """Send GET request for URL and expect a 404 status from socket."""
    async with connect(socket) as (reader, writer):
        writer.write(f'GET {url}\r\n'.encode())
        await writer.drain()
        response = await reader.readuntil(b'\r\n')
        assert response == b'HTTP/1.1 404 Not Found\r\n'


@given(data())
@settings(suppress_health_check=[HealthCheck.too_slow])
async def test_unrecognized_url(drawer):
    base_url = drawer.draw(urls().filter(is_base_url), label='base URL')
    url = drawer.draw(urls().filter(lambda url: not is_root(base_url, url)),
                      label='request URL')
    with tmp_cert_file(()) as cert_file:
        handler = partial(handle, cert_file, base_url)
        async with await start_server(handler, 'localhost') as server:
            await check_server(server.sockets, not_found, urlsplit(url).path)


async def method_not_allowed(socket, request):
    """Expect from socket a HTTP response with status 405."""
    async with connect(socket) as (reader, writer):
        writer.write(f'{request}\r\n'.encode())
        await writer.drain()
        response = await reader.readuntil(b'\r\n')
        assert response == b'HTTP/1.1 405 Method Not Allowed\r\n'


@given(urls(), text().filter(lambda method: not method.startswith('GET ')))
async def test_unallowed_method(base_url, request):
    with tmp_cert_file(()) as cert_file:
        handler = partial(handle, cert_file, base_url)
        async with await start_server(handler, 'localhost') as server:
            await check_server(server.sockets, method_not_allowed, request)