# 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 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, example, 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, path, 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>'''


@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_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
            and not url_path.startswith('//'))


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())
    try:
        yield reader, writer
    finally:
        writer.close()


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(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()


@given(urls().filter(has_usual_path), lists(certificates(), min_size=1))
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:
            socket, *_ = server.sockets
            feed = await fetch_xml(socket, base_path, '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))


@example(type('//', (), {'draw': lambda *a, **kw: 'https://a.example//b'}))
@given(data())
@settings(suppress_health_check=[HealthCheck.too_slow])
async def test_http_404(drawer):
    base_url = drawer.draw(urls(), 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:
            async with connect(server.sockets[0]) as (reader, writer):
                writer.write(f'GET {urlsplit(url).path}\r\n'.encode())
                await writer.drain()
                response = await reader.read()
                assert response == b'HTTP/1.1 404 Not Found\r\n'


@given(urls(), text().filter(lambda method: not method.startswith('GET ')))
async def test_http_405(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:
            async with connect(server.sockets[0]) as (reader, writer):
                writer.write(f'{request}\r\n'.encode())
                await writer.drain()
                response = await reader.read()
                assert response == b'HTTP/1.1 405 Method Not Allowed\r\n'