import unittest
from datetime import datetime, timezone
from typing import Optional

import httpx
from pwo import async_test

from kaya.core import KayaApp, HttpContext
from kaya.session import Session, SessionMixin
from kaya.session.memcache import MemcacheSessionStore


class FakeClock:
    def __init__(self, start: float = 1_000_000.0) -> None:
        self._now = start

    def __call__(self) -> float:
        return self._now

    def advance(self, seconds: float) -> None:
        self._now += seconds


class StubMemcacheClient:
    """In-memory stub implementing the aiomcache.Client subset used by the store."""

    def __init__(self, clock: FakeClock) -> None:
        self._clock = clock
        self._data: dict[bytes, bytes] = {}
        self._expires: dict[bytes, float] = {}
        self.set_exptimes: list[int] = []
        self.touch_exptimes: list[int] = []

    def _expired(self, key: bytes) -> bool:
        expires = self._expires.get(key)
        return expires is not None and self._clock() > expires

    async def get(self, key: bytes) -> Optional[bytes]:
        if self._expired(key):
            self._data.pop(key, None)
            self._expires.pop(key, None)
            return None
        return self._data.get(key)

    async def set(self, key: bytes, value: bytes, exptime: int = 0) -> bool:
        self.set_exptimes.append(exptime)
        self._data[key] = value
        if exptime > 0:
            self._expires[key] = self._clock() + exptime
        else:
            self._expires.pop(key, None)
        return True

    async def delete(self, key: bytes) -> bool:
        existed = key in self._data
        self._data.pop(key, None)
        self._expires.pop(key, None)
        return existed

    async def touch(self, key: bytes, exptime: int) -> bool:
        self.touch_exptimes.append(exptime)
        if self._expired(key) or key not in self._data:
            return False
        self._expires[key] = self._clock() + exptime
        return True


class MemcacheSessionStoreTest(unittest.TestCase):
    clock: FakeClock
    client: StubMemcacheClient
    store: MemcacheSessionStore

    def setUp(self) -> None:
        self.clock = FakeClock()
        self.client = StubMemcacheClient(self.clock)
        self.store = MemcacheSessionStore(self.client, clock=self.clock)  # type: ignore[arg-type]

    @async_test
    async def test_save_and_load_round_trip(self) -> None:
        session = Session('abc', {'foo': 'bar', 'n': 42})
        await self.store.save('abc', session)
        loaded = await self.store.load('abc')
        self.assertIsNotNone(loaded)
        assert loaded is not None
        self.assertEqual('abc', loaded.id)
        self.assertEqual({'foo': 'bar', 'n': 42}, dict(loaded))

    @async_test
    async def test_load_unknown_session_returns_none(self) -> None:
        self.assertIsNone(await self.store.load('missing'))

    @async_test
    async def test_delete_removes_session(self) -> None:
        await self.store.save('abc', Session('abc', {'foo': 'bar'}))
        await self.store.delete('abc')
        self.assertIsNone(await self.store.load('abc'))

    @async_test
    async def test_save_with_max_age_expires(self) -> None:
        await self.store.save('abc', Session('abc', {'foo': 'bar'}), max_age=60)
        self.assertIsNotNone(await self.store.load('abc'))
        self.clock.advance(61)
        self.assertIsNone(await self.store.load('abc'))

    @async_test
    async def test_save_without_max_age_never_expires(self) -> None:
        await self.store.save('abc', Session('abc', {'foo': 'bar'}))
        self.assertEqual([0], self.client.set_exptimes)
        self.clock.advance(10_000_000)
        self.assertIsNotNone(await self.store.load('abc'))

    @async_test
    async def test_load_slides_expiry_when_max_age_given(self) -> None:
        await self.store.save('abc', Session('abc', {'foo': 'bar'}), max_age=60)
        self.clock.advance(50)
        loaded = await self.store.load('abc', max_age=60)
        self.assertIsNotNone(loaded)
        self.assertEqual([60], self.client.touch_exptimes)
        self.clock.advance(50)
        self.assertIsNotNone(await self.store.load('abc'))

    @async_test
    async def test_exptime_over_30_days_converted_to_absolute_timestamp(self) -> None:
        max_age = 40 * 24 * 60 * 60
        await self.store.save('abc', Session('abc', {'foo': 'bar'}), max_age=max_age)
        self.assertEqual([int(self.clock()) + max_age], self.client.set_exptimes)

    @async_test
    async def test_exptime_exactly_30_days_stays_relative(self) -> None:
        max_age = 30 * 24 * 60 * 60
        await self.store.save('abc', Session('abc', {'foo': 'bar'}), max_age=max_age)
        self.assertEqual([max_age], self.client.set_exptimes)

    @async_test
    async def test_touch_over_30_days_converted_to_absolute_timestamp(self) -> None:
        max_age = 40 * 24 * 60 * 60
        await self.store.save('abc', Session('abc', {'foo': 'bar'}), max_age=max_age)
        self.clock.advance(100)
        await self.store.load('abc', max_age=max_age)
        self.assertEqual([int(self.clock()) + max_age], self.client.touch_exptimes)

    @async_test
    async def test_pickle_round_trip_of_non_json_values(self) -> None:
        now = datetime(2026, 7, 20, 12, 0, 0, tzinfo=timezone.utc)
        session = Session('abc', {'when': now, 'blob': b'\x00\x01', 'items': {1, 2, 3}})
        await self.store.save('abc', session)
        loaded = await self.store.load('abc')
        self.assertIsNotNone(loaded)
        assert loaded is not None
        self.assertEqual(now, loaded['when'])
        self.assertEqual(b'\x00\x01', loaded['blob'])
        self.assertEqual({1, 2, 3}, loaded['items'])

    @async_test
    async def test_custom_prefix(self) -> None:
        store = MemcacheSessionStore(self.client, prefix='myapp:sess:', clock=self.clock)  # type: ignore[arg-type]
        await store.save('abc', Session('abc', {'foo': 'bar'}))
        self.assertIn(b'myapp:sess:abc', self.client._data)
        self.assertNotIn(b'kaya:session:abc', self.client._data)

    @async_test
    async def test_custom_serializer(self) -> None:
        import json

        store = MemcacheSessionStore(
            self.client,  # type: ignore[arg-type]
            dumps=lambda d: json.dumps(d).encode('utf-8'),
            loads=lambda b: json.loads(b.decode('utf-8')),
            clock=self.clock,
        )
        await store.save('abc', Session('abc', {'foo': 'bar'}))
        self.assertEqual(b'{"foo": "bar"}', self.client._data[b'kaya:session:abc'])
        loaded = await store.load('abc')
        self.assertIsNotNone(loaded)
        assert loaded is not None
        self.assertEqual({'foo': 'bar'}, dict(loaded))


class MemcacheSessionIntegrationTest(unittest.TestCase):
    app: KayaApp

    def setUp(self) -> None:
        store = MemcacheSessionStore(StubMemcacheClient(FakeClock()))  # type: ignore[arg-type]
        self.app = KayaApp(mixins=[SessionMixin(store)])

        @self.app.GET('/')
        async def home(ctx: HttpContext) -> None:
            n = ctx.session.get('visits', 0) + 1
            ctx.session['visits'] = n
            await ctx.send_str(200, f'visits: {n}')

    @async_test
    async def test_session_persists_across_requests(self) -> None:
        transport = httpx.ASGITransport(app=self.app)
        async with httpx.AsyncClient(transport=transport, base_url='http://127.0.0.1:80') as client:
            r = await client.get('/')
            self.assertEqual(200, r.status_code)
            self.assertEqual('visits: 1', r.text)
            self.assertIn('Set-Cookie', r.headers)

            r = await client.get('/')
            self.assertEqual(200, r.status_code)
            self.assertEqual('visits: 2', r.text)