"""Guards that stop one bad YouTube answer from cascading: the subscription prune guard, the
playlist-push circuit breaker, and RSS telling a failure apart from an empty feed."""

import logging

import httpx
import pytest

from app.sync import runner
from app.sync.playlists import FAILED, _Breaker
from app.sync.subscriptions import should_prune
from app.youtube import rss
from app.youtube.client import YouTubeError


class TestShouldPrune:
    def test_a_normal_fetch_prunes(self):
        assert should_prune(fetched_count=12, existing_count=15) is True

    def test_an_empty_fetch_against_existing_rows_never_prunes(self):
        # The data-loss case: one anomalous empty-but-200 response must not wipe 15 rows.
        assert should_prune(fetched_count=0, existing_count=15) is False

    def test_an_empty_fetch_with_nothing_local_is_fine(self):
        # A brand-new account: nothing to lose, so the (no-op) prune may run.
        assert should_prune(fetched_count=0, existing_count=0) is True

    def test_a_single_remaining_subscription_still_prunes(self):
        assert should_prune(fetched_count=1, existing_count=200) is True


class TestBreaker:
    def test_open_until_the_limit_is_reached(self):
        b = _Breaker(limit=3)
        for _ in range(2):
            b.hit(False)
            assert b.open()
        b.hit(False)
        assert not b.open() and b.tripped

    def test_a_success_re_arms_the_streak(self):
        b = _Breaker(limit=3)
        b.hit(False)
        b.hit(False)
        b.hit(True)  # one write went through — this isn't an account-wide failure
        b.hit(False)
        b.hit(False)
        assert b.open()

    def test_stays_tripped_once_tripped(self):
        b = _Breaker(limit=2)
        b.hit(False)
        b.hit(False)
        b.hit(True)
        assert not b.open()


def _quota_dead():
    """A write op that fails the way a quota-exhausted / scope-revoked account fails."""
    raise YouTubeError("quota exceeded")


class TestBreakerRun:
    def test_returns_the_ops_result_and_leaves_failures_alone(self):
        b, failed = _Breaker(), []
        assert b.run(lambda: "item-1", lambda: failed.append("v1")) == "item-1"
        assert failed == []

    def test_a_youtube_error_records_the_failure_and_counts_towards_the_trip(self):
        b, failed = _Breaker(limit=2), []
        assert b.run(_quota_dead, lambda: failed.append("v1")) is FAILED
        assert failed == ["v1"] and b.open()
        b.run(_quota_dead, lambda: failed.append("v2"))
        assert not b.open()

    def test_a_tripped_breaker_never_calls_the_op(self):
        b, failed, calls = _Breaker(limit=1), [], []
        b.run(_quota_dead, lambda: failed.append("v1"))
        assert b.run(lambda: calls.append("called"), lambda: failed.append("v2")) is FAILED
        assert calls == []  # the whole point: no more quota spent
        assert failed == ["v1", "v2"]  # …but the item is still reported

    def test_other_exceptions_are_not_swallowed(self):
        # Only YouTubeError is a "write failed" signal; a bug must still surface.
        def boom():
            raise ValueError("bug")

        with pytest.raises(ValueError):
            _Breaker().run(boom, lambda: None)


class _StubDb:
    """Just enough Session for run_rss_poll when the caller supplies the channel list."""

    def __init__(self):
        self.rollbacks = 0

    def rollback(self):
        self.rollbacks += 1


class _StubChannel:
    def __init__(self, cid):
        self.id = cid


class TestRssPollResult:
    """`failed` must count every channel that did not get polled — feed-side AND apply-side.
    Counting only the fetch failures would move the "a broken run looks like a quiet hour" blind
    spot rather than remove it."""

    def _run(self, monkeypatch, *, fetch, apply_, channels=("UC1", "UC2")):
        monkeypatch.setattr(runner, "fetch_channel_feed", fetch)
        monkeypatch.setattr(runner, "apply_rss_feed", apply_)
        # The API fallback has its own DB-lane tests (test_feed_fallback.py); here it reads nothing.
        monkeypatch.setattr(
            runner, "run_feed_fallback", lambda db, ids: {"read": 0, "new": 0, "failed": 0}
        )
        return runner.run_rss_poll(_StubDb(), [_StubChannel(c) for c in channels])

    def test_a_healthy_run_reports_no_failures(self, monkeypatch):
        out = self._run(monkeypatch, fetch=lambda cid: [{"id": "v"}], apply_=lambda db, ch, e: 1)
        assert out == {"new": 2, "failed": 0, "fallback": 0}

    def test_unreadable_feeds_are_counted(self, monkeypatch):
        # One dead channel among healthy ones: counted, but the run itself is still a run.
        def fetch(cid):
            if cid == "UC_dead":
                raise rss.RssError("404", "http_404")
            return [{"id": "v"}]

        out = self._run(
            monkeypatch, fetch=fetch, apply_=lambda db, ch, e: 1, channels=("UC1", "UC_dead")
        )
        assert out == {"new": 1, "failed": 1, "fallback": 0}

    def test_apply_failures_are_counted_too(self, monkeypatch):
        # A per-row write failure (a constraint clash on one channel) while the rest store fine.
        def apply_(db, ch, entries):
            if ch.id == "UC_bad":
                raise RuntimeError("constraint")
            return 1

        out = self._run(
            monkeypatch,
            fetch=lambda cid: [{"id": "v"}],
            apply_=apply_,
            channels=("UC1", "UC_bad"),
        )
        assert out == {"new": 1, "failed": 1, "fallback": 0}, (
            "an unstored channel must not read as ok"
        )

    def test_many_failures_write_one_warning_with_counts_not_one_per_channel(
        self, monkeypatch, caplog
    ):
        # YouTube's RSS outage of 2026-09-16: ~900 of 979 feeds failed on every 20-minute poll and
        # each wrote its own WARNING — 11k lines in four hours, which the log_events table would
        # have stored too. One summary per poll, per-channel detail at DEBUG.
        channels = [f"UC{i}" for i in range(40)]

        def fetch(cid):
            n = int(cid[2:])
            if n < 30:
                raise rss.RssError(f"RSS fetch for {cid} returned HTTP 404", "http_404")
            if n < 35:
                raise rss.RssError(f"RSS fetch failed for {cid}: timed out", "transport")
            return [{"id": "v"}]

        caplog.set_level(logging.DEBUG, logger="siftlode.sync")
        out = self._run(monkeypatch, fetch=fetch, apply_=lambda db, ch, e: 1, channels=channels)
        assert out == {"new": 5, "failed": 35, "fallback": 0}
        warnings = [r for r in caplog.records if r.levelno >= logging.WARNING]
        assert len(warnings) == 1
        assert warnings[0].event == "sync.rss.failed"
        assert warnings[0].attrs["reasons"] == {"http_404": 30, "transport": 5}
        assert len(warnings[0].attrs["examples"]) == runner.RSS_FAILURE_EXAMPLES
        assert sum(r.levelno == logging.DEBUG for r in caplog.records) == 35

    def test_a_failure_on_our_side_gets_one_traceback_per_poll_not_one_per_channel(
        self, monkeypatch, caplog
    ):
        # A read-only database fails every channel's apply identically. The first gets a traceback
        # at ERROR; repeating it for each of 979 channels would be the RSS flood all over again.
        def apply_(db, ch, entries):
            raise RuntimeError("read-only transaction")

        caplog.set_level(logging.DEBUG, logger="siftlode.sync")
        with pytest.raises(RuntimeError):
            self._run(
                monkeypatch,
                fetch=lambda cid: [{"id": "v"}],
                apply_=apply_,
                channels=("A", "B", "C"),
            )
        errors = [r for r in caplog.records if r.levelno == logging.ERROR]
        assert len(errors) == 1 and errors[0].exc_info is not None
        assert (
            sum(r.levelno == logging.DEBUG and r.exc_info is not None for r in caplog.records) == 2
        )

    def test_a_quiet_hour_is_distinguishable_from_an_outage(self, monkeypatch):
        quiet = self._run(monkeypatch, fetch=lambda cid: [], apply_=lambda db, ch, e: 0)
        assert quiet == {
            "new": 0,
            "failed": 0,
            "fallback": 0,
        }  # same "new", different "failed" — that's the point

    def test_a_total_outage_raises_instead_of_returning_ok(self, monkeypatch):
        # Every feed unreachable (the tinyproxy-lost-the-boot-race incident). Returning a result
        # here recorded the scheduler run as "ok", with the outage only visible inside the summary
        # text — a green pill for a run that did nothing at all.
        def boom(cid):
            raise rss.RssError("Connection refused", "transport")

        with pytest.raises(RuntimeError, match="all 2 channels"):
            self._run(monkeypatch, fetch=boom, apply_=lambda db, ch, e: 1)

    def test_the_outage_message_carries_the_underlying_error(self, monkeypatch):
        # "all N channels failed" is ALSO what one dead feed id looks like on a small instance.
        # The card has to say which: `HTTP 404` = fix the subscription, `Connection refused` =
        # the egress is down.
        def dead(cid):
            raise rss.RssError(f"RSS fetch for {cid} returned HTTP 404", "http_404")

        with pytest.raises(RuntimeError, match="HTTP 404"):
            self._run(monkeypatch, fetch=dead, apply_=lambda db, ch, e: 1, channels=("UC_dead",))

    def test_a_read_only_database_is_a_total_outage_too(self, monkeypatch):
        # Every feed reads fine, nothing can be stored: just as un-polled, just as red.
        def boom(db, ch, entries):
            raise RuntimeError("read-only transaction")

        with pytest.raises(RuntimeError, match="read-only transaction"):
            self._run(monkeypatch, fetch=lambda cid: [{"id": "v"}], apply_=boom)

    def test_only_the_unreadable_feeds_go_to_the_api_and_what_it_reads_counts(
        self, monkeypatch, caplog
    ):
        # A feed that answered 404 is the fallback's; a channel whose rows failed to STORE is not —
        # the API would hand the same rows to the same broken write.
        seen = []

        def fetch(cid):
            if cid == "UC_dark":
                raise rss.RssError("404", "http_404")
            return [{"id": "v"}]

        def apply_(db, ch, entries):
            if ch.id == "UC_badrow":
                raise RuntimeError("constraint")
            return 1

        def fallback(db, ids):
            seen.extend(ids)
            return {"read": 1, "new": 3, "failed": 0}

        monkeypatch.setattr(runner, "fetch_channel_feed", fetch)
        monkeypatch.setattr(runner, "apply_rss_feed", apply_)
        monkeypatch.setattr(runner, "run_feed_fallback", fallback)
        out = runner.run_rss_poll(
            _StubDb(), [_StubChannel(c) for c in ("UC_ok", "UC_dark", "UC_badrow")]
        )
        assert seen == ["UC_dark"]
        assert out == {"new": 4, "failed": 2, "fallback": 1}
        # ...and the one line the stored log keeps says so (an INFO line outside a request is not).
        (warning,) = [r for r in caplog.records if getattr(r, "event", None) == "sync.rss.failed"]
        assert warning.attrs["fallback_read"] == 1 and warning.attrs["fallback_new"] == 3

    def test_no_channels_at_all_is_not_an_outage(self, monkeypatch):
        # A fresh instance with nothing subscribed must not report an error every poll.
        out = self._run(monkeypatch, fetch=lambda cid: [], apply_=lambda db, ch, e: 0, channels=())
        assert out == {"new": 0, "failed": 0, "fallback": 0}


class TestRssErrorVsEmpty:
    """A failed poll must RAISE (so the caller leaves `last_rss_at` alone); only a genuinely
    empty feed may return []."""

    def _patch(self, monkeypatch, **kwargs):
        def fake_get(url, **_):
            if "exc" in kwargs:
                raise kwargs["exc"]
            return httpx.Response(
                kwargs["status"],
                content=kwargs.get("body", b""),
                request=httpx.Request("GET", url),
            )

        monkeypatch.setattr(rss.httpx, "get", fake_get)
        monkeypatch.setattr(rss.time, "sleep", lambda s: None)

    def _answers(self, monkeypatch, *answers):
        """The endpoint answers each try with the next of `answers` (a status or an exception);
        returns the list of tries made and the waits between them."""
        tries, waits = [], []
        queue = list(answers)

        def fake_get(url, **_):
            answer = queue.pop(0)
            tries.append(answer)
            if isinstance(answer, Exception):
                raise answer
            body = self.FEED if answer == 200 else b""
            return httpx.Response(answer, content=body, request=httpx.Request("GET", url))

        monkeypatch.setattr(rss.httpx, "get", fake_get)
        monkeypatch.setattr(rss.time, "sleep", waits.append)
        return tries, waits

    FEED = b"""<?xml version="1.0"?>
    <feed xmlns="http://www.w3.org/2005/Atom" xmlns:yt="http://www.youtube.com/xml/schemas/2015">
      <entry><yt:videoId>abc123</yt:videoId><title>Hello</title></entry>
    </feed>"""

    def test_a_feed_that_fails_and_then_answers_is_read(self, monkeypatch):
        # The endpoint's measured behaviour: the same channel 404s, 500s, then answers.
        tries, waits = self._answers(monkeypatch, 404, 500, 200)
        assert [e["id"] for e in rss.fetch_channel_feed("UC_flaky")] == ["abc123"]
        assert (len(tries), waits) == (3, list(rss.RETRY_DELAYS))

    def test_a_dropped_connection_is_tried_again_too(self, monkeypatch):
        tries, _ = self._answers(monkeypatch, httpx.ConnectError("reset"), 200)
        assert rss.fetch_channel_feed("UC_blip")
        assert len(tries) == 2

    def test_a_timeout_is_not_tried_again(self, monkeypatch):
        # A hung request already cost the full timeout; retrying it would triple a poll over a
        # dead egress.
        tries, waits = self._answers(monkeypatch, httpx.ReadTimeout("hung"), 200)
        with pytest.raises(rss.RssError) as err:
            rss.fetch_channel_feed("UC_hung")
        assert (len(tries), waits, err.value.reason) == (1, [], "transport")

    def test_a_feed_that_keeps_failing_raises_its_last_failure(self, monkeypatch):
        tries, _ = self._answers(monkeypatch, 500, 404, 404)
        with pytest.raises(rss.RssError) as err:
            rss.fetch_channel_feed("UC_gone")
        assert (len(tries), err.value.reason) == (3, "http_404")

    def test_a_refusal_is_not_tried_again(self, monkeypatch):
        tries, waits = self._answers(monkeypatch, 403)
        with pytest.raises(rss.RssError) as err:
            rss.fetch_channel_feed("UC_forbidden")
        assert (len(tries), waits, err.value.reason) == (1, [], "http_403")

    def test_non_200_raises(self, monkeypatch):
        self._patch(monkeypatch, status=404)
        with pytest.raises(rss.RssError):
            rss.fetch_channel_feed("UC_dead")

    def test_transport_error_raises(self, monkeypatch):
        self._patch(monkeypatch, exc=httpx.ConnectError("no route"))
        with pytest.raises(rss.RssError):
            rss.fetch_channel_feed("UC_offline")

    def test_an_empty_but_valid_feed_returns_empty(self, monkeypatch):
        feed = b"""<?xml version="1.0"?><feed xmlns="http://www.w3.org/2005/Atom"></feed>"""
        self._patch(monkeypatch, status=200, body=feed)
        assert rss.fetch_channel_feed("UC_quiet") == []

    def test_entries_are_parsed(self, monkeypatch):
        feed = b"""<?xml version="1.0"?>
        <feed xmlns="http://www.w3.org/2005/Atom" xmlns:yt="http://www.youtube.com/xml/schemas/2015">
          <entry><yt:videoId>abc123</yt:videoId><title>Hello</title>
          <published>2026-07-23T10:00:00+00:00</published></entry>
        </feed>"""
        self._patch(monkeypatch, status=200, body=feed)
        out = rss.fetch_channel_feed("UC_live")
        assert [e["id"] for e in out] == ["abc123"]
        assert out[0]["channel_id"] == "UC_live"