"""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 httpx
import pytest

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()


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(lambda: (_ for _ in ()).throw(YouTubeError("quota")), lambda: failed.append("v1")) is FAILED
        assert failed == ["v1"] and b.open()
        b.run(lambda: (_ for _ in ()).throw(YouTubeError("quota")), 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(lambda: (_ for _ in ()).throw(YouTubeError("quota")), 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.
        with pytest.raises(ValueError):
            _Breaker().run(lambda: (_ for _ in ()).throw(ValueError("bug")), lambda: None)


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)

    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"