"""SearchService: the backend orchestration policy.

Which backend to try, in what order, when to fall back, and what counts as
evidence a backend is unhealthy. None of this needs an HTTP layer, so none
of these tests use one.

Each test builds a service with its own circuit breaker. That replaces the
autouse fixture that used to reset a process-wide singleton between tests -
the breaker being shared across every request is correct in production and
was only a problem because tests had no way to opt out of it.
"""


import services as services_module
from circuit_breaker import CircuitBreaker
from serp import DuckDuckGoBlockedException, SerpQuery
from services import SearchService, shape_serp_results


class FakeOPSTokens:
    def __init__(self, configured: bool):
        self.configured = configured


def make_service(*, ops_configured: bool = False, breaker: CircuitBreaker = None,
                 browser=None) -> SearchService:
    return SearchService(
        http_client=None,
        browser_provider=lambda: browser,
        circuit_breaker=breaker or CircuitBreaker(),
        ops_tokens=FakeOPSTokens(ops_configured),
    )


# --------------------------------- result shaping ---------------------------------


class TestShapeSerpResults:
    def test_flattens_successful_lists(self):
        result = shape_serp_results([[{"a": 1}], [{"b": 2}, {"c": 3}]])
        assert result.results == [{"a": 1}, {"b": 2}, {"c": 3}]
        assert result.error is None

    def test_surfaces_last_error_when_all_failed(self):
        result = shape_serp_results([ValueError("first"), RuntimeError("second")])
        assert result.results == []
        assert "second" in result.error

    def test_ignores_failures_when_some_succeed(self):
        result = shape_serp_results([[{"a": 1}], RuntimeError("boom")])
        assert result.results == [{"a": 1}]
        assert result.error is None

    def test_is_total_for_an_empty_list(self):
        """Defence in depth: the request models bound the query list, but
        this helper is shared by every search path and must not depend on
        its caller having validated anything."""
        result = shape_serp_results([])
        assert result.results == []
        assert result.error is not None


# ------------------------------- per-query dispatch -------------------------------


async def test_every_query_is_dispatched_with_the_result_count():
    calls = []

    async def fn(q, n):
        calls.append((q, n))
        return [{"q": q}]

    result = await make_service()._run_queries(
        fn, SerpQuery(queries=["x", "y"], n_results=5), "test context")

    assert sorted(calls) == [("x", 5), ("y", 5)]
    assert sorted(result.results, key=str) == sorted([{"q": "x"}, {"q": "y"}], key=str)


async def test_arxiv_flattens_results_from_all_queries(monkeypatch):
    async def fake_query_arxiv(client, q, n):
        return [{"title": f"paper about {q}"}]

    monkeypatch.setattr(services_module, "query_arxiv", fake_query_arxiv)

    result = await make_service().arxiv(SerpQuery(queries=["a", "b"], n_results=5))

    assert {r["title"] for r in result.results} == {"paper about a", "paper about b"}
    assert result.error is None


async def test_arxiv_reports_an_error_when_every_query_fails(monkeypatch):
    async def failing(client, q, n):
        raise RuntimeError(f"boom for {q}")

    monkeypatch.setattr(services_module, "query_arxiv", failing)

    result = await make_service().arxiv(SerpQuery(queries=["a"], n_results=5))

    assert result.results == []
    assert "boom for a" in result.error


# ------------------------------ patents + OPS fallback ------------------------------


async def test_patents_does_not_fall_back_when_google_patents_succeeds(monkeypatch):
    ops_called = False

    async def fake_ops(client, q, n):
        nonlocal ops_called
        ops_called = True
        return []

    monkeypatch.setattr(
        services_module, "query_google_patents",
        lambda b, q, n: _ok([{"id": "US1", "title": "t"}]))
    monkeypatch.setattr(services_module, "ops_search", fake_ops)

    result = await make_service(ops_configured=True).patents(
        SerpQuery(queries=["widget"], n_results=5))

    assert result.results == [{"id": "US1", "title": "t"}]
    assert ops_called is False


async def _ok(value):
    return value


async def test_patents_falls_back_to_ops_when_google_patents_is_empty(monkeypatch):
    monkeypatch.setattr(services_module, "query_google_patents", lambda b, q, n: _ok([]))
    monkeypatch.setattr(
        services_module, "ops_search", lambda c, q, n: _ok([{"id": "US123", "title": "OPS"}]))

    result = await make_service(ops_configured=True).patents(
        SerpQuery(queries=["widget"], n_results=5))

    assert result.results == [{"id": "US123", "title": "OPS"}]


async def test_patents_does_not_fall_back_when_ops_is_unconfigured(monkeypatch):
    monkeypatch.setattr(services_module, "query_google_patents", lambda b, q, n: _ok([]))

    result = await make_service(ops_configured=False).patents(
        SerpQuery(queries=["widget"], n_results=5))

    assert result.results == []
    assert result.error is None


async def test_ops_fallback_runs_concurrently_not_one_query_at_a_time(monkeypatch):
    """This path exists for when Google Patents is unavailable, which is
    exactly when a request can least afford N sequential round-trips to the
    slower backend."""
    import asyncio

    in_flight = 0
    peak = 0

    async def slow_ops(client, q, n):
        nonlocal in_flight, peak
        in_flight += 1
        peak = max(peak, in_flight)
        await asyncio.sleep(0.02)
        in_flight -= 1
        return [{"id": q}]

    monkeypatch.setattr(services_module, "query_google_patents", lambda b, q, n: _ok([]))
    monkeypatch.setattr(services_module, "ops_search", slow_ops)

    await make_service(ops_configured=True).patents(
        SerpQuery(queries=["a", "b", "c", "d"], n_results=5))

    assert peak > 1, "OPS fallback queries were issued one at a time"


async def test_a_failing_ops_fallback_does_not_lose_other_queries_results(monkeypatch):
    async def selective_ops(client, q, n):
        if q == "bad":
            raise RuntimeError("OPS down")
        return [{"id": q}]

    monkeypatch.setattr(services_module, "query_google_patents", lambda b, q, n: _ok([]))
    monkeypatch.setattr(services_module, "ops_search", selective_ops)

    result = await make_service(ops_configured=True).patents(
        SerpQuery(queries=["good", "bad"], n_results=5))

    assert result.results == [{"id": "good"}]


# -------------------------------- the fallback chain --------------------------------


async def test_returns_the_first_backend_that_succeeds(monkeypatch):
    calls = []

    async def fake_ddg(q, n):
        calls.append("ddg")
        return [{"title": "from ddg"}]

    async def fake_brave(browser, q, n):
        calls.append("brave")
        return [{"title": "from brave"}]

    monkeypatch.setattr(services_module, "query_ddg_search", fake_ddg)
    monkeypatch.setattr(services_module, "query_brave_search", fake_brave)

    q, results, err = await make_service()._search_one("widget", 5)

    assert calls == ["ddg"]
    assert results == [{"title": "from ddg"}]
    assert err is None


async def test_falls_through_to_the_next_backend_on_failure(monkeypatch):
    calls = []

    async def failing_ddg(q, n):
        calls.append("ddg")
        raise RuntimeError("ddg blocked")

    async def fake_brave(browser, q, n):
        calls.append("brave")
        return [{"title": "from brave"}]

    monkeypatch.setattr(services_module, "query_ddg_search", failing_ddg)
    monkeypatch.setattr(services_module, "query_brave_search", fake_brave)

    q, results, err = await make_service()._search_one("widget", 5)

    assert calls == ["ddg", "brave"]
    assert results == [{"title": "from brave"}]
    assert err is None


async def test_reports_an_error_when_every_backend_fails(monkeypatch):
    async def failing(*args):
        raise RuntimeError("blocked")

    for name in ("query_ddg_search", "query_brave_search", "query_bing_search"):
        monkeypatch.setattr(services_module, name, failing)

    q, results, err = await make_service()._search_one("widget", 5)

    assert results == []
    assert "widget" in err
    # Each backend is named with what it did, rather than collapsed into a
    # single "all backends failed" with only the last error attached.
    for backend in ("DuckDuckGo", "Brave Search", "Bing"):
        assert f"{backend}: failed" in err
    assert "blocked" in err


# ------------------------------ the circuit breaker ------------------------------


async def test_skips_a_backend_whose_circuit_is_open(monkeypatch):
    """A backend that's failed `failure_threshold` times in a row shouldn't
    be attempted again until its cooldown elapses - repeatedly hammering a
    backend that's already rate-limiting us only makes that worse.
    """
    ddg_calls = []

    async def failing_ddg(q, n):
        ddg_calls.append(q)
        raise RuntimeError("ddg blocked")

    async def fake_brave(browser, q, n):
        return [{"title": "from brave"}]

    monkeypatch.setattr(services_module, "query_ddg_search", failing_ddg)
    monkeypatch.setattr(services_module, "query_brave_search", fake_brave)

    service = make_service(breaker=CircuitBreaker(failure_threshold=1, cooldown_seconds=60))

    await service._search_one("first query", 5)
    assert ddg_calls == ["first query"]

    q, results, err = await service._search_one("second query", 5)

    assert ddg_calls == ["first query"]  # unchanged - DDG was skipped
    assert results == [{"title": "from brave"}]


async def test_a_zero_result_query_does_not_open_the_circuit(monkeypatch):
    """An empty result is ambiguous - it can mean the query genuinely has no
    hits, or that the backend served an anti-bot page that parsed to
    nothing. The breaker is shared across every request, so counting the
    ambiguous case meant a few unusual-but-legitimate queries could disable
    the primary backend for everyone for a full cooldown.
    """
    ddg_calls = []

    async def empty_ddg(q, n):
        ddg_calls.append(q)
        raise DuckDuckGoBlockedException()

    monkeypatch.setattr(services_module, "query_ddg_search", empty_ddg)
    monkeypatch.setattr(
        services_module, "query_brave_search", lambda b, q, n: _ok([{"title": "brave"}]))

    service = make_service(breaker=CircuitBreaker(failure_threshold=1, cooldown_seconds=60))

    await service._search_one("obscure", 5)
    await service._search_one("another obscure", 5)

    assert ddg_calls == ["obscure", "another obscure"]


async def test_an_empty_result_still_falls_through_to_the_next_backend(monkeypatch):
    """Not counting it against the backend must not stop the fallback: the
    caller still needs results from somewhere."""
    async def empty_ddg(q, n):
        raise DuckDuckGoBlockedException()

    monkeypatch.setattr(services_module, "query_ddg_search", empty_ddg)
    monkeypatch.setattr(
        services_module, "query_brave_search", lambda b, q, n: _ok([{"title": "from brave"}]))

    _q, results, err = await make_service()._search_one("widget", 5)

    assert results == [{"title": "from brave"}]
    assert err is None


async def test_a_real_backend_error_still_opens_the_circuit(monkeypatch):
    """The distinction has to cut both ways: a backend raising a genuine
    error (a rate limit, a transport failure) is still evidence."""
    ddg_calls = []

    async def failing_ddg(q, n):
        ddg_calls.append(q)
        raise RuntimeError("rate limited")

    monkeypatch.setattr(services_module, "query_ddg_search", failing_ddg)
    monkeypatch.setattr(
        services_module, "query_brave_search", lambda b, q, n: _ok([{"title": "brave"}]))

    service = make_service(breaker=CircuitBreaker(failure_threshold=1, cooldown_seconds=60))

    await service._search_one("first", 5)
    await service._search_one("second", 5)

    assert ddg_calls == ["first"]


# ------------------------------- search aggregation -------------------------------


async def test_search_merges_results_from_every_query(monkeypatch):
    monkeypatch.setattr(
        services_module, "query_ddg_search", lambda q, n: _ok([{"title": f"result for {q}"}]))

    result = await make_service().search(SerpQuery(queries=["a", "b"], n_results=5))

    assert {r["title"] for r in result.results} == {"result for a", "result for b"}
    assert result.error is None


async def test_search_reports_partial_failure_alongside_results(monkeypatch):
    """A query no backend could answer must be reported even when another
    query succeeded - otherwise the caller silently receives fewer results
    than they asked for with no indication why."""
    async def selective_ddg(q, n):
        if q == "bad":
            raise RuntimeError("blocked")
        return [{"title": f"result for {q}"}]

    async def failing(*args):
        raise RuntimeError("blocked")

    monkeypatch.setattr(services_module, "query_ddg_search", selective_ddg)
    monkeypatch.setattr(services_module, "query_brave_search", failing)
    monkeypatch.setattr(services_module, "query_bing_search", failing)

    result = await make_service().search(SerpQuery(queries=["good", "bad"], n_results=5))

    assert [r["title"] for r in result.results] == ["result for good"]
    assert "bad" in result.error


async def test_search_names_every_failed_query_not_just_the_last(monkeypatch):
    async def failing(*args):
        raise RuntimeError("blocked")

    for name in ("query_ddg_search", "query_brave_search", "query_bing_search"):
        monkeypatch.setattr(services_module, name, failing)

    result = await make_service().search(SerpQuery(queries=["a", "b"], n_results=5))

    assert result.results == []
    assert "'a'" in result.error and "'b'" in result.error


async def test_a_scholar_block_is_reported_as_such_to_the_caller(monkeypatch):
    """The point of the dedicated exception is the message the caller sees:
    "Google Scholar blocked the request" tells an operator their IP is
    rate-limited, where the bare "Timeout 30000ms exceeded" it replaced read
    like a broken selector.
    """
    from serp import GoogleScholarBlockedException

    async def blocked(browser, q, n):
        raise GoogleScholarBlockedException()

    monkeypatch.setattr(services_module, "query_google_scholar", blocked)

    result = await make_service().google_scholar(SerpQuery(queries=["anything"]))

    assert result.results == []
    assert "blocked" in result.error.lower()
    assert "timeout" not in result.error.lower()


# ------------------- an empty answer is not an answer -------------------
# A backend returning [] without raising used to end the fallback chain and
# be reported as success. Brave does that whenever its block page lacks the
# word "suspicious", and Bing whenever no result item yields a title+href.
# The caller then got zero results and the invented explanation "All
# backends are rate-limited." - a guess, not evidence. Observed once
# against the live deployment.


async def test_an_empty_backend_result_falls_through_to_the_next_backend(monkeypatch):
    calls = []

    async def empty_ddg(q, n):
        calls.append("ddg")
        return []

    async def fake_brave(browser, q, n):
        calls.append("brave")
        return [{"title": "from brave"}]

    monkeypatch.setattr(services_module, "query_ddg_search", empty_ddg)
    monkeypatch.setattr(services_module, "query_brave_search", fake_brave)

    _q, results, err = await make_service()._search_one("widget", 5)

    assert calls == ["ddg", "brave"], "an empty result ended the chain"
    assert results == [{"title": "from brave"}]
    assert err is None


async def test_every_backend_empty_reports_that_and_not_rate_limiting(monkeypatch):
    """The message has to describe what happened. "Rate-limited" was
    asserted without evidence, and sent whoever read it looking for a
    throttling problem that may not exist.
    """
    async def empty(*args):
        return []

    for name in ("query_ddg_search", "query_brave_search", "query_bing_search"):
        monkeypatch.setattr(services_module, name, empty)

    _q, results, err = await make_service()._search_one("widget", 5)

    assert results == []
    assert "rate-limit" not in err.lower()
    for backend in ("DuckDuckGo", "Brave Search", "Bing"):
        assert backend in err, f"{backend}'s outcome is missing from {err!r}"


async def test_the_error_distinguishes_failing_from_returning_nothing(monkeypatch):
    """"Failed" and "answered with nothing" are different problems and lead
    somewhere different - one is an outage, the other may just be an
    obscure query."""
    async def failing_ddg(q, n):
        raise RuntimeError("connection reset")

    async def empty_brave(browser, q, n):
        return []

    async def failing_bing(browser, q, n):
        raise RuntimeError("connection reset")

    monkeypatch.setattr(services_module, "query_ddg_search", failing_ddg)
    monkeypatch.setattr(services_module, "query_brave_search", empty_brave)
    monkeypatch.setattr(services_module, "query_bing_search", failing_bing)

    _q, _results, err = await make_service()._search_one("widget", 5)

    assert "connection reset" in err, "a real failure must still surface its cause"
    assert "no results" in err.lower(), "an empty answer must be described as such"


async def test_a_skipped_backend_is_reported_as_skipped_not_failed(monkeypatch):
    """A backend whose circuit is open was never asked, so saying it failed
    for this query is wrong."""
    async def empty(*args):
        return []

    for name in ("query_ddg_search", "query_brave_search", "query_bing_search"):
        monkeypatch.setattr(services_module, name, empty)

    breaker = CircuitBreaker(failure_threshold=1, cooldown_seconds=60)
    breaker.record_failure("Bing")
    service = make_service(breaker=breaker)

    _q, _results, err = await service._search_one("widget", 5)

    assert "skipped" in err.lower()


async def test_an_empty_answer_does_not_clear_an_accumulating_failure_count(monkeypatch):
    """Empty is ambiguous, so it is evidence neither way. Recording it as a
    success would reset a backend part-way to tripping its breaker, which
    is how a soft-blocking backend stays in rotation forever.
    """
    breaker = CircuitBreaker(failure_threshold=2, cooldown_seconds=60)
    breaker.record_failure("DuckDuckGo")  # one strike already

    async def empty_ddg(q, n):
        return []

    monkeypatch.setattr(services_module, "query_ddg_search", empty_ddg)
    monkeypatch.setattr(
        services_module, "query_brave_search", lambda b, q, n: _ok([{"title": "brave"}]))

    await make_service(breaker=breaker)._search_one("widget", 5)

    assert breaker._states["DuckDuckGo"].failure_count == 1, (
        "an empty result cleared DuckDuckGo's failure count")


async def test_search_never_invents_a_rate_limit_explanation(monkeypatch):
    """The endpoint-level guard for the same thing."""
    async def empty(*args):
        return []

    for name in ("query_ddg_search", "query_brave_search", "query_bing_search"):
        monkeypatch.setattr(services_module, name, empty)

    result = await make_service().search(SerpQuery(queries=["a", "b"]))

    assert result.results == []
    assert result.error and "rate-limit" not in result.error.lower()


async def test_the_aggregate_fallback_message_states_a_fact_not_a_diagnosis():
    """`_search_one` always explains itself, so `search`'s fallback text is
    unreachable in practice - which is exactly how the rate-limit guess
    survived unnoticed for so long. Reach it directly so the defensive
    branch says something defensible too.
    """
    service = make_service()

    async def silent_search_one(q, n_results):
        return q, [], None

    service._search_one = silent_search_one

    result = await service.search(SerpQuery(queries=["a"]))

    assert result.results == []
    assert "rate-limit" not in result.error.lower()
    assert result.error, "an empty result set must still carry an explanation"