"""evaluate_gate: baseline-vs-candidate comparison and per-tag regression detection."""

from __future__ import annotations

import pytest

from ragcore.evaluation.metrics import (
    AggregateMetrics,
    MetricsError,
    MetricsReport,
    RegressionMetric,
    RegressionThresholds,
    evaluate_gate,
)


def make_aggregate(**changes: object) -> AggregateMetrics:
    value: dict[str, object] = {
        "case_count": 10,
        "mean_recall_at_5": 0.8,
        "mean_recall_at_10": 0.9,
        "mean_reciprocal_rank": 0.7,
        "mean_ndcg_at_10": 0.85,
        "zero_result_rate": 0.05,
    }
    value.update(changes)
    return AggregateMetrics(**value)


def make_report(
    overall: AggregateMetrics, per_tag: dict[str, AggregateMetrics] | None = None
) -> MetricsReport:
    return MetricsReport(
        dataset_id="ds", dataset_version="v1", overall=overall, per_tag=per_tag or {}
    )


def default_thresholds(**changes: object) -> RegressionThresholds:
    value: dict[str, object] = {"version": "gate-v1"}
    value.update(changes)
    return RegressionThresholds(**value)


def test_identical_metrics_pass_the_gate() -> None:
    metrics = make_aggregate()
    result = evaluate_gate(make_report(metrics), make_report(metrics), default_thresholds())

    assert result.passed
    assert result.regressions == ()


def test_improved_metrics_pass_the_gate() -> None:
    baseline = make_aggregate(mean_recall_at_10=0.8)
    candidate = make_aggregate(mean_recall_at_10=0.95)
    result = evaluate_gate(make_report(baseline), make_report(candidate), default_thresholds())

    assert result.passed


def test_recall_drop_beyond_threshold_fails_the_gate() -> None:
    baseline = make_aggregate(mean_recall_at_10=0.9)
    candidate = make_aggregate(mean_recall_at_10=0.80)  # 0.10 drop > default 0.05
    result = evaluate_gate(make_report(baseline), make_report(candidate), default_thresholds())

    assert not result.passed
    assert any(f.metric is RegressionMetric.RECALL_AT_10 for f in result.regressions)


def test_recall_drop_within_threshold_passes() -> None:
    baseline = make_aggregate(mean_recall_at_10=0.90)
    candidate = make_aggregate(mean_recall_at_10=0.87)  # 0.03 drop <= default 0.05
    result = evaluate_gate(make_report(baseline), make_report(candidate), default_thresholds())

    assert result.passed


def test_zero_result_rate_rise_fails_the_gate() -> None:
    baseline = make_aggregate(zero_result_rate=0.02)
    candidate = make_aggregate(zero_result_rate=0.10)  # 0.08 rise > default 0.02
    result = evaluate_gate(make_report(baseline), make_report(candidate), default_thresholds())

    assert not result.passed
    assert any(f.metric is RegressionMetric.ZERO_RESULT_RATE for f in result.regressions)


def test_per_tag_regression_is_highlighted_even_when_overall_passes() -> None:
    baseline = make_report(
        make_aggregate(),
        per_tag={
            "exact-identifier": make_aggregate(mean_recall_at_10=0.95),
            "conceptual": make_aggregate(mean_recall_at_10=0.85),
        },
    )
    candidate = make_report(
        make_aggregate(),  # overall unchanged
        per_tag={
            "exact-identifier": make_aggregate(mean_recall_at_10=0.70),  # regressed
            "conceptual": make_aggregate(mean_recall_at_10=0.86),  # slightly improved
        },
    )

    result = evaluate_gate(baseline, candidate, default_thresholds())

    assert not result.passed
    tag_regressions = {finding.tag for finding in result.regressions}
    assert "exact-identifier" in tag_regressions
    assert "conceptual" not in tag_regressions


def test_tags_only_present_in_one_report_are_not_compared() -> None:
    baseline = make_report(make_aggregate(), per_tag={"old-tag": make_aggregate()})
    candidate = make_report(
        make_aggregate(), per_tag={"new-tag": make_aggregate(mean_recall_at_10=0.0)}
    )

    result = evaluate_gate(baseline, candidate, default_thresholds())

    assert result.passed  # only overall is compared; mismatched tags are skipped


def test_gate_rejects_mismatched_datasets() -> None:
    baseline = MetricsReport(dataset_id="a", dataset_version="v1", overall=make_aggregate())
    candidate = MetricsReport(dataset_id="b", dataset_version="v1", overall=make_aggregate())

    with pytest.raises(MetricsError, match="same dataset"):
        evaluate_gate(baseline, candidate, default_thresholds())


def test_gate_result_invariants_are_enforced() -> None:
    from ragcore.evaluation.metrics import GateResult, RegressionFinding

    with pytest.raises(MetricsError, match="must not carry regressions"):
        GateResult(
            thresholds_version="v1",
            passed=True,
            regressions=(
                RegressionFinding(
                    metric=RegressionMetric.RECALL_AT_5,
                    tag=None,
                    baseline_value=0.9,
                    candidate_value=0.5,
                    delta=-0.4,
                ),
            ),
        )
    with pytest.raises(MetricsError, match="at least one regression"):
        GateResult(thresholds_version="v1", passed=False, regressions=())