"""Two report-only /metrics series: cost-estimator calibration, and latency.

Both are MEASUREMENT SURFACES. Neither is read by routing, and the tests that
matter most here are the ones pinning that: a live experiment
(``objective.incumbent_cache_pricing``) is running while these landed, and a
series that quietly reached the ranker would confound it.

Every test seeds a throwaway SQLite DB from ``config/schema.sql`` and asserts
on queried aggregates, never on mock calls — the convention ``test_metrics.py``
established here.
"""

from __future__ import annotations

import inspect
import sqlite3
from datetime import datetime, timedelta, timezone
from pathlib import Path
from types import SimpleNamespace

import pytest

import metrics
from metrics import cost_estimate_calibration, latency_series

ROOT = Path(__file__).resolve().parent.parent
SCHEMA_SQL = (ROOT / "config" / "schema.sql").read_text()

CFG = SimpleNamespace(
    objective=SimpleNamespace(
        cost_calibration_window_hours=168,
        cost_calibration_min_observations=3,
        latency_window_hours=168,
        latency_min_observations=3,
    )
)


def _cfg(**overrides) -> SimpleNamespace:
    base = dict(
        cost_calibration_window_hours=168,
        cost_calibration_min_observations=3,
        latency_window_hours=168,
        latency_min_observations=3,
    )
    base.update(overrides)
    return SimpleNamespace(objective=SimpleNamespace(**base))


@pytest.fixture()
def conn(tmp_path):
    c = sqlite3.connect(tmp_path / "m.db")
    c.executescript(SCHEMA_SQL)
    c.row_factory = sqlite3.Row
    yield c
    c.close()


def _ago(hours: float) -> str:
    return (datetime.now(timezone.utc) - timedelta(hours=hours)).isoformat()


def _pair(
    conn,
    request_id,
    model_id,
    provider,
    est,
    billed,
    *,
    age_hours=1.0,
    task_category="coding_general",
    eo_model_id=None,
    eo_provider=None,
):
    """One decision plus the energy row its completion produced."""
    at = _ago(age_hours)
    conn.execute(
        "INSERT INTO route_decisions "
        "(kind, task_category, selected_model, selected_provider, "
        " est_cost_usd, request_id, observed_at) "
        "VALUES ('chat', ?, ?, ?, ?, ?, ?)",
        (task_category, model_id, provider, est, request_id, at),
    )
    conn.execute(
        "INSERT INTO energy_observations "
        "(model_id, provider, request_id, task_category, cost_usd, observed_at) "
        "VALUES (?, ?, ?, ?, ?, ?)",
        (
            eo_model_id or model_id,
            eo_provider or provider,
            request_id,
            task_category,
            billed,
            at,
        ),
    )


def _latency_row(
    conn,
    model_id,
    provider,
    wall,
    ttft,
    *,
    age_hours=1.0,
    task_category="coding_general",
):
    conn.execute(
        "INSERT INTO energy_observations "
        "(model_id, provider, task_category, router_wall_seconds, "
        " router_ttft_seconds, observed_at) "
        "VALUES (?, ?, ?, ?, ?, ?)",
        (model_id, provider, task_category, wall, ttft, _ago(age_hours)),
    )


# ---------------------------------------------------------------------------
# Item 1 — cost-estimator calibration
# ---------------------------------------------------------------------------


def test_correction_factor_is_billed_over_estimate(conn):
    """The two ratios are reciprocals, and each points the direction it says."""
    for i in range(4):
        _pair(conn, f"r{i}", "m", "neuralwatt", est=4.0, billed=1.0)
    conn.commit()

    series = cost_estimate_calibration(conn, _cfg())

    assert series["observations"] == 4
    assert series["est_cost_usd"] == pytest.approx(16.0)
    assert series["billed_cost_usd"] == pytest.approx(4.0)
    # est/billed: the estimator charged the ranker 4x what the account paid.
    assert series["overestimate_ratio"] == pytest.approx(4.0)
    # billed/est: what you would multiply INTO the estimate. Nothing does.
    assert series["correction_factor"] == pytest.approx(0.25)

    entry = series["by_model"][0]
    assert (entry["provider"], entry["model_id"]) == ("neuralwatt", "m")
    assert entry["est_per_request_usd"] == pytest.approx(4.0)
    assert entry["billed_per_request_usd"] == pytest.approx(1.0)
    assert entry["overestimate_ratio"] == pytest.approx(4.0)
    assert entry["correction_factor"] == pytest.approx(0.25)


def test_spread_is_the_reported_headline_not_the_scale(conn):
    """A uniform scale error reorders nothing; the spread is what does.

    This is the whole reason the series exists rather than a single global
    factor, so it is pinned with the live shape: two models whose estimates
    rank one way and whose bills rank the other.
    """
    # cheap-by-estimate, expensive-by-bill
    for i in range(4):
        _pair(conn, f"a{i}", "under", "openrouter", est=3.0, billed=0.66)
    # expensive-by-estimate, cheap-by-bill
    for i in range(4):
        _pair(conn, f"b{i}", "over", "neuralwatt", est=4.1, billed=0.51)
    conn.commit()

    series = cost_estimate_calibration(conn, _cfg())

    by_key = {(e["provider"], e["model_id"]): e for e in series["by_model"]}
    under = by_key[("openrouter", "under")]
    over = by_key[("neuralwatt", "over")]

    # The estimator orders them one way...
    assert under["est_per_request_usd"] < over["est_per_request_usd"]
    # ...and the bill orders them the other. That inversion is the finding.
    assert under["billed_per_request_usd"] > over["billed_per_request_usd"]

    assert series["spread"] == pytest.approx(
        over["overestimate_ratio"] / under["overestimate_ratio"]
    )
    assert series["spread"] > 1.5
    assert series["spread_low"]["model_id"] == "under"
    assert series["spread_high"]["model_id"] == "over"


def test_thin_groups_are_listed_but_excluded_from_spread(conn):
    """A ratio over one request is information, never the headline."""
    for i in range(4):
        _pair(conn, f"a{i}", "thick", "neuralwatt", est=4.0, billed=1.0)
    _pair(conn, "solo", "thin", "neuralwatt", est=100.0, billed=1.0)
    conn.commit()

    series = cost_estimate_calibration(conn, _cfg())

    by_key = {e["model_id"]: e for e in series["by_model"]}
    assert by_key["thin"]["sufficient"] is False
    assert by_key["thin"]["overestimate_ratio"] == pytest.approx(100.0)
    assert by_key["thick"]["sufficient"] is True

    # One qualifying group -> spread 1.0, and the 100x outlier does not set it.
    assert series["spread"] == pytest.approx(1.0)
    assert series["spread_high"]["model_id"] == "thick"


def test_seed_reference_is_excluded_from_both_sides(conn):
    """Sweep traffic is a fixed 400/400 shape no real request resembles."""
    for i in range(4):
        _pair(conn, f"real{i}", "m", "neuralwatt", est=4.0, billed=1.0)
    for i in range(20):
        _pair(
            conn,
            f"seed{i}",
            "m",
            "neuralwatt",
            est=1.0,
            billed=1.0,
            task_category="seed_reference",
        )
    conn.commit()

    series = cost_estimate_calibration(conn, _cfg())

    assert series["observations"] == 4
    assert series["overestimate_ratio"] == pytest.approx(4.0)


def test_a_failover_row_does_not_pair_one_models_estimate_with_anothers_bill(conn):
    """The request id alone is not enough to join on.

    Live on router.db: 5 of 4,143 joined rows carry a decision that selected
    `qwen3.6-35b` (neuralwatt) against a completion billed by
    `qwen/qwen3.6-35b-a3b` (openrouter) — a cross-provider failover. Joining
    on request_id alone would price one model's estimate against another
    model's bill, which is precisely the contamination this series cannot
    afford.
    """
    for i in range(4):
        _pair(conn, f"ok{i}", "picked", "neuralwatt", est=4.0, billed=1.0)
    _pair(
        conn,
        "failover",
        "picked",
        "neuralwatt",
        est=4.0,
        billed=99.0,
        eo_model_id="answered",
        eo_provider="openrouter",
    )
    conn.commit()

    series = cost_estimate_calibration(conn, _cfg())

    assert series["observations"] == 4
    assert {e["model_id"] for e in series["by_model"]} == {"picked"}
    assert series["billed_cost_usd"] == pytest.approx(4.0)


def test_unbilled_and_unestimated_rows_are_dropped(conn):
    """A zero or NULL bill is a row the provider did not price, not a free one."""
    for i in range(4):
        _pair(conn, f"ok{i}", "m", "neuralwatt", est=4.0, billed=1.0)
    _pair(conn, "zero", "m", "neuralwatt", est=4.0, billed=0.0)
    _pair(conn, "null-bill", "m", "neuralwatt", est=4.0, billed=None)
    _pair(conn, "null-est", "m", "neuralwatt", est=None, billed=1.0)
    conn.commit()

    series = cost_estimate_calibration(conn, _cfg())
    assert series["observations"] == 4


def test_rows_outside_the_window_are_dropped(conn):
    for i in range(4):
        _pair(conn, f"new{i}", "m", "neuralwatt", est=4.0, billed=1.0)
    for i in range(10):
        _pair(
            conn, f"old{i}", "m", "neuralwatt", est=1.0, billed=1.0, age_hours=200
        )
    conn.commit()

    series = cost_estimate_calibration(conn, _cfg(cost_calibration_window_hours=168))
    assert series["observations"] == 4


def test_empty_database_returns_a_shaped_series(conn):
    """No data is not an error, and every key a consumer reads still exists."""
    series = cost_estimate_calibration(conn, _cfg())
    assert series["observations"] == 0
    assert series["by_model"] == []
    for key in ("overestimate_ratio", "correction_factor", "spread"):
        assert series[key] is None


def test_config_defaults_are_used_when_the_knobs_are_absent(conn):
    """An older config file, or a SimpleNamespace in a test, must not crash."""
    bare = SimpleNamespace(objective=SimpleNamespace())
    series = cost_estimate_calibration(conn, bare)
    assert series["window_hours"] == metrics._COST_CALIBRATION_WINDOW_HOURS
    assert series["min_observations"] == metrics._COST_CALIBRATION_MIN_OBSERVATIONS


# ---------------------------------------------------------------------------
# Item 2 — latency
# ---------------------------------------------------------------------------


def test_percentiles_per_model(conn):
    for wall, ttft in [(1.0, 0.5), (2.0, 1.0), (3.0, 1.5), (100.0, 50.0)]:
        _latency_row(conn, "slow", "openrouter", wall, ttft)
    conn.commit()

    series = latency_series(conn, _cfg())

    entry = series["by_model"][0]
    assert entry["wall_observations"] == 4
    assert entry["ttft_observations"] == 4
    assert entry["wall_p50"] == pytest.approx(2.5)
    assert entry["wall_p95"] == pytest.approx(85.45)
    assert entry["ttft_p50"] == pytest.approx(1.25)
    assert entry["wall_sufficient"] is True
    assert entry["ttft_sufficient"] is True
    # The aggregate is over the same rows when there is only one model.
    assert series["wall_p50"] == pytest.approx(2.5)


def test_wall_and_ttft_counts_are_independent(conn):
    """TTFT is streaming-only, so a group can be thick on wall and thin on TTFT.

    Reporting one count for both would let a handful of streamed requests
    borrow the credibility of a large buffered sample.
    """
    for i in range(6):
        _latency_row(conn, "m", "neuralwatt", 2.0 + i, None)
    _latency_row(conn, "m", "neuralwatt", 2.0, 1.0)
    conn.commit()

    series = latency_series(conn, _cfg(latency_min_observations=3))
    entry = series["by_model"][0]

    assert entry["wall_observations"] == 7
    assert entry["ttft_observations"] == 1
    assert entry["wall_sufficient"] is True
    assert entry["ttft_sufficient"] is False
    assert entry["ttft_p50"] == pytest.approx(1.0)
    assert series["wall_observations"] == 7
    assert series["ttft_observations"] == 1


def test_a_group_with_no_ttft_at_all_reports_none_not_zero(conn):
    """No measurement is not a measurement of zero."""
    for i in range(4):
        _latency_row(conn, "buffered", "neuralwatt", 3.0, None)
    conn.commit()

    entry = latency_series(conn, _cfg())["by_model"][0]
    assert entry["ttft_observations"] == 0
    assert entry["ttft_p50"] is None
    assert entry["ttft_p95"] is None
    assert entry["wall_p50"] == pytest.approx(3.0)


def test_seed_reference_is_excluded_from_latency(conn):
    """Redundant today (the sweep writes no wall clock) and kept anyway."""
    _latency_row(conn, "m", "neuralwatt", 2.0, 1.0)
    for i in range(20):
        _latency_row(
            conn, "m", "neuralwatt", 999.0, 999.0, task_category="seed_reference"
        )
    conn.commit()

    series = latency_series(conn, _cfg())
    assert series["wall_observations"] == 1
    assert series["wall_p50"] == pytest.approx(2.0)


def test_rows_outside_the_latency_window_are_dropped(conn):
    _latency_row(conn, "m", "neuralwatt", 2.0, 1.0)
    _latency_row(conn, "m", "neuralwatt", 999.0, 999.0, age_hours=200)
    conn.commit()

    series = latency_series(conn, _cfg(latency_window_hours=168))
    assert series["wall_observations"] == 1


def test_latency_degrades_rather_than_raising_without_the_columns(tmp_path):
    """Both columns arrive by ALTER, and `admin` may open a pre-migration DB.

    A missing column must degrade this series, never 500 the whole /metrics
    payload — the contract `cache_rate_series` already keeps.
    """
    schema = SCHEMA_SQL.replace("    router_wall_seconds REAL,\n", "").replace(
        "    router_ttft_seconds REAL,\n", ""
    )

    c = sqlite3.connect(tmp_path / "old.db")
    c.executescript(schema)
    c.row_factory = sqlite3.Row
    try:
        # Assert on the DB, not on the SQL text: both names also appear in
        # schema.sql's prose comments, so a substring check on the source
        # would pass while the columns were still there.
        cols = {r[1] for r in c.execute("PRAGMA table_info(energy_observations)")}
        assert "router_wall_seconds" not in cols
        assert "router_ttft_seconds" not in cols

        series = latency_series(c, _cfg())
    finally:
        c.close()

    assert series["wall_observations"] == 0
    assert series["wall_p50"] is None
    assert series["by_model"] == []


def test_latency_config_defaults_when_the_knobs_are_absent(conn):
    bare = SimpleNamespace(objective=SimpleNamespace())
    series = latency_series(conn, bare)
    assert series["window_hours"] == metrics._LATENCY_WINDOW_HOURS
    assert series["min_observations"] == metrics._LATENCY_MIN_OBSERVATIONS


# ---------------------------------------------------------------------------
# The constraint both series are under
# ---------------------------------------------------------------------------


def test_neither_series_is_read_by_the_routing_path():
    """Measurement only. A live experiment is running; a series that reached
    the ranker would confound it.

    Asserted against the module source rather than trusted to review: the two
    names must not appear in routing.py or on dispatcher's dispatch path at
    all. ``dispatcher`` calls them exactly once each, from the /metrics
    endpoint.
    """
    import dispatcher
    import routing

    routing_src = inspect.getsource(routing)
    for name in ("cost_estimate_calibration", "latency_series"):
        assert name not in routing_src, (
            f"{name} reached routing.py. Both series are report-only; "
            "applying one changes which model gets picked."
        )

    dispatcher_src = inspect.getsource(dispatcher)
    for name in ("cost_estimate_calibration", "latency_series"):
        # Once in the import block, once in the /metrics payload.
        assert dispatcher_src.count(name) == 2, (
            f"{name} is referenced {dispatcher_src.count(name)} times in "
            "dispatcher.py; it should appear only in the import and in the "
            "/metrics payload."
        )


def test_metrics_still_imports_without_dispatcher():
    """metrics.py must never import dispatcher — the circular-import break."""
    src = inspect.getsource(metrics)
    assert "import dispatcher" not in src