from __future__ import annotations

from datetime import UTC, datetime, timedelta

import pytest

from modelforge_api.services.gpu_scheduler import (
    AttributionConfidence,
    LeaseAllocation,
    PlacementInput,
    PlacementVerdict,
    PressureHysteresis,
    PressureState,
    ResidentCandidate,
    SchedulerPolicy,
    calculate_accounting,
    dynamic_reserve,
    plan_placement,
    required_envelope,
)

GIB = 1024**3
POLICY = SchedulerPolicy()


def accounting(
    observed: int | None, resident: int = 0, leases: list[LeaseAllocation] | None = None
):
    return calculate_accounting(
        total_bytes=16 * GIB,
        observed_used_bytes=observed,
        resident_bytes=resident,
        leases=leases or [],
        policy=POLICY,
    )


@pytest.mark.parametrize(
    ("observed", "resident", "external"),
    [(0, 0, 0), (4 * GIB, 0, 4 * GIB), (2 * GIB, 2 * GIB, 0), (6 * GIB, 2 * GIB, 4 * GIB)],
)
def test_accounting_attributes_observed_usage_without_double_count(
    observed: int, resident: int, external: int
) -> None:
    result = accounting(observed, resident)
    assert result.external_bytes == external
    assert result.schedulable_bytes == 16 * GIB - observed - result.reserve_bytes
    assert result.invariant_delta_bytes == 0
    assert result.attribution is AttributionConfidence.KNOWN


def test_accounting_only_subtracts_unmaterialized_lease_bytes() -> None:
    result = accounting(
        5 * GIB,
        2 * GIB,
        [LeaseAllocation(3 * GIB, 2 * GIB), LeaseAllocation(GIB, GIB)],
    )
    assert result.future_lease_bytes == GIB
    assert result.schedulable_bytes == 16 * GIB - 5 * GIB - GIB - result.reserve_bytes


def test_unknown_or_stale_telemetry_fails_closed() -> None:
    unknown = accounting(None)
    stale = calculate_accounting(
        total_bytes=16 * GIB,
        observed_used_bytes=0,
        resident_bytes=0,
        leases=[],
        policy=POLICY,
        telemetry_fresh=False,
    )
    assert unknown.attribution is AttributionConfidence.UNKNOWN
    assert unknown.schedulable_bytes == stale.schedulable_bytes == 0
    assert unknown.pressure is stale.pressure is PressureState.CRITICAL


def test_accounting_is_non_negative_under_noisy_attribution() -> None:
    result = accounting(GIB, 2 * GIB)
    assert result.external_bytes == 0
    assert result.schedulable_bytes >= 0
    assert result.attribution is AttributionConfidence.ESTIMATED


def test_reserve_and_envelope_margin_are_central_and_conservative() -> None:
    assert dynamic_reserve(16 * GIB, POLICY) >= GIB
    assert required_envelope(GIB, POLICY) == GIB + POLICY.deployment_margin_minimum_bytes
    assert required_envelope(10 * GIB, POLICY) == 11 * GIB


def request(**updates: object) -> PlacementInput:
    values: dict[str, object] = {
        "deployment_id": "requested",
        "capability": "speech.transcription",
        "node_id": "gpu_node",
        "accelerator_id": "gpu",
        "priority": "interactive",
        "required_bytes": 2 * GIB,
        "cold_load_ms": 3000.0,
        "is_resident": False,
        "envelope_stale": False,
        "runtime_healthy": True,
        "node_eligible": True,
    }
    values.update(updates)
    return PlacementInput(**values)  # type: ignore[arg-type]


def candidate(**updates: object) -> ResidentCandidate:
    values: dict[str, object] = {
        "deployment_id": "lab",
        "capability": "vision.embedding",
        "resident_bytes": 2 * GIB,
        "active_requests": 0,
        "priority": "lab",
        "policy": "lab_only",
        "idle_since": datetime.now(UTC) - timedelta(minutes=5),
        "cold_load_ms": 1000.0,
        "last_used_at": datetime.now(UTC) - timedelta(minutes=5),
    }
    values.update(updates)
    return ResidentCandidate(**values)  # type: ignore[arg-type]


def test_planner_admits_with_measured_headroom() -> None:
    decision = plan_placement(request(), accounting(4 * GIB), [], POLICY)
    assert decision.verdict is PlacementVerdict.ADMIT
    assert decision.headroom_after_bytes >= 0


def test_planner_evicts_only_idle_lower_priority_managed_residency() -> None:
    snapshot = accounting(13 * GIB, 2 * GIB)
    decision = plan_placement(request(required_bytes=3 * GIB), snapshot, [candidate()], POLICY)
    assert decision.verdict is PlacementVerdict.ADMIT_AFTER_EVICTION
    assert decision.evictions[0].reason == "IDLE_LAB_EVICTED_FOR_PRODUCTION"


@pytest.mark.parametrize(
    "protected", [{"active_requests": 1}, {"pinned": True}, {"policy": "always_warm"}]
)
def test_planner_never_evicts_active_or_pinned_residency(protected: dict[str, object]) -> None:
    decision = plan_placement(
        request(required_bytes=3 * GIB),
        accounting(13 * GIB, 2 * GIB),
        [candidate(**protected)],
        POLICY,
    )
    assert not decision.evictions
    assert decision.verdict in {PlacementVerdict.QUEUE, PlacementVerdict.REJECT_CAPACITY}


@pytest.mark.parametrize(
    ("updates", "verdict", "reason"),
    [
        ({"runtime_healthy": False}, PlacementVerdict.REJECT_HEALTH, "RUNTIME_UNHEALTHY"),
        ({"node_eligible": False}, PlacementVerdict.REJECT_HEALTH, "NODE_UNAVAILABLE"),
        ({"envelope_stale": True}, PlacementVerdict.REJECT_HEALTH, "SCHEDULER_STATE_STALE"),
        (
            {"deadline_remaining_ms": 100.0},
            PlacementVerdict.REJECT_POLICY,
            "DEADLINE_CANNOT_BE_MET",
        ),
    ],
)
def test_planner_typed_rejections(
    updates: dict[str, object], verdict: PlacementVerdict, reason: str
) -> None:
    decision = plan_placement(request(**updates), accounting(4 * GIB), [], POLICY)
    assert decision.verdict is verdict
    assert reason in decision.reason_codes


def test_lab_pause_is_policy_block_and_fingerprint_is_deterministic() -> None:
    policy = SchedulerPolicy(lab_paused=True)
    first = plan_placement(request(priority="lab"), accounting(4 * GIB), [], policy)
    second = plan_placement(request(priority="lab"), accounting(4 * GIB), [], policy)
    assert first.verdict is PlacementVerdict.REJECT_POLICY
    assert first.fingerprint == second.fingerprint


def test_hysteresis_requires_sustained_candidate_and_prevents_flapping() -> None:
    start = datetime.now(UTC)
    hysteresis = PressureHysteresis()
    assert hysteresis.observe(PressureState.HIGH, start, 30) is PressureState.NORMAL
    assert (
        hysteresis.observe(PressureState.NORMAL, start + timedelta(seconds=10), 30)
        is PressureState.NORMAL
    )
    assert (
        hysteresis.observe(PressureState.HIGH, start + timedelta(seconds=20), 30)
        is PressureState.NORMAL
    )
    assert (
        hysteresis.observe(PressureState.HIGH, start + timedelta(seconds=51), 30)
        is PressureState.HIGH
    )
    assert (
        hysteresis.observe(PressureState.NORMAL, start + timedelta(seconds=60), 30)
        is PressureState.HIGH
    )
    assert (
        hysteresis.observe(PressureState.NORMAL, start + timedelta(seconds=91), 30)
        is PressureState.NORMAL
    )