from __future__ import annotations

import importlib.util
from pathlib import Path

import pytest


ROOT = Path(__file__).resolve().parents[2]
POLICY_PATH = ROOT / "ops" / "gitea-deploy-broker" / "runner_capacity_policy.py"


@pytest.fixture
def policy_module():
    spec = importlib.util.spec_from_file_location("appops_runner_capacity_policy_test", POLICY_PATH)
    assert spec and spec.loader
    module = importlib.util.module_from_spec(spec)
    spec.loader.exec_module(module)
    return module


def _state(policy_module, **overrides):
    values = {
        "queue_depth": 0,
        "oldest_queued_seconds": None,
        "load_ratio": 0.30,
        "available_memory_bytes": 20 * policy_module.GIB,
        "burst_running": False,
        "burst_busy": False,
        "burst_disabled": True,
        "seconds_since_demand": 600,
        "seconds_since_action": 600,
        "swap_critical": False,
        "cache_free_bytes": 100 * policy_module.GIB,
    }
    values.update(overrides)
    return policy_module.BurstCapacityInput(**values)


def test_burst_starts_only_for_queue_demand_with_headroom(policy_module):
    decision = policy_module.decide_burst_capacity(
        _state(policy_module, queue_depth=2)
    )

    assert decision.action == "start"
    assert decision.reason == "queue_pressure_with_host_headroom"
    assert decision.pressure == "headroom"


def test_old_job_can_trigger_burst_even_with_single_queued_job(policy_module):
    decision = policy_module.decide_burst_capacity(
        _state(policy_module, queue_depth=1, oldest_queued_seconds=60)
    )

    assert decision.action == "start"


@pytest.mark.parametrize(
    ("load_ratio", "memory_gib", "swap_critical"),
    [
        (0.75, 20, False),
        (0.30, 10, False),
        (0.30, 20, True),
    ],
)
def test_burst_does_not_start_without_headroom(
    policy_module, load_ratio, memory_gib, swap_critical
):
    decision = policy_module.decide_burst_capacity(
        _state(
            policy_module,
            queue_depth=3,
            load_ratio=load_ratio,
            available_memory_bytes=memory_gib * policy_module.GIB,
            swap_critical=swap_critical,
        )
    )

    assert decision.action == "hold"
    assert decision.reason == "queue_pressure_but_host_headroom_insufficient"


def test_high_pressure_drains_busy_burst_instead_of_stopping_it(policy_module):
    decision = policy_module.decide_burst_capacity(
        _state(
            policy_module,
            queue_depth=3,
            load_ratio=0.95,
            burst_running=True,
            burst_busy=True,
            burst_disabled=False,
        )
    )

    assert decision.action == "drain"
    assert decision.reason == "host_pressure_drain_after_current_job"


def test_high_pressure_stops_only_already_drained_idle_burst(policy_module):
    decision = policy_module.decide_burst_capacity(
        _state(
            policy_module,
            load_ratio=0.95,
            burst_running=True,
            burst_busy=False,
            burst_disabled=True,
            seconds_since_action=600,
        )
    )

    assert decision.action == "stop"
    assert decision.reason == "host_pressure_idle_burst_can_stop"


def test_idle_burst_is_drained_before_stop(policy_module):
    first = policy_module.decide_burst_capacity(
        _state(
            policy_module,
            burst_running=True,
            burst_disabled=False,
            seconds_since_demand=600,
            seconds_since_action=600,
        )
    )
    second = policy_module.decide_burst_capacity(
        _state(
            policy_module,
            burst_running=True,
            burst_disabled=True,
            seconds_since_demand=600,
            seconds_since_action=600,
        )
    )

    assert first.action == "drain"
    assert second.action == "stop"


def test_disabled_running_burst_reenables_when_demand_returns(policy_module):
    decision = policy_module.decide_burst_capacity(
        _state(
            policy_module,
            queue_depth=2,
            burst_running=True,
            burst_disabled=True,
            seconds_since_action=600,
        )
    )

    assert decision.action == "enable"


def test_start_cooldown_prevents_flapping(policy_module):
    decision = policy_module.decide_burst_capacity(
        _state(
            policy_module,
            queue_depth=2,
            seconds_since_action=30,
        )
    )

    assert decision.action == "hold"


def test_burst_does_not_start_when_cache_headroom_is_low(policy_module):
    decision = policy_module.decide_burst_capacity(
        _state(
            policy_module,
            queue_depth=3,
            cache_free_bytes=20 * policy_module.GIB,
        )
    )
    assert decision.action == "hold"
    assert decision.reason == "queue_pressure_but_host_headroom_insufficient"


def test_low_cache_headroom_drains_busy_burst(policy_module):
    decision = policy_module.decide_burst_capacity(
        _state(
            policy_module,
            queue_depth=3,
            burst_running=True,
            burst_busy=True,
            burst_disabled=False,
            cache_free_bytes=10 * policy_module.GIB,
        )
    )
    assert decision.action == "drain"
    assert decision.pressure == "critical"