"""DS-Mac-mini-26B-Priority-Gate-1 (B-1) unit smoke — 6 scenario.

heap + inflight 기반 MLX gate 의 ordering/cancellation/fast-path 검증. 실 LLM
호출 없이 gate 자체의 acquire/release/dispatch 만 시뮬레이션.
"""

from __future__ import annotations

import asyncio
import logging

import pytest

from services.search.llm_gate import (
    Priority,
    _reset_for_test,
    acquire_mlx_gate,
    get_mlx_gate,
)


@pytest.fixture(autouse=True)
def _reset_gate():
    """각 테스트 시작 시 gate 상태 reset (fresh event loop 마다)."""
    _reset_for_test()
    yield
    _reset_for_test()


async def _hold(priority: Priority, duration_s: float, log: list, label: str):
    """단순 gate holder — acquire 후 sleep 후 release."""
    async with acquire_mlx_gate(priority):
        log.append(("acquired", label))
        await asyncio.sleep(duration_s)
        log.append(("released", label))


# ─── Scenario 1: FIFO within same priority ────────────────────────────────


@pytest.mark.asyncio
async def test_fifo_within_same_priority():
    """BACKGROUND 3건 직렬 enqueue → 순서대로 dispatch (1→2→3)."""
    log: list = []

    async def acquirer(label: str, started: asyncio.Event):
        async with acquire_mlx_gate(Priority.BACKGROUND):
            log.append(label)
            started.set()
            await asyncio.sleep(0.05)

    e1, e2, e3 = asyncio.Event(), asyncio.Event(), asyncio.Event()
    t1 = asyncio.create_task(acquirer("bg1", e1))
    await asyncio.sleep(0.001)  # bg1 이 fast-path 먼저
    t2 = asyncio.create_task(acquirer("bg2", e2))
    await asyncio.sleep(0.001)
    t3 = asyncio.create_task(acquirer("bg3", e3))

    await asyncio.gather(t1, t2, t3)
    assert log == ["bg1", "bg2", "bg3"], f"FIFO 위반: {log}"


# ─── Scenario 2: Foreground jumps queue ───────────────────────────────────


@pytest.mark.asyncio
async def test_foreground_jumps_queue():
    """BACKGROUND 5건 enqueue (1 inflight, 2~5 대기) → FOREGROUND 1건 enqueue
    → 1번 release 후 다음은 FOREGROUND (2~5 모두 뒤로).
    """
    log: list = []
    bg_release_signals = [asyncio.Event() for _ in range(5)]
    fg_release_signal = asyncio.Event()

    async def bg(i: int):
        async with acquire_mlx_gate(Priority.BACKGROUND):
            log.append(f"bg{i}")
            await bg_release_signals[i].wait()

    async def fg():
        async with acquire_mlx_gate(Priority.FOREGROUND):
            log.append("fg")
            await fg_release_signal.wait()

    # bg0 fast-path inflight
    t_bg0 = asyncio.create_task(bg(0))
    await asyncio.sleep(0.01)  # bg0 이 inflight 확실해질 때까지
    # bg1~4 enqueue (대기)
    t_bgs = [asyncio.create_task(bg(i)) for i in range(1, 5)]
    await asyncio.sleep(0.01)
    # fg enqueue (대기) — 모든 background 보다 앞으로 jump 해야 함
    t_fg = asyncio.create_task(fg())
    await asyncio.sleep(0.01)

    # bg0 release → 다음 dispatch 는 FG
    bg_release_signals[0].set()
    await asyncio.sleep(0.05)
    assert log == ["bg0", "fg"], f"FG jump 위반 (bg1 먼저 들어옴?): {log}"

    # fg release → bg1
    fg_release_signal.set()
    await asyncio.sleep(0.05)
    assert log == ["bg0", "fg", "bg1"], f"FIFO 위반: {log}"

    # 나머지 풀어줌
    for i in range(1, 5):
        bg_release_signals[i].set()
    await asyncio.gather(t_bg0, *t_bgs, t_fg)

    assert log == ["bg0", "fg", "bg1", "bg2", "bg3", "bg4"], (
        f"최종 순서: {log}"
    )


# ─── Scenario 3: Long-running background blocks foreground (intended) ────


@pytest.mark.asyncio
async def test_long_running_background_blocks_foreground():
    """이미 inflight 인 background 는 끊지 않는다 (preemption X). foreground 들어와도
    현재 점유 background 의 남은 시간만큼 대기.
    """
    log: list = []

    async def bg():
        async with acquire_mlx_gate(Priority.BACKGROUND):
            log.append(("bg_start", asyncio.get_event_loop().time()))
            await asyncio.sleep(0.3)
            log.append(("bg_end", asyncio.get_event_loop().time()))

    async def fg():
        await asyncio.sleep(0.05)  # bg 가 inflight 진입한 후 fg 시도
        async with acquire_mlx_gate(Priority.FOREGROUND):
            log.append(("fg_start", asyncio.get_event_loop().time()))

    t_bg = asyncio.create_task(bg())
    t_fg = asyncio.create_task(fg())
    await asyncio.gather(t_bg, t_fg)

    events = {label: t for label, t in log}
    # fg 는 bg_end 이후에만 시작 가능
    assert events["fg_start"] >= events["bg_end"] - 0.01, (
        f"preemption 발생? fg_start={events['fg_start']} bg_end={events['bg_end']}"
    )


# ─── Scenario 4: Mixed concurrent enqueue (FG FIFO 먼저, BG FIFO 후) ──


@pytest.mark.asyncio
async def test_mixed_concurrent_enqueue():
    """2 FOREGROUND + 3 BACKGROUND 가 거의 동시 → FG fifo 먼저, BG fifo 후."""
    log: list = []
    holder_started = asyncio.Event()
    holder_release = asyncio.Event()

    async def holder():
        async with acquire_mlx_gate(Priority.BACKGROUND):
            holder_started.set()
            await holder_release.wait()

    async def fg(i: int):
        async with acquire_mlx_gate(Priority.FOREGROUND):
            log.append(f"fg{i}")
            await asyncio.sleep(0.005)

    async def bg(i: int):
        async with acquire_mlx_gate(Priority.BACKGROUND):
            log.append(f"bg{i}")
            await asyncio.sleep(0.005)

    # holder 가 fast-path 점유
    t_h = asyncio.create_task(holder())
    await holder_started.wait()

    # 거의 동시 enqueue (gather)
    tasks = [
        asyncio.create_task(fg(0)),
        asyncio.create_task(bg(0)),
        asyncio.create_task(fg(1)),
        asyncio.create_task(bg(1)),
        asyncio.create_task(bg(2)),
    ]
    await asyncio.sleep(0.01)  # 모두 enqueue 까지 진행

    # holder release → priority 순서대로 dispatch
    holder_release.set()
    await asyncio.gather(t_h, *tasks)

    # fg0, fg1 가 먼저 (FG FIFO) → bg0, bg1, bg2 (BG FIFO)
    assert log == ["fg0", "fg1", "bg0", "bg1", "bg2"], f"priority order 위반: {log}"


# ─── Scenario 5: Backward compat — async with get_mlx_gate() ──────────────


@pytest.mark.asyncio
async def test_backward_compat_get_mlx_gate():
    """`async with get_mlx_gate():` legacy 형태가 BACKGROUND priority 로 매핑."""
    log: list = []

    async def legacy_caller():
        async with get_mlx_gate():
            log.append("legacy")
            await asyncio.sleep(0.01)

    async def fg_caller():
        async with acquire_mlx_gate(Priority.FOREGROUND):
            log.append("fg")
            await asyncio.sleep(0.01)

    # 동시 enqueue
    bg_holder_started = asyncio.Event()
    bg_holder_release = asyncio.Event()

    async def bg_holder():
        async with acquire_mlx_gate(Priority.BACKGROUND):
            bg_holder_started.set()
            await bg_holder_release.wait()

    t_h = asyncio.create_task(bg_holder())
    await bg_holder_started.wait()

    t_legacy = asyncio.create_task(legacy_caller())
    await asyncio.sleep(0.005)
    t_fg = asyncio.create_task(fg_caller())
    await asyncio.sleep(0.01)

    bg_holder_release.set()
    await asyncio.gather(t_h, t_legacy, t_fg)

    # legacy 는 BACKGROUND 매핑이므로 fg 가 먼저 (priority order)
    assert log == ["fg", "legacy"], f"legacy 가 FOREGROUND 로 처리됨? {log}"


# ─── Scenario 6: Cancelled waiter skip ────────────────────────────────────


@pytest.mark.asyncio
async def test_cancelled_waiter_skip():
    """bg1 inflight → bg2 enqueue → fg1 enqueue → bg2 cancel → bg1 release →
    다음 dispatch 가 fg1 (죽은 bg2 entry skip).
    """
    log: list = []
    bg1_release = asyncio.Event()

    async def bg1():
        async with acquire_mlx_gate(Priority.BACKGROUND):
            log.append("bg1")
            await bg1_release.wait()

    async def bg2():
        async with acquire_mlx_gate(Priority.BACKGROUND):
            log.append("bg2")  # 도달 안 해야 함 (cancel)

    async def fg1():
        async with acquire_mlx_gate(Priority.FOREGROUND):
            log.append("fg1")

    t_bg1 = asyncio.create_task(bg1())
    await asyncio.sleep(0.01)  # bg1 fast-path inflight
    t_bg2 = asyncio.create_task(bg2())
    await asyncio.sleep(0.01)  # bg2 enqueue 대기
    t_fg1 = asyncio.create_task(fg1())
    await asyncio.sleep(0.01)  # fg1 enqueue 대기

    # bg2 cancel — Future 가 cancelled 상태로 heap 잔존
    t_bg2.cancel()
    try:
        await t_bg2
    except asyncio.CancelledError:
        pass

    # bg1 release — 다음 dispatch 는 fg1 (bg2 죽은 entry skip)
    bg1_release.set()
    await asyncio.gather(t_bg1, t_fg1)

    # bg2 도달 안 함 (cancelled), 순서 = bg1, fg1
    assert log == ["bg1", "fg1"], (
        f"cancelled bg2 가 dispatch 됐거나 gate stuck: {log}"
    )