"""Offline unit tests for GPUUsageTracker ZeroGPU quota telemetry.

Pure logic tests with an injected fake clock; no network, no ZeroGPU
dependency, no writes outside pytest tmp_path.
"""

from __future__ import annotations

import importlib.util
import os
import sys
from typing import Any, Dict, List

import pytest

_REPO = os.path.join(os.path.dirname(__file__), "..", "..")


def _load_app():
    """Import app.py with mocked heavy deps (gradio, spaces, llama_cpp)."""
    sys.path.insert(0, _REPO)
    import app  # noqa: F401  (mock fallbacks make this importable offline)
    return app


@pytest.fixture()
def tracker():
    app = _load_app()
    clock = {"t": 1_000_000.0}

    def fake_clock():
        return clock["t"]

    t = app.GPUUsageTracker(clock=fake_clock)
    t._advance = lambda s: clock.__setitem__("t", clock["t"] + s)
    return t


def test_lease_roundtrip_records_wall_seconds(tracker):
    call_id = tracker.lease_start("chat")
    tracker._advance(12.5)
    record = tracker.lease_end(call_id, model="Qwen3.8-9B-Q8_0.gguf", kind="chat")
    assert record["lease_seconds"] == 12.5
    assert record["model"] == "Qwen3.8-9B-Q8_0.gguf"
    assert record["error"] == ""


def test_lease_end_unknown_id_returns_empty(tracker):
    assert tracker.lease_end("missing-id") == {}


def test_daily_usage_rolls_up_same_day(tracker):
    for lease in (10.0, 20.0, 5.0):
        cid = tracker.lease_start("chat")
        tracker._advance(lease)
        tracker.lease_end(cid, kind="chat")
    usage = tracker.daily_usage()
    assert usage["calls_total"] == 3
    assert usage["calls_ok"] == 3
    assert usage["gpu_seconds_used"] == 35.0
    assert usage["gpu_minutes_used"] == 0.58  # rounded to 2 decimals by tracker
    assert usage["daily_quota_minutes"] == 40
    assert usage["quota_consumed_percent"] == 1.5  # rounded to 1 decimal by tracker
    assert usage["quota_exhausted_observed"] is False


def test_quota_error_marks_exhaustion_state(tracker):
    cid = tracker.lease_start("chat")
    tracker._advance(3.0)
    tracker.lease_end(cid, kind="chat", error="Space app has reached its GPU limit")
    usage = tracker.daily_usage()
    assert usage["calls_failed"] == 1
    assert usage["quota_exhausted_observed"] is True
    assert "GPU limit" in usage["last_quota_error"]["detail"]


def test_stale_quota_error_flag_expires_after_ttl(tracker):
    """A quota error must not stick for the whole UTC day (rolling-24h HF
    window can free up in the meantime). After the TTL the flag expires and a
    real generation attempt arbitrates."""
    cid = tracker.lease_start("chat")
    tracker._advance(3.0)
    tracker.lease_end(cid, kind="chat", error="exceeded your ZeroGPU quota")
    assert tracker.daily_usage()["quota_exhausted_observed"] is True

    # still fresh just before TTL
    tracker._advance(tracker.QUOTA_FLAG_TTL_SECONDS - 10)
    assert tracker.daily_usage()["quota_exhausted_observed"] is True

    # past TTL: stale flag must be ignored
    tracker._advance(11)
    usage = tracker.daily_usage()
    assert usage["quota_exhausted_observed"] is False
    # raw error is still retained for diagnostics
    assert usage["last_quota_error"]["detail"].endswith("ZeroGPU quota")


def test_ttl_env_override_respected():
    app = _load_app()
    import subprocess  # noqa: F401
    # constant must read env override at import time
    assert isinstance(app.GPUUsageTracker.QUOTA_FLAG_TTL_SECONDS, int)
    assert app.GPUUsageTracker.QUOTA_FLAG_TTL_SECONDS > 0


def test_daily_usage_ignores_previous_days(tracker):
    cid = tracker.lease_start("chat")
    tracker._advance(60.0)
    tracker.lease_end(cid, kind="chat")
    # advance a full day: 24h + a bit
    tracker._advance(24 * 3600 + 5)
    cid2 = tracker.lease_start("chat")
    tracker._advance(10.0)
    tracker.lease_end(cid2, kind="chat")
    usage = tracker.daily_usage()
    assert usage["calls_total"] == 1
    assert usage["gpu_seconds_used"] == 10.0


def test_summary_throughput_and_queue(tracker):
    # chat call: 600 completion tokens over 30s lease, 2s queue wait
    cid = tracker.lease_start("chat")
    tracker._advance(30.0)
    rec = tracker.lease_end(cid, kind="chat", queue_wait_s=2.0)
    rec["completion_tokens"] = 600
    profile = tracker.summary()
    assert profile["total_calls"] == 1
    assert profile["avg_queue_wait_seconds"] == 2.0
    assert profile["chat_throughput_tokens_per_gpu_second"] == pytest.approx(20.0)


def test_summary_ignores_failed_calls_for_throughput(tracker):
    cid = tracker.lease_start("chat")
    tracker._advance(5.0)
    tracker.lease_end(cid, kind="chat", error="boom")
    profile = tracker.summary()
    assert profile["total_calls"] == 1
    assert profile["chat_throughput_tokens_per_gpu_second"] == 0.0


def test_usage_snapshot_shape(tracker):
    cid = tracker.lease_start("chat")
    tracker._advance(1.0)
    tracker.lease_end(cid, kind="chat")
    snap: Dict[str, Any] = tracker.usage_snapshot()
    assert set(snap.keys()) == {"daily", "profile"}
    assert set(snap["daily"].keys()) >= {"date", "gpu_seconds_used", "quota_consumed_percent"}
    assert set(snap["profile"].keys()) >= {"total_calls", "avg_queue_wait_seconds"}


@pytest.fixture()
def fresh_usage():
    app = _load_app()
    app.GPU_USAGE = app.GPUUsageTracker()
    yield app
    app.GPU_USAGE = app.GPUUsageTracker()  # restore module-level state


def test_gpu_tracked_call_records_usage(fresh_usage):
    """Regression: gpu_tracked_call must open a lease BEFORE invoking the
    GPU body, otherwise lease_end finds no active call and usage stays 0
    (caught live: successful chat calls were not recorded)."""
    app = fresh_usage
    result = app.gpu_tracked_call(
        "chat",
        lambda *a, **k: {"choices": [{"message": {"content": "ok"}}]},
        [],
        model="test.gguf",
    )
    assert result["choices"][0]["message"]["content"] == "ok"
    snap = app.GPU_USAGE.usage_snapshot()
    assert snap["daily"]["calls_total"] == 1
    assert snap["daily"]["calls_ok"] == 1
    assert snap["profile"]["total_calls"] == 1


def test_gpu_tracked_call_cold_start_worker_side(fresh_usage):
    """ZeroGPU runs @spaces.GPU bodies in a worker process: get_model sets
    _llm/_loaded_file there and those globals never reach the web process.
    Cold-start detection must therefore run inside the body (returns DO
    propagate back). Regression for the live finding where cold_start was
    always 0.0 (the -1.0 sentinel was silently dropped by summary())."""
    app = fresh_usage
    app._llm = None
    app._loaded_file = None

    def loader(msgs, model_file, *a, **k):
        # mimic get_model side effect inside the worker
        app._llm = object()
        app._loaded_file = model_file
        return {"choices": [{"message": {"content": "ok"}}]}

    model = "Qwen3.8-9B-Q8_0.gguf"
    app.gpu_tracked_call("chat", loader, [], model, 0.7, 30, model=model)
    cold_rec = app.GPU_USAGE._calls[-1]
    assert cold_rec["cold_start_seconds"] >= 0.0
    assert cold_rec["lease_seconds"] >= cold_rec["cold_start_seconds"]

    def warm(msgs, model_file, *a, **k):
        return {"choices": [{"message": {"content": "ok"}}]}

    app.gpu_tracked_call("chat", warm, [], model, 0.7, 30, model=model)
    warm_rec = app.GPU_USAGE._calls[-1]
    assert warm_rec["cold_start_seconds"] == 0.0


def test_gpu_tracked_call_completion_tokens(fresh_usage):
    """Usage.completion_tokens from the chat result feed the throughput
    metric (tokens per GPU-second); absent/None must degrade to 0."""
    app = fresh_usage
    res = {"choices": [{"message": {"content": "ok"}}],
           "usage": {"completion_tokens": 42}}
    app.gpu_tracked_call("chat", lambda *a, **k: res, [], "m.gguf", model="m.gguf")
    rec = app.GPU_USAGE._calls[-1]
    assert rec["completion_tokens"] == 42
    prof = app.GPU_USAGE.summary()
    assert prof["chat_throughput_tokens_per_gpu_second"] > 0

    app.gpu_tracked_call("chat", lambda *a, **k: {"choices": []}, [], "m.gguf", model="m.gguf")
    rec2 = app.GPU_USAGE._calls[-1]
    assert rec2["completion_tokens"] == 0


def test_quota_error_marks_exhaustion(tracker):
    cid = tracker.lease_start("chat")
    tracker.lease_end(cid, kind="chat", error="ZeroGPU quota exceeded: limit reached")
    daily = tracker.daily_usage()
    assert daily["calls_failed"] == 1
    assert daily["quota_exhausted_observed"] is True
    assert daily["last_quota_error"] is not None
    assert "limit" in daily["last_quota_error"]["detail"]


def test_gpu_tracked_call_records_error_path(fresh_usage):
    app = fresh_usage
    with pytest.raises(RuntimeError):
        app.gpu_tracked_call(
            "chat",
            lambda *a, **k: (_ for _ in ()).throw(RuntimeError("boom")),
            [],
            model="test.gguf",
        )
    snap = app.GPU_USAGE.usage_snapshot()
    assert snap["daily"]["calls_total"] == 1
    assert snap["daily"]["calls_failed"] == 1

# ── Restart-honesty regression: the ledger must survive a process bounce ──────
# Before this, the counter lived only in memory, so every Space reload reported a
# full 40 minutes while Hugging Face was already refusing leases ("31/40 left"
# on screen next to a 429 "Space app has reached its GPU limit").

def test_ledger_persists_usage_across_restart(tmp_path):
    app = _load_app()
    ledger = str(tmp_path / "zerogpu_quota_ledger.json")
    clock = {"t": 2_000_000.0}

    def fake_clock():
        return clock["t"]

    first = app.GPUUsageTracker(clock=fake_clock, state_path=ledger)
    cid = first.lease_start("chat")
    clock["t"] += 540.0  # 9 minutes of billed GPU time
    first.lease_end(cid, kind="chat", model="Qwen3.8-9B-Q8_0.gguf")
    assert first.remaining_seconds() == 40 * 60 - 540.0

    # Simulate the Space restarting: a brand-new tracker over the same ledger.
    second = app.GPUUsageTracker(clock=fake_clock, state_path=ledger)
    assert second.remaining_seconds() == 40 * 60 - 540.0, (
        "a restart must not restore phantom GPU minutes"
    )
    assert second.used_seconds_today() == 540.0


def test_ledger_keeps_quota_error_and_expires_at_window_end(tmp_path):
    app = _load_app()
    ledger = str(tmp_path / "zerogpu_quota_ledger.json")
    clock = {"t": 3_000_000.0}

    def fake_clock():
        return clock["t"]

    t = app.GPUUsageTracker(clock=fake_clock, state_path=ledger)
    cid = t.lease_start("chat")
    clock["t"] += 4.0
    t.lease_end(cid, kind="chat", error="Space app has reached its GPU limit")
    assert t.daily_usage()["quota_exhausted_observed"] is True

    bounced = app.GPUUsageTracker(clock=fake_clock, state_path=ledger)
    assert bounced.daily_usage()["quota_exhausted_observed"] is True, (
        "a restart must not hide an observed platform refusal"
    )

    # Past the documented 24h window the allowance is genuinely fresh again.
    clock["t"] += app.GPUUsageTracker.WINDOW_SECONDS + 1
    reset = app.GPUUsageTracker(clock=fake_clock, state_path=ledger)
    assert reset.remaining_seconds() == 40 * 60
    assert reset.daily_usage()["quota_exhausted_observed"] is False


def test_daily_usage_reports_window_reset_time(tmp_path):
    app = _load_app()
    clock = {"t": 4_000_000.0}

    def fake_clock():
        return clock["t"]

    t = app.GPUUsageTracker(clock=fake_clock, state_path=str(tmp_path / "l.json"))
    assert t.daily_usage()["quota_window_resets_at"] is None
    t.lease_start("chat")
    usage = t.daily_usage()
    assert usage["quota_window_resets_at"] == 4_000_000 + app.GPUUsageTracker.WINDOW_SECONDS
    assert usage["quota_window_seconds_remaining"] == app.GPUUsageTracker.WINDOW_SECONDS
    assert usage["ledger_persisted"] is True


def test_observed_refusal_reports_zero_remaining_minutes(tmp_path):
    """A platform refusal must not coexist with a positive minutes-left readout.

    This is the exact reported bug: the UI showed ~31/40 minutes while every
    request came back 429 "Space app has reached its GPU limit".
    """
    app = _load_app()
    clock = {"t": 5_000_000.0}

    def fake_clock():
        return clock["t"]

    t = app.GPUUsageTracker(clock=fake_clock, state_path=str(tmp_path / "l.json"))
    cid = t.lease_start("chat")
    clock["t"] += 60.0
    t.lease_end(cid, kind="chat")
    usage = t.daily_usage()
    assert usage["quota_remaining_seconds"] == 39 * 60
    assert usage["quota_remaining_minutes"] == 39.0
    assert usage["quota_headroom_known"] is True

    refused = t.lease_start("chat")
    clock["t"] += 0.2
    t.lease_end(
        refused,
        kind="chat",
        error="Space app has reached its GPU limit. Try re-running outside of examples",
    )
    usage = t.daily_usage()
    assert usage["quota_exhausted_observed"] is True
    assert usage["quota_remaining_seconds"] == 0.0
    assert usage["quota_remaining_minutes"] == 0.0
    assert usage["quota_headroom_known"] is False