"""The bounded model cache: lazy loading, least recently used out, budget kept."""
import sys
from pathlib import Path

sys.path.insert(0, str(Path(__file__).resolve().parent.parent))

from webapp.model_cache import ModelCache  # noqa: E402

SIZES = {"a": 400.0, "b": 500.0, "c": 1000.0, "big": 5000.0}


def _cache(budget):
    loads = []
    cache = ModelCache(lambda path: loads.append(path) or {"path": path}, budget=budget,
                       estimate=lambda path: SIZES[path])
    return cache, loads


def test_loads_on_first_use_only():
    cache, loads = _cache(2000)
    assert cache.loaded_ids() == []
    cache.get("a", "a")
    cache.get("a", "a")
    assert loads == ["a"] and cache.loaded_ids() == ["a"]


def test_least_recently_used_goes_first():
    cache, loads = _cache(1500)
    cache.get("a", "a")
    cache.get("b", "b")
    cache.get("a", "a")          # a is now the most recent
    cache.get("c", "c")          # 400 + 500 + 1000 > 1500: b goes, then a still fits? 400 + 1000 <= 1500
    assert cache.loaded_ids() == ["a", "c"]
    assert cache.used_mb() <= 1500


def test_a_model_larger_than_the_budget_is_still_loaded_alone():
    cache, loads = _cache(1500)
    cache.get("a", "a")
    cache.get("big", "big")
    assert cache.loaded_ids() == ["big"]


def test_budget_from_environment(monkeypatch):
    from webapp import model_cache
    monkeypatch.setenv(model_cache.BUDGET_ENV, "1234")
    assert ModelCache(lambda p: p).budget == 1234
    monkeypatch.setenv(model_cache.BUDGET_ENV, "lots")
    assert ModelCache(lambda p: p).budget == model_cache.DEFAULT_BUDGET_MB