# -------------------------------------------------------------------
# This source file is available under the terms of the
# Pimcore Open Core License (POCL)
# Full copyright and license information is available in
# LICENSE.md which is distributed with this source code.
# -------------------------------------------------------------------
"""The cache has to forget. Callers name the model, so the set of models a running instance is
asked for is open-ended; without a bound, every distinct id ever requested stays resident and the
container eventually dies. Least-recently-used is the right eviction order here because the working
set in practice is a couple of models used constantly plus a long tail used once.
"""

import logging

import pytest
from src.model_cache import LruCache


def _cache(max_entries: int = 2) -> LruCache:
    return LruCache(max_entries=max_entries, name="test", logger=logging.getLogger("test"))


def test_stores_and_returns_values():
    cache = _cache()
    cache["a"] = 1

    assert "a" in cache
    assert cache["a"] == 1


def test_reports_absent_keys():
    cache = _cache()

    assert "missing" not in cache


def test_evicts_the_least_recently_used_entry_when_full():
    cache = _cache(max_entries=2)
    cache["a"] = 1
    cache["b"] = 2

    cache["c"] = 3

    assert "a" not in cache, "the oldest entry should have been evicted"
    assert "b" in cache
    assert "c" in cache
    assert len(cache) == 2


def test_reading_an_entry_makes_it_recently_used():
    """Otherwise the model being hammered by every request would be the one evicted."""
    cache = _cache(max_entries=2)
    cache["a"] = 1
    cache["b"] = 2

    _ = cache["a"]  # refreshes "a", making "b" the coldest
    cache["c"] = 3

    assert "a" in cache
    assert "b" not in cache
    assert "c" in cache


def test_overwriting_an_existing_key_does_not_evict():
    cache = _cache(max_entries=2)
    cache["a"] = 1
    cache["b"] = 2

    cache["a"] = 99

    assert len(cache) == 2
    assert cache["a"] == 99
    assert "b" in cache


def test_capacity_is_at_least_one():
    """A zero or negative limit would evict the entry a request just loaded, before it could be
    used, and turn every single request into a fresh load."""
    cache = _cache(max_entries=0)
    cache["a"] = 1

    assert cache["a"] == 1
    assert len(cache) == 1


def test_eviction_is_logged(caplog):
    """Thrashing is invisible otherwise — the symptom is only slowness."""
    cache = _cache(max_entries=1)
    with caplog.at_level(logging.INFO):
        cache["a"] = 1
        cache["b"] = 2

    assert any("a" in record.message for record in caplog.records)


def test_evicted_entries_are_gone_not_merely_hidden():
    """The point is to release the reference so the weights can be garbage collected."""
    cache = _cache(max_entries=1)
    cache["a"] = object()
    cache["b"] = object()

    with pytest.raises(KeyError):
        _ = cache["a"]