"""Unit tests for :mod:`physix.training.scorer`."""

from __future__ import annotations

import numpy as np
import pytest

from physix.systems import get_system
from physix.training.scorer import Scorer, SystemContext


def _build_context_for(system_id: str, seed: int = 5) -> SystemContext:
    system = get_system(system_id)
    rng = np.random.default_rng(seed)
    traj = system.simulate(rng)
    return SystemContext(
        system_id=system_id,
        state_variables=system.state_variables,
        parameters=system.parameters,
        initial_conditions=system.initial_conditions,
        timestamps=traj.timestamps,
        observed=traj.states,
        previous_total=0.0,
    )


def test_scorer_returns_high_match_for_ground_truth() -> None:
    scorer = Scorer()
    ctx = _build_context_for("free_fall")
    breakdown = scorer.score('{"equation": "d2y/dt2 = -9.81"}', ctx)

    assert breakdown.format == 1.0
    assert breakdown.match >= 0.9


def test_scorer_returns_zero_format_on_garbage() -> None:
    scorer = Scorer()
    ctx = _build_context_for("free_fall")
    breakdown = scorer.score("this is not an equation", ctx)

    assert breakdown.format == 0.0
    assert breakdown.match == 0.0


def test_scorer_caches_by_key() -> None:
    scorer = Scorer()
    ctx = _build_context_for("simple_pendulum")
    completion = '{"equation": "d2theta/dt2 = -9.81 * sin(theta)"}'

    first = scorer.score(completion, ctx, cache_key=42)
    second = scorer.score(completion, ctx, cache_key=42)
    assert first is second


def test_scorer_progress_shrinks_when_previous_total_is_high() -> None:
    scorer = Scorer()
    ctx_low = _build_context_for("free_fall_drag", seed=3)
    completion = '{"equation": "d2y/dt2 = -9.81 + 0.05 * vy**2"}'

    no_prev = scorer.score(completion, ctx_low)
    if no_prev.match < 0.5:
        pytest.skip("rng selection produced an awkward instance")

    ctx_high = ctx_low.model_copy(update={"previous_total": no_prev.match * 0.9})
    with_prev = scorer.score(completion, ctx_high)

    # progress = max(0, match - prev_total). Higher prev_total => smaller progress.
    assert with_prev.progress <= no_prev.progress + 1e-9