import numpy as np
import pytest
import sys, os
sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

import config


def run_solver_with(x_src):
    """Run solver with a temporary X_SRC override."""
    original = config.X_SRC
    config.X_SRC = x_src
    try:
        from fdm import solver
        import importlib
        importlib.reload(solver)
        return solver.solve()
    finally:
        config.X_SRC = original


def test_shape():
    """Output deve avere forma (NX, NT)."""
    T, x, t = run_solver_with(0.0)
    assert T.shape == (config.NX, config.NT)
    assert len(x) == config.NX
    assert len(t) == config.NT


def test_initial_condition():
    """La prima colonna deve essere uniforme a T0."""
    T, x, t = run_solver_with(0.0)
    np.testing.assert_allclose(T[:, 0], config.T0)


def test_temperature_increases_near_source_center():
    """Con x_src=0.5 e a fine simulazione, il nodo centrale
    deve essere più caldo di quello iniziale."""
    T, x, t = run_solver_with(0.5)
    i_src = int(np.argmin(np.abs(x - 0.5)))
    assert T[i_src, -1] > config.T0


def test_temperature_increases_near_source_left():
    """Con x_src=0.0 il nodo sinistro deve scaldarsi."""
    T, x, t = run_solver_with(0.0)
    assert T[0, -1] > config.T0


def test_temperature_increases_near_source_right():
    """Con x_src=L il nodo destro deve scaldarsi."""
    T, x, t = run_solver_with(config.L)
    assert T[-1, -1] > config.T0


def test_x_src_position_affects_profile():
    """Spostandosi la sorgente da 0.1 a 0.9, il massimo del profilo
    finale deve spostarsi verso destra."""
    T_left, x, _ = run_solver_with(0.1)
    T_right, _, _ = run_solver_with(0.9)
    x_max_left = x[np.argmax(T_left[:, -1])]
    x_max_right = x[np.argmax(T_right[:, -1])]
    assert x_max_right > x_max_left


def test_no_nan_or_inf():
    """La soluzione non deve contenere NaN o Inf."""
    for x_src in [0.0, 0.25, 0.5, 0.75, 1.0]:
        T, _, _ = run_solver_with(x_src)
        assert np.all(np.isfinite(T)), f"NaN/Inf con x_src={x_src}"