import pytest
from micrograd.engine import Value


def test_value_init():
    v = Value(1)
    assert v.data == 1


def test_value_repr():
    v = Value(2.0)
    assert "Value(data=2.0)" == repr(v)


def test_value_add_opt():
    v1 = Value(2.0)
    v2 = Value(4.0)
    assert (v1 + v2).data == 6.0
    assert "Value(data=6.0)" == repr(v1 + v2)


def test_value_sub_opt():
    v1 = Value(2.0)
    v2 = Value(4.0)
    assert (v1 - v2).data == -2.0
    assert "Value(data=-2.0)" == repr(v1 - v2)


def test_value_mul_opt():
    v1 = Value(2.0)
    v2 = Value(4.0)
    v3 = Value(-1.0)
    assert (v1 * v2).data == 8.0
    assert (v1 * v3).data == -2.0


def test_value_rmul_opt():
    a = Value(2.0)
    b = 2 * a
    assert b.data == 4.0


def test_value_pow_opt():
    a = Value(2.0)
    b = a ** 2
    assert b.data == 4.0


def test_value_exp_opt():
    a = Value(1.0)
    b = a.exp()
    assert pytest.approx(b.data, 0.1) == 2.7


def test_value_int_opt():
    a = Value(2.0)
    b = a - 1
    assert b.data == 1.0


def test_value_div_opt():
    a = Value(2.0)
    b = a / 2
    assert b.data == 1.0


def test_value_mul_add():
    v1 = Value(2.0)
    v2 = Value(4.0)
    v3 = Value(-1.0)
    assert ((v1 * v3) + v2).data == 2.0


def test_children():
    v1 = Value(2.0)
    v2 = Value(4.0)
    out = v1 * v2
    assert len(out._prev) == 2
    assert v1 in out._prev
    assert v2 in out._prev


def test_operations():
    v1 = Value(2.0)
    v2 = Value(4.0)
    mul = v1 * v2
    add = v1 + v2
    assert mul._op == '*'
    assert add._op == '+'


def test_tanh():
    t = Value(2.0).tanh()
    assert t.data > 0
    assert t.data < 1

    t = Value(0.0).tanh()
    assert t.data == 0

    t = Value(-2.0).tanh()
    assert t.data < 0
    assert t.data > -1