import sys
from pathlib import Path

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

import pytest
from tokenizer import tokenize
from parser import Parser
from evaluator import evaluate, evaluate_traced, EvalError


def eval_expr(expr):
    """Helper: tokenize -> parse -> evaluate in one step."""
    tokens = tokenize(expr)
    ast = Parser(tokens).parse()
    return evaluate(ast)


# ---------- Basic arithmetic ----------

def test_addition():
    assert eval_expr("3 + 4") == 7.0

def test_subtraction():
    assert eval_expr("10 - 3") == 7.0

def test_multiplication():
    assert eval_expr("3 * 4") == 12.0

def test_division():
    assert eval_expr("10 / 4") == 2.5

def test_power():
    assert eval_expr("2 ^ 10") == 1024.0


# ---------- Precedence ----------

def test_standard_precedence():
    assert eval_expr("3 + 4 * 2") == 11.0

def test_parentheses():
    assert eval_expr("(3 + 4) * 2") == 14.0

def test_power_precedence():
    assert eval_expr("2 * 3 ^ 2") == 18.0

def test_right_associative_power():
    # 2^(2^3) = 2^8 = 256
    assert eval_expr("2 ^ 2 ^ 3") == 256.0


# ---------- Unary minus ----------

def test_negation():
    assert eval_expr("-5") == -5.0

def test_double_negation():
    assert eval_expr("--5") == 5.0

def test_negation_with_power():
    # -(3^2) = -9, not (-3)^2 = 9
    assert eval_expr("-3 ^ 2") == -9.0

def test_negation_in_parens():
    assert eval_expr("(-3) ^ 2") == 9.0


# ---------- Decimals ----------

def test_decimal_addition():
    assert eval_expr("0.1 + 0.2") == pytest.approx(0.3)

def test_leading_dot():
    assert eval_expr(".5 + .5") == 1.0


# ---------- Edge cases ----------

def test_nested_parens():
    assert eval_expr("((((3))))") == 3.0

def test_complex_expression():
    assert eval_expr("(2 + 3) * (7 - 2) / 5 ^ 1") == 5.0

def test_long_chain():
    assert eval_expr("1 + 2 + 3 + 4 + 5") == 15.0

def test_mixed_operations():
    assert eval_expr("2 + 3 * 4 - 6 / 2") == 11.0


# ---------- Division by zero ----------

def test_division_by_zero():
    with pytest.raises(EvalError):
        eval_expr("1 / 0")

def test_division_by_zero_in_expression():
    with pytest.raises(EvalError):
        eval_expr("5 + 3 / (2 - 2)")


# ---------- Traced evaluation ----------

def test_traced_returns_correct_result():
    tokens = tokenize("3 + 4 * 2")
    ast = Parser(tokens).parse()
    result, steps = evaluate_traced(ast)
    assert result == 11.0
    assert len(steps) > 0

def test_traced_step_count():
    """A simple binary op has 3 evaluation events: left, right, combine."""
    tokens = tokenize("3 + 4")
    ast = Parser(tokens).parse()
    result, steps = evaluate_traced(ast)
    assert result == 7.0
    # NumberNode(3), NumberNode(4), BinOp(+)
    assert len(steps) == 3