"""Tests for calc.parser — asserts on AST structure, not evaluation."""

import unittest
from calc.lexer import tokenize
from calc.parser import parse, ParseError, Num, BinOp, Unary


def p(src: str):
    return parse(tokenize(src))


class TestPrecedence(unittest.TestCase):
    """D1 — * and / bind tighter than + and -."""

    def test_add_then_mul(self):
        # 1+2*3 → BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))
        self.assertEqual(
            p("1+2*3"),
            BinOp("+", Num(1), BinOp("*", Num(2), Num(3))),
        )

    def test_mul_then_add(self):
        # 2*3+1 → BinOp('+', BinOp('*', Num(2), Num(3)), Num(1))
        self.assertEqual(
            p("2*3+1"),
            BinOp("+", BinOp("*", Num(2), Num(3)), Num(1)),
        )

    def test_sub_then_div(self):
        # 10-6/3 → BinOp('-', Num(10), BinOp('/', Num(6), Num(3)))
        self.assertEqual(
            p("10-6/3"),
            BinOp("-", Num(10), BinOp("/", Num(6), Num(3))),
        )

    def test_mul_and_div_same_precedence_left(self):
        # 4*3/2 → BinOp('/', BinOp('*', Num(4), Num(3)), Num(2))
        self.assertEqual(
            p("4*3/2"),
            BinOp("/", BinOp("*", Num(4), Num(3)), Num(2)),
        )


class TestAssociativity(unittest.TestCase):
    """D2 — same-precedence operators associate left."""

    def test_sub_left_assoc(self):
        # 8-3-2 → BinOp('-', BinOp('-', Num(8), Num(3)), Num(2))
        self.assertEqual(
            p("8-3-2"),
            BinOp("-", BinOp("-", Num(8), Num(3)), Num(2)),
        )

    def test_div_left_assoc(self):
        # 8/4/2 → BinOp('/', BinOp('/', Num(8), Num(4)), Num(2))
        self.assertEqual(
            p("8/4/2"),
            BinOp("/", BinOp("/", Num(8), Num(4)), Num(2)),
        )

    def test_add_left_assoc(self):
        # 1+2+3 → BinOp('+', BinOp('+', Num(1), Num(2)), Num(3))
        self.assertEqual(
            p("1+2+3"),
            BinOp("+", BinOp("+", Num(1), Num(2)), Num(3)),
        )

    def test_mul_left_assoc(self):
        # 2*3*4 → BinOp('*', BinOp('*', Num(2), Num(3)), Num(4))
        self.assertEqual(
            p("2*3*4"),
            BinOp("*", BinOp("*", Num(2), Num(3)), Num(4)),
        )


class TestParentheses(unittest.TestCase):
    """D3 — parens override precedence."""

    def test_parens_force_add_under_mul(self):
        # (1+2)*3 → BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))
        self.assertEqual(
            p("(1+2)*3"),
            BinOp("*", BinOp("+", Num(1), Num(2)), Num(3)),
        )

    def test_nested_parens(self):
        # ((2+3)) → BinOp('+', Num(2), Num(3))
        self.assertEqual(p("((2+3))"), BinOp("+", Num(2), Num(3)))

    def test_parens_right_side(self):
        # 3*(1+2) → BinOp('*', Num(3), BinOp('+', Num(1), Num(2)))
        self.assertEqual(
            p("3*(1+2)"),
            BinOp("*", Num(3), BinOp("+", Num(1), Num(2))),
        )


class TestUnaryMinus(unittest.TestCase):
    """D4 — leading and nested unary minus."""

    def test_leading_unary(self):
        # -5 → Unary('-', Num(5))
        self.assertEqual(p("-5"), Unary("-", Num(5)))

    def test_unary_in_parens(self):
        # -(1+2) → Unary('-', BinOp('+', Num(1), Num(2)))
        self.assertEqual(
            p("-(1+2)"),
            Unary("-", BinOp("+", Num(1), Num(2))),
        )

    def test_unary_right_operand(self):
        # 3 * -2 → BinOp('*', Num(3), Unary('-', Num(2)))
        self.assertEqual(
            p("3 * -2"),
            BinOp("*", Num(3), Unary("-", Num(2))),
        )

    def test_double_unary(self):
        # --5 → Unary('-', Unary('-', Num(5)))
        self.assertEqual(p("--5"), Unary("-", Unary("-", Num(5))))

    def test_unary_in_addition(self):
        # 1 + -2 → BinOp('+', Num(1), Unary('-', Num(2)))
        self.assertEqual(
            p("1 + -2"),
            BinOp("+", Num(1), Unary("-", Num(2))),
        )


class TestErrors(unittest.TestCase):
    """D5 — malformed input raises ParseError."""

    def test_trailing_operator(self):
        with self.assertRaises(ParseError):
            p("1 +")

    def test_unclosed_paren(self):
        with self.assertRaises(ParseError):
            p("(1")

    def test_two_numbers_no_op(self):
        with self.assertRaises(ParseError):
            p("1 2")

    def test_close_before_open(self):
        with self.assertRaises(ParseError):
            p(")(")

    def test_empty_string(self):
        with self.assertRaises(ParseError):
            p("")

    def test_only_operator(self):
        with self.assertRaises(ParseError):
            p("*")

    def test_mismatched_parens_extra_close(self):
        with self.assertRaises(ParseError):
            p("(1+2))")


if __name__ == "__main__":
    unittest.main()