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

import unittest
from .lexer import tokenize
from .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_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_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_div(self):
        # 10-4/2  =>  BinOp('-', Num(10), BinOp('/', Num(4), Num(2)))
        self.assertEqual(p("10-4/2"), BinOp("-", Num(10), BinOp("/", Num(4), Num(2))))

    def test_mixed_four_ops(self):
        # 1+2*3-4/2  =>  BinOp('-', BinOp('+', Num(1), BinOp('*', Num(2), Num(3))),
        #                              BinOp('/', Num(4), Num(2)))
        self.assertEqual(
            p("1+2*3-4/2"),
            BinOp(
                "-",
                BinOp("+", Num(1), BinOp("*", Num(2), Num(3))),
                BinOp("/", Num(4), Num(2)),
            ),
        )


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

    def test_subtraction_left(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_division_left(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_addition_left(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_multiplication_left(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 — parentheses override precedence."""

    def test_paren_add_then_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_paren_nested(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_paren_changes_assoc(self):
        # 8-(3-2)  =>  BinOp('-', Num(8), BinOp('-', Num(3), Num(2)))
        self.assertEqual(p("8-(3-2)"), BinOp("-", Num(8), BinOp("-", Num(3), Num(2))))

    def test_paren_single_number(self):
        self.assertEqual(p("(42)"), Num(42))


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

    def test_simple_unary(self):
        self.assertEqual(p("-5"), Unary("-", Num(5)))

    def test_unary_paren(self):
        # -(1+2)  =>  Unary('-', BinOp('+', Num(1), Num(2)))
        self.assertEqual(p("-(1+2)"), Unary("-", BinOp("+", Num(1), Num(2))))

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

    def test_close_open_paren(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("*")


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