"""Tests for calc/parser.py — covers D1–D5."""
import unittest

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


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

    def test_add_div(self):
        # 1+8/4 → BinOp('+', Num(1), BinOp('/', Num(8), Num(4)))
        self.assertEqual(p("1+8/4"), BinOp("+", Num(1), BinOp("/", Num(8), Num(4))))

    def test_sub_mul(self):
        # 10-2*3 → BinOp('-', Num(10), BinOp('*', Num(2), Num(3)))
        self.assertEqual(
            p("10-2*3"), BinOp("-", Num(10), BinOp("*", Num(2), Num(3)))
        )

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

    def test_single_float(self):
        self.assertEqual(p("3.14"), Num(3.14))


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

    def test_sub_sub(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_div(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_add(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_mul(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_parens_override_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):
        # ((1+2)) → BinOp('+', Num(1), Num(2))
        self.assertEqual(p("((1+2))"), BinOp("+", Num(1), Num(2)))

    def test_parens_inside_add(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_parens_alone(self):
        self.assertEqual(p("(5)"), Num(5))


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

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

    def test_unary_of_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_add(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 _raises(self, src):
        with self.assertRaises(ParseError):
            p(src)

    def test_trailing_op(self):
        self._raises("1 +")

    def test_unclosed_paren(self):
        self._raises("(1")

    def test_two_numbers(self):
        self._raises("1 2")

    def test_close_before_open(self):
        self._raises(")(")

    def test_empty(self):
        self._raises("")

    def test_just_op(self):
        self._raises("*")

    def test_mismatched_parens(self):
        self._raises("(1+2")

    def test_extra_close(self):
        self._raises("(1+2))")


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