"""Tests for calc.parser — covers D1-D5 of the parse phase."""

import unittest

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


def p(src: str):
    """Convenience: tokenize and parse in one call."""
    return parse(tokenize(src))


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

    def test_mul_over_add(self):
        # 1+2*3 => BinOp('+', Num(1), BinOp('*', Num(2), Num(3)))
        tree = p('1+2*3')
        self.assertEqual(tree, BinOp('+', Num(1), BinOp('*', Num(2), Num(3))))

    def test_div_over_sub(self):
        # 6-4/2 => BinOp('-', Num(6), BinOp('/', Num(4), Num(2)))
        tree = p('6-4/2')
        self.assertEqual(tree, BinOp('-', Num(6), BinOp('/', Num(4), Num(2))))

    def test_mul_over_sub_left(self):
        # 1+2*3+4 => BinOp('+', BinOp('+', Num(1), BinOp('*', Num(2), Num(3))), Num(4))
        tree = p('1+2*3+4')
        expected = BinOp('+', BinOp('+', Num(1), BinOp('*', Num(2), Num(3))), Num(4))
        self.assertEqual(tree, expected)


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

    def test_sub_left(self):
        # 8-3-2 => BinOp('-', BinOp('-', Num(8), Num(3)), Num(2))
        tree = p('8-3-2')
        self.assertEqual(tree, BinOp('-', BinOp('-', Num(8), Num(3)), Num(2)))

    def test_div_left(self):
        # 8/4/2 => BinOp('/', BinOp('/', Num(8), Num(4)), Num(2))
        tree = p('8/4/2')
        self.assertEqual(tree, BinOp('/', BinOp('/', Num(8), Num(4)), Num(2)))

    def test_add_left(self):
        # 1+2+3 => BinOp('+', BinOp('+', Num(1), Num(2)), Num(3))
        tree = p('1+2+3')
        self.assertEqual(tree, BinOp('+', BinOp('+', Num(1), Num(2)), Num(3)))

    def test_mul_left(self):
        # 2*3*4 => BinOp('*', BinOp('*', Num(2), Num(3)), Num(4))
        tree = p('2*3*4')
        self.assertEqual(tree, BinOp('*', BinOp('*', Num(2), Num(3)), Num(4)))


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

    def test_paren_add_over_mul(self):
        # (1+2)*3 => BinOp('*', BinOp('+', Num(1), Num(2)), Num(3))
        tree = p('(1+2)*3')
        self.assertEqual(tree, BinOp('*', BinOp('+', Num(1), Num(2)), Num(3)))

    def test_paren_nested(self):
        # ((2+3)) => BinOp is gone, we get Num-ish
        tree = p('((2+3))')
        self.assertEqual(tree, BinOp('+', Num(2), Num(3)))

    def test_paren_right_side(self):
        # 3*(1+2) => BinOp('*', Num(3), BinOp('+', Num(1), Num(2)))
        tree = p('3*(1+2)')
        self.assertEqual(tree, BinOp('*', Num(3), BinOp('+', Num(1), Num(2))))


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

    def test_simple_unary(self):
        tree = p('-5')
        self.assertEqual(tree, Unary('-', Num(5)))

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

    def test_unary_in_binop(self):
        # 3 * -2 => BinOp('*', Num(3), Unary('-', Num(2)))
        tree = p('3 * -2')
        self.assertEqual(tree, BinOp('*', Num(3), Unary('-', Num(2))))

    def test_double_unary(self):
        # --5 => Unary('-', Unary('-', Num(5)))
        tree = p('--5')
        self.assertEqual(tree, Unary('-', Unary('-', Num(5))))

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


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

    def test_trailing_op(self):
        with self.assertRaises(ParseError):
            p('1 +')

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

    def test_adjacent_numbers(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_just_op(self):
        with self.assertRaises(ParseError):
            p('*')

    def test_mismatched_parens(self):
        with self.assertRaises(ParseError):
            p('(1+2')


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