"""Test suite for calc.parser — asserts on AST structure."""
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)))
        tree = p("1+2*3")
        self.assertEqual(tree, 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))
        tree = p("2*3+1")
        self.assertEqual(tree, BinOp('+', BinOp('*', Num(2), Num(3)), Num(1)))

    def test_sub_then_div(self):
        # 10-6/2 → BinOp('-', Num(10), BinOp('/', Num(6), Num(2)))
        tree = p("10-6/2")
        self.assertEqual(tree, BinOp('-', Num(10), BinOp('/', Num(6), Num(2))))

    def test_mul_and_div_chain(self):
        # 2+3*4-1 → BinOp('-', BinOp('+', Num(2), BinOp('*', Num(3), Num(4))), Num(1))
        tree = p("2+3*4-1")
        expected = BinOp('-', BinOp('+', Num(2), BinOp('*', Num(3), Num(4))), Num(1))
        self.assertEqual(tree, expected)


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

    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 — parentheses override precedence."""

    def test_paren_overrides_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_overrides_div(self):
        # 6/(1+2) → BinOp('/', Num(6), BinOp('+', Num(1), Num(2)))
        tree = p("6/(1+2)")
        self.assertEqual(tree, BinOp('/', Num(6), BinOp('+', Num(1), Num(2))))

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

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


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

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

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

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

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

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


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