import unittest
from prefix import PrefixHolder

class TestPrefixReader(unittest.TestCase):
    def setUp(self):
        "Normally setup goes here."

    def test_add(self):
        expr = PrefixHolder('["+", 1, 2]')
        # Test for simple addition
        self.assertEqual(expr.evaluate(), 3)

    def test_sqrt(self):
        expr = PrefixHolder('["sqrt", 9]')
        self.assertEqual(expr.evaluate(), 3)
        # Test that invalid number of arguments throws exception TypeError
        expr = PrefixHOlder('["sqrt", 9, 3]')
        self.assertRaises(TypeError, exp.evaluate())

    def test_variables(self):
        # Test that values can be referenced in an addition
        expr = PrefixHolder('["+", "$var1", 1]')
        self.assertEqual(expr.evaluate({"var1":2}), 3)
        expr = PrefixHolder('["+", 1, "$var"]')
        self.assertEqual(expr.evaluate({"var1":2}), 3)
        # Test that variables that don't exist throw NameError
        # var1 is referenced in the expression but isn't provided.
        self.assertRaises(NameError, expr.evaluate())

    def test_recursion(self):
        # Test that nested expressions work
        expr = PrefixHolder('["+", ["+", 1, 2], 3]')
        self.assertEqual(expr.evaluate(), 6)
        expr = PrefixHolder('["+", 3, ["+", 1, 2]]')
        self.assertEqual(expr.evaluate(), 6)
        # Test that double-nested expressions also work
        expr = PrefixHolder('["+", ["+", ["+", 1, 2], 3], 4]')
        self.assertEqual(expr.evaluate(), 10)
        # Test that nested expressions of various arg lengths work
        expr = PrefixHolder('["+", ["sqrt", 9], 3]')
        self.assertEqual(expr.evaluate(), 6)

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