from __future__ import annotations
from typing import Union

# As you might have noticed in prep exercises 2 and 3, the support
# for recursive data types in ‹mypy› is somewhat spotty. When
# designing new types, though, there is a compromise that types okay
# in ‹mypy› – at the price of creating a monomorphic wrapper for
# every recursive type in evidence. In other words, you can pick any
# two of [ recursive types, generic types, sanity ]. The ‹JSON› type
# will look as follows:

JSON = Union[ 'JsonArray', 'JsonObject', 'JsonInt', 'JsonStr' ]
JsonKey = Union[ str, int ] # for ‹get› and ‹set›

# Now implement the classes ‹JsonArray› and ‹JsonObject›, with ‹get›
# and ‹set› methods (which take a key/index) and in the case of
# ‹JsonArray›, an ‹append› and a ‹pop› method. The ‹set› methods
# should also accept ‘raw’ ‹str› and ‹int› objects.

class JsonArray:  pass
class JsonObject: pass

# The classes ‹JsonStr› and ‹JsonInt› are going to be a little
# special, since they should behave like ‹str› and ‹int›, but also
# provide ‹get›/‹set› (which fail with an assertion) to make life
# easier for the user.

class JsonInt: pass
class JsonStr: pass


def test_basic() -> None:
    x = JsonObject()
    x.set( 'foo', 7 )
    y = JsonArray()
    y.append( x )
    assert x.get( 'foo' ) == 7
    assert y.get( 0 ).get( 'foo' ) == 7

if __name__ == '__main__':
    test_basic()