#!/usr/bin/env python
# coding: utf-8

# This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://github.com/donnemartin/interactive-coding-challenges).

# # Challenge Notebook

# ## Problem: Implement a function to reverse a string (a list of characters), in-place.
# 
# * [Constraints](#Constraints)
# * [Test Cases](#Test-Cases)
# * [Algorithm](#Algorithm)
# * [Code](#Code)
# * [Unit Test](#Unit-Test)
# * [Solution Notebook](#Solution-Notebook)

# ## Constraints
# 
# * Can we assume the string is ASCII?
#     * Yes
#     * Note: Unicode strings could require special handling depending on your language
# * Since we need to do this in-place, it seems we cannot use the slice operator or the reversed function?
#     * Correct
# * Since Python string are immutable, can we use a list of characters instead?
#     * Yes

# ## Test Cases
# 
# * None -> None
# * [''] -> ['']
# * ['f', 'o', 'o', ' ', 'b', 'a', 'r'] -> ['r', 'a', 'b', ' ', 'o', 'o', 'f']

# ## Algorithm
# 
# Refer to the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/reverse_string/reverse_string_solution.ipynb).  If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start.

# ## Code

# In[ ]:


class ReverseString(object):

    def reverse(self, chars):
        # TODO: Implement me
        pass


# ## Unit Test

# 
# 
# **The following unit test is expected to fail until you solve the challenge.**

# In[ ]:


# %load test_reverse_string.py
import unittest


class TestReverse(unittest.TestCase):

    def test_reverse(self, func):
        self.assertEqual(func(None), None)
        self.assertEqual(func(['']), [''])
        self.assertEqual(func(
            ['f', 'o', 'o', ' ', 'b', 'a', 'r']),
            ['r', 'a', 'b', ' ', 'o', 'o', 'f'])
        print('Success: test_reverse')

    def test_reverse_inplace(self, func):
        target_list = ['f', 'o', 'o', ' ', 'b', 'a', 'r']
        func(target_list)
        self.assertEqual(target_list, ['r', 'a', 'b', ' ', 'o', 'o', 'f'])
        print('Success: test_reverse_inplace')


def main():
    test = TestReverse()
    reverse_string = ReverseString()
    test.test_reverse(reverse_string.reverse)
    test.test_reverse_inplace(reverse_string.reverse)


if __name__ == '__main__':
    main()


# ## Solution Notebook
# 
# Review the [Solution Notebook](http://nbviewer.ipython.org/github/donnemartin/interactive-coding-challenges/blob/master/arrays_strings/reverse_string/reverse_string_solution.ipynb) for a discussion on algorithms and code solutions.