Coding dojo: SQL code generator for an SQL comment to describe items to exclude.

dojo_sql_comment_excludes.py

"""
Coding dojo: SQL code generator for an SQL comment to describe items to
exclude.

Write a function that generates an SQL comment describing a list of items to
exclude. Long lists of items should be broken into multiple lines. To make the
test case more managable, the maximum line length is 30.

For example, ['one', 'two'] should result in

    -- Excluding: one, two

while ['one', 'two', 'some_more', 'even_more'] should result in

    -- Excluding: one, two,
    -- some_more, even_more

You can make the following assumptions for the list of items to exclude:

* The list is neither empty nor ``None``.
* All items are unicode strings.
* All items fite in one line (have less than 27 characters).

Below you can find an example implementation and test cases.

Things you can learn form this dojo:

1. The textwrap module can be handy.
2. str.join() makes it easy to build a text of comma separated parts.
"""
import unittest
import textwrap

WIDTH = 30  # Maximum length of each line in the generated SQL comment.


def sql_exclude_comment(items_to_exclude):
    assert items_to_exclude
    for item in items_to_exclude:
        assert 1 <= len(item) <= WIDTH - 4

    item_text = ', '.join(items_to_exclude)
    wrapper = textwrap.TextWrapper(
        initial_indent='-- Excluding: ', subsequent_indent='-- ', width=WIDTH)
    return wrapper.fill(item_text) + '\n'


class SqlExcludeCommentTest(unittest.TestCase):

    def test_can_generate_one_item(self):
        self.assertEqual(
            '-- Excluding: one\n',
            sql_exclude_comment(['one']))

    def test_can_generate_two_items(self):
        self.assertEqual(
            '-- Excluding: one, two\n',
            sql_exclude_comment(['one', 'two']))

    def test_can_break_line(self):
        self.assertEqual(
            '-- Excluding: one, two,\n-- some_more, even_more\n',
            sql_exclude_comment(['one', 'two', 'some_more', 'even_more']))

    def test_can_break_multiple_lines(self):
        self.assertEqual(
            '-- Excluding: one, two,\n'
            '-- some_more, even_more,\n'
            '-- almost_done, the_end\n',
            sql_exclude_comment([
                'one', 'two', 'some_more', 'even_more', 'almost_done',
                'the_end'
            ]))


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