Crunch Python Coding Test: Coconut Island
=========================================

.. figure:: ./Coconut_Palms_on_the_Beach_5800249336.jpg

You are shipwrecked on a desert island by yourself without any internet or electronic
communications. Your resources include:

- a laptop computer with 2 hours of battery life left (so try to complete this test in
  that amount of time or less)
- coconut trees and lots of fallen coconuts
- a big, flat, sandy beach

You know there are airplanes flying overhead searching for you. You decide to spell the
word **HELP** in big letters on the beach so it can be seen from above. You decide to
write the letters by placing coconuts on the beach at specific coordinates.  Using a
palm tree on the edge of the beach as the origin, you will walk a certain integral
number of paces east (x-axis) and then a certain integral number of paces south (y-axis)
to place each coconut. You are very good at making each pace repeatably the same length.

Part 1: Design the font
-----------------------

Create a module named ``font.py``.

Design a data structure to encode a font. The font will be rendered as coconuts placed
at integer coordinates. Although your font only needs four letters (HELP), as a software
developer you must generalize. So design your data structure so that you can easily
extend your font to include more characters.

In the ``font`` module create an instance of your font data structure and populate it
with the letters H, E, L, and P. Each letter should fill a rectangle 5 paces wide and 7
paces tall.

Define a function in the ``font`` module also named ``font()`` that returns this font
instance.

Part 2: Emit the render instructions
------------------------------------

Create another module named ``render.py``.

Define in it a function with this signature::

    def render_text(font, text):
        """
        Given a font and a text string, return a list of coordinates that
        renders that text using that font. Assume a constant character width of
        5 paces and put 3 paces of horizontal space between each character
        rendered. Do not worry about newlines or other control characters.

        font: Font data structure returned by font.font()
        text: string containing text to be rendered

        Return:
            A list of integer coordinates at which coconuts should be placed.
            Each coordinate pair is in the form (x, y) where x is the number
            of paces west from the reference tree, and y is the number of paces
            south.

        Example return value:
            [(1, 1), (1, 2), (1, 3), ...  (27, 4), (26, 4)]
        """

Implement the ``render_text()`` function according to the docstring.

Part 3: Test the rendered instructions
--------------------------------------

Once you render the list of coordinates at which to place coconuts to form the letters,
you realize that you don't want to blindly follow those instructions, pacing all over
the beach, without knowing if the instructions are correct. You must test them on your
computer first.

Create a module named ``plot.py``.

In the ``plot`` module define a function with this signature::

    def plot_instructions(instructions):
        """
        instructions: Sequence of (x, y) tuples as returned by render_instructions().

        Clear the screen, then plot each coordinate location in the
        instructions by moving the cursor to a calculated row and column
        location and printing the '*' character.  Do not worry about any
        distortion due to the fact that character cells are not square.
        """

Implement the ``plot_instructions()`` function according to the docstring.

Implementation Hint
...................

Most operating systems can run programs in a terminal emulater or console that handles
basic ANSI escape sequences for cursor movement. Here are two helpful escape sequences
you can print to control the terminal:

+-------------------+-----------------------------------------------------+
| Escape sequence   | Effect                                              |
+===================+=====================================================+
| ``\x1b[2J``       | Clear the screen                                    |
+-------------------+-----------------------------------------------------+
| ``\x1b[Y;XH``     | Move the cursor to location X, Y where X is the     |
|                   | column number starting at 1 and Y is the row number.|
|                   | Note: the order of numbers in the escape sequence is|
|                   | reversed: Y, X instead of X, Y.                     |
+-------------------+-----------------------------------------------------+

Final Check
...........

Write a ``main.py`` script with this code::

    import font
    import plot
    import render

    instructions = render.render_text(font.font(), "HELP")
    plot.plot_instructions(instructions)

For your test to pass, the ``main.py`` script must clear the screen and the print HELP
in large letters made of '*' characters. Then finally you will have a hope of being
rescued off of the island. Good luck!