# write a function that takes an animal and its sound,
# use the given animal and sound and
# print the "Old MacDonald had a farm song"
# note: an animal is always given
#       but its sound is not

# hint: think about the things that can be optional

# practice writing function, with optional arguments
# difference between print and return
# practice conditional statements

# Old MacDonald had a farm
# E-I-E-I-O
# And on his farm he had a cow
# E-I-E-I-O
# With a moo-moo here
# And a moo-moo there
# Here a moo, there a moo
# Everywhere a moo-moo
# Old MacDonald had a farm
# E-I-E-I-O


def old_macdonald(animal, sound=None):
    """
    This function takes an animal and its sound
    and print an Old MacDonald had a farm song
    :param animal:
    :param sound: optional (default is None)
    :return: None
    """
    if sound is None:
        sound = "????"

    # is will return True if two variables point to the same object
    # == if the objects referred to by the variables are equal
    # Generally, we can use == to compare value
    # However, in this example, since we set a default value to None
    # and None is an object, it is common to use is operator to compare
    # objects

    print("Old MacDonald had a farm",
          "E-I-E-I-O",
          "And on his farm he had a ", animal,
          "E-I-E-I-O",
          "With a", sound, "-", sound, "here",
          "And a", sound, "-", sound, "there",
          "Here a", sound, ", there a", sound,
          "Everywhere a", sound, "-", sound,
          "Old MacDonald had a farm",
          "E-I-E-I-O")


print("=== call old_macdonald ===")
old_macdonald("cow", "moo")
# old_macdonald("pig", "oink")
old_macdonald("pig")

print("=== call old_macdonald and print the result ===")
# notice that the function return nothing
print(old_macdonald("cow", "moo"))
print(old_macdonald("pig"))


print("=================")


# modify the function to return the song instead of print
def old_macdonald2(animal, sound=None):
    """
    This function takes an animal and its sound
    and return an Old MacDonald had a farm song
    :param animal:
    :param sound: optional (default is None)
    :return: string representing old macdonald song
    """
    if sound is None:
        sound = "????"

    # is will return True if two variables point to the same object
    # == if the objects referred to by the variables are equal
    # Generally, we can use == to compare value
    # However, in this example, since we set a default value to None
    # and None is an object, it is common to use is operator to compare
    # objects

    # return ("Old MacDonald had a farm",
    #       "E-I-E-I-O",
    #       "And on his farm he had a ", animal,
    #       "E-I-E-I-O",
    #       "With a", sound, "-", sound, "here",
    #       "And a", sound, "-", sound, "there",
    #       "Here a", sound, ", there a", sound,
    #       "Everywhere a", sound, "-", sound,
    #       "Old MacDonald had a farm",
    #       "E-I-E-I-O")

    # there are many ways to format strings
    # here is another way to format string, store it in a variable
    # then return the variable
    result = """Old MacDonald had a farm
                E-I-E-I-O
                And on his farm he had a """ + animal
    result += " E-I-E-I-O With a " + sound + " " + "-" + " " + sound + " " + "here"
    result += " And a" + sound + " " + "-" + " " + sound + " " + "there"
    result += " Here a" + " " + sound + " " + ", there a" + " " + sound + " " \
              " Everywhere a" + " " + sound + " " + "-" + " " + sound + " "
    result += "Old MacDonald had a farm" + " " + "E-I-E-I-O"
    return result


print("=== call old_macdonald2 ===")
old_macdonald2("cow", "moo")
# old_macdonald("pig", "oink")
old_macdonald2("pig")

# notice that the function doesn't print anything, it only returns
# calling the function does not show anything on screen

print("=== call old_macdonald2 and print the result ===")
print(old_macdonald2("cow", "moo"))
# old_macdonald("pig", "oink")
print(old_macdonald2("pig"))