Simple Text Protocol

manifest.py

# a - j, Z, M,K,P,Q

"""
Thoughts
Consider the message a tree, walk the message until we meet the valid 
considition which there's no more charactors. 

When we encouter a - j, we substract one from the message. When we see
Z, we look for next valid message, when we counter M,K,P,Q, we look
for two valid message.
"""
def is_valid(message):
    return helper(message) == ""
    
def helper(message):
    if message is None or len(message) == 0:
        return False
    first_char = message[0]
    lower_charset = [chr(97 + i) for i in xrange(10)]
    if first_char in lower_charset:
        return message[1:]
    if first_char == 'Z' and len(message) >= 2:
        return helper(message[1:])
    if first_char in ['M', 'K', 'P', 'Q'] and len(message) >= 3:
        return helper(helper(message[1:]))
    return message


VALID = True
INVALID = False
assert is_valid("Qa") == INVALID
assert is_valid("Zj") == VALID
assert is_valid("MZca") == VALID
assert is_valid("Khfa") == INVALID
assert is_valid('Ma') == INVALID



# We have decided to extend the protocol to accept an arbitrary number of valid messages. 
# If a message begins with a number, precisely that number of valid messages must follow.
"""
Thoughts:
We will use the number to determine how many loop/valid message we will need to get. 
in the helper we will have a loop to go through the number of valid message. It fails when
we don't have that many valid messages in the following. 
"""