def next_token(current=None):
"""Generates the next token based on a current token
: param current: the previous token to the one that needs to be generated
"""
if not current:
return ALPHABET[0] * START_URL_TOKEN_LENGTH
else:
# Check the length
if len(current) < START_URL_TOKEN_LENGTH:
raise LinkShortenerLengthError()
result = list(current)
#Check every char from left to right
for index in range(len(current) - 1, -1, -1):
char = current[index]
# Reset this token to
if char == ALPHABET[len(ALPHABET) - 1]:
result[index] = ALPHABET[0]
# Take the next character
else:
result[index] = ALPHABET[ALPHABET.index(char) + 1]
break
# Join all the chars to get the final result
result = "".join(result)
# Maximun of combinations reached? add one more!
# We know because the number is reseted to the start number
if result == len(current) * ALPHABET[0]:
result = ALPHABET[1] + result
return result
def token_to_counter(token):
"""Translates an alphabet token to a decimal numeric number
:param token: The token string
"""
if not isinstance(token, str):
token = str(token)
#Remove left 0's
token = token.lstrip("0")
#split each character and reverse
token = list(token)
token.reverse()
result = 0
#Translate
#(Xn * (length ^ n)) + (Xn-1 * (length ^ n-1)) ... (X0 * (length ^ 0))
for it, char in enumerate(token):
result += ALPHABET.index(char) * (len(ALPHABET) ** it)
return result
