import token

def get_tokens_from_expression_string(expression_string):
	"""
	Takes user input of an actuarial formula and parses the formula to id its components.
	:return: tokens (List of objects of CToken class).
	"""
	tokens = []  # List of objects of CToken class
	tmp = ""
	parsing_number = False
	symbols_dic = {}  # Dictionary to keep track of the no. of times each variable appears.

	for i in range(0, len(expression_string)):
		c = expression_string[i]
		if c == '.' or c.isdigit():
			if tmp.count('.') == 1:
				raise ValueError("Invalid grammar, to many periods in number!")
			if len(tokens) > 1:
				lookBehind = tokens[-1]
				if lookBehind.type == token.TokenType.exp_end:
					tokens.append(token.CToken("^", token.TokenType.power))
			if (i + 1) == len(expression_string):
				tokens.append(token.CToken(tmp + c, token.TokenType.constant))
			parsing_number = True
			tmp = tmp + c
			continue
		elif c == '(':
			if parsing_number:
				tokens.append(token.CToken(tmp, token.TokenType.constant))
				tokens.append(token.CToken("*", token.TokenType.multiply))
			tokens.append(token.CToken("(", token.TokenType.exp_start))
			parsing_number = False
			tmp = ""
			continue
		elif c == ')':
			if parsing_number:				
				tokens.append(token.CToken(tmp, token.TokenType.constant))
			tokens.append(token.CToken(")", token.TokenType.exp_end))
			parsing_number = False
			tmp = ""
			continue
		elif token.TokenType.get_operator(c) != token.TokenType.unknown:
			if parsing_number:
				tokens.append(token.CToken(tmp, token.TokenType.constant))
			tokens.append(token.CToken(c, token.TokenType.get_operator(c)))
			parsing_number = False
			tmp = ""
			continue
		elif c != ' ':
			if len(tokens) > 1:
				lookBehind = tokens[-1]
				if lookBehind.type == TokenType.exp_end:
					tokens.append(token.CToken("^", token.TokenType.power))
			if (i + 1) < len(expression_string):
				lookAHead = expression_string[i + 1]
				if lookAHead == '(':
					tokens.append(token.CToken(c, token.TokenType.variable))
					tokens.append(token.CToken("*", token.TokenType.multiply))
					tmp = ""
					parsing_number = False
					continue
			if parsing_number:
				tokens.append(token.CToken(tmp, token.TokenType.constant))
				tokens.append(token.CToken("*", token.TokenType.multiply))
			if c in symbols_dic.keys():
				symbols_dic[c] += 1
			else:
				symbols_dic[c] = 1
			tokens.append(token.CToken(c + str(symbols_dic[c]), token.TokenType.variable))
			parsing_number = False
			tmp = ""

	return tokens

def operate(n1, n2, tokenType):
	if tokenType == token.TokenType.add:
		print("Adding %d and %d to get %d." %(n1, n2, n1 + n2))
	elif tokenType == token.TokenType.subtract:
		print("Subtracting %d and %d to get %d." %(n1, n2, n1 - n2))
	elif tokenType == token.TokenType.multiply:
		print("Multiplying %d and %d to get %d" %(n1, n2, n1 * n2))
	elif tokenType == token.TokenType.divide:
		print("Dividing %d and %d to get %d" %(n1, n2, n1 / n2))
	elif tokenType == token.TokenType.power:
		print("Raising %d to the power of %d to get %d" %(n1, n2, n1**n2))
	else:
		raise ValueError("Invalid operator value.")