import ptoken as 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 c == '.' and tmp.count('.') == 1:
				raise SyntaxError("Invalid grammar, to many periods in number. Found at position " + str (i) + ".")
			if len(tokens) > 1:
				lookBehind = tokens[-1]
				if lookBehind.type == token.TokenType.exp_end:
					tokens.append(token.Token("^", token.TokenType.power))
			if (i + 1) == len(expression_string):
				tokens.append(token.Token(tmp + c, token.TokenType.constant))
			parsing_number = True
			tmp = tmp + c
			continue
		elif c == '(':
			if parsing_number:
				tokens.append(token.Token(tmp, token.TokenType.constant))
				tokens.append(token.Token("*", token.TokenType.multiply))
			tokens.append(token.Token("(", token.TokenType.exp_start))
			parsing_number = False
			tmp = ""
			continue
		elif c == ')':
			if parsing_number:				
				tokens.append(token.Token(tmp, token.TokenType.constant))
			tokens.append(token.Token(")", token.TokenType.exp_end))
			parsing_number = False
			tmp = ""
			continue
		elif token.TokenType.get_operator(c) != token.TokenType.unknown:
			if parsing_number:
				tokens.append(token.Token(tmp, token.TokenType.constant))
			tokens.append(token.Token(c, token.TokenType.get_operator(c)))
			parsing_number = False
			tmp = ""
			continue
		elif c != ' ':
			if len(tokens) > 1:
				lookBehind = tokens[-1]
				if lookBehind.type == token.TokenType.exp_end:
					tokens.append(token.Token("^", token.TokenType.power))
			if (i + 1) < len(expression_string):
				lookAHead = expression_string[i + 1]
				if lookAHead == '(':
					tokens.append(token.Token(c, token.TokenType.variable))
					tokens.append(token.Token("*", token.TokenType.multiply))
					tmp = ""
					parsing_number = False
					continue
			if parsing_number:
				tokens.append(token.Token(tmp, token.TokenType.constant))
				tokens.append(token.Token("*", token.TokenType.multiply))
			if c in symbols_dic.keys():
				symbols_dic[c] += 1
			else:
				symbols_dic[c] = 1
			tokens.append(token.Token(c + str(symbols_dic[c]), token.TokenType.variable))
			parsing_number = False
			tmp = ""
	
	return tokens


def replace_variables(tokens, new_constants):
	newTokenList = []
	for t in tokens:
		if t.type == token.TokenType.variable:
			newTokenList.append(token.Token(new_constants.pop(0), token.TokenType.constant))
		else:
			newTokenList.append(token.Token(t.value, t.type))
			
	return newTokenList