import re

def isWhiteSpace(s):
    return bool(re.match(r'\s', s))

def isDigit(s):
    return bool(re.match(r'[0-9]', s))

def isQuote(s):
    return s == '"'

def isPunc(s):
    return s in ':}{,[]'

def isKeyword(s):
    return s in [ 'true', 'false', 'null' ]

def isAlpha(s):
    return bool(re.match(r'[a-zA-Z]', s))

class Lexer:
    def __init__(self, json):
        self.json = json
        self.i = 0
        self.c = ''
        self.tokens = []

    def end(self):
        return self.i >= len(self.json)

    def addToken(self, tp, val = ''):
        self.tokens.append({ "type": tp, "val": val })

    def peek(self):
        if self.end():
            return None
        self.c = self.json[self.i]
        return self.c

    def advance(self):
        self.i += 1
        return self.peek()

    def lex(self):
        while not self.end():
            self.peek()
            if isWhiteSpace(self.c):
                self.advance()
            elif isDigit(self.c):
                num = self.c
                while isDigit(self.advance()):
                    num += self.c
                if self.c == '.':
                    num += self.c
                    while isDigit(self.advance()):
                        num += self.c
                self.addToken('num', num)
            elif isQuote(self.c):
                s = ''
                while not isQuote(self.advance()):
                    s += self.c
                self.addToken('str', s)
                self.advance()
            elif isPunc(self.c):
                self.addToken(self.c)
                self.advance()
            elif isAlpha(self.c):
                word = self.c
                while isAlpha(self.advance()):
                    word += self.c
                if not isKeyword(word):
                    self.error('Unrecognized keyword \'' + word + '\'. Expected true | false | null')
                self.addToken('kw', word)
            else:
                self.error('Unrecognized token ' + self.c)

        return self.tokens

    def error(self, message):
        raise Exception('[LEXER]:[ERROR] ' + message);