import re
from ppci import CompilerError, SourceLocation, Token, make_num
from baselex import BaseLexer

"""
 Lexical analyzer part. Splits the input character stream into tokens.
"""

keywords = ['and', 'or', 'not', 'true', 'false',
            'else', 'if', 'while', 'for', 'return',
            'switch', 'case', 'default',
            'function', 'var', 'type', 'const',
            'struct', 'cast', 'sizeof',
            'import', 'module']


class Lexer(BaseLexer):
    """ Generates a sequence of token from an input stream """
    def __init__(self, diag):
        self.diag = diag
        tok_spec = [
            ('REAL', r'\d+\.\d+', lambda typ, val: (typ, float(val))),
            ('HEXNUMBER', r'0x[\da-fA-F]+',
             lambda typ, val: ('NUMBER', make_num(val))),
            ('NUMBER', r'\d+', lambda typ, val: (typ, int(val))),
            ('ID', r'[A-Za-z][A-Za-z\d_]*', self.handle_id),
            ('NEWLINE', r'\n', lambda typ, val: self.newline()),
            ('SKIP', r'[ \t]', None),
            ('COMMENTS', r'//.*', None),
            ('LONGCOMMENTBEGIN', r'\/\*', self.handle_comment_start),
            ('LONGCOMMENTEND', r'\*\/', self.handle_comment_stop),
            ('LEESTEKEN',
             r'==|->|<<|>>|!=|\+\+|[\.,=:;\-+*\[\]/\(\)]|>=|<=|<>|>|<|{|}|&|\^|\|',
             lambda typ, val: (val, val)),
            ('STRING', r'".*?"', lambda typ, val: (typ, val[1:-1]))
            ]
        super().__init__(tok_spec)

    def lex(self, input_file):
        filename = input_file.name if hasattr(input_file, 'name') else ''
        s = input_file.read()
        input_file.close()
        self.diag.addSource(filename, s)
        self.filename = filename
        return self.tokenize(s)

    def handle_comment_start(self, typ, val):
        self.incomment = True

    def handle_comment_stop(self, typ, val):
        self.incomment = False

    def tokenize(self, text):
        """ Keeps track of the long comments """
        self.incomment = False
        for token in super().tokenize(text):
            if self.incomment:
                pass    # Wait until we are not in a comment section
            else:
                yield token
        loc = SourceLocation(self.filename, self.line, 0, 0)
        yield Token('EOF', 'EOF', loc)

    def handle_id(self, typ, val):
        if val in keywords:
            typ = val
        return typ, val