# Copyright (C) 2008 Andi Albrecht, albrecht.andi@gmail.com
#
# This module is part of python-sqlparse and is released under
# the BSD License: http://www.opensource.org/licenses/bsd-license.php.

"""SQL Lexer"""

# This code is based on the SqlLexer in pygments.
# http://pygments.org/
# It's separated from the rest of pygments to increase performance
# and to allow some customizations.

import re

from sqlparse.keywords import KEYWORDS, KEYWORDS_COMMON
from sqlparse.tokens import *
from sqlparse.tokens import _TokenType


class include(str):
    pass

class combined(tuple):
    """Indicates a state combined from multiple states."""

    def __new__(cls, *args):
        return tuple.__new__(cls, args)

    def __init__(self, *args):
        # tuple.__init__ doesn't do anything
        pass

def is_keyword(value):
    test = value.upper()
    return KEYWORDS_COMMON.get(test, KEYWORDS.get(test, Name)), value


def apply_filters(stream, filters, lexer=None):
    """
    Use this method to apply an iterable of filters to
    a stream. If lexer is given it's forwarded to the
    filter, otherwise the filter receives `None`.
    """
    def _apply(filter_, stream):
        for token in filter_.filter(lexer, stream):
            yield token
    for filter_ in filters:
        stream = _apply(filter_, stream)
    return stream


class LexerMeta(type):
    """
    Metaclass for Lexer, creates the self._tokens attribute from
    self.tokens on the first instantiation.
    """

    def _process_state(cls, unprocessed, processed, state):
        assert type(state) is str, "wrong state name %r" % state
        assert state[0] != '#', "invalid state name %r" % state
        if state in processed:
            return processed[state]
        tokens = processed[state] = []
        rflags = cls.flags
        for tdef in unprocessed[state]:
            if isinstance(tdef, include):
                # it's a state reference
                assert tdef != state, "circular state reference %r" % state
                tokens.extend(cls._process_state(unprocessed, processed, str(tdef)))
                continue

            assert type(tdef) is tuple, "wrong rule def %r" % tdef

            try:
                rex = re.compile(tdef[0], rflags).match
            except Exception, err:
                raise ValueError("uncompilable regex %r in state %r of %r: %s" %
                                 (tdef[0], state, cls, err))

            assert type(tdef[1]) is _TokenType or callable(tdef[1]), \
                   'token type must be simple type or callable, not %r' % (tdef[1],)

            if len(tdef) == 2:
                new_state = None
            else:
                tdef2 = tdef[2]
                if isinstance(tdef2, str):
                    # an existing state
                    if tdef2 == '#pop':
                        new_state = -1
                    elif tdef2 in unprocessed:
                        new_state = (tdef2,)
                    elif tdef2 == '#push':
                        new_state = tdef2
                    elif tdef2[:5] == '#pop:':
                        new_state = -int(tdef2[5:])
                    else:
                        assert False, 'unknown new state %r' % tdef2
                elif isinstance(tdef2, combined):
                    # combine a new state from existing ones
                    new_state = '_tmp_%d' % cls._tmpname
                    cls._tmpname += 1
                    itokens = []
                    for istate in tdef2:
                        assert istate != state, 'circular state ref %r' % istate
                        itokens.extend(cls._process_state(unprocessed,
                                                          processed, istate))
                    processed[new_state] = itokens
                    new_state = (new_state,)
                elif isinstance(tdef2, tuple):
                    # push more than one state
                    for state in tdef2:
                        assert (state in unprocessed or
                                state in ('#pop', '#push')), \
                               'unknown new state ' + state
                    new_state = tdef2
                else:
                    assert False, 'unknown new state def %r' % tdef2
            tokens.append((rex, tdef[1], new_state))
        return tokens

    def process_tokendef(cls):
        cls._all_tokens = {}
        cls._tmpname = 0
        processed = cls._all_tokens[cls.__name__] = {}
        #tokendefs = tokendefs or cls.tokens[name]
        for state in cls.tokens.keys():
            cls._process_state(cls.tokens, processed, state)
        return processed

    def __call__(cls, *args, **kwds):
        if not hasattr(cls, '_tokens'):
            cls._all_tokens = {}
            cls._tmpname = 0
            if hasattr(cls, 'token_variants') and cls.token_variants:
                # don't process yet
                pass
            else:
                cls._tokens = cls.process_tokendef()

        return type.__call__(cls, *args, **kwds)




class Lexer:

    __metaclass__ = LexerMeta

    encoding = 'utf-8'
    stripall = False
    stripnl = False
    tabsize = 0
    flags = re.IGNORECASE

    tokens = {
        'root': [
            (r'\s+', Whitespace),
            (r'--.*?\n', Comment.Single),
            (r'/\*', Comment.Multiline, 'multiline-comments'),
            (r'[+*/<>=~!@#%^&|`?^-]', Operator),
            (r'[0-9]+', Number.Integer),
            # TODO: Backslash escapes?
            (r"'(''|[^'])*'", String.Single),
            (r'"(""|[^"])*"', String.Symbol), # not a real string literal in ANSI SQL
            (r'(LEFT |RIGHT )?(INNER |OUTER )?JOIN', Keyword),
            (r'[a-zA-Z_][a-zA-Z0-9_]*', is_keyword),
            (r'\$([a-zA-Z_][a-zA-Z0-9_]*)?\$', Name.Builtin),
            (r'[;:()\[\],\.]', Punctuation),
        ],
        'multiline-comments': [
            (r'/\*', Comment.Multiline, 'multiline-comments'),
            (r'\*/', Comment.Multiline, '#pop'),
            (r'[^/\*]+', Comment.Multiline),
            (r'[/*]', Comment.Multiline)
        ]
    }

    def __init__(self):
        self.filters = []

    def add_filter(self, filter_, **options):
        from sqlparse.filters import Filter
        if not isinstance(filter_, Filter):
            filter_ = filter_(**options)
        self.filters.append(filter_)

    def get_tokens(self, text, unfiltered=False):
        """
        Return an iterable of (tokentype, value) pairs generated from
        `text`. If `unfiltered` is set to `True`, the filtering mechanism
        is bypassed even if filters are defined.

        Also preprocess the text, i.e. expand tabs and strip it if
        wanted and applies registered filters.
        """
        add_newline = text.endswith('\n')
        if isinstance(text, unicode):
            text = u'\n'.join(text.splitlines())
        else:
            text = '\n'.join(text.splitlines())
            if self.encoding == 'guess':
                try:
                    text = text.decode('utf-8')
                    if text.startswith(u'\ufeff'):
                        text = text[len(u'\ufeff'):]
                except UnicodeDecodeError:
                    text = text.decode('latin1')
            elif self.encoding == 'chardet':
                try:
                    import chardet
                except ImportError:
                    raise ImportError('To enable chardet encoding guessing, '
                                      'please install the chardet library '
                                      'from http://chardet.feedparser.org/')
                enc = chardet.detect(text)
                text = text.decode(enc['encoding'])
            else:
                text = text.decode(self.encoding)
        if add_newline:
            text += '\n'
        if self.stripall:
            text = text.strip()
        elif self.stripnl:
            text = text.strip('\n')
        if self.tabsize > 0:
            text = text.expandtabs(self.tabsize)
#        if not text.endswith('\n'):
#            text += '\n'

        def streamer():
            for i, t, v in self.get_tokens_unprocessed(text):
                yield t, v
        stream = streamer()
        if not unfiltered:
            stream = apply_filters(stream, self.filters, self)
        return stream


    def get_tokens_unprocessed(self, text, stack=('root',)):
        """
        Split ``text`` into (tokentype, text) pairs.

        ``stack`` is the inital stack (default: ``['root']``)
        """
        pos = 0
        tokendefs = self._tokens
        statestack = list(stack)
        statetokens = tokendefs[statestack[-1]]
        known_names = {}
        while 1:
            for rexmatch, action, new_state in statetokens:
                m = rexmatch(text, pos)
                if m:
                    # print rex.pattern
                    value = m.group()
                    if value in known_names:
                        yield pos, known_names[value], value
                    elif type(action) is _TokenType:
                        yield pos, action, value
                    elif hasattr(action, '__call__'):
                        ttype, value = action(value)
                        known_names[value] = ttype
                        yield pos, ttype, value
                    else:
                        for item in action(self, m):
                            yield item
                    pos = m.end()
                    if new_state is not None:
                        # state transition
                        if isinstance(new_state, tuple):
                            for state in new_state:
                                if state == '#pop':
                                    statestack.pop()
                                elif state == '#push':
                                    statestack.append(statestack[-1])
                                else:
                                    statestack.append(state)
                        elif isinstance(new_state, int):
                            # pop
                            del statestack[new_state:]
                        elif new_state == '#push':
                            statestack.append(statestack[-1])
                        else:
                            assert False, "wrong state def: %r" % new_state
                        statetokens = tokendefs[statestack[-1]]
                    break
            else:
                try:
                    if text[pos] == '\n':
                        # at EOL, reset state to "root"
                        pos += 1
                        statestack = ['root']
                        statetokens = tokendefs['root']
                        yield pos, Text, u'\n'
                        continue
                    yield pos, Error, text[pos]
                    pos += 1
                except IndexError:
                    break


def tokenize(sql):
    """Tokenize sql.

    Tokenize *sql* using the :class:`Lexer` and return a 2-tuple stream
    of ``(token type, value)`` items.
    """
    lexer = Lexer()
    return lexer.get_tokens(sql)
