"""ANTLR3 runtime package"""

# begin[licence]

#

# [The "BSD licence"]

# Copyright (c) 2005-2008 Terence Parr

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#    documentation and/or other materials provided with the distribution.

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from antlr3.constants import EOF

from antlr3.exceptions import NoViableAltException, BacktrackingFailed

class DFA(object):

    """@brief A DFA implemented as a set of transition tables.

    Any state that has a semantic predicate edge is special; those states

    are generated with if-then-else structures in a specialStateTransition()

    which is generated by cyclicDFA template.

    """

    def __init__(

        self,

        recognizer, decisionNumber,

        eot, eof, min, max, accept, special, transition

        ):

        ## Which recognizer encloses this DFA?  Needed to check backtracking

        self.recognizer = recognizer

        self.decisionNumber = decisionNumber

        self.eot = eot

        self.eof = eof

        self.min = min

        self.max = max

        self.accept = accept

        self.special = special

        self.transition = transition

    def predict(self, input):

        """

        From the input stream, predict what alternative will succeed

	using this DFA (representing the covering regular approximation

	to the underlying CFL).  Return an alternative number 1..n.  Throw

	 an exception upon error.

	"""

        mark = input.mark()

        s = 0 # we always start at s0

        try:

            for _ in xrange(50000):

                #print "***Current state = %d" % s

                specialState = self.special[s]

                if specialState >= 0:

                    #print "is special"

                    s = self.specialStateTransition(specialState, input)

                    if s == -1:

                        self.noViableAlt(s, input)

                        return 0

                    input.consume()

                    continue

                if self.accept[s] >= 1:

                    #print "accept state for alt %d" % self.accept[s]

                    return self.accept[s]

                # look for a normal char transition

                c = input.LA(1)

                #print "LA = %d (%r)" % (c, unichr(c) if c >= 0 else 'EOF')

                #print "range = %d..%d" % (self.min[s], self.max[s])

                if c >= self.min[s] and c <= self.max[s]:

                    # move to next state

                    snext = self.transition[s][c-self.min[s]]

                    #print "in range, next state = %d" % snext

                    if snext < 0:

                        #print "not a normal transition"

                        # was in range but not a normal transition

                        # must check EOT, which is like the else clause.

                        # eot[s]>=0 indicates that an EOT edge goes to another

                        # state.

                        if self.eot[s] >= 0: # EOT Transition to accept state?

                            #print "EOT trans to accept state %d" % self.eot[s]

                            s = self.eot[s]

                            input.consume()

                            # TODO: I had this as return accept[eot[s]]

                            # which assumed here that the EOT edge always

                            # went to an accept...faster to do this, but

                            # what about predicated edges coming from EOT

                            # target?

                            continue

                        #print "no viable alt"

                        self.noViableAlt(s, input)

                        return 0

                    s = snext

                    input.consume()

                    continue

                if self.eot[s] >= 0:

                    #print "EOT to %d" % self.eot[s]

                    s = self.eot[s]

                    input.consume()

                    continue

                # EOF Transition to accept state?

                if c == EOF and self.eof[s] >= 0:

                    #print "EOF Transition to accept state %d" \

                    #  % self.accept[self.eof[s]]

                    return self.accept[self.eof[s]]

                # not in range and not EOF/EOT, must be invalid symbol

                self.noViableAlt(s, input)

                return 0

            else:

                raise RuntimeError("DFA bang!")

        finally:

            input.rewind(mark)

    def noViableAlt(self, s, input):

        if self.recognizer._state.backtracking > 0:

            raise BacktrackingFailed

        nvae = NoViableAltException(

            self.getDescription(),

            self.decisionNumber,

            s,

            input

            )

        self.error(nvae)

        raise nvae

    def error(self, nvae):

        """A hook for debugging interface"""

        pass

    def specialStateTransition(self, s, input):

        return -1

    def getDescription(self):

        return "n/a"

##     def specialTransition(self, state, symbol):

##         return 0

    def unpack(cls, string):

        """@brief Unpack the runlength encoded table data.

        Terence implemented packed table initializers, because Java has a

        size restriction on .class files and the lookup tables can grow

        pretty large. The generated JavaLexer.java of the Java.g example

        would be about 15MB with uncompressed array initializers.

        Python does not have any size restrictions, but the compilation of

        such large source files seems to be pretty memory hungry. The memory

        consumption of the python process grew to >1.5GB when importing a

        15MB lexer, eating all my swap space and I was to impacient to see,

        if it could finish at all. With packed initializers that are unpacked

        at import time of the lexer module, everything works like a charm.

        """

        ret = []

        for i in range(len(string) / 2):

            (n, v) = ord(string[i*2]), ord(string[i*2+1])

            # Is there a bitwise operation to do this?

            if v == 0xFFFF:

                v = -1

            ret += [v] * n

        return ret

    unpack = classmethod(unpack)