//
// [The "BSD license"]
//  Copyright (c) 2013 Terence Parr
//  Copyright (c) 2013 Sam Harwell
//  Copyright (c) 2014 Eric Vergnaud
//  All rights reserved.
//
//  Redistribution and use in source and binary forms, with or without
//  modification, are permitted provided that the following conditions
//  are met:
//
//  1. Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
//  2. Redistributions in binary form must reproduce the above copyright
//     notice, this list of conditions and the following disclaimer in the
//     documentation and/or other materials provided with the distribution.
//  3. The name of the author may not be used to endorse or promote products
//     derived from this software without specific prior written permission.
//
//  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
//  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
//  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
//  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
//  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
//  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
//  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
//  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
//  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
//  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
///

var DFAState = require('./../dfa/DFAState').DFAState;
var ATNConfigSet = require('./ATNConfigSet').ATNConfigSet;
var getCachedPredictionContext = require('./../PredictionContext').getCachedPredictionContext;

function ATNSimulator(atn, sharedContextCache) {

    // The context cache maps all PredictionContext objects that are ==
    //  to a single cached copy. This cache is shared across all contexts
    //  in all ATNConfigs in all DFA states.  We rebuild each ATNConfigSet
    //  to use only cached nodes/graphs in addDFAState(). We don't want to
    //  fill this during closure() since there are lots of contexts that
    //  pop up but are not used ever again. It also greatly slows down closure().
    //
    //  <p>This cache makes a huge difference in memory and a little bit in speed.
    //  For the Java grammar on java.*, it dropped the memory requirements
    //  at the end from 25M to 16M. We don't store any of the full context
    //  graphs in the DFA because they are limited to local context only,
    //  but apparently there's a lot of repetition there as well. We optimize
    //  the config contexts before storing the config set in the DFA states
    //  by literally rebuilding them with cached subgraphs only.</p>
    //
    //  <p>I tried a cache for use during closure operations, that was
    //  whacked after each adaptivePredict(). It cost a little bit
    //  more time I think and doesn't save on the overall footprint
    //  so it's not worth the complexity.</p>
    ///
    this.atn = atn;
    this.sharedContextCache = sharedContextCache;
    return this;
}

// Must distinguish between missing edge and edge we know leads nowhere///
ATNSimulator.ERROR = new DFAState(0x7FFFFFFF, new ATNConfigSet());


ATNSimulator.prototype.getCachedContext = function (context) {
    if (this.sharedContextCache === null) {
        return context;
    }
    var visited = {};
    return getCachedPredictionContext(context, this.sharedContextCache, visited);
};

exports.ATNSimulator = ATNSimulator;
