/*
 * Copyright 2007 Wishnu Prasetya.
 *
 * This file is part of T2.
 * T2 is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License (GPL) as published by the
 * Free Software Foundation; either version 3 of the License, or any
 * later version.
 * 
 * T2 is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * for more details.
 *
 * A copy of the GNU General Public License can be found in T2 distribution.
 * If it is missing, see http://www.gnu.org/licenses.
 */
package Sequenic.T2.Engines;
import Sequenic.T2.Seq.* ;
import java.util.* ;
import java.lang.reflect.* ;

/**
 * This is an abstract class for generators that try to combinatorically 
 * generates sequences. It extends the abstract class {@link BaseEngineSeqGenerator},
 * and proving a default implementation of the its primitives. Implementation
 * of this class now has to implement a different set, but more abstract,
 * primitives. The primitive {@link CombinatoricSeqGenerator#next_sequence()} 
 * should implement the procedure that produces a test 
 * sequence. The primitive {@link CombinatoricSeqGenerator#META_mkArguments(java.lang.Class[]) } 
 * should implement the procedure for generating arguments for a method call.
 * 
 * <p>The sequences generated by this generator are made of only from field
 * updates and method calls targeting the target-object (so we don't include
 * static methods in the scope).
 */
abstract public class AbstractCombinatoricSeqGenerator extends BaseEngineSeqGenerator {

    private List currentSequence  ;
    private int currentStep ;
    private boolean exhausted ;
    
    static public boolean debug = false ;
    
    abstract public void init() ;
    
   
    @Override
    public MkValStep META_mkTargetObject(Class C) { 
        currentStep = 0 ;
        currentSequence = next_sequence() ;
        exhausted = currentSequence==null ;
        if (exhausted) return null ;
        if (debug) assert currentSequence.size()>0 ;
        Constructor con = (Constructor) currentSequence.get(0) ;
        currentStep++ ;
        return new CREATE_OBJECT(con, META_mkArguments(con.getParameterTypes()),-1) ;
    }

    // Helper
    private TraceStep generate_teststep(Object abstractstep, int indexOfTargetObj){
        
        if (abstractstep instanceof Field) {
            Field field = (Field) abstractstep ;
            MkValStep[] args = META_mkArguments(new Class[] {field.getType()}) ;
            return new UPDATE_FIELD(field, args[0]) ;
        }
        // Else step is a method call:
        Method meth = (Method) abstractstep  ;     
        return new CALL_METHOD(meth, 
                new REF(indexOfTargetObj),
                META_mkArguments(meth.getParameterTypes())
                ) ;   
    }
    
    
    @Override
    public TraceStep META_mkTestStep(Trace sigma) {
        
        assert currentSequence != null ;
        
        // Case 1: we have complete traverse the current sequence:
        if (currentStep >= currentSequence.size()) return null ;
        
        // Else take the next step in the current sequence:
        TraceStep step = generate_teststep(currentSequence.get(currentStep),sigma.indexOfTargetObj) ;
        currentStep++ ;
        return step ;
    }


    @Override
    public boolean isExhausted() {
        return exhausted ;
    }

    /**
     * This implements the procedure to construct the arguments to the test
     * steps. The default implementation here is to generate them randomly,
     * using the procedure implemented in {@link BaseEngine}.
     */
    public MkValStep[] META_mkArguments(Class[] argtypes) {
        MkValStep[] args = new MkValStep[argtypes.length] ;
        for (int i=0; i<argtypes.length; i++) 
            args[i] = engine.META_mkObject(argtypes[i],0,true) ;
        return args ;
    }
    
    /**
     * This should implement the procedure for generating a whole sequence.
     * It produces a sequence of instances of Constructor, Field, or Method.
     * The first in the list should be an instance of Constructor, and the
     * rest should be either a Field or a Method. Note that such a sequence
     *  does not specify what arguments are to be passed to each step. The
     * arguments will be filled later when the engine calls META_mkTargetObject
     * or META_mkTestStep. The method META_mkArguments implements the procedure
     * for generating these arguments.
     * 
     * <p>The engine does not call this method directly.
     * 
     * <p>If a null is returned, then this is interpreted as the generator has
     * no more sequence to generate (exhausted).
     */
    abstract public List next_sequence() ;
        
    abstract public int totalNumberOfCombinations() ;
    
}