/**************************************************************************[PbSolver_convertBdd.cc]
Copyright (c) 2005-2010, Niklas Een, Niklas Sorensson

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associated documentation files (the "Software"), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge, publish, distribute,
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furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or
substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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**************************************************************************************************/

#include "PbSolver.h"
#include "monosat/pb/ADTs/FEnv.h"
#include "Debug.h"

namespace Monosat {
namespace PB {

//=================================================================================================


static
//Formula buildBDD(const Linear& c, int size, int lower_limit, int upper_limit, int material_left, Map<Pair<int,Int>,Formula>& memo, int max_cost)
Formula buildBDD(const Linear& c, int size, Int sum, Int material_left, Map<Pair<int, Int>, Formula>& memo,
                 int max_cost){
    Int lower_limit = (c.lo == Int_MIN) ? Int_MIN : c.lo - sum;
    Int upper_limit = (c.hi == Int_MAX) ? Int_MAX : c.hi - sum;

    if(lower_limit <= 0 && upper_limit >= material_left)
        return _1_;
    else if(lower_limit > material_left || upper_limit < 0)
        return _0_;
    else if(FEnv::topSize() > max_cost)
        return _undef_;     // (mycket elegant!)

    Pair<int, Int> key = Pair_new(size, lower_limit);
    Formula ret;

    if(!memo.peek(key, ret)){
        assert(size != 0);
        size--;
        material_left -= c(size);
        Int hi_sum = sign(c[size]) ? sum : sum + c(size);
        Int lo_sum = sign(c[size]) ? sum + c(size) : sum;
        Formula hi = buildBDD(c, size, hi_sum, material_left, memo, max_cost);
        if(hi == _undef_) return _undef_;
        Formula lo = buildBDD(c, size, lo_sum, material_left, memo, max_cost);
        if(lo == _undef_) return _undef_;
        ret = ITE(var(var(c[size])), hi, lo);
        memo.set(key, ret);
    }
    return ret;
}


// New school: Use the new 'ITE' construction of the formula environment 'FEnv'.
//
Formula convertToBdd(const Linear& c, int max_cost){
    Map<Pair<int, Int>, Formula> memo;

    Int sum = 0;
    for(int j = 0; j < c.size; j++)
        sum += c(j);

    FEnv::push();
    Formula ret = buildBDD(c, c.size, 0, sum, memo, max_cost);
    if(ret == _undef_)
        FEnv::pop();
    else{
        if(opt_verbosity >= 1)
            reportf("BDD-cost:%5d\n", FEnv::topSize());
        FEnv::keep();
    }
    return ret;
}
}
}