/***************************************************************************************
SLIME -- Copyright (c) 2021, Oscar Riveros, oscar.riveros@peqnp.science,
Santiago, Chile. https://github.com/maxtuno/SLIME

DurianSat -- Copyright (c) 2020, Arijit Shaw, Kuldeep S. Meel

SLIME -- Copyright (c) 2019, Oscar Riveros, oscar.riveros@peqnp.science,
Santiago, Chile. https://maxtuno.github.io/slime-sat-solver

Maple_LCM_Dist_Chrono -- Copyright (c) 2018, Vadim Ryvchin, Alexander Nadel

GlucoseNbSAT -- Copyright (c) 2016,Chu Min LI,Mao Luo and Fan Xiao
                           Huazhong University of science and technology, China
                           MIS, Univ. Picardie Jules Verne, France

MapleSAT -- Copyright (c) 2016, Jia Hui Liang, Vijay Ganesh

MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
           Copyright (c) 2007-2010  Niklas Sorensson

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is 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
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
**************************************************************************************************/

#ifndef SLIME_SIMPSOLVER_H
#define SLIME_SIMPSOLVER_H

#include "mtl/Queue.h"
#include "Solver.h"


namespace SLIME {

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


    class SimpSolver : public Solver {
    public:
        bool log, simplify_ready, render;

        // Constructor/Destructor:
        //
        SimpSolver();

        ~SimpSolver();

        // Problem specification:
        //
        Var newVar(bool polarity = true, bool dvar = true);
        bool addClause(const vec<Lit> &ps);
        bool addEmptyClause();               // Add the empty clause to the solver.
        bool addClause(Lit p);               // Add a unit clause to the solver.
        bool addClause(Lit p, Lit q);        // Add a binary clause to the solver.
        bool addClause(Lit p, Lit q, Lit r); // Add a ternary clause to the solver.
        bool addClause_(vec<Lit> &ps);

        // Variable mode:
        //
        void setFrozen(Var v, bool b); // If a variable is frozen it will not be eliminated.
        bool isEliminated(Var v) const;

        // Solving:
        //
        lbool solveLimited(const vec<Lit> &assumps, bool do_simp = true, bool turn_off_simp = false);
        bool eliminate(bool turn_off_elim = false);  // Perform variable elimination based simplification.
        bool eliminate_();

        void removeSatisfied();

        // Memory managment:
        //
        virtual void garbageCollect();


        // Generate a (possibly simplified) DIMACS file:
        //
#if 0
        void    toDimacs  (const char* file, const vec<Lit>& assumps);
        void    toDimacs  (const char* file);
        void    toDimacs  (const char* file, Lit p);
        void    toDimacs  (const char* file, Lit p, Lit q);
        void    toDimacs  (const char* file, Lit p, Lit q, Lit r);
#endif

        // Mode of operation:
        //
        bool parsing;
        int grow;              // Allow a variable elimination step to grow by a number of clauses (default to zero).
        int clause_lim;        // Variables are not eliminated if it produces a resolvent with a length above this limit.
        // -1 means no limit.
        int subsumption_lim;   // Do not check if subsumption against a clause larger than this. -1 means no limit.
        double simp_garbage_frac; // A different limit for when to issue a GC during simplification (Also see 'garbage_frac').

        bool use_asymm;         // Shrink clauses by asymmetric branching.
        bool use_rcheck;        // Check if a clause is already implied. Prett costly, and subsumes subsumptions :)
        bool use_elim;          // Perform variable elimination.

        // Statistics:
        //
        int merges;
        int asymm_lits;
        int eliminated_vars;

    protected:

        // Helper structures:
        //
        struct ElimLt {
            const vec<int> &n_occ;

            explicit ElimLt(const vec<int> &no) : n_occ(no) {}

            uint64_t cost(Var x) const { return (uint64_t) n_occ[toInt(mkLit(x))] * (uint64_t) n_occ[toInt(~mkLit(x))]; }

            bool operator()(Var x, Var y) const { return cost(x) < cost(y); }
        };

        struct ClauseDeleted {
            const ClauseAllocator &ca;

            explicit ClauseDeleted(const ClauseAllocator &_ca) : ca(_ca) {}

            bool operator()(const CRef &cr) const { return ca[cr].mark() == 1; }
        };

        bool use_simplification;
        vec<uint32_t> elimclauses;
        vec<char> touched;
        OccLists<Var, vec<CRef>, ClauseDeleted> occurs;
        vec<int> n_occ;
        Heap<ElimLt> elim_heap;
        Queue<CRef> subsumption_queue;
        vec<char> frozen;
        vec<char> eliminated;
        int bwdsub_assigns;
        int n_touched;

        // Temporaries:
        //
        CRef bwdsub_tmpunit;

        // Main internal methods:
        //
        lbool solve_(bool do_simp = true, bool turn_off_simp = false);

        bool asymm(Var v, CRef cr);

        bool asymmVar(Var v);

        void updateElimHeap(Var v);

        void gatherTouchedClauses();

        bool merge(const Clause &_ps, const Clause &_qs, Var v, vec<Lit> &out_clause);

        bool merge(const Clause &_ps, const Clause &_qs, Var v, int &size);

        bool backwardSubsumptionCheck(bool verbose = false);

        bool eliminateVar(Var v);

        void extendModel();

        void removeClause(CRef cr);

        bool strengthenClause(CRef cr, Lit l);

        bool implied(const vec<Lit> &c);

        void relocAll(ClauseAllocator &to);
    };


//=================================================================================================
// Implementation of inline methods:


    inline bool SimpSolver::isEliminated(Var v) const { return eliminated[v]; }

    inline void SimpSolver::updateElimHeap(Var v) {
        assert(use_simplification);
        // if (!frozen[v] && !isEliminated(v) && value(v) == l_Undef)
        if (elim_heap.inHeap(v) || (!frozen[v] && !isEliminated(v) && value(v) == l_Undef))
            elim_heap.update(v);
    }

    inline bool SimpSolver::addClause(const vec<Lit> &ps) {
        ps.copyTo(add_tmp);
        return addClause_(add_tmp);
    }
    inline bool SimpSolver::addEmptyClause() {
        add_tmp.clear();
        return addClause_(add_tmp);
    }
    inline bool SimpSolver::addClause(Lit p) {
        add_tmp.clear();
        add_tmp.push(p);
        return addClause_(add_tmp);
    }
    inline bool SimpSolver::addClause(Lit p, Lit q) {
        add_tmp.clear();
        add_tmp.push(p);
        add_tmp.push(q);
        return addClause_(add_tmp);
    }
    inline bool SimpSolver::addClause(Lit p, Lit q, Lit r) {
        add_tmp.clear();
        add_tmp.push(p);
        add_tmp.push(q);
        add_tmp.push(r);
        return addClause_(add_tmp);
    }

    inline void SimpSolver::setFrozen(Var v, bool b) {
        frozen[v] = (char) b;
        if (use_simplification && !b) { updateElimHeap(v); }
    }

    inline lbool SimpSolver::solveLimited(const vec<Lit> &assumps, bool do_simp, bool turn_off_simp) {
        assumps.copyTo(assumptions);
        return solve_(do_simp, turn_off_simp);
    }

//=================================================================================================
}

#endif
