// -*- coding: utf-8 -*-
// Copyright (C) 2009, 2011, 2013, 2014 Laboratoire de Recherche et
// Développement de l'Epita (LRDE).
// Copyright (C) 2003, 2004, 2005 Laboratoire d'Informatique de
// Paris 6 (LIP6), département Systèmes Répartis Coopératifs (SRC),
// Université Pierre et Marie Curie.
//
// This file is part of Spot, a model checking library.
//
// Spot is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
//
// Spot 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.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

#ifndef SPOT_TGBA_TGBA_HH
# define SPOT_TGBA_TGBA_HH

#include "state.hh"
#include "bdddict.hh"
#include "succiter.hh"

namespace spot
{
  class tgba_succ_iterator;

  /// \defgroup tgba TGBA (Transition-based Generalized Büchi Automata)
  ///
  /// Spot is centered around the spot::tgba type.  This type and its
  /// cousins are listed \ref tgba_essentials "here".  This is an
  /// abstract interface.  Its implementations are either \ref
  /// tgba_representation "concrete representations", or \ref
  /// tgba_on_the_fly_algorithms "on-the-fly algorithms".  Other
  /// algorithms that work on spot::tgba are \ref tgba_algorithms
  /// "listed separately".

  /// \addtogroup tgba_essentials Essential TGBA types
  /// \ingroup tgba

  /// \ingroup tgba_essentials
  /// \brief A Transition-based Generalized Büchi Automaton.
  ///
  /// The acronym TGBA (Transition-based Generalized Büchi Automaton)
  /// was coined by Dimitra Giannakopoulou and Flavio Lerda
  /// in "From States to Transitions: Improving Translation of LTL
  /// Formulae to Büchi Automata".  (FORTE'02)
  ///
  /// TGBAs are transition-based, meanings their labels are put
  /// on arcs, not on nodes.  They use Generalized Büchi acceptance
  /// conditions: there are several acceptance sets (of
  /// transitions), and a path can be accepted only if it traverses
  /// at least one transition of each set infinitely often.
  ///
  /// Browsing such automaton can be achieved using two functions:
  /// \c get_init_state, and \c succ_iter.  The former returns
  /// the initial state while the latter lists the
  /// successor states of any state.
  ///
  /// Note that although this is a transition-based automata,
  /// we never represent transitions!  Transition informations are
  /// obtained by querying the iterator over the successors of
  /// a state.
  class SPOT_API tgba
  {
  protected:
    tgba();
    // Any iterator returned via release_iter.
    mutable tgba_succ_iterator* iter_cache_;

  public:

#ifndef SWIG
    class succ_iterable
    {
    protected:
      const tgba* aut_;
      tgba_succ_iterator* it_;
    public:
      succ_iterable(const tgba* aut, tgba_succ_iterator* it)
	: aut_(aut), it_(it)
      {
      }

      succ_iterable(succ_iterable&& other)
	: aut_(other.aut_), it_(other.it_)
      {
	other.it_ = nullptr;
      }

      ~succ_iterable()
      {
	if (it_)
	  aut_->release_iter(it_);
      }

      internal::succ_iterator begin()
      {
	return it_->first() ? it_ : nullptr;
      }

      internal::succ_iterator end()
      {
	return nullptr;
      }
    };
#endif

    virtual ~tgba();

    /// \brief Get the initial state of the automaton.
    ///
    /// The state has been allocated with \c new.  It is the
    /// responsability of the caller to \c destroy it when no
    /// longer needed.
    virtual state* get_init_state() const = 0;

    /// \brief Get an iterator over the successors of \a local_state.
    ///
    /// The iterator has been allocated with \c new.  It is the
    /// responsability of the caller to \c delete it when no
    /// longer needed.
    virtual tgba_succ_iterator*
    succ_iter(const state* local_state) const = 0;

#ifndef SWIG
    /// \brief Build an iterable over the successors of \a s.
    ///
    /// This is meant to be used as
    /// <code>for (auto i: aut->out(s)) { /* i->current_state() */ }</code>.
    succ_iterable
    succ(const state* s) const
    {
      return {this, succ_iter(s)};
    }
#endif

    /// \brief Release an iterator after usage.
    ///
    /// This iterator can then be reused by succ_iter() to avoid
    /// memory allocation.
    void release_iter(tgba_succ_iterator* i) const
    {
      if (iter_cache_)
	delete i;
      else
	iter_cache_ = i;
    }

    /// \brief Get a formula that must hold whatever successor is taken.
    ///
    /// \return A formula which must be verified for all successors
    ///  of \a state.
    ///
    /// This can be as simple as \c bddtrue, or more completely
    /// the disjunction of the condition of all successors.  This
    /// is used as an hint by \c succ_iter() to reduce the number
    /// of successor to compute in a product.
    ///
    /// Sub classes should implement compute_support_conditions(),
    /// this function is just a wrapper that will cache the
    /// last return value for efficiency.
    bdd support_conditions(const state* state) const;

    /// \brief Get the dictionary associated to the automaton.
    ///
    /// Atomic propositions and acceptance conditions are represented
    /// as BDDs.  The dictionary allows to map BDD variables back to
    /// formulae, and vice versa.  This is useful when dealing with
    /// several automata (which may use the same BDD variable for
    /// different formula), or simply when printing.
    virtual bdd_dict* get_dict() const = 0;

    /// \brief Format the state as a string for printing.
    ///
    /// This formating is the responsability of the automata
    /// that owns the state.
    virtual std::string format_state(const state* state) const = 0;

    /// \brief Return a possible annotation for the transition
    /// pointed to by the iterator.
    ///
    /// You may decide to use annotations when building a tgba class
    /// that represents the state space of a model, for instance to
    /// indicate how the tgba transitions relate to the original model
    /// (e.g. the annotation could be the name of a PetriNet
    /// transition, or the line number of some textual formalism).
    ///
    /// Implementing this method is optional; the default annotation
    /// is the empty string.
    ///
    /// This method is used for instance in dotty_reachable(),
    /// and replay_tgba_run().
    ///
    /// \param t a non-done tgba_succ_iterator for this automaton
    virtual std::string
    transition_annotation(const tgba_succ_iterator* t) const;

    /// \brief Project a state on an automaton.
    ///
    /// This converts \a s, into that corresponding spot::state for \a
    /// t.  This is useful when you have the state of a product, and
    /// want restrict this state to a specific automata occuring in
    /// the product.
    ///
    /// It goes without saying that \a s and \a t should be compatible
    /// (i.e., \a s is a state of \a t).
    ///
    /// \return 0 if the projection fails (\a s is unrelated to \a t),
    ///    or a new \c state* (the projected state) that must be
    ///    destroyed by the caller.
    virtual state* project_state(const state* s, const tgba* t) const;

    /// \brief Return the set of all acceptance conditions used
    /// by this automaton.
    ///
    /// The goal of the emptiness check is to ensure that
    /// a strongly connected component walks through each
    /// of these acceptiong conditions.  I.e., the union
    /// of the acceptiong conditions of all transition in
    /// the SCC should be equal to the result of this function.
    virtual bdd all_acceptance_conditions() const = 0;

    /// The number of acceptance conditions.
    virtual unsigned int number_of_acceptance_conditions() const;

    /// \brief Return the conjuction of all negated acceptance
    /// variables.
    ///
    /// For instance if the automaton uses variables <tt>Acc[a]</tt>,
    /// <tt>Acc[b]</tt> and <tt>Acc[c]</tt> to describe acceptance sets,
    /// this function should return <tt>!Acc[a]\&!Acc[b]\&!Acc[c]</tt>.
    ///
    /// This is useful when making products: each operand's condition
    /// set should be augmented with the neg_acceptance_conditions() of
    /// the other operand.
    virtual bdd neg_acceptance_conditions() const = 0;

  protected:
    /// Do the actual computation of tgba::support_conditions().
    virtual bdd compute_support_conditions(const state* state) const = 0;
    mutable const state* last_support_conditions_input_;
  private:
    mutable bdd last_support_conditions_output_;
    mutable int num_acc_;
  };

  /// \addtogroup tgba_representation TGBA representations
  /// \ingroup tgba

  /// \addtogroup tgba_algorithms TGBA algorithms
  /// \ingroup tgba

  /// \addtogroup tgba_on_the_fly_algorithms TGBA on-the-fly algorithms
  /// \ingroup tgba_algorithms

  /// \addtogroup tgba_io Input/Output of TGBA
  /// \ingroup tgba_algorithms

  /// \addtogroup tgba_ltl Translating LTL formulae into TGBA
  /// \ingroup tgba_algorithms

  /// \addtogroup tgba_generic Algorithm patterns
  /// \ingroup tgba_algorithms

  /// \addtogroup tgba_reduction TGBA simplifications
  /// \ingroup tgba_algorithms

  /// \addtogroup tgba_misc Miscellaneous algorithms on TGBA
  /// \ingroup tgba_algorithms
}

#endif // SPOT_TGBA_TGBA_HH