// -*- coding: utf-8 -*-
// Copyright (C) 2008, 2009, 2010, 2012, 2013, 2014, 2015 Laboratoire de
// Recherche et Développement de l'Epita (LRDE).
// Copyright (C) 2004, 2005, 2007 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/>.

#include "randomgraph.hh"
#include "tgba/tgbagraph.hh"
#include "misc/random.hh"
#include "misc/bddlt.hh"
#include "ltlast/atomic_prop.hh"
#include <sstream>
#include <list>
#include <set>
#include <iterator>
#include <vector>

namespace spot
{

  namespace
  {
    unsigned
    random_deterministic_labels_rec(std::vector<bdd>& labels, int *props,
				    int props_n, bdd current, unsigned n)
    {
      if (n >  1 && props_n >= 1)
        {
	  bdd ap = bdd_ithvar(*props);
          ++props;
	  --props_n;

	  // There are m labels generated from "current & ap"
	  // and n - m labels generated from "current & !ap"
          unsigned m = rrand(1, n - 1);
	  if (2 * m < n)
	    {
	      m = n - m;
	      ap = !ap;
	    }

	  unsigned res = random_deterministic_labels_rec(labels, props,
							 props_n,
							 current & ap, m);
	  res += random_deterministic_labels_rec(labels, props, props_n,
						 current & !ap, n - res);
          return res;
        }
      else
        {
	  labels.push_back(current);
          return 1;
        }
    }

    std::vector<bdd>
    random_deterministic_labels(int *props, int props_n, unsigned n)
    {
      std::vector<bdd> bddvec;
      random_deterministic_labels_rec(bddvec, props, props_n, bddtrue, n);
      return bddvec;
    }

    acc_cond::mark_t
    random_acc_cond(twa_graph_ptr aut, unsigned n_accs, float a)
    {
      acc_cond::mark_t m = 0U;
      for (unsigned i = 0U; i < n_accs; ++i)
	if (drand() < a)
	  m |= aut->acc().mark(i);
      return m;
    }

    bdd
    random_labels(int* props, int props_n, float t)
    {
      int val = 0;
      int size = 0;
      bdd p = bddtrue;
      while (props_n)
	{
	  if (size == 8 * sizeof(int))
	    {
	      p &= bdd_ibuildcube(val, size, props);
	      props += size;
	      val = 0;
	      size = 0;
	    }
	  val <<= 1;
	  val |= (drand() < t);
	  ++size;
	  --props_n;
	}
      if (size > 0)
	p &= bdd_ibuildcube(val, size, props);

      return p;
    }
  }

  twa_graph_ptr
  random_graph(int n, float d,
	       const ltl::atomic_prop_set* ap, const bdd_dict_ptr& dict,
	       unsigned n_accs, float a, float t,
	       bool deterministic, bool state_acc)
  {
    assert(n > 0);
    auto res = make_twa_graph(dict);
    if (deterministic)
      res->prop_deterministic();
    if (state_acc)
      res->prop_state_based_acc();

    int props_n = ap->size();
    int* props = new int[props_n];

    int pi = 0;
    for (auto i: *ap)
      props[pi++] = dict->register_proposition(i, res);

    res->set_generalized_buchi(n_accs);

    // Using std::unordered_set instead of std::set for these sets is 3
    // times slower (tested on a 50000 nodes example).
    typedef std::set<int> node_set;
    node_set nodes_to_process;
    node_set unreachable_nodes;

    res->new_states(n);

    std::vector<unsigned> state_randomizer(n);
    state_randomizer[0] = 0;
    nodes_to_process.insert(0);

    for (int i = 1; i < n; ++i)
      {
	state_randomizer[i] = i;
	unreachable_nodes.insert(i);
      }

    // We want to connect each node to a number of successors between
    // 1 and n.  If the probability to connect to each successor is d,
    // the number of connected successors follows a binomial distribution.
    barand<nrand> bin(n - 1, d);

    while (!nodes_to_process.empty())
      {
	auto src = *nodes_to_process.begin();
	nodes_to_process.erase(nodes_to_process.begin());

	// Choose a random number of successors (at least one), using
	// a binomial distribution.
	unsigned nsucc = 1 + bin.rand();

	bool saw_unreachable = false;

	// Create NSUCC random labels.
	std::vector<bdd> labels;
	if (deterministic)
	  {
	    labels = random_deterministic_labels(props, props_n, nsucc);

	    // if nsucc > 2^props_n, we cannot produce nsucc deterministic
	    // transitions so we set it to labels.size()
	    nsucc = labels.size();
	  }
	else
	  for (unsigned i = 0; i < nsucc; ++i)
	    labels.push_back(random_labels(props, props_n, t));

        int possibilities = n;
	unsigned dst;
	acc_cond::mark_t m = 0U;
	if (state_acc)
	  m = random_acc_cond(res, n_accs, a);

	for (auto& l: labels)
	  {
	    if (!state_acc)
	      m = random_acc_cond(res, n_accs, a);

	    // No connection to unreachable successors so far.  This
	    // is our last chance, so force it now.
	    if (--nsucc == 0
		&& !unreachable_nodes.empty()
		&& !saw_unreachable)
	      {
		// Pick a random unreachable node.
		int index = mrand(unreachable_nodes.size());
		node_set::const_iterator i = unreachable_nodes.begin();
		std::advance(i, index);

		// Link it from src.
		res->new_transition(src, *i, l, m);
		nodes_to_process.insert(*i);
		unreachable_nodes.erase(*i);
		break;
	      }

            // Pick the index of a random node.
            int index = mrand(possibilities--);

            // Permute it with state_randomizer[possibilities], so
            // we cannot pick it again.
            dst = state_randomizer[index];
            state_randomizer[index] = state_randomizer[possibilities];
            state_randomizer[possibilities] = dst;

            res->new_transition(src, dst, l, m);
            auto j = unreachable_nodes.find(dst);
            if (j != unreachable_nodes.end())
              {
                nodes_to_process.insert(dst);
                unreachable_nodes.erase(j);
                saw_unreachable = true;
              }
	  }

	// The node must have at least one successor.
	assert(res->get_graph().state_storage(src).succ);
      }
    // All nodes must be reachable.
    assert(unreachable_nodes.empty());
    delete[] props;
    return res;
  }

  acc_cond::acc_code random_acceptance(unsigned n_accs)
  {
    // With 0 acceptance sets, we always generate the true acceptance.
    // (Working with false is somehow pointless, and the formulas we
    // generate for n_accs>0 are always satisfiable, so it makes sense
    // that it should be satisfiable for n_accs=0 as well.)
    if (n_accs == 0)
      return {};

    acc_cond acc(n_accs);
    std::vector<acc_cond::acc_code> codes;
    codes.reserve(n_accs);
    for (unsigned i = 0; i < n_accs; ++i)
      if (drand() < 0.5)
	codes.push_back(acc.inf(acc.mark(i)));
      else
	codes.push_back(acc.fin(acc.mark(i)));

    int s = codes.size();
    while (s > 1)
      {
	// Pick a random code and put it at the end
	int p1 = mrand(s--);
	std::swap(codes[p1], codes[s]);
	// and another one
	int p2 = mrand(s);

	if (drand() < 0.5)
	  codes[p2].append_or(std::move(codes.back()));
	else
	  codes[p2].append_and(std::move(codes.back()));

	codes.pop_back();
      }
    return codes[0];
  }

}