/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
 *  Main authors:
 *     Christian Schulte <schulte@gecode.org>
 *
 *  Copyright:
 *     Christian Schulte, 2004
 *
 *  Last modified:
 *     $Date: 2008-02-21 07:49:55 +0100 (Thu, 21 Feb 2008) $ by $Author: schulte $
 *     $Revision: 6262 $
 *
 *  This file is part of Gecode, the generic constraint
 *  development environment:
 *     http://www.gecode.org
 *
 *  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.
 *
 */

#include <climits>
#include <algorithm>

namespace Gecode { namespace Int { namespace Extensional {

  /**
   * \brief States are described by number of incoming and outgoing edges
   */
  class State {
  public:
    unsigned int i_deg;
    unsigned int o_deg;
  };

  /**
   * \brief %Edge in the layered graph
   */
  class Edge {
  public:
    State* i_state; ///< Pointer to in-state
    State* o_state; ///< Pointer to out-state
    Edge*  next;    ///< Next edge in support list
    /// Construct new edge and increment states
    Edge(State& i, State& o, Edge* n);
    static void  operator delete(void*, size_t);
    static void  operator delete(void*,Space*);
    static void* operator new(size_t, Space*);
  };

  forceinline
  Edge::Edge(State& i, State& o, Edge* n)
    : i_state(&i), o_state(&o), next(n) {
    i_state->o_deg++; o_state->i_deg++;
  }
  forceinline void
  Edge::operator delete(void*, size_t) {}
  forceinline void
  Edge::operator delete(void*,Space*) {}
  forceinline void*
  Edge::operator new(size_t s, Space* home) {
    return home->alloc(s);
  }


  /// Support information for a value
  class Support {
  public:
    int   val;   ///< Supported value
    Edge* edges; ///< Supporting edges in layered graph
  };

  /// Layer for a view in the layered graph
  class Layer {
  public:
    unsigned int size;     ///< Number of supported values
    Support*     support;  ///< Supported values
  };

  /// Iterator for telling variable domains by scanning support
  class LayerValues {
  private:
    const Support* s1; ///< Current support
    const Support* s2; ///< End of support
  public:
    /// Default constructor
    LayerValues(void);
    /// Initialize for support of layer \a l
    LayerValues(const Layer& l);
    /// Initialize for support of layer \a l
    void init(const Layer& l);
    /// Test whether more values supported
    bool operator()(void) const;
    /// Move to next supported value
    void operator++(void);
    /// Return supported value
    int val(void) const;
  };

  forceinline
  LayerValues::LayerValues(void) {}
  forceinline
  LayerValues::LayerValues(const Layer& l)
    : s1(l.support), s2(l.support+l.size) {}
  forceinline void
  LayerValues::init(const Layer& l) {
    s1=l.support; s2=l.support+l.size;
  }
  forceinline bool
  LayerValues::operator()(void) const {
    return s1<s2;
  }
  forceinline void
  LayerValues::operator++(void) {
    s1++;
  }
  forceinline int
  LayerValues::val(void) const {
    return s1->val;
  }


  /*
   * Index advisors
   *
   */
  template <class View>
  forceinline
  LayeredGraph<View>::Index::Index(Space* home, Propagator* p,
                                   Council<Index>& c, int i0)
    : Advisor(home,p,c), i(i0) {}

  template <class View>
  forceinline
  LayeredGraph<View>::Index::Index(Space* home, bool share, Index& a)
    : Advisor(home,share,a), i(a.i) {}

  template <class View>
  forceinline void
  LayeredGraph<View>::Index::dispose(Space* home, Council<Index>& c) {
    Advisor::dispose(home,c);
  }


  /*
   * Index ranges
   *
   */
  template <class View>
  forceinline
  LayeredGraph<View>::IndexRange::IndexRange(void) 
    : _fst(INT_MAX), _lst(INT_MIN) {}
  template <class View>
  forceinline void
  LayeredGraph<View>::IndexRange::reset(void) {
    _fst=INT_MAX; _lst=INT_MIN;
  }
  template <class View>
  forceinline void
  LayeredGraph<View>::IndexRange::add(int i) {
    _fst=std::min(_fst,i); _lst=std::max(_lst,i);
  }
  template <class View>
  forceinline int
  LayeredGraph<View>::IndexRange::fst(void) const {
    return _fst;
  }
  template <class View>
  forceinline int
  LayeredGraph<View>::IndexRange::lst(void) const {
    return _lst;
  }


  
  /*
   * The layered graph
   *
   */

  template <class View>
  forceinline bool
  LayeredGraph<View>::constructed(void) const {
    return layers != NULL;
  }

  template <class View>
  forceinline void
  LayeredGraph<View>::eliminate(void) {
    if (!constructed() || (layers[0].size > 1))
      return;
    assert(layers[0].size == 1);
    // Skip all layers corresponding to assigned views
    int i = 1;
    while (layers[i].size == 1)
      i++;
    // There is only a single edge
    Edge* e = layers[i-1].support[0].edges;
    assert((e->next == NULL) && (e->o_state->i_deg == 1));
    // Map the state address to the state
    start = static_cast<int>(e->o_state-states) % dfa.n_states();
    layers += i;
    x.drop_fst(i);
    for (Advisors<Index> as(c); as(); ++as)
      as.advisor()->i -= i;
  }

  template <class View>
  forceinline ExecStatus
  LayeredGraph<View>::construct(Space* home) {
    int n = x.size();
    layers = static_cast<Layer*>(home->alloc(sizeof(Layer)*(n+2)))+1;
    
    unsigned int n_states = dfa.n_states();

    // Allocate memory
    states = static_cast<State*>
      (home->alloc(sizeof(State)*(n+1)*n_states));

    // Initialize states (indegree and outdegree)
    for (int i = (n+1)*n_states; i--; )
      states[i].i_deg = states[i].o_deg = 0;

    // Mark initial state as being reachable
    states[start].i_deg = 1;

    // Mark final states as reachable as well
    for (int s = dfa.final_fst(); s < dfa.final_lst(); s++)
      states[n*n_states + s].o_deg = 1;

    // Forward pass: add transitions
    for (int i=0; i<n; i++) {
      layers[i].support = 
        static_cast<Support*>(home->alloc(x[i].size()*sizeof(Support)));
      unsigned int j=0;
      // Enter links leaving reachable states (indegree != 0)
      for (ViewValues<View> nx(x[i]); nx(); ++nx) {
        Edge* e = NULL;
        for (DFA::Transitions t(dfa,nx.val()); t(); ++t)
          if (states[i*n_states + t.i_state()].i_deg != 0)
            e = new (home) Edge(states[i*n_states + t.i_state()],
                                states[(i+1)*n_states +  t.o_state()],
                                e);
        // Found support for value
        if (e != NULL) {
          layers[i].support[j].val   = nx.val();
          layers[i].support[j].edges = e;
          j++;
        }
      }
      if ((layers[i].size = j) == 0)
        return ES_FAILED;
    }

    // Backward pass: prune all transitions that do not lead to final state
    for (int i=n; i--; ) {
      unsigned int k=0;
      for (unsigned int j=0; j<layers[i].size; j++) {
        Edge** p = &layers[i].support[j].edges;
        Edge*  e = *p;
        do {
          if (e->o_state->o_deg != 0) {
            // This state is still reachable, keep edge
            p = &e->next;
          } else {
            // Unreachable state, prune edge
            e->i_state->o_deg--; e->o_state->i_deg--;
            *p = e->next;
          }
          e = e->next;
        } while (e != NULL);
        // Write endmarker for edges
        *p = NULL;
        // Value has support, copy the support information
        if (layers[i].support[j].edges != NULL)
          layers[i].support[k++]=layers[i].support[j];
      }
      if ((layers[i].size = k) == 0)
        return ES_FAILED;
      LayerValues lv(layers[i]);
      GECODE_ME_CHECK(x[i].narrow_v(home,lv,false));
    }

    if (c.empty())
      return ES_SUBSUMED(this,home);
    return ES_FIX;
  }

  template <class View>
  forceinline ExecStatus
  LayeredGraph<View>::prune(Space* home) {
    // Forward pass
    for (int i=i_ch.fst(); i<=i_ch.lst(); i++) {
      bool i_mod = false;
      bool o_mod = false;
      unsigned int j=0;
      unsigned int k=0;
      unsigned int s=layers[i].size;
      do {
        // Some edges might have lost support
        Edge** p = &layers[i].support[j].edges;
        Edge*  e = *p;
        do {
          if (e->i_state->i_deg == 0) {
            // Adapt states
            o_mod |= ((--e->i_state->o_deg) == 0);
            i_mod |= ((--e->o_state->i_deg) == 0);
            // Remove edge
            *p = e->next;
          } else {
            // Keep edge
            p = &e->next;
          }
          e = e->next;
        } while (e != NULL);
        // Write endmarker for edges
        *p=NULL;
        // Check whether value is still supported
        if (layers[i].support[j].edges == NULL) {
          layers[i].size--;
          GECODE_ME_CHECK(x[i].nq(home,layers[i].support[j++].val));
        } else {
          layers[i].support[k++]=layers[i].support[j++];
        }
      } while (j<s);
      assert(k > 0);
      // Update modification information
      if (o_mod) o_ch.add(i-1);
      if (i_mod) i_ch.add(i+1);
    }
    i_ch.reset();

    // Backward pass
    for (int i=o_ch.lst(); i>=o_ch.fst(); i--) {
      bool o_mod = false;
      unsigned int j=0;
      unsigned int k=0;
      unsigned int s=layers[i].size;
      do {
        Edge** p = &layers[i].support[j].edges;
        Edge*  e = *p;
        do {
          if (e->o_state->o_deg != 0) {
            // This state is still reachable, keep edge
            p = &e->next;
          } else {
            // Unreachable state, prune edge
            o_mod |= (--e->i_state->o_deg == 0);
            --e->o_state->i_deg;
            *p = e->next;
          }
          e = e->next;
        } while (e != NULL);
        // Write endmarker for edges
        *p = NULL;
        // Check whether value has still support
        if (layers[i].support[j].edges == NULL) {
          layers[i].size--;
          GECODE_ME_CHECK(x[i].nq(home,layers[i].support[j++].val));
        } else {
          layers[i].support[k++]=layers[i].support[j++];
        }
      } while (j<s);
      assert(k > 0);
      // Update modification information
      if (o_mod) o_ch.add(i-1);
    }
    o_ch.reset();

    // Check subsumption
    if (c.empty())
      return ES_SUBSUMED(this,home);
    return ES_FIX;
  }

  template <class View>
  ExecStatus
  LayeredGraph<View>::advise(Space* home, Advisor* _a, const Delta* d) {
    Index* a = static_cast<Index*>(_a);
    int i = a->i;
    bool i_mod = false;
    bool o_mod = false;
    Layer& l = layers[i];
    if (!constructed())
      goto nofix;

    if (l.size == x[i].size())
      goto fix;
    if (View::modevent(d) == ME_INT_VAL) {
      int n = x[i].val();
      unsigned int j=0;
      for (; l.support[j].val < n; j++)
        // Supported value not any longer in view
        for (Edge* e=l.support[j].edges; e!=NULL; e=e->next) {
          // Adapt states
          o_mod |= ((--e->i_state->o_deg) == 0);
          i_mod |= ((--e->o_state->i_deg) == 0);
        }
      assert(l.support[j].val == n);
      l.support[0] = l.support[j++];
      unsigned int s=l.size;
      l.size = 1;
      for (; j<s; j++)
        for (Edge* e=l.support[j].edges; e!=NULL; e=e->next) {
          // Adapt states
          o_mod |= ((--e->i_state->o_deg) == 0);
          i_mod |= ((--e->o_state->i_deg) == 0);
        }
    } else if (x[i].any(d)) {
      unsigned int j=0;
      unsigned int k=0;
      unsigned int s=l.size;
      for (ViewRanges<View> rx(x[i]); rx() && (j<s);)
        if (l.support[j].val < rx.min()) {
          // Supported value not any longer in view
          for (Edge* e=l.support[j].edges; e!=NULL; e=e->next) {
            // Adapt states
            o_mod |= ((--e->i_state->o_deg) == 0);
            i_mod |= ((--e->o_state->i_deg) == 0);
          }
          ++j;
        } else if (l.support[j].val > rx.max()) {
          ++rx;
        } else {
          l.support[k++]=l.support[j++];
        }
      assert(k > 0);
      l.size = k;
      // Remove remaining values
      for (; j<s; j++)
        for (Edge* e=l.support[j].edges; e!=NULL; e=e->next) {
          // Adapt states
          o_mod |= ((--e->i_state->o_deg) == 0);
          i_mod |= ((--e->o_state->i_deg) == 0);
        }
    } else {
      int min = x[i].min(d);
      unsigned int j=0;
      // Skip values smaller than min (to keep)
      for (; l.support[j].val < min; j++) {}
      int max = x[i].max(d);
      unsigned int k=j;
      unsigned int s=l.size;
      // Remove pruned values
      for (; (j<s) && (l.support[j].val <= max); j++)
        for (Edge* e=l.support[j].edges; e!=NULL; e=e->next) {
          // Adapt states
          o_mod |= ((--e->i_state->o_deg) == 0);
          i_mod |= ((--e->o_state->i_deg) == 0);
        }
      // Keep remaining values
      while (j<s)
        l.support[k++]=l.support[j++];
      l.size =k;
      assert(k > 0);        
    }
    if (!i_mod && !o_mod)
      goto fix;
    if (o_mod) o_ch.add(i-1);
    if (i_mod) i_ch.add(i+1);
    goto nofix;
  nofix:
    return (View::modevent(d) == ME_INT_VAL) 
      ? ES_SUBSUMED_NOFIX(a,home,c) : ES_NOFIX;
  fix:
    if (View::modevent(d) == ME_INT_VAL) {
      a->dispose(home,c);
      return c.empty() ? ES_NOFIX : ES_FIX;
    }
    return ES_FIX;
  }

  template <class View>
  ExecStatus
  LayeredGraph<View>::propagate(Space* home, ModEventDelta) {
    ExecStatus es = constructed() ? prune(home) : construct(home);
    return es;
  }

  template <class View>
  forceinline
  LayeredGraph<View>::LayeredGraph(Space* home, ViewArray<View>& x0, DFA& d)
    : Propagator(home), c(home), x(x0), dfa(d), start(0), layers(NULL) {
    assert(x.size() > 0);
    ModEvent me = ME_INT_BND;
    for (int i=x.size(); i--; )
      if (x[i].assigned())
        me = ME_INT_VAL;
      else
        x[i].subscribe(home, new (home) Index(home,this,c,i));
    View::schedule(home,this,me);
    this->force(home);
  }

  template <>
  forceinline
  LayeredGraph<BoolView>::LayeredGraph(Space* home, ViewArray<BoolView>& x0,
                                       DFA& d)
    : Propagator(home), c(home), x(x0), dfa(d), start(0), layers(NULL) {
    assert(x.size() > 0);
    for (int i=x.size(); i--; )
      if (!x[i].assigned())
        x[i].subscribe(home, new (home) Index(home,this,c,i));
    BoolView::schedule(home,this,ME_BOOL_VAL);
    this->force(home);
  }

  template <class View>
  forceinline size_t
  LayeredGraph<View>::dispose(Space* home) {
    this->unforce(home);
    c.dispose(home);
    dfa.~DFA();
    (void) Propagator::dispose(home);
    return sizeof(*this);
  }

  template <class View>
  ExecStatus
  LayeredGraph<View>::post(Space* home, ViewArray<View>& x, DFA& d) {
    if (x.size() == 0) {
      // Check whether the start state 0 is also a final state
      if ((d.final_fst() <= 0) && (d.final_lst() >= 0))
        return ES_OK;
      return ES_FAILED;
    }
    assert(x.size() > 0);
    for (int i=x.size(); i--; ) {
      DFA::Symbols s(d);
      GECODE_ME_CHECK(x[i].inter_v(home,s,false));
    }
    (void) new (home) LayeredGraph<View>(home,x,d);
    return ES_OK;
  }

  template <class View>
  forceinline
  LayeredGraph<View>::LayeredGraph(Space* home, bool share, 
                                   LayeredGraph<View>& p)
    : Propagator(home,share,p), layers(NULL) {
    assert(p.x.size() > 0);
    p.eliminate();
    c.update(home,share,p.c);
    x.update(home,share,p.x);
    dfa.update(home,share,p.dfa);
    start = p.start;
  }

  template <class View>
  PropCost
  LayeredGraph<View>::cost(ModEventDelta) const {
    return cost_hi(x.size(), PC_LINEAR_HI);
  }

  template <class View>
  Gecode::Support::Symbol
  LayeredGraph<View>::ati(void) {
    return Reflection::mangle<View>("Gecode::Int::Extensional::LayeredGraph");
  }

  template <class View>
  Reflection::ActorSpec
  LayeredGraph<View>::spec(const Space* home, Reflection::VarMap& m) const {
    Reflection::ActorSpec s(ati());
    return s << x.spec(home, m)
             << dfa.spec(m);
  }

  template <class View>
  void
  LayeredGraph<View>::post(Space* home, Reflection::VarMap& vars,
                           const Reflection::ActorSpec& spec) {
    spec.checkArity(2);
    ViewArray<View> x(home, vars, spec[0]);
    DFA dfa(vars, spec[1]);
    (void) new (home) LayeredGraph<View>(home,x,dfa);    
  }

  template <class View>
  Actor*
  LayeredGraph<View>::copy(Space* home, bool share) {
    return new (home) LayeredGraph<View>(home,share,*this);
  }

}}}

// STATISTICS: int-prop