//===-- <Support/ilist> - Intrusive Linked List Template ---------*- C++ -*--=//
//
// This file defines classes to implement an intrusive doubly linked list class
// (ie each node of the list must contain a next and previous field for the
// list.
//
// The ilist_traits trait class is used to gain access to the next and previous
// fields of the node type that the list is instantiated with.  If it is not
// specialized, the list defaults to using the getPrev(), getNext() method calls
// to get the next and previous pointers.
//
// The ilist class itself, should be a plug in replacement for list, assuming
// that the nodes contain next/prev pointers.  This list replacement does not
// provides a constant time size() method, so be careful to use empty() when you
// really want to know if it's empty.
//
// The ilist class is implemented by allocating a 'tail' node when the list is
// created (using ilist_traits<>::createEndMarker()).  This tail node is
// absolutely required because the user must be able to compute end()-1. Because
// of this, users of the direct next/prev links will see an extra link on the
// end of the list, which should be ignored.
//
// Requirements for a user of this list:
//
//   1. The user must provide {g|s}et{Next|Prev} methods, or specialize
//      ilist_traits to provide an alternate way of getting and setting next and
//      prev links.
//
//===----------------------------------------------------------------------===//

#ifndef INCLUDED_SUPPORT_ILIST
#define INCLUDED_SUPPORT_ILIST

#include <assert.h>
#include <algorithm>
#include <Support/iterator>

template<typename NodeTy, typename Traits> class iplist;
template<typename NodeTy> class ilist_iterator;

// Template traits for intrusive list.  By specializing this template class, you
// can change what next/prev fields are used to store the links...
template<typename NodeTy>
struct ilist_traits {
  static NodeTy *getPrev(NodeTy *N) { return N->getPrev(); }
  static NodeTy *getNext(NodeTy *N) { return N->getNext(); }
  static const NodeTy *getPrev(const NodeTy *N) { return N->getPrev(); }
  static const NodeTy *getNext(const NodeTy *N) { return N->getNext(); }

  static void setPrev(NodeTy *N, NodeTy *Prev) { N->setPrev(Prev); }
  static void setNext(NodeTy *N, NodeTy *Next) { N->setNext(Next); }

  static NodeTy *createNode() { return new NodeTy(); }
  static NodeTy *createNode(const NodeTy &V) { return new NodeTy(V); }


  void addNodeToList(NodeTy *NTy) {}
  void removeNodeFromList(NodeTy *NTy) {}
  void transferNodesFromList(iplist<NodeTy, ilist_traits> &L2,
                             ilist_iterator<NodeTy> first,
                             ilist_iterator<NodeTy> last) {}
};

// Const traits are the same as nonconst traits...
template<typename Ty>
struct ilist_traits<const Ty> : public ilist_traits<Ty> {};


//===----------------------------------------------------------------------===//
// ilist_iterator<Node> - Iterator for intrusive list.
//
template<typename NodeTy>
class ilist_iterator
  : public bidirectional_iterator<NodeTy, ptrdiff_t> {
  typedef ilist_traits<NodeTy> Traits;
  typedef bidirectional_iterator<NodeTy, ptrdiff_t> super;

  typedef typename super::pointer pointer;
  typedef typename super::reference reference;
  pointer NodePtr;
public:
  typedef size_t size_type;

  ilist_iterator(pointer NP) : NodePtr(NP) {}
  ilist_iterator() : NodePtr(0) {}

  // This is templated so that we can allow constructing a const iterator from
  // a nonconst iterator...
  template<class node_ty>
  ilist_iterator(const ilist_iterator<node_ty> &RHS)
    : NodePtr(RHS.getNodePtrUnchecked()) {}

  // This is templated so that we can allow assigning to a const iterator from
  // a nonconst iterator...
  template<class node_ty>
  const ilist_iterator &operator=(const ilist_iterator<node_ty> &RHS) {
    NodePtr = RHS.getNodePtrUnchecked();
    return *this;
  }

  // Accessors...
  operator pointer() const {
    assert(Traits::getNext(NodePtr) != 0 && "Dereferencing end()!");
    return NodePtr;
  }

  reference operator*() const {
    assert(Traits::getNext(NodePtr) != 0 && "Dereferencing end()!");
    return *NodePtr;
  }
  pointer operator->() { return &operator*(); }
  const pointer operator->() const { return &operator*(); }

  // Comparison operators
  bool operator==(const ilist_iterator &RHS) const {
    return NodePtr == RHS.NodePtr;
  }
  bool operator!=(const ilist_iterator &RHS) const {
    return NodePtr != RHS.NodePtr;
  }

  // Increment and decrement operators...
  ilist_iterator &operator--() {      // predecrement - Back up
    NodePtr = Traits::getPrev(NodePtr);
    assert(NodePtr && "--'d off the beginning of an ilist!");
    return *this;
  }
  ilist_iterator &operator++() {      // preincrement - Advance
    NodePtr = Traits::getNext(NodePtr);
    assert(NodePtr && "++'d off the end of an ilist!");
    return *this;
  }
  ilist_iterator operator--(int) {    // postdecrement operators...
    ilist_iterator tmp = *this;
    --*this;
    return tmp;
  }
  ilist_iterator operator++(int) {    // postincrement operators...
    ilist_iterator tmp = *this;
    ++*this;
    return tmp;
  }


  // Dummy operators to make errors apparent...
  template<class X> void operator+(X Val) {}
  template<class X> void operator-(X Val) {}

  // Internal interface, do not use...
  pointer getNodePtrUnchecked() const { return NodePtr; }
};


//===----------------------------------------------------------------------===//
//
// iplist - The subset of list functionality that can safely be used on nodes of
// polymorphic types, ie a heterogeneus list with a common base class that holds
// the next/prev pointers...
//
template<typename NodeTy, typename Traits=ilist_traits<NodeTy> >
class iplist : public Traits {
  NodeTy *Head, *Tail;

  static bool op_less(NodeTy &L, NodeTy &R) { return L < R; }
  static bool op_equal(NodeTy &L, NodeTy &R) { return L == R; }
public:
  typedef NodeTy *pointer;
  typedef const NodeTy *const_pointer;
  typedef NodeTy &reference;
  typedef const NodeTy &const_reference;
  typedef NodeTy value_type;
  typedef ilist_iterator<NodeTy> iterator;
  typedef ilist_iterator<const NodeTy> const_iterator;
  typedef size_t size_type;
  typedef ptrdiff_t difference_type;
  typedef std::reverse_iterator<const_iterator>  const_reverse_iterator;
  typedef std::reverse_iterator<iterator>  reverse_iterator;

  iplist() : Head(createNode()), Tail(Head) {
    setNext(Head, 0);
    setPrev(Head, 0);
  }
  ~iplist() { clear(); delete Tail; }

  // Iterator creation methods...
  iterator begin()             { return iterator(Head); }
  const_iterator begin() const { return const_iterator(Head); }
  iterator end()               { return iterator(Tail); }
  const_iterator end() const   { return const_iterator(Tail); }

  // reverse iterator creation methods...
  reverse_iterator rbegin()            { return reverse_iterator(end()); }
  const_reverse_iterator rbegin() const{ return const_reverse_iterator(end()); }
  reverse_iterator rend()              { return reverse_iterator(begin()); }
  const_reverse_iterator rend() const  {return const_reverse_iterator(begin());}

  // Miscellaneous inspection routines...
  size_type max_size() const { return size_type(-1); }
  bool empty() const { return Head == Tail; }

  // Front and back accessor functions...
  reference front() {
    assert(!empty() && "Called front() on empty list!");
    return *Head;
  }
  const_reference front() const {
    assert(!empty() && "Called front() on empty list!");
    return *Head;
  }
  reference back() {
    assert(!empty() && "Called back() on empty list!");
    return *getPrev(Tail);
  }
  const_reference back() const {
    assert(!empty() && "Called back() on empty list!");
    return *getPrev(Tail);
  }

  void swap(iplist &RHS) {
    abort();     // Swap does not use list traits callback correctly yet!
    std::swap(Head, RHS.Head);
    std::swap(Tail, RHS.Tail);
  }

  iterator insert(iterator where, NodeTy *New) {
    NodeTy *CurNode = where.getNodePtrUnchecked(), *PrevNode = getPrev(CurNode);
    setNext(New, CurNode);
    setPrev(New, PrevNode);

    if (PrevNode)
      setNext(PrevNode, New);
    else
      Head = New;
    setPrev(CurNode, New);

    addNodeToList(New);  // Notify traits that we added a node...
    return New;
  }

  NodeTy *remove(iterator &IT) {
    assert(IT != end() && "Cannot remove end of list!");
    NodeTy *Node = &*IT;
    NodeTy *NextNode = getNext(Node);
    NodeTy *PrevNode = getPrev(Node);

    if (PrevNode)
      setNext(PrevNode, NextNode);
    else
      Head = NextNode;
    setPrev(NextNode, PrevNode);
    IT = NextNode;
    removeNodeFromList(Node);  // Notify traits that we added a node...
    return Node;
  }

  NodeTy *remove(const iterator &IT) {
    iterator MutIt = IT;
    return remove(MutIt);
  }

  // erase - remove a node from the controlled sequence... and delete it.
  iterator erase(iterator where) {
    delete remove(where);
    return where;
  }


private:
  // transfer - The heart of the splice function.  Move linked list nodes from
  // [first, last) into position.
  //
  void transfer(iterator position, iplist &L2, iterator first, iterator last) {
    assert(first != last && "Should be checked by callers");
    if (position != last) {
      // Remove [first, last) from its old position.
      NodeTy *First = &*first, *Prev = getPrev(First);
      NodeTy *Next = last.getNodePtrUnchecked(), *Last = getPrev(Next);
      if (Prev)
        setNext(Prev, Next);
      else
        L2.Head = Next;
      setPrev(Next, Prev);

      // Splice [first, last) into its new position.
      NodeTy *PosNext = position.getNodePtrUnchecked();
      NodeTy *PosPrev = getPrev(PosNext);

      // Fix head of list...
      if (PosPrev)
        setNext(PosPrev, First);
      else
        Head = First;
      setPrev(First, PosPrev);

      // Fix end of list...
      setNext(Last, PosNext);
      setPrev(PosNext, Last);

      transferNodesFromList(L2, First, PosNext);
    }
  }

public:

  //===----------------------------------------------------------------------===
  // Functionality derived from other functions defined above...
  //

  size_type size() const {
#if __GNUC__ == 3
    size_type Result = std::distance(begin(), end());
#else
    size_type Result = 0;
    std::distance(begin(), end(), Result);
#endif
    return Result;
  }

  iterator erase(iterator first, iterator last) {
    while (first != last)
      first = erase(first);
    return last;
  }

  void clear() { erase(begin(), end()); }

  // Front and back inserters...
  void push_front(NodeTy *val) { insert(begin(), val); }
  void push_back(NodeTy *val) { insert(end(), val); }
  void pop_front() {
    assert(!empty() && "pop_front() on empty list!");
    erase(begin());
  }
  void pop_back() {
    assert(!empty() && "pop_back() on empty list!");
    iterator t = end(); erase(--t);
  }

  // Special forms of insert...
  template<class InIt> void insert(iterator where, InIt first, InIt last) {
    for (; first != last; ++first) insert(where, *first);
  }

  // Splice members - defined in terms of transfer...
  void splice(iterator where, iplist &L2) {
    if (!L2.empty())
      transfer(where, L2, L2.begin(), L2.end());
  }
  void splice(iterator where, iplist &L2, iterator first) {
    iterator last = first; ++last;
    if (where == first || where == last) return; // No change
    transfer(where, L2, first, last);
  }
  void splice(iterator where, iplist &L2, iterator first, iterator last) {
    if (first != last) transfer(where, L2, first, last);
  }



  //===----------------------------------------------------------------------===
  // High-Level Functionality that shouldn't really be here, but is part of list
  //

  // These two functions are actually called remove/remove_if in list<>, but
  // they actually do the job of erase, rename them accordingly.
  //
  void erase(const NodeTy &val) {
    for (iterator I = begin(), E = end(); I != E; ) {
      iterator next = I; ++next;
      if (*I == val) erase(I);
      I = next;
    }
  }
  template<class Pr1> void erase_if(Pr1 pred) {
    for (iterator I = begin(), E = end(); I != E; ) {
      iterator next = I; ++next;
      if (pred(*I)) erase(I);
      I = next;
    }
  }

  template<class Pr2> void unique(Pr2 pred) {
    if (empty()) return;
    for (iterator I = begin(), E = end(), Next = begin(); ++Next != E;) {
      if (pred(*I))
        erase(Next);
      else
        I = Next;
      Next = I;
    }
  }
  void unique() { unique(op_equal); }

  template<class Pr3> void merge(iplist &right, Pr3 pred) {
    iterator first1 = begin(), last1 = end();
    iterator first2 = right.begin(), last2 = right.end();
    while (first1 != last1 && first2 != last2)
      if (pred(*first2, *first1)) {
        iterator next = first2;
        transfer(first1, right, first2, ++next);
        first2 = next;
      } else {
        ++first1;
      }
    if (first2 != last2) transfer(last1, right, first2, last2);
  }
  void merge(iplist &right) { return merge(right, op_less); }

  template<class Pr3> void sort(Pr3 pred);
  void sort() { sort(op_less); }
  void reverse();
};


template<typename NodeTy>
struct ilist : public iplist<NodeTy> {
  typedef typename iplist<NodeTy>::size_type size_type;
  typedef typename iplist<NodeTy>::iterator iterator;

  ilist() {}
  ilist(const ilist &right) {
    insert(begin(), right.begin(), right.end());
  }
  explicit ilist(size_type count) {
    insert(begin(), count, NodeTy());
  } 
  ilist(size_type count, const NodeTy &val) {
    insert(begin(), count, val);
  }
  template<class InIt> ilist(InIt first, InIt last) {
    insert(begin(), first, last);
  }


  // Forwarding functions: A workaround for GCC 2.95 which does not correctly
  // support 'using' declarations to bring a hidden member into scope.
  //
  iterator insert(iterator a, NodeTy *b){ return iplist<NodeTy>::insert(a, b); }
  void push_front(NodeTy *a) { iplist<NodeTy>::push_front(a); }
  void push_back(NodeTy *a)  { iplist<NodeTy>::push_back(a); }
  

  // Main implementation here - Insert for a node passed by value...
  iterator insert(iterator where, const NodeTy &val) {
    return insert(where, createNode(val));
  }


  // Front and back inserters...
  void push_front(const NodeTy &val) { insert(begin(), val); }
  void push_back(const NodeTy &val) { insert(end(), val); }

  // Special forms of insert...
  template<class InIt> void insert(iterator where, InIt first, InIt last) {
    for (; first != last; ++first) insert(where, *first);
  }
  void insert(iterator where, size_type count, const NodeTy &val) {
    for (; count != 0; --count) insert(where, val);
  }

  // Assign special forms...
  void assign(size_type count, const NodeTy &val) {
    iterator I = begin();
    for (; I != end() && count != 0; ++I, --count)
      *I = val;
    if (count != 0)
      insert(end(), n, val);
    else
      erase(I, end());
  }
  template<class InIt> void assign(InIt first, InIt last) {
    iterator first1 = begin(), last1 = end();
    for ( ; first1 != last1 && first2 != last2; ++first1, ++first2)
      *first1 = *first2;
    if (first2 == last2)
      erase(first1, last1);
    else
      insert(last1, first2, last2);
  }


  // Resize members...
  void resize(size_type newsize, NodeTy val) {
    iterator i = begin();
    size_type len = 0;
    for ( ; i != end() && len < newsize; ++i, ++len) /* empty*/ ;

    if (len == newsize)
      erase(i, end());
    else                                          // i == end()
      insert(end(), newsize - len, val);
  }
  void resize(size_type newsize) { resize(newsize, NodeTy()); }
};

namespace std {
  // Ensure that swap uses the fast list swap...
  template<class Ty>
  void swap(iplist<Ty> &Left, iplist<Ty> &Right) {
    Left.swap(Right);
  }
}  // End 'std' extensions...

#endif
