// vi:set ft=cpp: -*- Mode: C++ -*-
/**
 * \file
 * \brief AVL set
 */
/*
 * (c) 2008-2009 Alexander Warg <warg@os.inf.tu-dresden.de>,
 *               Carsten Weinhold <weinhold@os.inf.tu-dresden.de>
 *     economic rights: Technische Universität Dresden (Germany)
 *
 * This file is part of TUD:OS and distributed under the terms of the
 * GNU General Public License 2.
 * Please see the COPYING-GPL-2 file for details.
 *
 * As a special exception, you may use this file as part of a free software
 * library without restriction.  Specifically, if other files instantiate
 * templates or use macros or inline functions from this file, or you compile
 * this file and link it with other files to produce an executable, this
 * file does not by itself cause the resulting executable to be covered by
 * the GNU General Public License.  This exception does not however
 * invalidate any other reasons why the executable file might be covered by
 * the GNU General Public License.
 */

#pragma once

#include <l4/cxx/std_alloc>
#include <l4/cxx/std_ops>
#include <l4/cxx/type_traits>
#include <l4/cxx/avl_tree>

namespace cxx {
namespace Bits {
/**
 * \internal
 * \brief Generic iterator for the AVL-tree based set.
 * \param Cmp the type of the comparison functor.
 * \param Node the type of a node.
 * \param Key the type of the item stored in a node.
 * \param Node_op the type used to determine the direction of the iterator.
 */
template< typename Node, typename Key, typename Node_op >
class Avl_set_iter : public __Bst_iter_b<Node, Node_op>
{
private:
  /// Super-class type
  typedef __Bst_iter_b<Node, Node_op> Base;

  /// our non-const key type
  typedef typename Type_traits<Key>::Non_const_type Non_const_key;

  /// our non-const iterator type
  typedef Avl_set_iter<Node, Non_const_key, Node_op> Non_const_iter;

  using Base::_n;
  using Base::_r;
  using Base::inc;

public:
  /// Create an invalid iterator (end marker)
  Avl_set_iter() = default;

  /**
   * Create an iterator for the given tree.
   * \param t the root node of the tree to iterate.
   */
  Avl_set_iter(Node const *t) : Base(t) {}

  /**
   * Create an iterator from a BST iterator.
   * \prarm o  The BST iterator that shall be copied.
   */
  Avl_set_iter(Base const &o) : Base(o) {}

  /// Allow copy of non-const iterator to const iterator versions.
  Avl_set_iter(Non_const_iter const &o)
  : Base(o) {}

  /// Allow assignment of non-const iterator to const iterator versions.
  Avl_set_iter &operator = (Non_const_iter const &o)
  { Base::operator = (o); return *this; }

  /**
   * \brief Dereference the iterator and get the item out of the tree.
   * \return A reference to the data stored in the AVL tree.
   */
  Key &operator * () const { return const_cast<Node*>(_n)->item; }
  /**
   * \brief Member access to the item the iterator points to.
   * \return A pointer to the item in the node.
   */
  Key *operator -> () const { return &const_cast<Node*>(_n)->item; }
  /**
   * \brief Set the iterator to the next element (pre increment).
   */
  Avl_set_iter &operator ++ () { inc(); return *this; }
  /**
   * \brief Set the iterator to the next element (post increment).
   */
  Avl_set_iter operator ++ (int)
  { Avl_set_iter tmp = *this; inc(); return tmp; }

};

/// Internal, key-getter for Avl_set nodes.
template<typename KEY_TYPE>
struct Avl_set_get_key
{
  typedef KEY_TYPE Key_type;
  template<typename NODE>
  static Key_type const &key_of(NODE const *n)
  { return n->item; }
};


/**
 * Internal: AVL set with internally managed nodes.
 *
 * Use Avl_set, Avl_map, or Avl_tree in applications.
 *
 * \tparam ITEM_TYPE  The type of the items to be stored in the set.
 * \tparam COMPARE    The relation to define the partial order, default is
 *                    to use operator '<'.
 * \tparam ALLOC      The allocator to use for the nodes of the AVL set.
 * \tparam GET_KEY    Sort-key getter (must provide the `Key_type` and
 *                    sort-key for an item (of `ITEM_TYPE`).
 */
template< typename ITEM_TYPE, class COMPARE,
          template<typename A> class ALLOC,
          typename GET_KEY>
class Base_avl_set
{
public:
  /**
   * Return status constants.
   *
   * These constants are compatible with the L4 error codes, see
   * #l4_error_code_t.
   */
  enum
  {
    E_noent =  2, ///< Item does not exist.
    E_exist = 17, ///< Item exists already.
    E_nomem = 12, ///< Memory allocation failed.
    E_inval = 22  ///< Internal error.
  };
  /// Type for the items store in the set
  typedef ITEM_TYPE Item_type;
  /// Key-getter type to derive the sort key of an internal node.
  typedef GET_KEY Get_key;
  /// Type of the sort key used for the items
  typedef typename GET_KEY::Key_type Key_type;
  /// Type used for const items within the set
  typedef typename Type_traits<Item_type>::Const_type Const_item_type;
  /// Type for the comparison functor.
  typedef COMPARE Item_compare;

private:
  /// Internal representation of a tree node.
  class _Node : public Avl_tree_node
  {
  public:
    /// The actual item stored in the node.
    Item_type  item;

    _Node() = default;

    _Node(Item_type const &item) : Avl_tree_node(), item(item) {}
  };

public:
  /**
   * \brief A smart pointer to a tree item.
   */
  class Node
  {
  private:
    struct No_type;
    friend class Base_avl_set<ITEM_TYPE, COMPARE, ALLOC, GET_KEY>;
    _Node const *_n;
    explicit Node(_Node const *n) : _n(n) {}

  public:
    /// Default construction for NIL pointer.
    Node() : _n(0) {}

    /**
     *  Dereference the pointer.
     *
     *  \pre Node is valid.
     */
    Item_type const &operator * () { return _n->item; }
    /**
     *  Dereferenced member access.
     *
     *  \pre Node is valid.
     */
    Item_type const *operator -> () { return &_n->item; }

    /**
     * \brief Validity check.
     * \return false if the pointer is NIL, true if valid.
     */
    bool valid() const { return _n; }

    /// Cast to a real item pointer.
    operator Item_type const * () { if (_n) return &_n->item; else return 0; }
  };

  /// Type for the node allocator.
  typedef ALLOC<_Node> Node_allocator;

private:
  typedef Avl_tree<_Node, GET_KEY, COMPARE> Tree;
  Tree _tree;
  /// The allocator for new nodes
  Node_allocator _alloc;

  Base_avl_set &operator = (Base_avl_set const &) = delete;

  typedef typename Tree::Fwd_iter_ops Fwd;
  typedef typename Tree::Rev_iter_ops Rev;

public:
  typedef typename Type_traits<Item_type>::Param_type Item_param_type;

  /// Forward iterator for the set.
  typedef Avl_set_iter<_Node, Item_type, Fwd> Iterator;
  typedef Iterator iterator;
  /// Constant forward iterator for the set.
  typedef Avl_set_iter<_Node, Const_item_type, Fwd> Const_iterator;
  typedef Const_iterator const_iterator;
  /// Backward iterator for the set.
  typedef Avl_set_iter<_Node, Item_type, Rev> Rev_iterator;
  typedef Rev_iterator reverse_iterator;
  /// Constant backward iterator for the set.
  typedef Avl_set_iter<_Node, Const_item_type, Rev> Const_rev_iterator;
  typedef Const_rev_iterator const_reverse_iterator;

  /**
   * \brief Create a AVL-tree based set.
   * \param alloc Node allocator.
   *
   * Create an empty set (AVL-tree based).
   */
  explicit Base_avl_set(Node_allocator const &alloc = Node_allocator()) 
  : _tree(), _alloc(alloc)
  {}

  ~Base_avl_set()
  {
    _tree.remove_all([this](_Node *n)
                     {
                       n->~_Node();
                       _alloc.free(n);
                     });
  }

  /**
   * Create a copy of an AVL-tree based set.
   *
   * \param o  The set to copy.
   *
   * Creates a deep copy of the set with all its items.
   */
  inline Base_avl_set(Base_avl_set const &o);

  /**
   * Insert an item into the set.
   *
   * \param item  The item to insert.
   *
   * \return A pair of iterator (`first`) and return value (`second`).
   *         `second` will be 0 if the element was inserted into the set
   *         and `-#E_exist` if the element was already in the set and
   *         the set was therefore not updated.
   *         In both cases, `first` contains an iterator that points to
   *         the element.
   *         `second` may also be `-#E_nomem` when memory for the node
   *         could not be allocated. `first` is then invalid.
   *
   * Insert a new item into the set, each item can only be once in
   * the set.
   */
  cxx::Pair<Iterator, int> insert(Item_type const &item);

  /**
   * Remove an item from the set.
   *
   * \param item  The item to remove.
   *
   * \retval 0         Success
   * \retval -E_noent  Item does not exist
   * \retval -E_inval  Internal error
   */
  int remove(Key_type const &item)
  {
    _Node *n = _tree.remove(item);
    if ((long)n == -E_inval)
      return -E_inval;

    if (n)
      {
        n->~_Node();
	_alloc.free(n);
	return 0;
      }

    return -E_noent;
  }

  /**
   * Erase the item with the given key.
   * \param item  The key of the item to remove.
   */
  int erase(Key_type const &item)
  { return remove(item); }

  /**
   * Lookup a node equal to `item`.
   *
   * \param item  The value to search for.
   *
   * \return A smart pointer to the element found.
   *         If no element was found the smart pointer will be invalid.
   */
  Node find_node(Key_type const &item) const
  { return Node(_tree.find_node(item)); }

  /**
   * Find the first node greater or equal to `key`.
   *
   * \param key  Minimum key to look for.
   *
   * \return Smart pointer to the first node greater or equal to `key`.
   *         Will be invalid if no such element was found.
   */
  Node lower_bound_node(Key_type const &key) const
  { return Node(_tree.lower_bound_node(key)); }

  Node lower_bound_node(Key_type &&key) const
  { return Node(_tree.lower_bound_node(key)); }

  /**
   * \brief Get the constant forward iterator for the first element in the set.
   * \return Constant forward iterator for the first element in the set.
   */
  Const_iterator begin() const { return _tree.begin(); }
  /**
   * \brief Get the end marker for the constant forward iterator.
   * \return The end marker for the constant forward iterator.
   */
  Const_iterator end() const   { return _tree.end(); }
  
  /**
   * \brief Get the mutable forward iterator for the first element of the set.
   * \return The mutable forward iterator for the first element of the set.
   */
  Iterator begin() { return _tree.begin(); }
  /**
   * \brief Get the end marker for the mutable forward iterator.
   * \return The end marker for mutable forward iterator.
   */
  Iterator end()   { return _tree.end(); }

  /**
   * \brief Get the constant backward iterator for the last element in the set.
   * \return The constant backward iterator for the last element in the set.
   */
  Const_rev_iterator rbegin() const { return _tree.rbegin(); }
  /**
   * \brief Get the end marker for the constant backward iterator.
   * \return The end marker for the constant backward iterator.
   */
  Const_rev_iterator rend() const   { return _tree.rend(); }

  /**
   * \brief Get the mutable backward iterator for the last element of the set.
   * \return The mutable backward iterator for the last element of the set.
   */
  Rev_iterator rbegin() { return _tree.rbegin(); }
  /**
   * \brief Get the end marker for the mutable backward iterator.
   * \return The end marker for mutable backward iterator.
   */
  Rev_iterator rend()   { return _tree.rend(); }

  Const_iterator find(Key_type const &item) const
  { return _tree.find(item); }
};


//----------------------------------------------------------------------------
/* Implementation of AVL Tree */

/* Create a copy */
template< typename Item, class Compare, template<typename A> class Alloc, typename KEY_TYPE>
Base_avl_set<Item,Compare,Alloc,KEY_TYPE>::Base_avl_set(Base_avl_set const &o)
  : _tree(), _alloc(o._alloc)
{
  for (Const_iterator i = o.begin(); i != o.end(); ++i)
    insert(*i);
}

/* Insert new _Node. */
template< typename Item, class Compare, template< typename A > class Alloc, typename KEY_TYPE>
Pair<typename Base_avl_set<Item,Compare,Alloc,KEY_TYPE>::Iterator, int>
Base_avl_set<Item,Compare,Alloc,KEY_TYPE>::insert(Item const &item)
{
  _Node *n = _alloc.alloc();
  if (!n)
    return cxx::pair(end(), -E_nomem);

  new (n, Nothrow()) _Node(item);
  Pair<_Node *, bool> err = _tree.insert(n);
  if (!err.second)
    {
      n->~_Node();
      _alloc.free(n);
    }

  return cxx::pair(Iterator(typename Tree::Iterator(err.first, err.first)), err.second ? 0 : -E_exist);
}

} // namespace Bits

/**
 * \brief AVL set for simple compareable items.
 *
 * The AVL set can store any kind of items where a partial order is defined.
 * The default relation is defined by the '<' operator.
 *
 * \tparam ITEM_TYPE  The type of the items to be stored in the set.
 * \tparam COMPARE    The relation to define the partial order, default is
 *                    to use operator '<'.
 * \tparam ALLOC      The allocator to use for the nodes of the AVL set.
 */
template< typename ITEM_TYPE, class COMPARE = Lt_functor<ITEM_TYPE>,
          template<typename A> class ALLOC = New_allocator>
class Avl_set :
  public Bits::Base_avl_set<ITEM_TYPE, COMPARE, ALLOC,
                            Bits::Avl_set_get_key<ITEM_TYPE> >
{
private:
  typedef Bits::Base_avl_set<ITEM_TYPE, COMPARE, ALLOC,
                             Bits::Avl_set_get_key<ITEM_TYPE> > Base;

public:
  typedef typename Base::Node_allocator Node_allocator;
  Avl_set() = default;
  Avl_set(Node_allocator const &alloc)
  : Base(alloc)
  {}
};

} // namespace cxx