/*==LICENSE==*

CyanWorlds.com Engine - MMOG client, server and tools
Copyright (C) 2011  Cyan Worlds, Inc.

This program 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.

This program 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/>.

Additional permissions under GNU GPL version 3 section 7

If you modify this Program, or any covered work, by linking or
combining it with any of RAD Game Tools Bink SDK, Autodesk 3ds Max SDK,
NVIDIA PhysX SDK, Microsoft DirectX SDK, OpenSSL library, Independent
JPEG Group JPEG library, Microsoft Windows Media SDK, or Apple QuickTime SDK
(or a modified version of those libraries),
containing parts covered by the terms of the Bink SDK EULA, 3ds Max EULA,
PhysX SDK EULA, DirectX SDK EULA, OpenSSL and SSLeay licenses, IJG
JPEG Library README, Windows Media SDK EULA, or QuickTime SDK EULA, the
licensors of this Program grant you additional
permission to convey the resulting work. Corresponding Source for a
non-source form of such a combination shall include the source code for
the parts of OpenSSL and IJG JPEG Library used as well as that of the covered
work.

You can contact Cyan Worlds, Inc. by email legal@cyan.com
 or by snail mail at:
      Cyan Worlds, Inc.
      14617 N Newport Hwy
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*==LICENSE==*/
/*****************************************************************************
*
*   $/Plasma20/Sources/Plasma/NucleusLib/pnUtils/Private/pnUtSkipList.h
*   
***/

#ifdef PLASMA20_SOURCES_PLASMA_NUCLEUSLIB_PNUTILS_PRIVATE_PNUTSKIPLIST_H
#error "Header $/Plasma20/Sources/Plasma/NucleusLib/pnUtils/Private/pnUtSkipList.h included more than once"
#endif
#define PLASMA20_SOURCES_PLASMA_NUCLEUSLIB_PNUTILS_PRIVATE_PNUTSKIPLIST_H


/*****************************************************************************
*
*   Macros
*
***/

#define SKIPLIST(type, keyType, keyField, cmp)      TSkipList< type, keyType, offsetof(type, keyField), cmp >
#define SKIPLIST_NUMERIC(type, keyType, keyField)   SKIPLIST(type, keyType, keyField, TSkipListNumericCmp<keyType>)
#define SKIPLIST_STRING(type, keyType, keyField)    SKIPLIST(type, keyType, keyField, TSkipListStringCmp<keyType>)
#define SKIPLIST_STRINGI(type, keyType, keyField)   SKIPLIST(type, keyType, keyField, TSkipListStringCmpI<keyType>)



/*****************************************************************************
*
*   Typedefs
*
***/

typedef void * SkipListTag;


/*****************************************************************************
*
*   Comparers
*
***/


template<class K>
class TSkipListNumericCmp {
public:
    static bool Eq (const K & a, const K & b) { return a == b; }
    static bool Lt (const K & a, const K & b) { return a < b;  }
};

template<class K>
class TSkipListStringCmp {
public:
    static bool Eq (const K & a, const K & b) { return StrCmp(a, b, (unsigned)-1) == 0; }
    static bool Lt (const K & a, const K & b) { return StrCmp(a, b, (unsigned)-1) < 0;  }
};

template<class K>
class TSkipListStringCmpI {
public:
    static bool Eq (const K & a, const K & b) { return StrCmpI(a, b, (unsigned)-1) == 0; }
    static bool Lt (const K & a, const K & b) { return StrCmpI(a, b, (unsigned)-1) < 0;  }
};


/*****************************************************************************
*
*   TSkipList
*
***/

template<class T, class K, unsigned keyOffset, class Cmp>
class TSkipList {
private:
    enum { kMaxLevels = 32 };

    template<class T2, class K2>
    struct TNode {
        const K2 *     key;
        T2 *           object;
        unsigned      level;
        TNode<T2, K2> * prev;
        TNode<T2, K2> * next[1];      // variable size array
    };
    typedef TNode<T,K> Node;

    unsigned    m_level;
    Node *      m_head;
    Node *      m_stop;
    unsigned    m_randomBits;
    unsigned    m_randomsLeft;

    Node *      AllocNode (unsigned levels);
    void        FreeNode (Node * node);
    unsigned    RandomLevel ();

public:
    inline TSkipList ();
    inline ~TSkipList ();
    inline void Clear ();
    inline void Delete (T * object);
    inline T *  Find (const K & key, SkipListTag * tag = nil) const;
    inline T *  FindNext (SkipListTag * tag) const;
    inline T *  Head (SkipListTag * tag) const;
    inline T *  Next (SkipListTag * tag) const;
    inline T *  Prev (SkipListTag * tag) const;
    inline T *  Tail (SkipListTag * tag) const;
    inline void Link (T * object);
    inline void Unlink (T * object);
    inline void Unlink (SkipListTag * tag);
    inline void UnlinkAll ();
    
    #ifdef HS_DEBUGGING
    inline void Print () const;
    #endif
};


/*****************************************************************************
*
*   TSkipList private member functions
*
***/

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
typename TSkipList<T,K,keyOffset,Cmp>::Node* TSkipList<T,K,keyOffset,Cmp>::AllocNode (unsigned level) {

    unsigned size = offsetof(Node, next) + (level + 1) * sizeof(Node);
    Node * node = (Node *)ALLOC(size);
    node->level = level;
    return node;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::FreeNode (TNode<T,K> * node) {

    free(node);
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
unsigned TSkipList<T,K,keyOffset,Cmp>::RandomLevel () {

    unsigned level = 0;
    unsigned bits  = 0;

    while (!bits) {
        bits = m_randomBits % 4;
        if (!bits)
            ++level;
        m_randomBits >>= 2;
        m_randomsLeft -= 2;
        if (!m_randomsLeft) {
            m_randomBits  = RandUnsigned();
            m_randomsLeft = 30;
        }
    }

    return level;
}


/*****************************************************************************
*
*   TSkipList public member functions
*
***/

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
TSkipList<T,K,keyOffset,Cmp>::TSkipList () {

    m_level       = 0; 
    m_head        = AllocNode(kMaxLevels);
    m_stop        = AllocNode(0);
    m_randomBits  = RandUnsigned();
    m_randomsLeft = 30;

    // Initialize header and stop skip node pointers
    m_stop->prev    = m_head;
    m_stop->object  = nil;
    m_stop->next[0] = nil;
    m_head->object  = nil;
    for (unsigned index = 0; index < kMaxLevels; ++index)
        m_head->next[index] = m_stop;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
TSkipList<T,K,keyOffset,Cmp>::~TSkipList () {

    UnlinkAll();
    ASSERT(m_stop->prev == m_head);
    FreeNode(m_head);
    FreeNode(m_stop);
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::Clear () {

    Node * ptr = m_head->next[0];
    while (ptr != m_stop) {
        Node * next = ptr->next[0];
        delete ptr->object;
        FreeNode(ptr);
        ptr = next;
    }

    m_stop->prev = m_head;
    for (unsigned index = 0; index < kMaxLevels; ++index)
        m_head->next[index] = m_stop;
    m_level = 0;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::Delete (T * object) {

    Unlink(object);
    delete object;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::Find (const K & key, SkipListTag * tag) const {

    Node * node = m_head;

    m_stop->key = &key;
    for (int level = (int)m_level; level >= 0; --level)
        while (Cmp::Lt(*node->next[level]->key, key))
            node = node->next[level];

    node = node->next[0];
    if (node != m_stop && Cmp::Eq(*node->key, *m_stop->key)) {
        if (tag)
            *tag = node;
        return node->object;
    }
    else {
        if (tag)
            *tag = nil;
        return nil;
    }
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::FindNext (SkipListTag * tag) const {

    Node * node = (Node *)*tag;

    m_stop->key = node->key;
    for (int level = (int)node->level; level >= 0; --level)
        while (Cmp::Lt(*node->next[level]->key, *m_stop->key))
            node = node->next[level];

    node = node->next[0];
    if (node != m_stop && Cmp::Eq(*node->key, *m_stop->key)) {
        *tag = node;
        return node->object;
    }
    else {
        *tag = nil;
        return nil;
    }
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::Head (SkipListTag * tag) const {

    ASSERT(tag);
    Node * first = m_head->next[0];
    if (first == m_stop) {
        *tag = nil;
        return nil;
    }

    *tag = first;
    return first->object;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::Next (SkipListTag * tag) const {

    ASSERT(tag);
    Node * node = (Node *)*tag;
    ASSERT(node);
    if (node->next[0] == m_stop) {
        *tag = nil;
        return nil;
    }

    *tag = node->next[0];
    return node->next[0]->object;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::Prev (SkipListTag * tag) const {

    ASSERT(tag);
    Node * node = (Node *)*tag;
    ASSERT(node);
    if (node->prev == m_head) {
        *tag = nil;
        return nil;
    }

    *tag = node->prev;
    return node->prev->object;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::Tail (SkipListTag * tag) const {

    ASSERT(tag);
    Node * last = m_stop->prev;
    if (last == m_head) {
        *tag = nil;
        return nil;
    }

    *tag = last;
    return last->object;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::Link (T * object) {

    const K * key = (const K *)((const uint8_t *)object + keyOffset);

    // Find the node's insertion point
    m_stop->key = key;
    Node * update[kMaxLevels];
    Node * node = m_head;
    for (int level = (int)m_level; level >= 0; --level) {
        while (Cmp::Lt(*node->next[level]->key, *key))
            node = node->next[level];
        update[level] = node;
    }
    node = node->next[0];

    {
        // Select a level for the skip node
        unsigned newLevel = RandomLevel();
        if (newLevel > m_level) {
            if (m_level < kMaxLevels - 1) {
                newLevel         = ++m_level;
                update[newLevel] = m_head;
            }
            else
                newLevel = m_level;
        }

        // Create the node and insert it into the skip list
        Node * node  = AllocNode(newLevel);
        node->key    = key;
        node->object = object;
        for (unsigned level = newLevel; level >= 1; --level) {
            node->next[level] = update[level]->next[level];
            update[level]->next[level] = node;
        }
        node->prev               = update[0];
        node->next[0]            = update[0]->next[0];
        update[0]->next[0]->prev = node;
        update[0]->next[0]       = node;
    }
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::Unlink (T * object) {

    const K * key = (const K *)((const uint8_t *)object + keyOffset);

    Node * node = m_head;
    Node * update[kMaxLevels];
    int    level = m_level;

    for (;;) {  
        // Find the node being unlinked
        m_stop->key = key;
        for (; level >= 0; --level) {
            while (Cmp::Lt(*node->next[level]->key, *key))
                node = node->next[level];
            update[level] = node;
        }
        node = node->next[0];

        // Node wasn't found so do nothing
        if (*node->key != *key || node == m_stop)
            return;
            
        if (node->object == object)
            break;
    }
    
    // Update all links
    for (level = m_level; level >= 1; --level) {
        if (update[level]->next[level] != node)
            continue;
        update[level]->next[level] = node->next[level];
    }
    ASSERT(update[0]->next[0] == node);
    node->next[0]->prev = update[0];
    update[0]->next[0]  = node->next[0];

    // Update header
    while (m_level && m_head->next[m_level] == m_stop)
        --m_level;

    FreeNode(node);
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::UnlinkAll () {

    Node * ptr = m_head->next[0];
    while (ptr != m_stop) {
        Node * next = ptr->next[0];
        FreeNode(ptr);
        ptr = next;
    }

    m_stop->prev = m_head;
    for (unsigned index = 0; index < kMaxLevels; ++index)
        m_head->next[index] = m_stop;
    m_level = 0;
}