/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright (c) 2007 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU Lesser
 * General Public License Version 2.1 only ("LGPL") or the Common Development and
 * Distribution License ("CDDL")(collectively, the "License"). You may not use this
 * file except in compliance with the License. You can obtain a copy of the CDDL at
 * http://www.opensource.org/licenses/cddl1.php and a copy of the LGPLv2.1 at
 * http://www.opensource.org/licenses/lgpl-license.php. See the License for the 
 * specific language governing permissions and limitations under the License. When
 * distributing the software, include this License Header Notice in each file and
 * include the full text of the License in the License file as well as the
 * following notice:
 * 
 * NOTICE PURSUANT TO SECTION 9 OF THE COMMON DEVELOPMENT AND DISTRIBUTION LICENSE
 * (CDDL)
 * For Covered Software in this distribution, this License shall be governed by the
 * laws of the State of California (excluding conflict-of-law provisions).
 * Any litigation relating to this License shall be subject to the jurisdiction of
 * the Federal Courts of the Northern District of California and the state courts
 * of the State of California, with venue lying in Santa Clara County, California.
 * 
 * Contributor(s):
 * 
 * If you wish your version of this file to be governed by only the CDDL or only
 * the LGPL Version 2.1, indicate your decision by adding "[Contributor]" elects to
 * include this software in this distribution under the [CDDL or LGPL Version 2.1]
 * license." If you don't indicate a single choice of license, a recipient has the
 * option to distribute your version of this file under either the CDDL or the LGPL
 * Version 2.1, or to extend the choice of license to its licensees as provided
 * above. However, if you add LGPL Version 2.1 code and therefore, elected the LGPL
 * Version 2 license, then the option applies only if the new code is made subject
 * to such option by the copyright holder. 
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <math.h>

#include "slm.h"

#ifdef HAVE_SYS_MMAN_H
#include <sys/mman.h>
#elif defined(BEOS_OS)
#include <be/kernel/OS.h>
#endif

bool
CThreadSlm::load(const char* fname, bool MMap)
{
    int fd = open(fname, O_RDONLY);
    if (fd == -1) {
        perror("open lm");
        return false;
    }
    
    m_bufSize = lseek(fd, 0, SEEK_END);
    lseek(fd, 0, SEEK_SET);

    m_bMMap = MMap;
    if (m_bMMap) {
#ifdef HAVE_SYS_MMAN_H
        void* p = mmap(NULL, m_bufSize, PROT_READ, MAP_SHARED, fd, 0);
        if (p == MAP_FAILED) {
            close(fd);
            return false;
        }
        m_buf = (char *)p;
#elif defined(BEOS_OS)
        char *p = NULL;
        area_id area = create_area("tmp", (void**)&p, B_ANY_ADDRESS,
                                   (m_bufSize + (B_PAGE_SIZE - 1)) & ~(B_PAGE_SIZE - 1),
                                   B_NO_LOCK, B_READ_AREA | B_WRITE_AREA);
        if (area < 0) {
            close(fd);
            return false;
        }
        m_buf = p;

        for (ssize_t len = m_bufSize; len > 0; ) {
            ssize_t n = read(fd, p, len);
            if (n < 0) break;
            p += n;
            len -= n;
        }
#else // Other OS
        #error "No implementation for mmap()"
#endif // HAVE_SYS_MMAN_H
    } else {
        if ((m_buf = new char[m_bufSize]) == NULL) {
            close(fd);
            return false;
        }
        if (read(fd, m_buf, m_bufSize) != m_bufSize) {
            perror("read lm");
            delete [] m_buf; m_buf = NULL;
            close(fd);
            return false;
        }
    }
    close(fd);

    m_N = *(unsigned*)m_buf;
    m_UseLogPr = *(((unsigned*)m_buf)+1);
    m_LevelSizes = ((unsigned*)m_buf)+2;
    m_prTable = (float*)(m_buf + 2*sizeof(unsigned) + (m_N+1)*sizeof(unsigned));
    m_bowTable = m_prTable + (1 << BITS_PR);

    TNode* pn = (TNode*)(m_bowTable + (1 << BITS_BOW));

    //Solaris CC would cause error in runtime if using some thing like
    //following even using (void**) conversion. So add PtrVoid definition
    //m_Levels = new (void*) [m_N + 1];
    m_Levels = new PtrVoid[m_N+1];

    for (int lvl = 0; lvl <= m_N; ++lvl) {
        m_Levels[lvl] = (void*)pn;
        pn += m_LevelSizes[lvl];
    }
    return true;
}

void
CThreadSlm::free()
{
    if (m_Levels) {
        delete [] m_Levels;
    }
    if (m_buf) {
        if (m_bMMap) {
#ifdef HAVE_SYS_MMAN_H
            munmap(m_buf, m_bufSize);
#elif defined(BEOS_OS)
            delete_area(area_for(m_buf));
#else // Other OS
            #error "No implementation for munmap()"
#endif // HAVE_SYS_MMAN_H
        } else {
            delete [] m_buf;
        }
    }
    m_buf = NULL;
    m_Levels = NULL;
}

template<class NodeT>
unsigned int
find_id(NodeT* base, unsigned int h, unsigned int t, unsigned int id)
{
    unsigned int tail = t;
    while (h < t) {
        int m = h + (t-h)/2;
        NodeT* pm = base+m;
        unsigned int thisId = pm->wid();
        if (thisId < id)
            h = m+1;
        else if (thisId > id)
            t = m;
        else
            return m;
    }
    return tail;
}

/**
* return value as the model suggested. The history state must be historified
* or the history's level should be 0. when level == 0 but idx != 0, the
* history is a psuedo unigram state used for this model to combine another
* bigram cache language model
*/
double
CThreadSlm::rawTransfer(TState history, unsigned int wid, TState& result)
{
    unsigned int lvl = history.getLevel();
    unsigned int pos = history.getIdx();

    double cost = (m_UseLogPr)?0.0:1.0;

    // NON_Word id must be dealed with special, let it transfer to root
    // without any cost
    if (ID_NOT_WORD == wid) {
        result = 0;
        return cost;
    }

    while (true) {
        //for psuedo cache model unigram state
        TNode* pn = ((TNode *)m_Levels[lvl]) + ((lvl)?pos:0);

        unsigned int t = (pn+1)->ch();

        if (lvl < m_N-1) {
            TNode* pBase =(TNode*)m_Levels[lvl+1];
            unsigned int idx = find_id(pBase, pn->ch(), t, wid);
            if (idx != t) {
                result.setIdx(idx);
                result.setLevel(lvl+1);
                double pr = m_prTable[pBase[idx].pr()];
                return (m_UseLogPr)?(cost+pr):(cost*pr);
            }

        } else {
            TLeaf* pBase =(TLeaf*)m_Levels[lvl+1];
            unsigned int idx = find_id(pBase, pn->ch(), t, wid);
            if (idx != t) {
                result.setIdx(idx);
                result.setLevel(lvl+1);
                double pr = m_prTable[pBase[idx].pr()];
                return (m_UseLogPr)?(cost+pr):(cost*pr);
            }

        }

        if (m_UseLogPr)
            cost += m_bowTable[pn->bow()];
        else
            cost *= m_bowTable[pn->bow()];
        if (lvl == 0)
            break;
        lvl = pn->bol();
        pos = pn->bon();
    }
    result.setLevel(0);
    result.setIdx(0);
    if (m_UseLogPr)
        return cost + m_prTable[((TNode *)m_Levels[0])->pr()];
    else
        return cost * m_prTable[((TNode *)m_Levels[0])->pr()];
}

double
CThreadSlm::transferNegLog(TState history, unsigned int wid, TState& result)
{
    double cost = rawTransfer(history, wid, result);
    if (m_UseLogPr)
        return cost;
    else
        return -log(cost);
}

double
CThreadSlm::transfer(TState history, unsigned int wid, TState& result)
{
    double cost = rawTransfer(history, wid, result);
    if (!m_UseLogPr)
        return cost;
    else
        return exp(-cost);
}

unsigned int
CThreadSlm::lastWordId(TState st)
{
    unsigned int lvl = st.getLevel();
    if (lvl >= m_N) {
        const TLeaf* pn = ((const TLeaf *)m_Levels[m_N]) + st.getIdx();
        return pn->wid();
    } else if (lvl > 0) {
        const TNode *pn = ((const TNode *)m_Levels[st.getLevel()]) + st.getIdx();
        return pn->wid();
    } else {
        unsigned int idx = st.getIdx();
        if (idx == 0) {
            const TNode *pn = ((const TNode *)m_Levels[st.getLevel()]) + st.getIdx();
            return pn->wid();
        }
        return idx; // return the psuedo state word id
    }
}

CThreadSlm::TState
CThreadSlm::history_state_of(TState st)
{
    if (st.getLevel() >= m_N) {
        TLeaf* pl = ((TLeaf *)m_Levels[m_N]) + st.getIdx();
        return TState(pl->bol(), pl->bon());
    } else {
        TNode* pn = ((TNode *)m_Levels[st.getLevel()]) + st.getIdx();
        if (pn->ch() == (pn+1)->ch())
            return TState(pn->bol(), pn->bon());
        else
            return st;
    }
}

CThreadSlm::TState&
CThreadSlm::historify(TState& st)
{
    if (st.getLevel() >= m_N) {
        TLeaf* pl = ((TLeaf *)m_Levels[m_N]) + st.getIdx();
        st.setLevel(pl->bol());
        st.setIdx(pl->bon());
    } else {
        TNode* pn = ((TNode *)m_Levels[st.getLevel()]) + st.getIdx();
        if (pn->ch() == (pn+1)->ch()) {
            st.setLevel(pn->bol());
            st.setIdx(pn->bon());
        }
    }
    return st;
}