/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
 * This file is part of the LibreOffice project.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * This file incorporates work covered by the following license notice:
 *
 *   Licensed to the Apache Software Foundation (ASF) under one or more
 *   contributor license agreements. See the NOTICE file distributed
 *   with this work for additional information regarding copyright
 *   ownership. The ASF licenses this file to you under the Apache
 *   License, Version 2.0 (the "License"); you may not use this file
 *   except in compliance with the License. You may obtain a copy of
 *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
 */

#include <svl/inethist.hxx>

#include <algorithm>
#include <string.h>

#include <rtl/crc.h>
#include <tools/debug.hxx>
#include <tools/urlobj.hxx>

/*
 * INetURLHistory internals.
 */
#define INETHIST_DEF_FTP_PORT    21
#define INETHIST_DEF_HTTP_PORT   80
#define INETHIST_DEF_HTTPS_PORT 443

#define INETHIST_SIZE_LIMIT   1024
#define INETHIST_MAGIC_HEAD   0x484D4849UL

class INetURLHistory_Impl
{
    struct head_entry
    {
        /** Representation.
        */
        sal_uInt32 m_nMagic;
        sal_uInt16 m_nNext;

        /** Initialization.
        */
        void initialize()
        {
            m_nMagic = INETHIST_MAGIC_HEAD;
            m_nNext  = 0;
        }
    };

    struct hash_entry
    {
        /** Representation.
        */
        sal_uInt32 m_nHash;
        sal_uInt16 m_nLru;

        /** Initialization.
        */
        void initialize (sal_uInt16 nLru)
        {
            m_nHash = 0;
            m_nLru  = nLru;
        }

        /** Comparison.
        */
        bool operator== (sal_uInt32 nHash) const
        {
            return (m_nHash == nHash);
        }
        bool operator< (sal_uInt32 nHash) const
        {
            return (m_nHash < nHash);
        }
    };

    struct lru_entry
    {
        /** Representation.
        */
        sal_uInt32 m_nHash;
        sal_uInt16 m_nNext;
        sal_uInt16 m_nPrev;

        /** Initialization.
        */
        void initialize (sal_uInt16 nThis)
        {
            m_nHash = 0;
            m_nNext = nThis;
            m_nPrev = nThis;
        }
    };

    /** Representation.
    */
    head_entry m_aHead;
    hash_entry m_pHash[INETHIST_SIZE_LIMIT];
    lru_entry  m_pList[INETHIST_SIZE_LIMIT];

    /** Initialization.
    */
    void initialize();

    static sal_uInt16 capacity()
    {
        return sal_uInt16(INETHIST_SIZE_LIMIT);
    }

    static sal_uInt32 crc32 (OUString const & rData)
    {
        return rtl_crc32 (0, rData.getStr(), rData.getLength() * sizeof(sal_Unicode));
    }

    sal_uInt16 find (sal_uInt32 nHash) const;

    void move (sal_uInt16 nSI, sal_uInt16 nDI);

    void backlink (sal_uInt16 nThis, sal_uInt16 nTail)
    {
        lru_entry &rThis = m_pList[nThis];
        lru_entry &rTail = m_pList[nTail];

        rTail.m_nNext = nThis;
        rTail.m_nPrev = rThis.m_nPrev;
        rThis.m_nPrev = nTail;
        m_pList[rTail.m_nPrev].m_nNext = nTail;
    }

    void unlink (sal_uInt16 nThis)
    {
        lru_entry &rThis = m_pList[nThis];

        m_pList[rThis.m_nPrev].m_nNext = rThis.m_nNext;
        m_pList[rThis.m_nNext].m_nPrev = rThis.m_nPrev;
        rThis.m_nNext = nThis;
        rThis.m_nPrev = nThis;
    }

public:
    INetURLHistory_Impl();
    INetURLHistory_Impl(const INetURLHistory_Impl&) = delete;
    INetURLHistory_Impl& operator=(const INetURLHistory_Impl&) = delete;

    /** putUrl/queryUrl.
    */
    void putUrl   (const OUString &rUrl);
    bool queryUrl (const OUString &rUrl) const;
};

INetURLHistory_Impl::INetURLHistory_Impl()
{
    initialize();
}

void INetURLHistory_Impl::initialize()
{
    m_aHead.initialize();

    sal_uInt16 i, n = capacity();
    for (i = 0; i < n; i++)
        m_pHash[i].initialize(i);
    for (i = 0; i < n; i++)
        m_pList[i].initialize(i);
    for (i = 1; i < n; i++)
        backlink (m_aHead.m_nNext, i);
}

sal_uInt16 INetURLHistory_Impl::find (sal_uInt32 nHash) const
{
    sal_uInt16 l = 0;
    sal_uInt16 r = capacity() - 1;
    sal_uInt16 c = capacity();

    while ((l < r) && (r < c))
    {
        sal_uInt16 m = ((l + r) / 2) & 0xFFFF;
        if (m_pHash[m] == nHash)
            return m;

        if (m_pHash[m] < nHash)
            l = m + 1;
        else
            r = m - 1;
    }
    return l;
}

void INetURLHistory_Impl::move (sal_uInt16 nSI, sal_uInt16 nDI)
{
    hash_entry e = m_pHash[nSI];
    if (nSI < nDI)
    {
        // shift left.
        memmove (
            &m_pHash[nSI    ],
            &m_pHash[nSI + 1],
            (nDI - nSI) * sizeof(hash_entry));
    }
    if (nSI > nDI)
    {
        // shift right.
        memmove (
            &m_pHash[nDI + 1],
            &m_pHash[nDI    ],
            (nSI - nDI) * sizeof(hash_entry));
    }
    m_pHash[nDI] = e;
}

void INetURLHistory_Impl::putUrl (const OUString &rUrl)
{
    sal_uInt32 h = crc32 (rUrl);
    sal_uInt16 k = find (h);
    if ((k < capacity()) && (m_pHash[k] == h))
    {
        // Cache hit.
        sal_uInt16 nMRU = m_pHash[k].m_nLru;
        if (nMRU != m_aHead.m_nNext)
        {
            // Update LRU chain.
            unlink (nMRU);
            backlink (m_aHead.m_nNext, nMRU);

            // Rotate LRU chain.
            m_aHead.m_nNext = m_pList[m_aHead.m_nNext].m_nPrev;
        }
    }
    else
    {
        // Cache miss. Obtain least recently used.
        sal_uInt16 nLRU = m_pList[m_aHead.m_nNext].m_nPrev;

        sal_uInt16 nSI = find (m_pList[nLRU].m_nHash);
        if (nLRU != m_pHash[nSI].m_nLru)
        {
            // Update LRU chain.
            nLRU = m_pHash[nSI].m_nLru;
            unlink (nLRU);
            backlink (m_aHead.m_nNext, nLRU);
        }

        // Rotate LRU chain.
        m_aHead.m_nNext = m_pList[m_aHead.m_nNext].m_nPrev;

        // Check source and destination.
        sal_uInt16 nDI = std::min (k, sal_uInt16(capacity() - 1));
        if (nSI < nDI && !(m_pHash[nDI] < h))
            nDI -= 1;
        if (nDI < nSI && m_pHash[nDI] < h)
            nDI += 1;

        // Assign data.
        m_pList[m_aHead.m_nNext].m_nHash = m_pHash[nSI].m_nHash = h;
        move (nSI, nDI);
    }
}

bool INetURLHistory_Impl::queryUrl (const OUString &rUrl) const
{
    sal_uInt32 h = crc32 (rUrl);
    sal_uInt16 k = find (h);
    // true if cache hit
    return (k < capacity()) && (m_pHash[k] == h);
}

INetURLHistory::INetURLHistory() : m_pImpl (new INetURLHistory_Impl())
{
}

INetURLHistory::~INetURLHistory()
{
}

/*
 * GetOrCreate.
 */
INetURLHistory* INetURLHistory::GetOrCreate()
{
    static INetURLHistory instance;
    return &instance;
}

void INetURLHistory::NormalizeUrl_Impl (INetURLObject &rUrl)
{
    switch (rUrl.GetProtocol())
    {
        case INetProtocol::File:
            if (!INetURLObject::IsCaseSensitive())
            {
                OUString aPath (rUrl.GetURLPath(INetURLObject::DecodeMechanism::NONE).toAsciiLowerCase());
                rUrl.SetURLPath (aPath, INetURLObject::EncodeMechanism::NotCanonical);
            }
            break;

        case INetProtocol::Ftp:
            if (!rUrl.HasPort())
                rUrl.SetPort (INETHIST_DEF_FTP_PORT);
            break;

        case INetProtocol::Http:
            if (!rUrl.HasPort())
                rUrl.SetPort (INETHIST_DEF_HTTP_PORT);
            if (!rUrl.HasURLPath())
                rUrl.SetURLPath(u"/");
            break;

        case INetProtocol::Https:
            if (!rUrl.HasPort())
                rUrl.SetPort (INETHIST_DEF_HTTPS_PORT);
            if (!rUrl.HasURLPath())
                rUrl.SetURLPath(u"/");
            break;

        default:
            break;
    }
}

void INetURLHistory::PutUrl_Impl (const INetURLObject &rUrl)
{
    DBG_ASSERT (m_pImpl, "PutUrl_Impl(): no Implementation");
    if (!m_pImpl)
        return;

    INetURLObject aHistUrl (rUrl);
    NormalizeUrl_Impl (aHistUrl);

    m_pImpl->putUrl (aHistUrl.GetMainURL(INetURLObject::DecodeMechanism::NONE));
    Broadcast (INetURLHistoryHint (&rUrl));

    if (aHistUrl.HasMark())
    {
        aHistUrl.SetURL (aHistUrl.GetURLNoMark(INetURLObject::DecodeMechanism::NONE),
                         INetURLObject::EncodeMechanism::NotCanonical);

        m_pImpl->putUrl (aHistUrl.GetMainURL(INetURLObject::DecodeMechanism::NONE));
        Broadcast (INetURLHistoryHint (&aHistUrl));
    }
}

bool INetURLHistory::QueryUrl(std::u16string_view rUrl) const
{
    INetProtocol eProto = INetURLObject::CompareProtocolScheme (rUrl);
    if (!QueryProtocol (eProto))
        return false;
    return QueryUrl_Impl( INetURLObject(rUrl) );
}


bool INetURLHistory::QueryUrl_Impl (INetURLObject rUrl) const
{
    DBG_ASSERT (m_pImpl, "QueryUrl_Impl(): no Implementation");
    if (m_pImpl)
    {
        NormalizeUrl_Impl (rUrl);

        return m_pImpl->queryUrl (rUrl.GetMainURL(INetURLObject::DecodeMechanism::NONE));
    }
    return false;
}


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