/******************************************************************************

 *

 * Project:  GDAL Core

 * Purpose:  Implementation of the GDAL PAM Proxy database interface.

 *           The proxy db is used to associate .aux.xml files in a temp

 *           directory - used for files for which aux.xml files can't be

 *           created (i.e. read-only file systems).

 * Author:   Frank Warmerdam, warmerdam@pobox.com

 *

 ******************************************************************************

 * Copyright (c) 2005, Frank Warmerdam <warmerdam@pobox.com>

 *

 * SPDX-License-Identifier: MIT

 ****************************************************************************/

#include "cpl_port.h"

#include "gdal_pam.h"

#include <cerrno>

#include <cstddef>

#include <cstdio>

#include <cstdlib>

#include <cstring>

#if HAVE_FCNTL_H

#include <fcntl.h>

#endif

#include <memory>

#include <string>

#include <vector>

#include "cpl_conv.h"

#include "cpl_error.h"

#include "cpl_multiproc.h"

#include "cpl_string.h"

#include "cpl_vsi.h"

#include "gdal_pam.h"

#include "ogr_spatialref.h"

/************************************************************************/

/* ==================================================================== */

/*                            GDALPamProxyDB                            */

/* ==================================================================== */

/************************************************************************/

class GDALPamProxyDB

{

  public:

    CPLString osProxyDBDir{};

    int nUpdateCounter = -1;

    std::vector<CPLString> aosOriginalFiles{};

    std::vector<CPLString> aosProxyFiles{};

    void CheckLoadDB();

    void LoadDB();

    void SaveDB();

};

static bool bProxyDBInitialized = FALSE;

static GDALPamProxyDB *poProxyDB = nullptr;

static CPLMutex *hProxyDBLock = nullptr;

/************************************************************************/

/*                            CheckLoadDB()                             */

/*                                                                      */

/*      Eventually we want to check if the file has changed, and if     */

/*      so, force it to be reloaded.  TODO:                             */

/************************************************************************/

void GDALPamProxyDB::CheckLoadDB()

{

    if (nUpdateCounter == -1)

        LoadDB();

}

/************************************************************************/

/*                               LoadDB()                               */

/*                                                                      */

/*      It is assumed the caller already holds the lock.                */

/************************************************************************/

void GDALPamProxyDB::LoadDB()

{

    /* -------------------------------------------------------------------- */

    /*      Open the database relating original names to proxy .aux.xml     */

    /*      file names.                                                     */

    /* -------------------------------------------------------------------- */

    const std::string osDBName =

        CPLFormFilenameSafe(osProxyDBDir, "gdal_pam_proxy", "dat");

    VSILFILE *fpDB = VSIFOpenL(osDBName.c_str(), "r");

    nUpdateCounter = 0;

    if (fpDB == nullptr)

        return;

    /* -------------------------------------------------------------------- */

    /*      Read header, verify and extract update counter.                 */

    /* -------------------------------------------------------------------- */

    const size_t nHeaderSize = 100;

    GByte abyHeader[nHeaderSize] = {'\0'};

    if (VSIFReadL(abyHeader, 1, nHeaderSize, fpDB) != nHeaderSize ||

        !STARTS_WITH(reinterpret_cast<char *>(abyHeader), "GDAL_PROXY"))

    {

        CPLError(CE_Failure, CPLE_AppDefined,

                 "Problem reading %s header - short or corrupt?",

                 osDBName.c_str());

        CPL_IGNORE_RET_VAL(VSIFCloseL(fpDB));

        return;

    }

    nUpdateCounter = atoi(reinterpret_cast<char *>(abyHeader) + 10);

    /* -------------------------------------------------------------------- */

    /*      Read the file in one gulp.                                      */

    /* -------------------------------------------------------------------- */

    if (VSIFSeekL(fpDB, 0, SEEK_END) != 0)

    {

        CPL_IGNORE_RET_VAL(VSIFCloseL(fpDB));

        return;

    }

    const int nBufLength = static_cast<int>(VSIFTellL(fpDB) - nHeaderSize);

    if (VSIFSeekL(fpDB, nHeaderSize, SEEK_SET) != 0)

    {

        CPL_IGNORE_RET_VAL(VSIFCloseL(fpDB));

        return;

    }

    char *pszDBData = static_cast<char *>(CPLCalloc(1, nBufLength + 1));

    if (VSIFReadL(pszDBData, 1, nBufLength, fpDB) !=

        static_cast<size_t>(nBufLength))

    {

        CPLFree(pszDBData);

        CPL_IGNORE_RET_VAL(VSIFCloseL(fpDB));

        return;

    }

    CPL_IGNORE_RET_VAL(VSIFCloseL(fpDB));

    /* -------------------------------------------------------------------- */

    /*      Parse the list of in/out names.                                 */

    /* -------------------------------------------------------------------- */

    int iNext = 0;

    while (iNext < nBufLength)

    {

        CPLString osOriginal;

        osOriginal.assign(pszDBData + iNext);

        for (; iNext < nBufLength && pszDBData[iNext] != '\0'; iNext++)

        {

        }

        if (iNext == nBufLength)

            break;

        iNext++;

        CPLString osProxy = osProxyDBDir;

        osProxy += "/";

        osProxy += pszDBData + iNext;

        for (; iNext < nBufLength && pszDBData[iNext] != '\0'; iNext++)

        {

        }

        iNext++;

        aosOriginalFiles.push_back(std::move(osOriginal));

        aosProxyFiles.push_back(std::move(osProxy));

    }

    CPLFree(pszDBData);

}

/************************************************************************/

/*                               SaveDB()                               */

/************************************************************************/

void GDALPamProxyDB::SaveDB()

{

    /* -------------------------------------------------------------------- */

    /*      Open the database relating original names to proxy .aux.xml     */

    /*      file names.                                                     */

    /* -------------------------------------------------------------------- */

    const std::string osDBName =

        CPLFormFilenameSafe(osProxyDBDir, "gdal_pam_proxy", "dat");

    void *hLock = CPLLockFile(osDBName.c_str(), 1.0);

    // proceed even if lock fails - we need CPLBreakLockFile()!

    if (hLock == nullptr)

    {

        CPLError(CE_Warning, CPLE_AppDefined,

                 "GDALPamProxyDB::SaveDB() - "

                 "Failed to lock %s file, proceeding anyways.",

                 osDBName.c_str());

    }

    VSILFILE *fpDB = VSIFOpenL(osDBName.c_str(), "w");

    if (fpDB == nullptr)

    {

        if (hLock)

            CPLUnlockFile(hLock);

        CPLError(CE_Failure, CPLE_AppDefined,

                 "Failed to save %s Pam Proxy DB.\n%s", osDBName.c_str(),

                 VSIStrerror(errno));

        return;

    }

    /* -------------------------------------------------------------------- */

    /*      Write header.                                                   */

    /* -------------------------------------------------------------------- */

    const size_t nHeaderSize = 100;

    GByte abyHeader[nHeaderSize] = {'\0'};

    memset(abyHeader, ' ', sizeof(abyHeader));

    memcpy(reinterpret_cast<char *>(abyHeader), "GDAL_PROXY", 10);

    snprintf(reinterpret_cast<char *>(abyHeader) + 10, sizeof(abyHeader) - 10,

             "%9d", nUpdateCounter);

    if (VSIFWriteL(abyHeader, 1, nHeaderSize, fpDB) != nHeaderSize)

    {

        CPLError(CE_Failure, CPLE_AppDefined,

                 "Failed to write complete %s Pam Proxy DB.\n%s",

                 osDBName.c_str(), VSIStrerror(errno));

        CPL_IGNORE_RET_VAL(VSIFCloseL(fpDB));

        VSIUnlink(osDBName.c_str());

        if (hLock)

            CPLUnlockFile(hLock);

        return;

    }

    /* -------------------------------------------------------------------- */

    /*      Write names.                                                    */

    /* -------------------------------------------------------------------- */

    for (unsigned int i = 0; i < aosOriginalFiles.size(); i++)

    {

        size_t nCount =

            VSIFWriteL(aosOriginalFiles[i].c_str(),

                       strlen(aosOriginalFiles[i].c_str()) + 1, 1, fpDB);

        const char *pszProxyFile = CPLGetFilename(aosProxyFiles[i]);

        nCount += VSIFWriteL(pszProxyFile, strlen(pszProxyFile) + 1, 1, fpDB);

        if (nCount != 2)

        {

            CPLError(CE_Failure, CPLE_AppDefined,

                     "Failed to write complete %s Pam Proxy DB.\n%s",

                     osDBName.c_str(), VSIStrerror(errno));

            CPL_IGNORE_RET_VAL(VSIFCloseL(fpDB));

            VSIUnlink(osDBName.c_str());

            if (hLock)

                CPLUnlockFile(hLock);

            return;

        }

    }

    if (VSIFCloseL(fpDB) != 0)

    {

        CPLError(CE_Failure, CPLE_FileIO, "I/O error");

    }

    if (hLock)

        CPLUnlockFile(hLock);

}

/************************************************************************/

/*                            InitProxyDB()                             */

/*                                                                      */

/*      Initialize ProxyDB (if it isn't already initialized).           */

/************************************************************************/

static void InitProxyDB()

{

    if (!bProxyDBInitialized)

    {

        CPLMutexHolderD(&hProxyDBLock);

        // cppcheck-suppress identicalInnerCondition

        // cppcheck-suppress knownConditionTrueFalse

        if (!bProxyDBInitialized)

        {

            const char *pszProxyDir =

                CPLGetConfigOption("GDAL_PAM_PROXY_DIR", nullptr);

            if (pszProxyDir)

            {

                poProxyDB = new GDALPamProxyDB();

                poProxyDB->osProxyDBDir = pszProxyDir;

            }

        }

        bProxyDBInitialized = true;

    }

}

/************************************************************************/

/*                          PamCleanProxyDB()                           */

/************************************************************************/

void PamCleanProxyDB()

{

    {

        CPLMutexHolderD(&hProxyDBLock);

        bProxyDBInitialized = false;

        delete poProxyDB;

        poProxyDB = nullptr;

    }

    CPLDestroyMutex(hProxyDBLock);

    hProxyDBLock = nullptr;

}

/************************************************************************/

/*                            PamGetProxy()                             */

/************************************************************************/

const char *PamGetProxy(const char *pszOriginal)

{

    InitProxyDB();

    if (poProxyDB == nullptr)

        return nullptr;

    CPLMutexHolderD(&hProxyDBLock);

    poProxyDB->CheckLoadDB();

    for (unsigned int i = 0; i < poProxyDB->aosOriginalFiles.size(); i++)

    {

        if (strcmp(poProxyDB->aosOriginalFiles[i], pszOriginal) == 0)

            return poProxyDB->aosProxyFiles[i];

    }

    return nullptr;

}

/************************************************************************/

/*                          PamAllocateProxy()                          */

/************************************************************************/

const char *PamAllocateProxy(const char *pszOriginal)

{

    InitProxyDB();

    if (poProxyDB == nullptr)

        return nullptr;

    CPLMutexHolderD(&hProxyDBLock);

    poProxyDB->CheckLoadDB();

    /* -------------------------------------------------------------------- */

    /*      Form the proxy filename based on the original path if           */

    /*      possible, but dummy out any questionable characters, path       */

    /*      delimiters and such.  This is intended to make the proxy        */

    /*      name be identifiable by folks digging around in the proxy       */

    /*      database directory.                                             */

    /*                                                                      */

    /*      We also need to be careful about length.                        */

    /* -------------------------------------------------------------------- */

    CPLString osRevProxyFile;

    int i = static_cast<int>(strlen(pszOriginal)) - 1;

    while (i >= 0 && osRevProxyFile.size() < 220)

    {

        if (i > 6 && STARTS_WITH_CI(pszOriginal + i - 5, ":::OVR"))

            i -= 6;

        // make some effort to break long names at path delimiters.

        if ((pszOriginal[i] == '/' || pszOriginal[i] == '\\') &&

            osRevProxyFile.size() > 200)

            break;

        if ((pszOriginal[i] >= 'A' && pszOriginal[i] <= 'Z') ||

            (pszOriginal[i] >= 'a' && pszOriginal[i] <= 'z') ||

            (pszOriginal[i] >= '0' && pszOriginal[i] <= '9') ||

            pszOriginal[i] == '.')

            osRevProxyFile += pszOriginal[i];

        else

            osRevProxyFile += '_';

        i--;

    }

    CPLString osOriginal = pszOriginal;

    CPLString osProxy = poProxyDB->osProxyDBDir + "/";

    CPLString osCounter;

    osCounter.Printf("%06d_", poProxyDB->nUpdateCounter++);

    osProxy += osCounter;

    for (i = static_cast<int>(osRevProxyFile.size()) - 1; i >= 0; i--)

        osProxy += osRevProxyFile[i];

    if (!osOriginal.endsWith(".gmac"))

    {

        if (osOriginal.find(":::OVR") != CPLString::npos)

            osProxy += ".ovr";

        else

            osProxy += ".aux.xml";

    }

    /* -------------------------------------------------------------------- */

    /*      Add the proxy and the original to the proxy list and resave     */

    /*      the database.                                                   */

    /* -------------------------------------------------------------------- */

    poProxyDB->aosOriginalFiles.push_back(std::move(osOriginal));

    poProxyDB->aosProxyFiles.push_back(std::move(osProxy));

    poProxyDB->SaveDB();

    return PamGetProxy(pszOriginal);

}