/******************************************************************************
 *
 * 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>

#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);
}