/*
 * Copyright (C) 2006,2009 Tommi Maekitalo
 *
 * 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 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * is provided AS IS, WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, and
 * NON-INFRINGEMENT.  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, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 *
 */

#include <zim/fileimpl.h>
#include <zim/error.h>
#include <zim/dirent.h>
#include <zim/endian.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sstream>
#include <errno.h>
#include <cstring>
#include "config.h"
#include "log.h"
#include "envvalue.h"
#include "md5stream.h"

log_define("zim.file.impl")

namespace zim
{
  //////////////////////////////////////////////////////////////////////
  // FileImpl
  //
  FileImpl::FileImpl(const char* fname)
    : zimFile(fname),
      direntCache(envValue("ZIM_DIRENTCACHE", DIRENT_CACHE_SIZE)),
      clusterCache(envValue("ZIM_CLUSTERCACHE", CLUSTER_CACHE_SIZE))
  {
    log_trace("read file \"" << fname << '"');

    if (!zimFile)
      throw ZimFileFormatError(std::string("can't open zim-file \"") + fname + '"');

    filename = fname;

    // read header
    zimFile >> header;
    if (zimFile.fail())
      throw ZimFileFormatError("error reading zim-file header");

    if (getCountClusters() == 0)
      log_warn("no clusters found");
    else
    {
      offset_type lastOffset = getClusterOffset(getCountClusters() - 1);
      log_debug("last offset=" << lastOffset << " file size=" << zimFile.fsize());
      if (lastOffset > static_cast<offset_type>(zimFile.fsize()))
      {
        log_fatal("last offset (" << lastOffset << ") larger than file size (" << zimFile.fsize() << ')');
        throw ZimFileFormatError("last cluster offset larger than file size; file corrupt");
      }
    }

    // read mime types
    zimFile.seekg(header.getMimeListPos());
    std::string mimeType;
    while (true)
    {
      std::getline(zimFile, mimeType, '\0');

      if (zimFile.fail())
        throw ZimFileFormatError("error reading mime type list");

      if (mimeType.empty())
        break;

      mimeTypes.push_back(mimeType);;
    }
  }

  Dirent FileImpl::getDirent(size_type idx)
  {
    log_trace("FileImpl::getDirent(" << idx << ')');

    zimFile.setBufsize(64);

    if (idx >= getCountArticles())
      throw ZimFileFormatError("article index out of range");

    if (!zimFile)
    {
      log_warn("file in error state");
      throw ZimFileFormatError("file in error state");
    }

    std::pair<bool, Dirent> v = direntCache.getx(idx);
    if (v.first)
    {
      log_debug("dirent " << idx << " found in cache; hits " << direntCache.getHits() << " misses " << direntCache.getMisses() << " ratio " << direntCache.hitRatio() * 100 << "% fillfactor " << direntCache.fillfactor());
      return v.second;
    }

    log_debug("dirent " << idx << " not found in cache; hits " << direntCache.getHits() << " misses " << direntCache.getMisses() << " ratio " << direntCache.hitRatio() * 100 << "% fillfactor " << direntCache.fillfactor());

    offset_type indexOffset = getOffset(header.getUrlPtrPos(), idx);

    zimFile.seekg(indexOffset);
    if (!zimFile)
    {
      log_warn("failed to seek to directory entry");
      throw ZimFileFormatError("failed to seek to directory entry");
    }

    Dirent dirent;
    zimFile >> dirent;

    if (!zimFile)
    {
      log_warn("failed to read to directory entry");
      throw ZimFileFormatError("failed to read directory entry");
    }

    log_debug("dirent read from " << indexOffset);
    direntCache.put(idx, dirent);

    return dirent;
  }

  Dirent FileImpl::getDirentByTitle(size_type idx)
  {
    if (idx >= getCountArticles())
      throw ZimFileFormatError("article index out of range");
    return getDirent(getIndexByTitle(idx));
  }

  size_type FileImpl::getIndexByTitle(size_type idx)
  {
    if (idx >= getCountArticles())
      throw ZimFileFormatError("article index out of range");

    zimFile.seekg(header.getTitleIdxPos() + sizeof(size_type) * idx);
    size_type ret;
    zimFile.read(reinterpret_cast<char*>(&ret), sizeof(size_type));

    if (!zimFile)
      throw ZimFileFormatError("error reading title index");

    if (isBigEndian())
      ret = fromLittleEndian(&ret);

    return ret;
  }

  Cluster FileImpl::getCluster(size_type idx)
  {
    log_trace("getCluster(" << idx << ')');

    if (idx >= getCountClusters())
      throw ZimFileFormatError("cluster index out of range");

    Cluster cluster = clusterCache.get(idx);
    if (cluster)
    {
      log_debug("cluster " << idx << " found in cache; hits " << clusterCache.getHits() << " misses " << clusterCache.getMisses() << " ratio " << clusterCache.hitRatio() * 100 << "% fillfactor " << clusterCache.fillfactor());
      return cluster;
    }

    zimFile.setBufsize(16384);

    offset_type clusterOffset = getClusterOffset(idx);
    log_debug("read cluster " << idx << " from offset " << clusterOffset);
    zimFile.seekg(clusterOffset);
    zimFile >> cluster;

    if (zimFile.fail())
      throw ZimFileFormatError("error reading cluster data");

    if (cluster.isCompressed())
    {
      log_debug("put cluster " << idx << " into cluster cache; hits " << clusterCache.getHits() << " misses " << clusterCache.getMisses() << " ratio " << clusterCache.hitRatio() * 100 << "% fillfactor " << clusterCache.fillfactor());
      clusterCache.put(idx, cluster);
    }
    else
      log_debug("cluster " << idx << " is not compressed - do not cache");

    return cluster;
  }

  offset_type FileImpl::getOffset(offset_type ptrOffset, size_type idx)
  {
    zimFile.seekg(ptrOffset + sizeof(offset_type) * idx);
    offset_type offset;
    zimFile.read(reinterpret_cast<char*>(&offset), sizeof(offset_type));

    if (!zimFile)
      throw ZimFileFormatError("error reading offset");

    if (isBigEndian())
      offset = fromLittleEndian(&offset);

    return offset;
  }

  size_type FileImpl::getNamespaceBeginOffset(char ch)
  {
    log_trace("getNamespaceBeginOffset(" << ch << ')');

    NamespaceCache::const_iterator it = namespaceBeginCache.find(ch);
    if (it != namespaceBeginCache.end())
      return it->second;

    size_type lower = 0;
    size_type upper = getCountArticles();
    Dirent d = getDirent(0);
    while (upper - lower > 1)
    {
      size_type m = lower + (upper - lower) / 2;
      Dirent d = getDirent(m);
      if (d.getNamespace() >= ch)
        upper = m;
      else
        lower = m;
    }

    size_type ret = d.getNamespace() < ch ? upper : lower;
    namespaceBeginCache[ch] = ret;

    return ret;
  }

  size_type FileImpl::getNamespaceEndOffset(char ch)
  {
    log_trace("getNamespaceEndOffset(" << ch << ')');

    NamespaceCache::const_iterator it = namespaceEndCache.find(ch);
    if (it != namespaceEndCache.end())
      return it->second;

    size_type lower = 0;
    size_type upper = getCountArticles();
    log_debug("namespace " << ch << " lower=" << lower << " upper=" << upper);
    while (upper - lower > 1)
    {
      size_type m = lower + (upper - lower) / 2;
      Dirent d = getDirent(m);
      if (d.getNamespace() > ch)
        upper = m;
      else
        lower = m;
      log_debug("namespace " << d.getNamespace() << " m=" << m << " lower=" << lower << " upper=" << upper);
    }

    namespaceEndCache[ch] = upper;

    return upper;

  }

  std::string FileImpl::getNamespaces()
  {
    if (namespaces.empty())
    {
      Dirent d = getDirent(0);
      namespaces = d.getNamespace();

      size_type idx;
      while ((idx = getNamespaceEndOffset(d.getNamespace())) < getCountArticles())
      {
        d = getDirent(idx);
        namespaces += d.getNamespace();
      }

    }
    return namespaces;
  }

  const std::string& FileImpl::getMimeType(uint16_t idx) const
  {
    if (idx > mimeTypes.size())
    {
      std::ostringstream msg;
      msg << "unknown mime type code " << idx;
      throw std::runtime_error(msg.str());
    }

    return mimeTypes[idx];
  }

  std::string FileImpl::getChecksum()
  {
    if (!header.hasChecksum())
      return std::string();

    zimFile.seekg(header.getChecksumPos());
    unsigned char chksum[16];
    zimFile.read(reinterpret_cast<char*>(chksum), 16);
    if (!zimFile)
    {
      log_warn("error reading checksum");
      return std::string();
    }

    char hexdigest[33];
    hexdigest[32] = '\0';
    static const char hex[] = "0123456789abcdef";
    char* p = hexdigest;
    for (int i = 0; i < 16; ++i)
    {
      *p++ = hex[chksum[i] >> 4];
      *p++ = hex[chksum[i] & 0xf];
    }
    log_debug("chksum=" << hexdigest);
    return hexdigest;
  }

  bool FileImpl::verify()
  {
    if (!header.hasChecksum())
      return false;

    Md5stream md5;

    zimFile.seekg(0);
    char ch;
    for (offset_type n = 0; n < header.getChecksumPos() && zimFile.get(ch); ++n)
      md5 << ch;

    unsigned char chksumFile[16];
    unsigned char chksumCalc[16];

    zimFile.read(reinterpret_cast<char*>(chksumFile), 16);

    if (!zimFile)
      throw ZimFileFormatError("failed to read checksum from zim file");

    md5.getDigest(chksumCalc);
    if (std::memcmp(chksumFile, chksumCalc, 16) != 0)
      throw ZimFileFormatError("invalid checksum in zim file");

    return true;
  }

}