/*  Zutils - Utilities dealing with compressed files
    Copyright (C) 2009, 2010 Antonio Diaz Diaz.

    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 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  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, see <http://www.gnu.org/licenses/>.
*/

#define _FILE_OFFSET_BITS 64

#include <cerrno>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <stdint.h>
#include <unistd.h>
#include <sys/wait.h>

#include "zutils.h"


const char * invocation_name = 0;
const char * util_name = program_name;

int verbosity = 0;


// Returns the number of bytes really read.
// If (returned value < size) and (errno == 0), means EOF was reached.
//
int readblock( const int fd, uint8_t * const buf, const int size ) throw()
  {
  int rest = size;
  errno = 0;
  while( rest > 0 )
    {
    errno = 0;
    const int n = read( fd, buf + size - rest, rest );
    if( n > 0 ) rest -= n;
    else if( n == 0 ) break;
    else if( errno != EINTR && errno != EAGAIN ) break;
    }
  return ( rest > 0 ) ? size - rest : size;
  }


// Returns the number of bytes really written.
// If (returned value < size), it is always an error.
//
int writeblock( const int fd, const uint8_t * const buf, const int size ) throw()
  {
  int rest = size;
  errno = 0;
  while( rest > 0 )
    {
    errno = 0;
    const int n = write( fd, buf + size - rest, rest );
    if( n > 0 ) rest -= n;
    else if( errno && errno != EINTR && errno != EAGAIN ) break;
    }
  return ( rest > 0 ) ? size - rest : size;
  }


bool feed_data( const int infd, const int outfd,
                const uint8_t * magic_data, const int magic_size )
  {
  if( writeblock( outfd, magic_data, magic_size ) != magic_size )
    { show_error( "Write error", errno ); return false; }
  enum { buffer_size = 4096 };
  uint8_t buffer[buffer_size];
  while( true )
    {
    const int size = readblock( infd, buffer, buffer_size );
    if( size != buffer_size && errno )
      { show_error( "Read error", errno ); return false; }
    if( size > 0 && writeblock( outfd, buffer, size ) != size )
      { show_error( "Write error", errno ); return false; }
    if( size < buffer_size ) break;
    }
  return true;
  }


bool set_data_feeder( int * const infdp, pid_t * const pidp )
  {
  std::string file_type;
  const uint8_t * magic_data;
  int magic_size;
  const bool compressed =
    test_format( *infdp, file_type, &magic_data, &magic_size );

  if( compressed )			// compressed with `file_type'
    {
    int fda[2];				// pipe from feeder
    int fda2[2];			// pipe from decompressor
    if( pipe( fda ) < 0 || pipe( fda2 ) < 0 )
      { show_error( "Can't create pipe", errno ); return false; }
    const int old_infd = *infdp;
    *infdp = fda2[0];
    const pid_t pid = fork();
    if( pid == 0 )			// child (decompressor feeder)
      {
      const pid_t pid2 = fork();
      if( pid2 == 0 )			// grandchild (decompressor)
        {
        if( dup2( fda[0], STDIN_FILENO ) >= 0 &&
            dup2( fda2[1], STDOUT_FILENO ) >= 0 &&
            close( fda[0] ) == 0 && close( fda[1] ) == 0 &&
            close( fda2[0] ) == 0 && close( fda2[1] ) == 0 )
          execlp( file_type.c_str(), file_type.c_str(), "-cdfq", (char *)0 );
        if( verbosity >= 0 )
          std::fprintf( stderr, "%s: Can't exec `%s': %s.\n",
                        util_name, file_type.c_str(), std::strerror( errno ) );
        _exit( 2 );
        }
      if( pid2 < 0 )
        {
        if( verbosity >= 0 )
          std::fprintf( stderr, "%s: Can't fork `%s': %s.\n",
                        util_name, file_type.c_str(), std::strerror( errno ) );
        _exit( 2 );
        }

      if( close( fda[0] ) != 0 ||
          close( fda2[0] ) != 0 || close( fda2[1] ) != 0 ||
          !feed_data( old_infd, fda[1], magic_data, magic_size ) )
        _exit( 2 );
      if( close( fda[1] ) != 0 )
        { show_error( "Can't close output of decompressor feeder", errno );
          _exit( 2 ); }
      _exit( wait_for_child( pid2, file_type.c_str() ) );
      }
					// parent
    close( fda[0] ); close( fda[1] ); close( fda2[1] );
    if( pid < 0 )
      { show_error( "Can't fork decompressor feeder", errno ); return false; }
    *pidp = pid;
    }
  else					// not compressed
    {
    int fda[2];				// pipe from feeder
    if( pipe( fda ) < 0 )
      { show_error( "Can't create pipe", errno ); return false; }
    const int old_infd = *infdp;
    *infdp = fda[0];
    const pid_t pid = fork();
    if( pid == 0 )			// child (feeder)
      {
      if( close( fda[0] ) != 0 ||
          !feed_data( old_infd, fda[1], magic_data, magic_size ) )
        _exit( 2 );
      if( close( fda[1] ) != 0 )
        { show_error( "Can't close output of data feeder", errno );
          _exit( 2 ); }
      _exit( 0 );
      }
					// parent
    close( fda[1] );
    if( pid < 0 )
      { show_error( "Can't fork data feeder", errno ); return false; }
    *pidp = pid;
    }
  return true;
  }


void show_help_addr() throw()
  {
  std::printf( "\nReport bugs to zutils-bug@nongnu.org\n" );
  std::printf( "Zutils home page: http://www.nongnu.org/zutils/zutils.html\n" );
  }


void show_version( const char * const Util_name ) throw()
  {
  if( !Util_name || !*Util_name )
    std::printf( "%s %s\n", Program_name, PROGVERSION );
  else
    std::printf( "%s (%s) %s\n", Util_name, program_name, PROGVERSION );
  std::printf( "Copyright (C) %s Antonio Diaz Diaz.\n", program_year );
  std::printf( "License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>\n" );
  std::printf( "This is free software: you are free to change and redistribute it.\n" );
  std::printf( "There is NO WARRANTY, to the extent permitted by law.\n" );
  }


void show_error( const char * const msg, const int errcode,
                 const bool help ) throw()
  {
  if( verbosity >= 0 )
    {
    if( msg && msg[0] )
      {
      std::fprintf( stderr, "%s: %s", util_name, msg );
      if( errcode > 0 )
        std::fprintf( stderr, ": %s", std::strerror( errcode ) );
      std::fprintf( stderr, "\n" );
      }
    if( help && invocation_name && invocation_name[0] )
      std::fprintf( stderr, "Try `%s --help' for more information.\n",
                    invocation_name );
    }
  }


void internal_error( const char * const msg )
  {
  if( verbosity >= 0 )
    std::fprintf( stderr, "%s: internal error: %s.\n", util_name, msg );
  std::exit( 3 );
  }


unsigned char xdigit( const int value ) throw()
  {
  if( value >= 0 && value <= 9 ) return '0' + value;
  if( value >= 10 && value <= 15 ) return 'A' + ( value - 10 );
  return 0;
  }


bool test_format( const int infd, std::string & file_type,
                  const uint8_t ** const magic_datap, int * const magic_sizep )
  {
  enum { buf_size = 5 };
  static uint8_t buf[buf_size];
  int i = 0;
  file_type.clear();
  if( readblock( infd, buf, 1 ) == 1 )
    {
    ++i;
    if( buf[0] == bzip2_magic[0] )
      {
      if( readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == bzip2_magic[1] &&
          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == bzip2_magic[2] )
        { file_type = "bzip2";
          *magic_datap = bzip2_magic; *magic_sizep = bzip2_magic_size; }
      }
    else if( buf[0] == gzip_magic[0] )
      {
      if( readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == gzip_magic[1] )
        { file_type = "gzip";
          *magic_datap = gzip_magic; *magic_sizep = gzip_magic_size; }
      }
    else if( buf[0] == lzip_magic[0] )
      {
      if( readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == lzip_magic[1] &&
          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == lzip_magic[2] &&
          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == lzip_magic[3] )
        { file_type = "lzip";
          *magic_datap = lzip_magic; *magic_sizep = lzip_magic_size; }
      }
    else if( buf[0] == xz_magic[0] )
      {
      if( readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == xz_magic[1] &&
          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == xz_magic[2] &&
          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == xz_magic[3] &&
          readblock( infd, &buf[i], 1 ) == 1 && buf[i++] == xz_magic[4] )
        { file_type = "xz";
          *magic_datap = xz_magic; *magic_sizep = xz_magic_size; }
      }
    }
  if( file_type.size() ) return true;
  for( int j = 0; j < i; ++j )
    {
    file_type += xdigit( buf[j] >> 4 );
    file_type += xdigit( buf[j] & 0x0F );
    }
  *magic_datap = buf; *magic_sizep = i;
  return false;
  }


int wait_for_child( const pid_t pid, const char * const name )
  {
  int status;
  while( waitpid( pid, &status, 0 ) == -1 )
    {
    if( errno != EINTR )
      {
      if( verbosity >= 0 )
        std::fprintf( stderr, "%s: Error waiting termination of `%s': %s.\n",
                  util_name, name, std::strerror( errno ) );
      _exit( 1 );
      }
    }

  if( WIFEXITED( status ) ) return WEXITSTATUS( status );
  else return 1;
  }