/*  Zcmp - decompress and compare two files byte by byte
    Copyright (C) 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 <cctype>
#include <cerrno>
#include <climits>
#include <csignal>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <vector>
#include <fcntl.h>
#include <stdint.h>
#include <unistd.h>
#include <sys/stat.h>
#if defined(__MSVCRT__) || defined(__OS2__)
#include <io.h>
#endif

#include "arg_parser.h"
#include "zutils.h"

#if CHAR_BIT != 8
#error "Environments where CHAR_BIT != 8 are not supported."
#endif

#ifndef LLONG_MAX
#define LLONG_MAX  0x7FFFFFFFFFFFFFFFLL
#endif
#ifndef LLONG_MIN
#define LLONG_MIN  (-LLONG_MAX - 1LL)
#endif
#ifndef ULLONG_MAX
#define ULLONG_MAX 0xFFFFFFFFFFFFFFFFULL
#endif


namespace {

#ifdef O_BINARY
const int o_binary = O_BINARY;
#else
const int o_binary = 0;
#endif

struct { const char * from; const char * to; } const known_extensions[] = {
  { ".bz2",  ""     },
  { ".tbz",  ".tar" },
  { ".tbz2", ".tar" },
  { ".gz",   ""     },
  { ".tgz",  ".tar" },
  { ".lz",   ""     },
  { ".tlz",  ".tar" },
  { ".xz",   ""     },
  { ".txz",  ".tar" },
  { 0,       0      } };


void show_help() throw()
  {
  std::printf( "Zcmp compares two files (\"-\" means standard input), and if they\n" );
  std::printf( "differ, tells the first byte and line number where they differ. Bytes\n" );
  std::printf( "and lines are numbered starting with 1. If any given file is compressed,\n" );
  std::printf( "its uncompressed content is used. Compressed files are uncompressed on\n" );
  std::printf( "the fly; no temporary files are created.\n" );
  std::printf( "The supported compressors are bzip2, gzip, lzip and xz.\n" );
  std::printf( "\nUsage: zcmp [options] file1 [file2]\n" );
  std::printf( "\nCompares <file1> to <file2>. If <file2> is omitted zcmp tries the\n" );
  std::printf( "following:\n" );
  std::printf( "If <file1> is compressed, compares <file1> to the file with the\n" );
  std::printf( "corresponding decompressed file name (removes the extension from\n" );
  std::printf( "<file1>).\n" );
  std::printf( "If <file1> is not compressed, compares <file1> to the uncompressed\n" );
  std::printf( "contents of <file1>.[bz2|gz|lz|xz] (the first one that is found).\n" );
  std::printf( "If no suitable file is found, compares <file1> to data read from\n" );
  std::printf( "standard input.\n" );
  std::printf( "\nExit status is 0 if inputs are identical, 1 if different, 2 if trouble.\n" );
  std::printf( "\nOptions:\n" );
  std::printf( "  -h, --help                       display this help and exit\n" );
  std::printf( "  -V, --version                    output version information and exit\n" );
  std::printf( "  -b, --print-bytes                print differing bytes\n" );
  std::printf( "  -i, --ignore-initial=<n>[,<n2>]  ignore differences in the first <n> bytes\n" );
  std::printf( "  -l, --list                       list position, value of all differing bytes\n" );
  std::printf( "  -n, --bytes=<n>                  compare at most <n> bytes\n" );
  std::printf( "  -q, --quiet                      suppress all messages\n" );
  std::printf( "  -s, --silent                     (same as --quiet)\n" );
  std::printf( "  -v, --verbose                    verbose mode (same as --list)\n" );
  std::printf( "Numbers may be followed by a multiplier: k = kB = 10^3 = 1000,\n" );
  std::printf( "Ki = KiB = 2^10 = 1024, M = 10^6, Mi = 2^20, G = 10^9, Gi = 2^30, etc...\n" );
  show_help_addr();
  }


long long getnum( const char * const ptr, const char ** const tailp = 0,
                  const long long llimit = LLONG_MIN + 1,
                  const long long ulimit = LLONG_MAX ) throw()
  {
  errno = 0;
  char * tail;
  long long result = strtoll( ptr, &tail, 0 );
  if( tail == ptr )
    {
    show_error( "Bad or missing numerical argument.", 0, true );
    std::exit( 2 );
    }

  if( !errno && tail[0] && std::isalpha( tail[0] ) )
    {
    int factor = ( tail[1] == 'i' ) ? 1024 : 1000;
    int exponent = 0;
    bool bad_multiplier = false;
    switch( tail[0] )
      {
      case 'Y': exponent = 8; break;
      case 'Z': exponent = 7; break;
      case 'E': exponent = 6; break;
      case 'P': exponent = 5; break;
      case 'T': exponent = 4; break;
      case 'G': exponent = 3; break;
      case 'M': exponent = 2; break;
      case 'K': if( factor == 1024 ) exponent = 1; else bad_multiplier = true;
                break;
      case 'k': if( factor == 1000 ) exponent = 1; else bad_multiplier = true;
                break;
      default : bad_multiplier = true;
      }
    if( bad_multiplier )
      {
      show_error( "Bad multiplier in numerical argument.", 0, true );
      std::exit( 2 );
      }
    for( int i = 0; i < exponent; ++i )
      {
      if( LLONG_MAX / factor >= llabs( result ) ) result *= factor;
      else { errno = ERANGE; break; }
      }
    }
  if( !errno && ( result < llimit || result > ulimit ) ) errno = ERANGE;
  if( errno )
    {
    show_error( "Numerical argument out of limits." );
    std::exit( 2 );
    }
  if( tailp ) *tailp = tail;
  return result;
  }


int open_instream( const std::string & input_filename ) throw()
  {
  int infd = open( input_filename.c_str(), O_RDONLY | o_binary );
  if( infd < 0 )
    show_error2( "Can't open input file", input_filename.c_str() );
  return infd;
  }


int open_other_instream( std::string & name ) throw()
  {
  for( int i = 0; known_extensions[i].from; ++i )
    {					// search uncompressed version
    const std::string from( known_extensions[i].from );
    if( name.size() > from.size() &&
        name.compare( name.size() - from.size(), from.size(), from ) == 0 )
      {
      name.resize( name.size() - from.size() );
      name += known_extensions[i].to;
      return open( name.c_str(), O_RDONLY | o_binary );
      }
    }
  for( int i = 0; simple_extensions[i]; ++i )
    {					// search compressed version
    const std::string s( name + simple_extensions[i] );
    const int infd = open( s.c_str(), O_RDONLY | o_binary );
    if( infd >= 0 ) { name = s; return infd; }
    }
  return -1;
  }


bool check_identical( const char * const name1, const char * const name2 ) throw()
  {
  if( !std::strcmp( name1, name2 ) ) return true;
  struct stat stat1, stat2;
  if( stat( name1, &stat1 ) || stat( name2, &stat2 ) ) return false;
  return ( stat1.st_ino == stat2.st_ino && stat1.st_dev == stat2.st_dev );
  }


void parse_ignore_initial( const char * const arg, long long ignore_initial[2] )
  {
  const char * tail;
  ignore_initial[0] = getnum( arg, &tail, 0 );
  if( *tail == ',' || *tail == ':' )
    ignore_initial[1] = getnum( ++tail, 0, 0 );
  else ignore_initial[1] = ignore_initial[0];
  }


bool skip_ignore_initial( const long long ignore_initial, const int infd )
  {
  if( ignore_initial > 0 )
    {
    enum { buffer_size = 4096 };
    long long rest = ignore_initial;
    uint8_t buffer[buffer_size];
    while( rest > 0 )
      {
      const int size = std::min( rest, (long long)buffer_size );
      const int rd = readblock( infd, buffer, size );
      if( rd != size && errno ) return false;
      if( rd < size ) break;
      rest -= rd;
      }
    }
  return true;
  }


// Put into buf the unsigned char c, making unprintable bytes
// visible by quoting like cat -t does.
void sprintc( char * const buf, unsigned char c )
  {
  int i = 0;

  if( c < 32 || c >= 127 )
    {
    if( c >= 128 ) { c -= 128; buf[i++] = 'M'; buf[i++] = '-'; }
    if( c < 32 ) { c += 64; buf[i++] = '^'; }
    else if( c == 127 ) { c = '?'; buf[i++] = '^'; }
    }
  buf[i++] = c;
  buf[i++] = 0;
  }


int block_compare( const uint8_t * const buffer0,
                   const uint8_t * const buffer1,
                   long long * line_numberp )
  {
  const uint8_t * p0 = buffer0;
  const uint8_t * p1 = buffer1;
  if( verbosity == 0 )
    {
    int nl_count = 0;
    while( *p0 == *p1 )
      { if( *p0 == '\n' ) { ++nl_count; } ++p0; ++p1; }
    *line_numberp += nl_count;
    }
  else while( *p0 == *p1 ) { ++p0; ++p1; }
  return p0 - buffer0;
  }


int cmp( const long long max_size, const int infd[2],
         const std::string filenames[2], const bool print_bytes )
  {
  enum { buffer_size = 4096 };
  long long byte_number = 1;
  long long line_number = 1;
  long long rest = max_size;	// remaining number of bytes to compare
  // buffers with space for sentinels at the end
  uint8_t * const buffer0 = new uint8_t[2*(buffer_size+1)];
  uint8_t * const buffer1 = buffer0 + buffer_size + 1;
  uint8_t * buffer[2];
  buffer[0] = buffer0; buffer[1] = buffer1;
  int different = 0;

  while( rest > 0 )
    {
    const int size = std::min( rest, (long long)buffer_size );
    int rd[2];			// number of bytes read from each file
    for( int i = 0; i < 2; ++i )
      {
      rd[i] = readblock( infd[i], buffer[i], size );
      if( rd[i] != size && errno )
        {
        show_error2( "Error reading file", filenames[i].c_str() );
        return 2;
        }
      }
    rest -= size;

    buffer0[rd[0]] = ~buffer1[rd[0]];	// sentinels for the block compare
    buffer1[rd[1]] = ~buffer0[rd[1]];

    int first_diff = block_compare( buffer0, buffer1, &line_number );
    byte_number += first_diff;
    const int min_rd = std::min( rd[0], rd[1] );

    if( first_diff < min_rd )
      {
      if( verbosity < 0 ) return 1;		// return status only
      if( verbosity == 0 )			// show first difference
        {
        if( !print_bytes )
          std::printf( "%s %s differ: byte %lld, line %lld\n",
                       filenames[0].c_str(), filenames[1].c_str(),
                       byte_number, line_number );
        else
          {
          const unsigned char c0 = buffer0[first_diff];
          const unsigned char c1 = buffer1[first_diff];
          char buf0[5], buf1[5];
          sprintc( buf0, c0 ); sprintc( buf1, c1 );
          std::printf( "%s %s differ: byte %lld, line %lld is %3o %s %3o %s\n",
                       filenames[0].c_str(), filenames[1].c_str(),
                       byte_number, line_number, c0, buf0, c1, buf1 );
          }
        return 1;
        }
      else			// verbosity > 0 ; show all differences
        {
        different = 1;
        for( ; first_diff < min_rd; ++byte_number, ++first_diff )
          {
          const unsigned char c0 = buffer0[first_diff];
          const unsigned char c1 = buffer1[first_diff];
          if( c0 != c1 )
            {
            if( !print_bytes )
              std::printf( "%lld %3o %3o\n", byte_number, c0, c1 );
            else
              {
              char buf0[5], buf1[5];
              sprintc( buf0, c0 ); sprintc( buf1, c1 );
              std::printf( "%lld %3o %-4s %3o %s\n",
                           byte_number, c0, buf0, c1, buf1 );
              }
            }
          }
        }
      }

    if( rd[0] != rd[1] )
      {
      if( verbosity >= 0 )
        std::fprintf( stderr, "%s: EOF on %s\n",
                      util_name, filenames[rd[1]<rd[0]].c_str() );
        return 1;
      }
    if( min_rd != buffer_size ) break;
    }

  delete[] buffer0;
  return different;
  }

} // end namespace


int main( const int argc, const char * const argv[] )
  {
  // number of initial bytes ignored for each file
  long long ignore_initial[2] = { 0, 0 };
  long long max_size = LLONG_MAX;
  bool print_bytes = false;
  invocation_name = argv[0];
  util_name = "zcmp";

  const Arg_parser::Option options[] =
    {
    { 'b', "print-bytes",    Arg_parser::no  },
    { 'h', "help",           Arg_parser::no  },
    { 'i', "ignore-initial", Arg_parser::yes },
    { 'l', "list",           Arg_parser::no  },
    { 'n', "bytes",          Arg_parser::yes },
    { 'q', "quiet",          Arg_parser::no  },
    { 's', "silent",         Arg_parser::no  },
    { 'v', "verbose",        Arg_parser::no  },
    { 'V', "version",        Arg_parser::no  },
    {  0 ,  0,               Arg_parser::no  } };

  const Arg_parser parser( argc, argv, options );
  if( parser.error().size() )				// bad option
    { show_error( parser.error().c_str(), 0, true ); return 2; }

  int argind = 0;
  for( ; argind < parser.arguments(); ++argind )
    {
    const int code = parser.code( argind );
    if( !code ) break;					// no more options
    const char * const arg = parser.argument( argind ).c_str();
    switch( code )
      {
      case 'b': print_bytes = true; break;
      case 'h': show_help(); return 0;
      case 'i': parse_ignore_initial( arg, ignore_initial ); break;
      case 'l': verbosity = 1; break;
      case 'n': max_size = getnum( arg, 0, 0 ); break;
      case 'q':
      case 's': verbosity = -1; break;
      case 'v': verbosity = 1; break;
      case 'V': show_version( "Zcmp" ); return 0;
      default : internal_error( "uncaught option" );
      }
    } // end process options

#if defined(__MSVCRT__) || defined(__OS2__)
  _setmode( STDIN_FILENO, O_BINARY );
  _setmode( STDOUT_FILENO, O_BINARY );
#endif

  if( argind >= parser.arguments() )
    { show_error( "No files given.", 0, true ); return 2; }
  if( argind + 2 < parser.arguments() )
    { show_error( "Too many files.", 0, true ); return 2; }

  const int files = parser.arguments() - argind;
  std::string filenames[2];		// file names of the two input files
  filenames[0] = parser.argument( argind );
  if( files == 2 ) filenames[1] = parser.argument( argind + 1 );

  int infd[2];				// file descriptors of the two files
  infd[0] = ( filenames[0] == "-" ) ?
    STDIN_FILENO : open_instream( filenames[0] );
  if( infd[0] < 0 ) return 2;

  if( ( files == 1 && filenames[0] == "-" ) ||
      ( files == 2 && check_identical( filenames[0].c_str(),
                                       filenames[1].c_str() ) ) )
    {
    if( ignore_initial[0] == ignore_initial[1] ) return 0;
    else { show_error( "Can't compare parts of same file." ); return 2; }
    }

  if( files == 2 )
    {
    infd[1] = ( filenames[1] == "-" ) ?
      STDIN_FILENO : open_instream( filenames[1] );
    if( infd[1] < 0 ) return 2;
    }
  else
    {
    filenames[1] = filenames[0];
    infd[1] = open_other_instream( filenames[1] );
    if( infd[1] < 0 ) { infd[1] = STDIN_FILENO; filenames[1] = "-"; }
    }

  int old_infd[2];		// copy of file descriptors of the two files
  old_infd[0] = infd[0]; old_infd[1] = infd[1];
  pid_t pid[2];
  if( !set_data_feeder( &infd[0], &pid[0] ) ||
      !set_data_feeder( &infd[1], &pid[1] ) )
    return 2;

  for( int i = 0; i < 2; ++i )
    if( !skip_ignore_initial( ignore_initial[i], infd[i] ) )
      {
      show_error2( "Can't skip initial bytes from file", filenames[i].c_str() );
      return 2;
      }

  int retval = cmp( max_size, infd, filenames, print_bytes );

  if( retval != 0 )
    {
    if( pid[0] ) kill( pid[0], SIGTERM );
    if( pid[1] ) kill( pid[1], SIGTERM );
    }
  else
    if( ( pid[0] && wait_for_child( pid[0], "data feeder" ) != 0 ) ||
        ( pid[1] && wait_for_child( pid[1], "data feeder" ) != 0 ) )
      retval = 2;

  for( int i = 0; i < 2; ++i )
    {
    if( close( infd[i] ) != 0 )
      { show_close_error( "data feeder" ); retval = 2; }
    if( filenames[i] != "-" && close( old_infd[i] ) != 0 )
      {
      show_error2( "Can't close input file", filenames[i].c_str() );
      retval = 2;
      }
    }
  if( std::fclose( stdout ) != 0 )
    {
    show_error( "Can't close stdout", errno );
    retval = 2;
    }

  return retval;
  }