/*  Zcmp - decompress and compare two files byte by byte
    Copyright (C) 2010-2019 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 2 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 <algorithm>
#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 "rc.h"
#include "zutils.h"

#ifndef LLONG_MAX
#define LLONG_MAX  0x7FFFFFFFFFFFFFFFLL
#endif


namespace {

#include "zcmpdiff.cc"

void show_help()
  {
  std::printf( "Zcmp compares two files ('-' means standard input), and if they differ,\n"
               "tells the first byte and line number where they differ. Bytes and lines\n"
               "are numbered starting with 1. If any given file is compressed, its\n"
               "decompressed content is used. Compressed files are decompressed on the\n"
               "fly; no temporary files are created.\n"
               "\nThe formats supported are bzip2, gzip, lzip and xz.\n"
               "\nUsage: zcmp [options] file1 [file2]\n"
               "\nZcmp compares file1 to file2. If file2 is omitted zcmp tries the\n"
               "following:\n"
               "\n  1. If file1 is compressed, compares its decompressed contents with\n"
               "  the corresponding uncompressed file (the name of file1 with the\n"
               "  extension removed).\n"
               "\n  2. If file1 is uncompressed, compares it with the decompressed\n"
               "  contents of file1.[lz|bz2|gz|xz] (the first one that is found).\n"
               "\n  3. If no suitable file is found, compares file1 with data read from\n"
               "  standard input.\n"
               "\nExit status is 0 if inputs are identical, 1 if different, 2 if trouble.\n"
               "\nOptions:\n"
               "  -h, --help                        display this help and exit\n"
               "  -V, --version                     output version information and exit\n"
               "  -b, --print-bytes                 print differing bytes\n"
               "  -i, --ignore-initial=<n>[:<n2>]   ignore differences in the first <n> bytes\n"
               "  -l, --list                        list position, value of all differing bytes\n"
               "  -M, --format=<list>               process only the formats in <list>\n"
               "  -n, --bytes=<n>                   compare at most <n> bytes\n"
               "  -N, --no-rcfile                   don't read runtime configuration file\n"
               "  -O, --force-format=[<f1>][,<f2>]  force given formats (bz2, gz, lz, xz)\n"
               "  -q, --quiet                       suppress all messages\n"
               "  -s, --silent                      (same as --quiet)\n"
               "  -v, --verbose                     verbose mode (same as --list)\n"
               "      --bz2=<command>               set compressor and options for bzip2 format\n"
               "      --gz=<command>                set compressor and options for gzip format\n"
               "      --lz=<command>                set compressor and options for lzip format\n"
               "      --xz=<command>                set compressor and options for xz format\n"
               "Numbers may be followed by a multiplier: k = kB = 10^3 = 1000,\n"
               "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 = 0,
                  const long long ulimit = LLONG_MAX )
  {
  char * tail;
  errno = 0;
  long long result = strtoll( ptr, &tail, 0 );
  if( tail == ptr )
    {
    show_error( "Bad or missing numerical argument.", 0, true );
    std::exit( 2 );
    }
  if( result < 0 ) errno = ERANGE;

  if( !errno && tail[0] && std::isalpha( tail[0] ) )
    {
    const unsigned char ch = *tail++;
    int factor;
    bool bsuf;					// 'B' suffix is present
    if( tail[0] == 'i' ) { ++tail; factor = 1024; } else factor = 1000;
    if( tail[0] == 'B' ) { ++tail; bsuf = true; } else bsuf = false;
    int exponent = -1;				// -1 = bad multiplier
    switch( ch )
      {
      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; break;
      case 'k': if( factor == 1000 ) exponent = 1; break;
      case 'B': if( factor == 1000 && !bsuf ) exponent = 0; break;
      }
    if( exponent < 0 )
      {
      show_error( "Bad multiplier in numerical argument.", 0, true );
      std::exit( 2 );
      }
    for( int i = 0; i < exponent; ++i )
      {
      if( ulimit / factor >= 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;
  }


void parse_ignore_initial( const char * const arg, long long ignore_initial[2] )
  {
  const char * tail;
  ignore_initial[0] = getnum( arg, &tail );
  if( *tail == ':' || *tail == ',' )
    ignore_initial[1] = getnum( ++tail );
  else if( *tail == 0 ) ignore_initial[1] = ignore_initial[0];
  else
    {
    show_error( "Bad separator in argument of '--ignore-initial'", 0, true );
    std::exit( 2 );
    }
  }


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,
                   unsigned long long * const 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 )
  {
  const int buffer_size = 4096;
  unsigned long long byte_number = 1;
  unsigned long long line_number = 1;
  // remaining number of bytes to compare
  long long rest = ( max_size >= 0 ) ? max_size : buffer_size;
  // 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( (long long)buffer_size, rest );
    if( max_size >= 0 ) rest -= 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_file_error( filenames[i].c_str(), "Read error", errno );
        return 2;
        }
      }

    const int min_rd = std::min( rd[0], rd[1] );
    buffer0[min_rd] = 0;		// sentinels for the block compare
    buffer1[min_rd] = 1;

    int first_diff = block_compare( buffer0, buffer1, &line_number );
    byte_number += first_diff;

    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 %llu, line %llu\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 %llu, line %llu is %3o %s %3o %s\n",
                       filenames[0].c_str(), filenames[1].c_str(),
                       byte_number, line_number, c0, buf0, c1, buf1 );
          }
        std::fflush( stdout );
        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( "%llu %3o %3o\n", byte_number, c0, c1 );
            else
              {
              char buf0[5], buf1[5];
              sprintc( buf0, c0 ); sprintc( buf1, c1 );
              std::printf( "%llu %3o %-4s %3o %s\n",
                           byte_number, c0, buf0, c1, buf1 );
              }
            }
          }
        std::fflush( stdout );
        }
      }

    if( rd[0] != rd[1] )
      {
      if( verbosity >= 0 )
        std::fprintf( stderr, "%s: EOF on %s\n",
                      program_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[] )
  {
  enum { bz2_opt = 256, gz_opt, lz_opt, xz_opt };
  // number of initial bytes ignored for each file
  long long ignore_initial[2] = { 0, 0 };
  long long max_size = -1;			// < 0 means unlimited size
  int format_types[2] = { -1, -1 };
  bool print_bytes = false;
  invocation_name = argv[0];
  program_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  },
    { 'M', "format",         Arg_parser::yes },
    { 'n', "bytes",          Arg_parser::yes },
    { 'N', "no-rcfile",      Arg_parser::no  },
    { 'O', "force-format",   Arg_parser::yes },
    { 'q', "quiet",          Arg_parser::no  },
    { 's', "silent",         Arg_parser::no  },
    { 'v', "verbose",        Arg_parser::no  },
    { 'V', "version",        Arg_parser::no  },
    { bz2_opt,    "bz2",     Arg_parser::yes },
    { gz_opt,     "gz",      Arg_parser::yes },
    { lz_opt,     "lz",      Arg_parser::yes },
    { xz_opt,     "xz",      Arg_parser::yes },
    {  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; }

  maybe_process_config_file( parser );

  int argind = 0;
  for( ; argind < parser.arguments(); ++argind )
    {
    const int code = parser.code( argind );
    if( !code ) break;					// no more options
    const std::string & arg = parser.argument( argind );
    switch( code )
      {
      case 'b': print_bytes = true; break;
      case 'h': show_help(); return 0;
      case 'i': parse_ignore_initial( arg.c_str(), ignore_initial ); break;
      case 'l': verbosity = 1; break;
      case 'M': parse_format_list( arg ); break;
      case 'n': max_size = getnum( arg.c_str() ); break;
      case 'N': break;
      case 'O': parse_format_types2( arg, format_types ); break;
      case 'q':
      case 's': verbosity = -1; break;
      case 'v': verbosity = 1; break;
      case 'V': show_version(); return 0;
      case bz2_opt: parse_compressor( arg, fmt_bz2 ); break;
      case gz_opt: parse_compressor( arg, fmt_gz ); break;
      case lz_opt: parse_compressor( arg, fmt_lz ); break;
      case xz_opt: parse_compressor( arg, fmt_xz ); break;
      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
    {
    if( format_types[0] >= 0 || format_types[1] >= 0 )
      { show_error( "Two files must be given when format is specified.", 0, true );
        return 2; }
    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];
  Children children[2];
  if( !set_data_feeder( filenames[0], &infd[0], children[0], format_types[0] ) ||
      !set_data_feeder( filenames[1], &infd[1], children[1], format_types[1] ) )
    return 2;

  for( int i = 0; i < 2; ++i )
    if( !skip_ignore_initial( ignore_initial[i], infd[i] ) )
      {
      show_file_error( filenames[i].c_str(),
                       "Read error skipping initial bytes", errno );
      return 2;
      }

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

  for( int i = 0; i < 2; ++i )
    if( !good_status( children[i], retval == 0 && max_size < 0 ) ) retval = 2;

  for( int i = 0; i < 2; ++i )
    {
    if( close( infd[i] ) != 0 )
      { show_close_error(); retval = 2; }
    if( filenames[i] != "-" && close( old_infd[i] ) != 0 )
      {
      show_file_error( filenames[i].c_str(), "Error closing input file", errno );
      retval = 2;
      }
    }
  if( std::fclose( stdout ) != 0 )
    {
    show_error( "Error closing stdout", errno );
    retval = 2;
    }

  return retval;
  }