/* Zcmp - decompress and compare two files byte by byte
   Copyright (C) 2010-2022 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 and, if they differ, writes to standard output the\n"
               "first byte and line number where they differ. Bytes and lines are numbered\n"
               "starting with 1. A hyphen '-' used as a file argument means standard input.\n"
               "If any file given is compressed, its decompressed content is used. Compressed\n"
               "files are decompressed on the fly; no temporary files are created.\n"
               "\nThe formats supported are bzip2, gzip, lzip, xz, and zstd.\n"
               "\nUsage: zcmp [options] file1 [file2]\n"
               "\nzcmp compares file1 to file2. The standard input is used only if file1 or\n"
               "file2 refers to standard input. If file2 is omitted zcmp tries the\n"
               "following:\n"
               "\n  - 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  - If file1 is uncompressed, compares it with the decompressed\n"
               "  contents of file1.[lz|bz2|gz|zst|xz] (the first one that is found).\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 the formats given (bz2,gz,lz,xz,zst)\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"
               "      --zst=<command>               set compressor and options for zstd format\n"
               "\nNumbers 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();
  }


// separate large numbers >= 100_000 in groups of 3 digits using '_'
const char * format_num3( long long num )
  {
  const char * const si_prefix = "kMGTPEZY";
  const char * const binary_prefix = "KMGTPEZY";
  enum { buffers = 8, bufsize = 4 * sizeof num };
  static char buffer[buffers][bufsize];	// circle of static buffers for printf
  static int current = 0;

  char * const buf = buffer[current++]; current %= buffers;
  char * p = buf + bufsize - 1;		// fill the buffer backwards
  *p = 0;	// terminator
  const bool negative = num < 0;
  if( negative ) num = -num;
  char prefix = 0;			// try binary first, then si
  for( int i = 0; i < 8 && num >= 1024 && num % 1024 == 0; ++i )
    { num /= 1024; prefix = binary_prefix[i]; }
  if( prefix ) *(--p) = 'i';
  else
    for( int i = 0; i < 8 && num >= 1000 && num % 1000 == 0; ++i )
      { num /= 1000; prefix = si_prefix[i]; }
  if( prefix ) *(--p) = prefix;
  const bool split = num >= 100000;

  for( int i = 0; ; )
    {
    *(--p) = num % 10 + '0'; num /= 10; if( num == 0 ) break;
    if( split && ++i >= 3 ) { i = 0; *(--p) = '_'; }
    }
  if( negative ) *(--p) = '-';
  return p;
  }


long long getnum( const char * const arg, const char * const option_name,
                  const char ** const tailp = 0,
                  const long long llimit = 0,
                  const long long ulimit = LLONG_MAX )
  {
  char * tail;
  errno = 0;
  long long result = strtoll( arg, &tail, 0 );
  if( tail == arg )
    {
    if( verbosity >= 0 )
      std::fprintf( stderr, "%s: Bad or missing numerical argument in "
                    "option '%s'.\n", program_name, option_name );
    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 )
      {
      if( verbosity >= 0 )
        std::fprintf( stderr, "%s: Bad multiplier in numerical argument of "
                      "option '%s'.\n", program_name, option_name );
      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 )
    {
    if( verbosity >= 0 )
      std::fprintf( stderr, "%s: Numerical argument out of limits [%s,%s] "
                    "in option '%s'.\n", program_name, format_num3( llimit ),
                    format_num3( ulimit ), option_name );
    std::exit( 2 );
    }
  if( tailp ) *tailp = tail;
  return result;
  }


void parse_ignore_initial( const char * const arg, const char * const pn,
                           long long ignore_initial[2] )
  {
  const char * tail;
  ignore_initial[0] = getnum( arg, pn, &tail );
  if( *tail == ':' || *tail == ',' )
    ignore_initial[1] = getnum( ++tail, pn );
  else if( *tail == 0 ) ignore_initial[1] = ignore_initial[0];
  else
    {
    if( verbosity >= 0 )
      std::fprintf( stderr, "%s: Bad separator in argument of option '%s'.\n",
                    program_name, pn );
    std::exit( 2 );
    }
  }


bool skip_ignore_initial( const long long ignore_initial, const int infd )
  {
  if( ignore_initial > 0 )
    {
    const int 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], bool finished[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; }
      }
    for( int i = 0; i < 2; ++i )
      if( rd[i] < size ) finished[i] = true;

    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, zst_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;
  program_name = "zcmp";
  invocation_name = ( argc > 0 ) ? argv[0] : program_name;

  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 },
    { zst_opt, "zst",        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 char * const pn = parser.parsed_name( argind ).c_str();
    const std::string & sarg = parser.argument( argind );
    const char * const arg = sarg.c_str();
    switch( code )
      {
      case 'b': print_bytes = true; break;
      case 'h': show_help(); return 0;
      case 'i': parse_ignore_initial( arg, pn, ignore_initial ); break;
      case 'l': verbosity = 1; break;
      case 'M': parse_format_list( sarg, pn ); break;
      case 'n': max_size = getnum( arg, pn ); break;
      case 'N': break;
      case 'O': parse_format_types2( sarg, pn, 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( sarg, fmt_bz2 ); break;
      case gz_opt: parse_compressor( sarg, fmt_gz ); break;
      case lz_opt: parse_compressor( sarg, fmt_lz ); break;
      case xz_opt: parse_compressor( sarg, fmt_xz ); break;
      case zst_opt: parse_compressor( sarg, fmt_zst ); 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( parser.arguments() - argind > 2 )
    { 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 == 2 )
    {
    if( 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; }
      }
    infd[1] = ( filenames[1] == "-" ) ?
      STDIN_FILENO : open_instream( filenames[1] );
    if( infd[1] < 0 ) return 2;
    }
  else
    {
    if( filenames[0] == "-" )
      { show_error( "Missing operand after '-'.", 0, true ); return 2; }
    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 )
      {
      if( verbosity >= 0 )
        std::fprintf( stderr, "%s: Can't find file to compare with '%s'.\n",
                      program_name, filenames[0].c_str() );
      show_error( 0, 0, true ); return 2;
      }
    }

  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;
      }

  bool finished[2] = { false, false };
  int retval = cmp( max_size, infd, filenames, finished, print_bytes );

  for( int i = 0; i < 2; ++i )
    if( !good_status( children[i], finished[i] ) ) 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;
  }
