/* Zupdate - recompress bzip2, gzip, xz, zstd files to lzip format
   Copyright (C) 2013-2023 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 <cerrno>
#include <climits>
#include <csignal>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <list>
#include <string>
#include <vector>
#include <dirent.h>
#include <fcntl.h>
#include <stdint.h>
#include <unistd.h>
#include <utime.h>
#include <sys/stat.h>
#include <sys/wait.h>
#if defined __MSVCRT__ || defined __OS2__
#include <io.h>
#endif

#include "arg_parser.h"
#include "rc.h"

#ifndef O_BINARY
#define O_BINARY 0
#endif


namespace {

#include "recursive.cc"

void show_help()
  {
  std::printf( "zupdate recompresses files from bzip2, gzip, xz, and zstd formats to lzip\n"
               "format. Each original is compared with the new file and then deleted.\n"
               "Only regular files with standard file name extensions are recompressed,\n"
               "other files are ignored. Compressed files are decompressed and then\n"
               "recompressed on the fly; no temporary files are created. The lzip format\n"
               "is chosen as destination because it is the most appropriate for\n"
               "long-term archiving.\n"
               "\nIf no files are specified, recursive searches examine the current\n"
               "working directory, and nonrecursive searches do nothing.\n"
               "\nIf the lzip-compressed version of a file already exists, the file is skipped\n"
               "unless the option '--force' is given. In this case, if the comparison with\n"
               "the existing lzip version fails, an error is returned and the original file\n"
               "is not deleted. The operation of zupdate is meant to be safe and not cause\n"
               "any data loss. Therefore, existing lzip-compressed files are never\n"
               "overwritten nor deleted.\n"
               "\nThe names of the original files must have one of the following extensions:\n"
               "\n'.bz2', '.gz', '.xz', '.zst', or '.Z', which are recompressed to '.lz'.\n"
               "\n'.tbz', '.tbz2', '.tgz', '.txz', or '.tzst', which are recompressed to '.tlz'.\n"
               "\nUsage: zupdate [options] [files]\n"
               "\nExit status is 0 if all the compressed files were successfully recompressed\n"
               "(if needed), compared, and deleted (if requested). 1 if a non-fatal error\n"
               "occurred (file not found or not regular, or has invalid format, or can't be\n"
               "deleted). 2 if a fatal error occurred (invalid command-line options,\n"
               "compressor can't be run, or comparison fails).\n"
               "\nOptions:\n"
               "  -h, --help                   display this help and exit\n"
               "  -V, --version                output version information and exit\n"
               "  -d, --destdir=<dir>          write recompressed files into <dir>\n"
               "  -e, --expand-extensions      expand combined extensions; tgz --> tar.lz\n"
               "  -f, --force                  don't skip a file even if the .lz exists\n"
               "  -i, --ignore-errors          ignore non-fatal errors\n"
               "  -k, --keep                   keep (don't delete) input files\n"
               "  -l, --lzip-verbose           pass one option -v to the lzip compressor\n"
               "  -M, --format=<list>          process only the formats in <list>\n"
               "  -N, --no-rcfile              don't read runtime configuration file\n"
               "  -q, --quiet                  suppress all messages\n"
               "  -r, --recursive              operate recursively on directories\n"
               "  -R, --dereference-recursive  recursively follow symbolic links\n"
               "  -v, --verbose                be verbose (a 2nd -v gives more)\n"
               "  -0 .. -9                     set compression level [default 9]\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"
               "\nValid formats for option '-M' are 'bz2', 'gz', 'lz', 'xz', and 'zst'.\n" );
  show_help_addr();
  }


void extract_srcdir_name( const std::string & name, std::string & srcdir )
  {
  if( name.empty() || name == "." ) return;		// leave srcdir empty
  if( name[name.size()-1] == '/' )			// remove last slash
    { srcdir.assign( name, 0, name.size() - 1 ); return; }
  struct stat st;
  if( stat( name.c_str(), &st ) == 0 && S_ISDIR( st.st_mode ) )
    { srcdir = name; return; }

  unsigned size = 0;	// size of srcdir without last slash nor basename
  for( unsigned i = name.size(); i > 0; --i )
    if( name[i-1] == '/' ) { size = i - 1; break; }
  if( size > 0 ) srcdir.assign( name, 0, size );
  }


bool make_dirs( const std::string & name )
  {
  static std::string cached_dirname;
  unsigned i = name.size();
  while( i > 0 && name[i-1] != '/' ) --i;	// remove last component
  while( i > 0 && name[i-1] == '/' ) --i;	// remove slash(es)
  if( i == 0 ) return true;			// dirname is '/' or empty
  const unsigned dirsize = i;	// size of dirname without trailing slash(es)
  if( cached_dirname.size() == dirsize &&
      cached_dirname.compare( 0, dirsize, name ) == 0 ) return true;

  for( i = 0; i < dirsize; )
    {
    while( i < dirsize && name[i] == '/' ) ++i;
    const unsigned first = i;
    while( i < dirsize && name[i] != '/' ) ++i;
    if( first < i )
      {
      const std::string partial( name, 0, i );
      const mode_t mode = S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH;
      struct stat st;
      if( stat( partial.c_str(), &st ) == 0 )
        { if( !S_ISDIR( st.st_mode ) ) { errno = ENOTDIR; return false; } }
      else if( mkdir( partial.c_str(), mode ) != 0 && errno != EEXIST )
        return false;		// if EEXIST, another process created the dir
      }
    }
  cached_dirname.assign( name, 0, dirsize );
  return true;
  }


void cant_execute( const std::string & command, const int status )
  {
  if( verbosity >= 0 )
    {
    if( WIFEXITED( status ) )
      std::fprintf( stderr, "%s: Error executing '%s'. Exit status = %d\n",
                    program_name, command.c_str(), WEXITSTATUS( status ) );
    else
      std::fprintf( stderr, "%s: Can't execute '%s'\n",
                    program_name, command.c_str() );
    }
  }


// Set permissions, owner, and times.
void set_permissions( const char * const rname, const struct stat & in_stats )
  {
  bool warning = false;
  const mode_t mode = in_stats.st_mode;
  // chown in many cases returns with EPERM, which can be safely ignored.
  if( chown( rname, in_stats.st_uid, in_stats.st_gid ) == 0 )
    { if( chmod( rname, mode ) != 0 ) warning = true; }
  else
    if( errno != EPERM ||
        chmod( rname, mode & ~( S_ISUID | S_ISGID | S_ISVTX ) ) != 0 )
      warning = true;
  struct utimbuf t;
  t.actime = in_stats.st_atime;
  t.modtime = in_stats.st_mtime;
  if( utime( rname, &t ) != 0 ) warning = true;
  if( warning && verbosity >= 2 )
    show_file_error( rname,
                     "warning: can't change output file attributes", errno );
  }


// Return value: 0 = success, -1 = file skipped, 1 = error, 2 = fatal error.
int zupdate_file( const std::string & name, const char * const lzip_name,
                  const std::vector< std::string > & lzip_args2,
                  const std::string & srcdir, const std::string & destdir,
                  const bool expand, const bool force,
                  const bool keep_input_files, const bool no_rcfile )
  {
  // bzip2, gzip, and lzip are the primary formats. xz and zstd are optional.
  static int disable_xz = -1;				// tri-state bool
  static int disable_zst = -1;				// tri-state bool
  int format_index = -1;				// undefined
  std::string rname;					// recompressed name

  const int eindex = extension_index( name );		// search extension
  if( eindex >= 0 )
    {
    format_index = extension_format( eindex );
    if( format_index == fmt_lz )
      {
      if( verbosity >= 2 )
        std::fprintf( stderr, "%s: %s: Input file already has '%s' suffix.\n",
                      program_name, name.c_str(), extension_from( eindex ) );
      return 0;					// ignore this file
      }
    if( destdir.size() )
      {
      if( srcdir.size() && name.compare( 0, srcdir.size(), srcdir ) != 0 )
        internal_error( "srcdir mismatch." );
      rname = destdir;
      if( rname[rname.size()-1] != '/' && name[srcdir.size()] != '/' )
        rname += '/';
      rname.append( name, srcdir.size(), name.size() - srcdir.size() -
                    std::strlen( extension_from( eindex ) ) );
      }
    else
      rname.assign( name, 0, name.size() - std::strlen( extension_from( eindex ) ) );
    rname += ( std::strcmp( extension_to( eindex ), ".tar" ) == 0 ) ?
             ( expand ? ".tar.lz" : ".tlz" ) : ".lz";
    }
  const char * const compressor_name = get_compressor_name( format_index );
  if( !compressor_name )
    {
    if( verbosity >= 2 )
      show_file_error( name.c_str(), "Unknown extension in file name -- ignored." );
    return 0;						// ignore this file
    }

  struct stat in_stats;
  if( stat( name.c_str(), &in_stats ) != 0 )		// check input file
    { show_file_error( name.c_str(), "Can't stat input file", errno );
      return 1; }
  if( !S_ISREG( in_stats.st_mode ) )
    { show_file_error( name.c_str(), "Input file is not a regular file." );
      return 1; }

  struct stat st;				// not used
  const std::string rname2( rname + ".lz" );	// produced by lzip < 1.20
  const bool lz_exists = ( stat( rname.c_str(), &st ) == 0 );
  // don't modify an existing 'rname.lz'
  const bool lz_lz_exists = ( stat( rname2.c_str(), &st ) == 0 );
  if( lz_exists && !force )
    {
    show_file_error( rname.c_str(), "Output file already exists, skipping." );
    return -1;
    }

  if( format_index == fmt_xz )
    {
    if( disable_xz < 0 )
      {
      std::string command( compressor_name ); command += " -V > /dev/null 2>&1";
      disable_xz = ( std::system( command.c_str() ) != 0 );
      if( disable_xz && verbosity >= 2 )
        show_file_error( compressor_name,
                         "Xz decompressor not found. Ignoring xz files." );
      }
    if( disable_xz ) return 0;		// ignore this file if no xz installed
    }
  else if( format_index == fmt_zst )
    {
    if( disable_zst < 0 )
      {
      std::string command( compressor_name ); command += " -V > /dev/null 2>&1";
      disable_zst = ( std::system( command.c_str() ) != 0 );
      if( disable_zst && verbosity >= 2 )
        show_file_error( compressor_name,
                         "Zstd decompressor not found. Ignoring zstd files." );
      }
    if( disable_zst ) return 0;		// ignore this file if no zstd installed
    }

  if( !lz_exists )					// recompress
    {
    if( verbosity >= 1 )
      std::fprintf( stderr, "Recompressing file '%s'\n", name.c_str() );
    if( destdir.size() && !make_dirs( rname ) )
      { show_file_error( rname.c_str(),
             "Error creating intermediate directory", errno ); return 2; }
    int fda[2];			// pipe between decompressor and compressor
    if( pipe( fda ) < 0 )
      { show_error( "Can't create pipe", errno ); return 2; }

    const pid_t pid = fork();
    if( pid == 0 )				// child1 (decompressor)
      {
      if( dup2( fda[1], STDOUT_FILENO ) >= 0 &&
          close( fda[0] ) == 0 && close( fda[1] ) == 0 )
        {
        const std::vector< std::string > & compressor_args =
          get_compressor_args( format_index );
        const int size = compressor_args.size();
        const char ** const argv = new const char *[size+5];
        argv[0] = compressor_name;
        for( int i = 0; i < size; ++i ) argv[i+1] = compressor_args[i].c_str();
        argv[size+1] = "-cd";
        argv[size+2] = "--";
        argv[size+3] = name.c_str();
        argv[size+4] = 0;
        execvp( argv[0], (char **)argv );
        }
      show_exec_error( compressor_name );
      _exit( 1 );
      }
    if( pid < 0 )				// parent
      { show_fork_error( compressor_name ); return 2; }

    const pid_t pid2 = fork();
    if( pid2 == 0 )				// child2 (lzip compressor)
      {
      if( dup2( fda[0], STDIN_FILENO ) >= 0 &&
          close( fda[0] ) == 0 && close( fda[1] ) == 0 )
        {
        const std::vector< std::string > & lzip_args =
          get_compressor_args( fmt_lz );
        const int size = lzip_args.size();		// from .conf or --lz
        const int size2 = lzip_args2.size();		// from command line
        const char ** const argv = new const char *[size+size2+5];
        argv[0] = lzip_name;
        argv[1] = "-9";
        for( int i = 0; i < size; ++i ) argv[i+2] = lzip_args[i].c_str();
        for( int i = 0; i < size2; ++i ) argv[i+size+2] = lzip_args2[i].c_str();
        argv[size+size2+2] = "-o";
        argv[size+size2+3] = rname.c_str();
        argv[size+size2+4] = 0;
        execvp( argv[0], (char **)argv );
        }
      show_exec_error( lzip_name );
      _exit( 1 );
      }
    if( pid2 < 0 )				// parent
      { show_fork_error( lzip_name ); return 2; }

    close( fda[0] ); close( fda[1] );
    const int retval = wait_for_child( pid, compressor_name );
    const int retval2 = wait_for_child( pid2, lzip_name );
    if( retval || retval2 )
      { if( !lz_lz_exists ) std::remove( rname2.c_str() );	// lzip < 1.20
        std::remove( rname.c_str() ); return retval2 ? 2 : 1; }
    if( stat( rname.c_str(), &st ) != 0 &&
        ( lz_lz_exists || stat( rname2.c_str(), &st ) != 0 ||
          std::rename( rname2.c_str(), rname.c_str() ) != 0 ) )
      { show_file_error( rname.c_str(), "Error renaming output file", errno );
        return 2; }						// lzip < 1.11
    set_permissions( rname.c_str(), in_stats );
    }

  {
  if( lz_exists && verbosity >= 1 )
    std::fprintf( stderr, "Comparing file '%s'\n", name.c_str() );
  // Quote names in zcmp_command to allow file/dir names with spaces.
  std::string zcmp_command( invocation_name );
  unsigned i = zcmp_command.size();
  while( i > 0 && zcmp_command[i-1] != '/' ) --i;	// strip "zupdate"
  zcmp_command.resize( i ); zcmp_command.insert( zcmp_command.begin(), '\'' );
  zcmp_command += "zcmp' ";				// '[dir/]zcmp'
  if( no_rcfile ) zcmp_command += "-N ";
  if( verbosity < 0 ) zcmp_command += "-q -s ";
  zcmp_command += '\''; zcmp_command += name;
  zcmp_command += "' '"; zcmp_command += rname; zcmp_command += '\'';
  int status = std::system( zcmp_command.c_str() );
  if( status != 0 )
    { if( !lz_exists ) std::remove( rname.c_str() );
      cant_execute( zcmp_command, status ); return 2; }
  }

  if( !keep_input_files && std::remove( name.c_str() ) != 0 && errno != ENOENT )
    { show_file_error( name.c_str(), "Can't delete input file", errno );
      return 1; }
  return 0;
  }

} // end namespace


int main( const int argc, const char * const argv[] )
  {
  enum { bz2_opt = 256, gz_opt, lz_opt, xz_opt, zst_opt };
  int recursive = 0;				// 1 = '-r', 2 = '-R'
  std::string destdir;				// write recompressed files here
  std::vector< std::string > lzip_args2;	// args to lzip, maybe empty
  bool expand = false;
  bool force = false;
  bool ignore_errors = false;
  bool keep_input_files = false;
  bool no_rcfile = false;
  program_name = "zupdate";
  invocation_name = ( argc > 0 ) ? argv[0] : program_name;

  const Arg_parser::Option options[] =
    {
    { '0',  0,                      Arg_parser::no  },
    { '1',  0,                      Arg_parser::no  },
    { '2',  0,                      Arg_parser::no  },
    { '3',  0,                      Arg_parser::no  },
    { '4',  0,                      Arg_parser::no  },
    { '5',  0,                      Arg_parser::no  },
    { '6',  0,                      Arg_parser::no  },
    { '7',  0,                      Arg_parser::no  },
    { '8',  0,                      Arg_parser::no  },
    { '9',  0,                      Arg_parser::no  },
    { 'd', "destdir",               Arg_parser::yes },
    { 'e', "expand-extensions",     Arg_parser::no  },
    { 'f', "force",                 Arg_parser::no  },
    { 'h', "help",                  Arg_parser::no  },
    { 'i', "ignore-errors",         Arg_parser::no  },
    { 'k', "keep",                  Arg_parser::no  },
    { 'l', "lzip-verbose",          Arg_parser::no  },
    { 'M', "format",                Arg_parser::yes },
    { 'N', "no-rcfile",             Arg_parser::no  },
    { 'q', "quiet",                 Arg_parser::no  },
    { 'r', "recursive",             Arg_parser::no  },
    { 'R', "dereference-recursive", 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 & arg = parser.argument( argind );
    switch( code )
      {
      case '0': case '1': case '2': case '3': case '4':
      case '5': case '6': case '7': case '8': case '9':
                lzip_args2.push_back( "-" ); lzip_args2.back() += code; break;
      case 'd': destdir = arg; break;
      case 'e': expand = true; break;
      case 'f': force = true; break;
      case 'h': show_help(); return 0;
      case 'i': ignore_errors = true; break;
      case 'k': keep_input_files = true; break;
      case 'l': lzip_args2.push_back( "-v" ); break;
      case 'M': parse_format_list( arg, pn ); break;
      case 'N': no_rcfile = true; break;
      case 'q': verbosity = -1; lzip_args2.push_back( "-q" ); break;
      case 'r': recursive = 1; break;
      case 'R': recursive = 2; break;
      case 'v': if( verbosity < 4 ) ++verbosity; break;
      case 'V': show_version(); return 0;
      case bz2_opt: parse_compressor( arg, pn, fmt_bz2, 1 ); break;
      case gz_opt: parse_compressor( arg, pn, fmt_gz, 1 ); break;
      case lz_opt: parse_compressor( arg, pn, fmt_lz, 1 ); break;
      case xz_opt: parse_compressor( arg, pn, fmt_xz, 1 ); break;
      case zst_opt: parse_compressor( arg, pn, fmt_zst, 1 ); 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

  const char * const lzip_name = get_compressor_name( fmt_lz );
  if( !lzip_name )
    { show_error( "Missing name of compressor for lzip format." ); return 2; }

  std::list< std::string > filenames;
  if( argind < parser.arguments() )
    filenames.push_back( parser.argument( argind++ ) );	// first argument
  else if( recursive ) filenames.push_back( "." );
  else return 0;				// nothing to do

  std::string input_filename;
  int retval = 0;
  bool error = false;
  while( true )
    {
    std::string srcdir;			// dirname to be replaced by destdir
    if( destdir.size() ) extract_srcdir_name( filenames.front(), srcdir );
    while( next_filename( filenames, input_filename, error, recursive, true ) )
      {
      int tmp = zupdate_file( input_filename, lzip_name, lzip_args2, srcdir,
                        destdir, expand, force, keep_input_files, no_rcfile );
      if( tmp < 0 ) error = true;			// file skipped
      if( tmp > retval ) retval = tmp;
      if( tmp >= 2 || ( tmp == 1 && !ignore_errors ) ) goto out;
      }
    if( argind >= parser.arguments() ) break;
    filenames.push_back( parser.argument( argind++ ) );
    }
out:
  if( error && retval == 0 ) retval = 1;
  return retval;
  }