/* Zutils - Utilities dealing with compressed files
   Copyright (C) 2009-2023 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 <csignal>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <vector>
#include <stdint.h>
#include <unistd.h>
#include <sys/wait.h>

#include "rc.h"
#include "zutils.h"


namespace {

inline bool isvalid_ds( const uint8_t ds )	// lzip valid dictionary_size
  {
  enum { min_dictionary_size = 1 << 12,
         max_dictionary_size = 1 << 29 };
  unsigned dictionary_size = ( 1 << ( ds & 0x1F ) );
  if( dictionary_size > min_dictionary_size )
    dictionary_size -= ( dictionary_size / 16 ) * ( ( ds >> 5 ) & 7 );
  return ( dictionary_size >= min_dictionary_size &&
           dictionary_size <= max_dictionary_size );
  }


/* Return -1 if child not terminated, 2 in case of error, or exit status of
   child process 'pid'. Return 0 if child was terminated by SIGPIPE.
*/
int child_status( const pid_t pid, const char * const name )
  {
  int status;
  while( true )
    {
    const int tmp = waitpid( pid, &status, WNOHANG );
    if( tmp == -1 && errno != EINTR )
      {
      if( verbosity >= 0 )
        std::fprintf( stderr, "%s: Error checking status of '%s': %s\n",
                      program_name, name, std::strerror( errno ) );
      _exit( 2 );
      }
    if( tmp == 0 ) return -1;			// child not terminated
    if( tmp == pid ) break;			// child terminated
    }
  if( WIFEXITED( status ) ) return WEXITSTATUS( status );
  if( WIFSIGNALED( status ) && WTERMSIG( status ) == SIGPIPE ) return 0;
  return 2;
  }

} // end namespace


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


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


// filename == "-" means stdin.
//
bool feed_data( const std::string & filename, const int infd, const int outfd,
                const uint8_t * magic_data, const int magic_size )
  {
  if( magic_size && 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_file_error( name_or_stdin( filename.c_str() ), "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 good_status( const Children & children, const bool finished )
  {
  bool error = false;
  for( int i = 0; i < 2; ++i )
    {
    const pid_t pid = children.pid[i];
    if( pid )
      {
      const char * const name =
        ( i == 0 ) ? "data feeder" : children.compressor_name;
      // even if compressor finished, trailing data may remain in data feeder
      if( i == 0 || !finished )
        {
        const int tmp = child_status( pid, name );	// 0 if SIGPIPE
        if( tmp < 0 )				// child not terminated
          { kill( pid, SIGTERM ); wait_for_child( pid, name ); }
        else if( tmp != 0 ) error = true;	// child status != 0
        }
      else
        if( wait_for_child( pid, name ) != 0 ) error = true;
      }
    }
  return !error;
  }


bool set_data_feeder( const std::string & filename, int * const infdp,
                      Children & children, int format_index )
  {
  uint8_t magic_data[magic_buf_size];
  int magic_size = 0;
  if( format_index < 0 )
    format_index = test_format( *infdp, magic_data, &magic_size );
  children.compressor_name = get_compressor_name( format_index );

  if( children.compressor_name )	// compressed
    {
    int fda[2];				// pipe from feeder
    int fda2[2];			// pipe from compressor
    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 1 (compressor feeder)
      {
      if( close( fda[0] ) != 0 ||
          close( fda2[0] ) != 0 || close( fda2[1] ) != 0 ||
          !feed_data( filename, old_infd, fda[1], magic_data, magic_size ) )
        _exit( 2 );
      if( close( fda[1] ) != 0 ) { show_close_error(); _exit( 2 ); }
      _exit( 0 );
      }
    if( pid < 0 )			// parent
      { show_fork_error( "data feeder" ); return false; }

    const pid_t pid2 = fork();
    if( pid2 == 0 )			// child 2 (compressor)
      {
      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 )
        {
        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+3];
        argv[0] = children.compressor_name;
        for( int i = 0; i < size; ++i )
          argv[i+1] = compressor_args[i].c_str();
        argv[size+1] = ( verbosity >= 0 ) ? "-d" : "-dq";
        argv[size+2] = 0;
        execvp( argv[0], (char **)argv );
        }
      show_exec_error( children.compressor_name );
      _exit( 2 );
      }
    if( pid2 < 0 )			// parent
      { show_fork_error( children.compressor_name ); return false; }

    close( fda[0] ); close( fda[1] ); close( fda2[1] );
    children.pid[0] = pid;
    children.pid[1] = pid2;
    }
  else					// uncompressed
    {
    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( filename, old_infd, fda[1], magic_data, magic_size ) )
        _exit( 2 );
      if( close( fda[1] ) != 0 ) { show_close_error(); _exit( 2 ); }
      _exit( 0 );
      }
    if( pid < 0 )			// parent
      { show_fork_error( "data feeder" ); return false; }
    close( fda[1] );
    children.pid[0] = pid;
    children.pid[1] = 0;
    }
  return true;
  }


// Return format_index, or -1 if uncompressed.
//
int test_format( const int infd, uint8_t magic_data[],
                 int * const magic_sizep )
  {
  enum { bzip2_magic_size = 3,
          gzip_magic_size = 2,
          lzip_magic_size = 5,
            xz_magic_size = 5,
          zstd_magic_size = 4,
      compress_magic_size = 2 };
  const uint8_t bzip2_magic[bzip2_magic_size] =
    { 0x42, 0x5A, 0x68 };				// "BZh"
  const uint8_t gzip_magic[gzip_magic_size] =
    { 0x1F, 0x8B };
  const uint8_t compress_magic[compress_magic_size] =
    { 0x1F, 0x9D };
  const uint8_t lzip_magic[lzip_magic_size] =
    { 0x4C, 0x5A, 0x49, 0x50, 0x01 };			// "LZIP\001"
  const uint8_t xz_magic[xz_magic_size] =
    { 0xFD, 0x37, 0x7A, 0x58, 0x5A };			// 0xFD, "7zXZ"
  const uint8_t zstd_magic[zstd_magic_size] =
    { 0x28, 0xB5, 0x2F, 0xFD };				// 0xFD2FB528 LE

  *magic_sizep = readblock( infd, magic_data, magic_buf_size );
  if( *magic_sizep == magic_buf_size )	// test formats in search order
    {
    if( std::memcmp( magic_data, lzip_magic, lzip_magic_size ) == 0 &&
        isvalid_ds( magic_data[lzip_magic_size] ) )
      return fmt_lz;
    if( std::memcmp( magic_data, bzip2_magic, bzip2_magic_size ) == 0 &&
        magic_data[3] >= '1' && magic_data[3] <= '9' &&
        std::memcmp( magic_data + 4, "1AY&SY", 6 ) == 0 )
      return fmt_bz2;
    if( std::memcmp( magic_data, gzip_magic, gzip_magic_size ) == 0 ||
        std::memcmp( magic_data, compress_magic, compress_magic_size ) == 0 )
      return fmt_gz;
    if( std::memcmp( magic_data, zstd_magic, zstd_magic_size ) == 0 )
      return fmt_zst;
    if( std::memcmp( magic_data, xz_magic, xz_magic_size ) == 0 )
      return fmt_xz;
    }
  return -1;
  }