/* Copyright (C) 2003  John Whitney
 *
 * 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.
 *
 * Author: John Whitney <jjw@linuxmail.org>
 */
 
#include <stdio.h>
#include <string.h>
#include "file.h"

bool copy_bytes_to_file(FILE *infile, FILE *outfile, unsigned numleft) {
  size_t numread;
  do {
    char buf[1024];
    numread = fread(buf, 1, numleft>1024?1024:numleft, infile);
    if (fwrite(buf, 1, numread, outfile) != numread) {
      printf("Could not write temporary data.  Possibly out of space\n");
      return false;
    }
    numleft-=numread;
  } while (numleft && !(numread < 1024 && numleft));
  return (numleft==0);
}

int main(int argc, char **argv) {
  if (argc!=4) {
    printf("needs a reference file, file to output, and patchfile:\n");
    printf("delta oldfile newfile patchfile\n");
    return 1;
  }
  
  if (!fileExists(argv[1]) || !fileExists(argv[3])) {
    printf("one of the input files does not exist\n");
    return 1;
  }

  FILE *patchfile = fopen(argv[3], "rb");
  char magic[3];
  fread(magic, 1, 3, patchfile);
  if (strncmp(magic, "BDT", 3)) {
    printf("Given file is not a recognized patchfile\n");
    return 1;
  }
  unsigned short version = read_word(patchfile);
  if (version!=1) {
    printf("unsupported patch version\n");
    return 1;
  }
  char intsize;
  fread(&intsize, 1, 1, patchfile);
  if (intsize!=4) {
    printf("unsupported file pointer size\n");
    return 1;
  }
  unsigned size1 = read_dword(patchfile), 
           size2 = read_dword(patchfile);

  unsigned nummatches = read_dword(patchfile);

  unsigned *copyloc1 = new unsigned[nummatches+1],
           *copyloc2 = new unsigned[nummatches+1],
	   *copynum  = new unsigned[nummatches+1];

  for (int i = 0; i < nummatches; ++i) {
    copyloc1[i] = read_dword(patchfile);
    copyloc2[i] = read_dword(patchfile);
    copynum[i] = read_dword(patchfile);
    size2-=copyloc2[i]+copynum[i];
  }
  if (size2) {
    copyloc1[nummatches]=0; copynum[nummatches]=0; 
    copyloc2[nummatches]=size2;
    ++nummatches;
  }
  
  FILE *ref = fopen(argv[1], "rb");
  FILE *outfile = fopen(argv[2], "wb");
  
  char *buf;
  for (int i = 0; i < nummatches; ++i) {
    if (!copy_bytes_to_file(patchfile, outfile, copyloc2[i])) {
      printf("Error.  patchfile is truncated\n");
      return -1;
    }

    int copyloc = copyloc1[i];
    fseek(ref, copyloc, SEEK_CUR);

    if (!copy_bytes_to_file(ref, outfile, copynum[i])) {
      printf("Error while copying from reference file\n");
      return -1;
    }
  }

  return 0;  
}