/* 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 <stdlib.h>
#include "bdelta.h"
#include "file.h"

const int BUFNUM=16;
class Buffered_File {
  FILE *f;
  char *buf[BUFNUM];
  unsigned bufplace[BUFNUM];
  int bufsize;
public:
  Buffered_File(char *fname, unsigned maxread) {
    f = fopen(fname, "rb");
    bufsize=maxread;
    for (int i = 0; i < BUFNUM; ++i) {
      buf[i] = new char[bufsize];
      bufplace[i] = 0;
    }
  }
  ~Buffered_File() {
    for (int i = 0; i < BUFNUM; ++i)
      delete buf[i];
    fclose(f);
  }
  void *read(unsigned place, unsigned num) {
    for (int i = 0; i < BUFNUM; ++i)
      if (bufplace[i] && place>bufplace[i] && place+num<bufplace[i]+bufsize) 
        return buf[i]+place-bufplace[i];
    char *lastbuf = buf[BUFNUM-1];
    for (int i = BUFNUM-1; i > 0; --i) {
      buf[i] = buf[i-1];
      bufplace[i] = bufplace[i-1];
    }
    buf[0]=lastbuf;
    bufplace[0]=place;
    fseek(f, place, SEEK_SET);
    fread(buf[0], 1, bufsize, f);
    return buf[0];
  }
};

Buffered_File *f1, *f2;

void *f1_read(unsigned place, unsigned num) {
  return f1->read(place, num);
}
void *f2_read(unsigned place, unsigned num) {
  return f2->read(place, num);
}

int main(int argc, char **argv) {
  if (argc!=4) {
    printf("needs two files to compare + output file:\n");
    printf("delta oldfile newfile patchfile\n");
    exit(1);
  }
  if (!fileExists(argv[1]) || !fileExists(argv[2])) {
    printf("one of the input files does not exist\n");
    exit(1);
  }
  unsigned size = getLenOfFile(argv[1]); 
  unsigned size2 = getLenOfFile(argv[2]);
  f1 = new Buffered_File(argv[1], 4096);
  f2 = new Buffered_File(argv[2], 4096);

  void *b = bdelta_init_alg(size, size2, f1_read, f2_read);
  int nummatches;
  for (int i = 512; i >= 16; i/=2)
    nummatches = bdelta_pass(b, i);

  unsigned copyloc1[nummatches+1];
  unsigned copyloc2[nummatches+1];
  unsigned copynum[nummatches+1];
  
  FILE *fout = fopen(argv[3], "wb");
  if (!fout) {
    printf("couldn't open output file\n");
    exit(1);
  }

  char *magic = "BDT";
  fwrite(magic, 1, 3, fout);
  unsigned short version = 1;
  write_word(fout, version);
  unsigned char intsize = 4;
  fwrite(&intsize, 1, 1, fout);
  write_dword(fout, size);
  write_dword(fout, size2);
  write_dword(fout, nummatches);

  unsigned lastp1 = 0,
           lastp2 = 0;
  for (int i = 0; i < nummatches; ++i) {
    unsigned p1, p2, num;
    bdelta_getMatch(b, i, &p1, &p2, &num);
//    printf("%*x, %*x, %*x, %*x\n", 10, p1, 10, p2, 10, num, 10, p2-lastp2);
    copyloc1[i] = p1-lastp1;
    write_dword(fout, copyloc1[i]);
    copyloc2[i] = p2-lastp2;
    write_dword(fout, copyloc2[i]);
    copynum[i] = num;
    write_dword(fout, copynum[i]);
    lastp1=p1+num;
    lastp2=p2+num;
  }
  if (size2!=lastp2) {
    copyloc1[nummatches]=0; copynum[nummatches]=0; 
    copyloc2[nummatches]=size2-lastp2;
    ++nummatches;
  }

//  write_unsigned_list(adds, nummatches+1, fout);
//  write_unsigned_list(copynum, nummatches, fout);
//  write_signed_list(copyloc, nummatches, fout);
  unsigned fp = 0;
  for (int i = 0; i < nummatches; ++i) {
    unsigned num = copyloc2[i];
    while (num>0) {
      unsigned towrite = num;
      if (towrite>4096) towrite=4096;
      void *buf = f2->read(fp, towrite);
      fwrite(buf, 1, towrite, fout);
      num-=towrite;
      fp+=towrite;
    }
//    fp+=copyloc2[i];
    if (i!=nummatches) fp+=copynum[i];
  }
 
  fclose(fout);
  
  bdelta_done_alg(b);
  
  delete f1;
  delete f2;
}