#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <zlib.h>



#include "Patch.h"



#ifndef _MSC_VER

#define _stricmp strcasecmp

#endif // ! _MSC_VER



static int readInt2(MFILE *f)

{

  int res = 0;

  int c = memfgetc(f);

  if(c == MEOF)

    return -1;

  res = c;

  c = memfgetc(f);

  if(c == MEOF)

    return -1;

  return c + (res<<8);

}



static int readInt3(MFILE *f)

{

  int res = 0;

  int c = memfgetc(f);

  if(c == MEOF)

    return -1;

  res = c;

  c = memfgetc(f);

  if(c == MEOF)

    return -1;

  res = c + (res<<8);

  c = memfgetc(f);

  if(c == MEOF)

    return -1;

  return c + (res<<8);

}



static s64 readInt4(MFILE *f)

{

  s64 tmp, res = 0;

  int c;



  for (int i = 0; i < 4; i++) {

    c = memfgetc(f);

    if (c == MEOF)

      return -1;

    tmp = c;

    res = res + (tmp << (i*8));

  }



  return res;

}



static s64 readInt8(MFILE *f)

{

  s64 tmp, res = 0;

  int c;



  for (int i = 0; i < 8; i++) {

    c = memfgetc(f);

    if (c == MEOF)

      return -1;

    tmp = c;

    res = res + (tmp << (i*8));

  }



  return res;

}



static s64 readVarPtr(MFILE *f)

{

  s64 offset = 0, shift = 1;

  for (;;) {

    int c = memfgetc(f);

    if (c == MEOF) return 0;

    offset += (c & 0x7F) * shift;

    if (c & 0x80) break;

    shift <<= 7;

    offset += shift;

  }

  return offset;

}



#ifndef MIN

#define MIN(a,b) (((a)<(b))?(a):(b))

#endif



static uLong computePatchCRC(MFILE *f, unsigned int size)

{

  Bytef buf[4096];

  long readed;



  uLong crc = crc32(0L, Z_NULL, 0);

  do {

    readed = memfread(buf, 1, MIN(size, sizeof(buf)), f);

    crc = crc32(crc, buf, readed);

    size -= readed;

  } while (readed > 0);

  return crc;

}



bool patchApplyIPS(MFILE *f, u8 **r, int *s)

{

  // from the IPS spec at http://zerosoft.zophar.net/ips.htm



  bool result = false;



  u8 *rom = *r;

  int size = *s;

  if(memfgetc(f) == 'P' &&

     memfgetc(f) == 'A' &&

     memfgetc(f) == 'T' &&

     memfgetc(f) == 'C' &&

     memfgetc(f) == 'H') {

    int b;

    int offset;

    int len;



    result = true;



    for(;;) {

      // read offset

      offset = readInt3(f);

      // if offset == MEOF, end of patch

      if(offset == 0x454f46 || offset == -1)

        break;

      // read length

      len = readInt2(f);

      if(!len) {

        // len == 0, RLE block

        len = readInt2(f);

        // byte to fill

        int c = memfgetc(f);

        if(c == -1)

          break;

        b = (u8)c;

      } else

        b= -1;

      // check if we need to reallocate our ROM

      if((offset + len) >= size) {

#ifdef GEKKO

        size = offset + len;

#else

        size *= 2;

        rom = (u8 *)realloc(rom, size);

#endif

        *r = rom;

        *s = size;

      }

      if(b == -1) {

        // normal block, just read the data

        if(memfread(&rom[offset], 1, len, f) != (size_t)len)

          break;

      } else {

        // fill the region with the given byte

        while(len--) {

          rom[offset++] = b;

        }

      }

    }

  }



  return result;

}



bool patchApplyUPS(MFILE *f, u8 **rom, int *size)

{

  s64 srcCRC, dstCRC, patchCRC;



  memfseek(f, 0, MSEEK_END);

  long int patchSize = memftell(f);

  if (patchSize < 20) {

    return false;

  }



  memfseek(f, 0, MSEEK_SET);

  if(memfgetc(f) != 'U' || memfgetc(f) != 'P' || memfgetc(f) != 'S' || memfgetc(f) != '1') {

    return false;

  }



  memfseek(f, -12, MSEEK_END);

  srcCRC = readInt4(f);

  dstCRC = readInt4(f);

  patchCRC = readInt4(f);

  if (srcCRC == -1 || dstCRC == -1 || patchCRC == -1) {

    return false;

  }



  memfseek(f, 0, MSEEK_SET);

  u32 crc = computePatchCRC(f, patchSize-4);



  if (crc != patchCRC) {

    return false;

  }



  crc = crc32(0L, Z_NULL, 0);

  crc = crc32(crc, *rom, *size);



  memfseek(f, 4, MSEEK_SET);

  s64 dataSize;

  s64 srcSize = readVarPtr(f);

  s64 dstSize = readVarPtr(f);



  if (crc == srcCRC) {

    if (srcSize != *size) {

      return false;

    }

    dataSize = dstSize;

  } else if (crc == dstCRC) {

    if (dstSize != *size) {

      return false;

    }

    dataSize = srcSize;

  } else {

    return false;

  }

  if (dataSize > *size) {

    *rom = (u8*)realloc(*rom, dataSize);

    memset(*rom + *size, 0, dataSize - *size);

    *size = dataSize;

  }



  s64 relative = 0;

  u8 *mem;

  while(memftell(f) < patchSize - 12) {

    relative += readVarPtr(f);

    if (relative > dataSize) continue;

    mem = *rom + relative;

    for(s64 i = relative; i < dataSize; i++) {

      int x = memfgetc(f);

      relative++;

      if (!x) break;

      if (i < dataSize) {

        *mem++ ^= x;

      }

    }

  }



  return true;

}



static int ppfVersion(MFILE *f)

{

  memfseek(f, 0, MSEEK_SET);

  if (memfgetc(f) != 'P' || memfgetc(f) != 'P' || memfgetc(f) != 'F') //-V501

    return 0;

  switch(memfgetc(f)){

    case '1': return 1;

    case '2': return 2;

    case '3': return 3;

    default: return 0;

  }

}



static int ppfFileIdLen(MFILE *f, int version)

{

  if (version == 2) {

    memfseek(f, -8, MSEEK_END);

  } else {

    memfseek(f, -6, MSEEK_END);

  }



  if (memfgetc(f) != '.' || memfgetc(f) != 'D' || memfgetc(f) != 'I' || memfgetc(f) != 'Z')

    return 0;



  return (version == 2) ? readInt4(f) : readInt2(f);

}



static bool patchApplyPPF1(MFILE *f, u8 **rom, int *size)

{

  memfseek(f, 0, MSEEK_END);

  int count = memftell(f);

  if (count < 56)

    return false;

  count -= 56;



  memfseek(f, 56, MSEEK_SET);



  u8 *mem = *rom;



  while (count > 0) {

    int offset = readInt4(f);

    if (offset == -1)

      break;

    int len = memfgetc(f);

    if (len == MEOF)

      break;

    if (offset+len > *size)

      break;

    if (memfread(&mem[offset], 1, len, f) != (size_t)len)

      break;

    count -= 4 + 1 + len;

  }



  return (count == 0);

}



static bool patchApplyPPF2(MFILE *f, u8 **rom, int *size)

{

  memfseek(f, 0, MSEEK_END);

  int count = memftell(f);

  if (count < 56+4+1024)

    return false;

  count -= 56+4+1024;



  memfseek(f, 56, MSEEK_SET);



  int datalen = readInt4(f);

  if (datalen != *size)

    return false;



  u8 *mem = *rom;



  u8 block[1024];

  memfread(&block, 1, 1024, f);

  if (memcmp(&mem[0x9320], &block, 1024) != 0)

    return false;



  int idlen = ppfFileIdLen(f, 2);

  if (idlen > 0)

    count -= 16 + 16 + idlen;



  memfseek(f, 56+4+1024, MSEEK_SET);



  while (count > 0) {

    int offset = readInt4(f);

    if (offset == -1)

      break;

    int len = memfgetc(f);

    if (len == MEOF)

      break;

    if (offset+len > *size)

      break;

    if (memfread(&mem[offset], 1, len, f) != (size_t)len)

      break;

    count -= 4 + 1 + len;

  }



  return (count == 0);

}



static bool patchApplyPPF3(MFILE *f, u8 **rom, int *size)

{

  memfseek(f, 0, MSEEK_END);

  int count = memftell(f);

  if (count < 56+4+1024)

    return false;

  count -= 56+4;



  memfseek(f, 56, MSEEK_SET);



  int imagetype = memfgetc(f);

  int blockcheck = memfgetc(f);

  int undo = memfgetc(f);

  memfgetc(f);



  u8 *mem = *rom;



  if (blockcheck) {

    u8 block[1024];

    memfread(&block, 1, 1024, f);

    if (memcmp(&mem[(imagetype == 0) ? 0x9320 : 0x80A0], &block, 1024) != 0)

      return false;

    count -= 1024;

  }



  int idlen = ppfFileIdLen(f, 2);

  if (idlen > 0)

    count -= 16 + 16 + idlen;



  memfseek(f, 56+4+(blockcheck ? 1024 : 0), MSEEK_SET);



  while (count > 0) {

    s64 offset = readInt8(f);

    if (offset == -1)

      break;

    int len = memfgetc(f);

    if (len == MEOF)

      break;

    if (offset+len > *size)

      break;

    if (memfread(&mem[offset], 1, len, f) != (size_t)len)

      break;

    if (undo) memfseek(f, len, MSEEK_CUR);

    count -= 8 + 1 + len;

    if (undo) count -= len;

  }



  return (count == 0);

}



bool patchApplyPPF(MFILE *f, u8 **rom, int *size)

{

  bool res = false;



  int version = ppfVersion(f);

  switch (version) {

    case 1: res = patchApplyPPF1(f, rom, size); break;

    case 2: res = patchApplyPPF2(f, rom, size); break;

    case 3: res = patchApplyPPF3(f, rom, size); break;

  }



  return res;

}



bool applyPatch(const char *patchname, u8 **rom, int *size)

{

    bool result = false;



    if (strlen(patchname) < 5)

        return false;

    const char * p = strrchr(patchname, '.');

    if (p == NULL)

        return false;



    FILE *f = fopen(patchname, "rb");

    if (!f)

        return false;



    // read in file

    fseek(f, 0, SEEK_END); // go to end of file

    int filesize = ftell(f); // get filesize

    fseek(f, 0, SEEK_SET); // go to start of file

    char * pbuffer = (char *) malloc(filesize);

    fread (pbuffer, 1, filesize, f);

    fclose(f);



    MFILE * mf = memfopen(pbuffer, filesize); // create memory file



    if (_stricmp(p, ".ips") == 0)

        result = patchApplyIPS(mf, rom, size);

    else if (_stricmp(p, ".ups") == 0)

        result = patchApplyUPS(mf, rom, size);

    else if (_stricmp(p, ".ppf") == 0)

        result = patchApplyPPF(mf, rom, size);



    memfclose(mf); // close memory file

    free(pbuffer); // free buffer



    return result;

}