/*  RetroArch - A frontend for libretro.
 *  Copyright (C) 2010-2014 - Hans-Kristian Arntzen
 *  Copyright (C) 2011-2016 - Daniel De Matteis
 * 
 *  RetroArch 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 Found-
 *  ation, either version 3 of the License, or (at your option) any later version.
 *
 *  RetroArch 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 RetroArch.
 *  If not, see <http://www.gnu.org/licenses/>.
 */

/* BPS/UPS/IPS implementation from bSNES (nall::).
 * Modified for RetroArch. */

#include <stdint.h>
#include <string.h>

#include <boolean.h>

#include <compat/msvc.h>
#include <file/file_path.h>
#include <file/archive_file.h>
#include <streams/file_stream.h>
#include <retro_stat.h>
#include <string/stdstring.h>

#include "patch.h"
#include "runloop.h"
#include "verbosity.h"

enum bps_mode
{
   SOURCE_READ = 0,
   TARGET_READ,
   SOURCE_COPY,
   TARGET_COPY
};

enum patch_error
{
   PATCH_UNKNOWN = 0,
   PATCH_SUCCESS,
   PATCH_PATCH_TOO_SMALL,
   PATCH_PATCH_INVALID_HEADER,
   PATCH_PATCH_INVALID,
   PATCH_SOURCE_TOO_SMALL,
   PATCH_TARGET_TOO_SMALL,
   PATCH_SOURCE_INVALID,
   PATCH_TARGET_INVALID,
   PATCH_SOURCE_CHECKSUM_INVALID,
   PATCH_TARGET_CHECKSUM_INVALID,
   PATCH_PATCH_CHECKSUM_INVALID
};

struct bps_data
{
   const uint8_t *modify_data, *source_data; 
   uint8_t *target_data;
   size_t modify_length, source_length, target_length;
   size_t modify_offset, source_offset, target_offset;
   uint32_t modify_checksum, source_checksum, target_checksum;

   size_t source_relative_offset, target_relative_offset, output_offset;
};

typedef enum patch_error (*patch_func_t)(const uint8_t*, size_t,
      const uint8_t*, size_t, uint8_t*, size_t*);

static uint8_t bps_read(struct bps_data *bps)
{
   uint8_t data = bps->modify_data[bps->modify_offset++];
#ifdef HAVE_ZLIB
   const struct file_archive_file_backend *stream_backend = 
      file_archive_get_default_file_backend();
   bps->modify_checksum = ~stream_backend->stream_crc_calculate(
         ~bps->modify_checksum, &data, 1);
#endif
   return data;
}

static uint64_t bps_decode(struct bps_data *bps)
{
   uint64_t data = 0, shift = 1;

   for (;;)
   {
      uint8_t x  = bps_read(bps);
      data      += (x & 0x7f) * shift;
      if (x & 0x80)
         break;
      shift    <<= 7;
      data      += shift;
   }

   return data;
}

static void bps_write(struct bps_data *bps, uint8_t data)
{
#ifdef HAVE_ZLIB
   const struct file_archive_file_backend *stream_backend = 
      file_archive_get_default_file_backend();
#endif
   if (!bps)
      return;

   bps->target_data[bps->output_offset++] = data;
#ifdef HAVE_ZLIB
   bps->target_checksum = ~stream_backend->stream_crc_calculate(~bps->target_checksum, &data, 1);
#endif
}

static enum patch_error bps_apply_patch(
      const uint8_t *modify_data, size_t modify_length,
      const uint8_t *source_data, size_t source_length,
      uint8_t *target_data, size_t *target_length)
{
   size_t i;
   size_t modify_source_size, modify_target_size,
          modify_markup_size;
   struct bps_data bps = {0};
   uint32_t modify_source_checksum = 0, modify_target_checksum = 0,
            modify_modify_checksum = 0, checksum;
#ifdef HAVE_ZLIB
   const struct file_archive_file_backend *stream_backend = 
      file_archive_get_default_file_backend();
#endif

   if (modify_length < 19)
      return PATCH_PATCH_TOO_SMALL;

   bps.modify_data = modify_data;
   bps.modify_length = modify_length;
   bps.target_data = target_data;
   bps.target_length = *target_length;
   bps.source_data = source_data;
   bps.source_length = source_length;
   bps.modify_checksum = ~0;
   bps.target_checksum = ~0;

   if ((bps_read(&bps) != 'B') || (bps_read(&bps) != 'P') ||
         (bps_read(&bps) != 'S') || (bps_read(&bps) != '1'))
      return PATCH_PATCH_INVALID_HEADER;

   modify_source_size = bps_decode(&bps);
   modify_target_size = bps_decode(&bps);
   modify_markup_size = bps_decode(&bps);
   for (i = 0; i < modify_markup_size; i++)
      bps_read(&bps);

   if (modify_source_size > bps.source_length)
      return PATCH_SOURCE_TOO_SMALL;
   if (modify_target_size > bps.target_length)
      return PATCH_TARGET_TOO_SMALL;

   while (bps.modify_offset < bps.modify_length - 12)
   {
      size_t length = bps_decode(&bps);
      unsigned mode = length & 3;

      length = (length >> 2) + 1;

      switch (mode)
      {
         case SOURCE_READ:
            while (length--)
               bps_write(&bps, bps.source_data[bps.output_offset]);
            break;

         case TARGET_READ:
            while (length--)
               bps_write(&bps, bps_read(&bps));
            break;

         case SOURCE_COPY:
         case TARGET_COPY:
         {
            int    offset = bps_decode(&bps);
            bool negative = offset & 1;

            offset >>= 1;

            if (negative)
               offset = -offset;

            if (mode == SOURCE_COPY)
            {
               bps.source_offset += offset;
               while (length--)
                  bps_write(&bps, bps.source_data[bps.source_offset++]);
            }
            else
            {
               bps.target_offset += offset;
               while (length--)
                  bps_write(&bps, bps.target_data[bps.target_offset++]);
               break;
            }
            break;
         }
      }
   }


   for (i = 0; i < 32; i += 8)
      modify_source_checksum |= bps_read(&bps) << i;
   for (i = 0; i < 32; i += 8)
      modify_target_checksum |= bps_read(&bps) << i;

   checksum = ~bps.modify_checksum;
   for (i = 0; i < 32; i += 8)
      modify_modify_checksum |= bps_read(&bps) << i;

#ifdef HAVE_ZLIB
   bps.source_checksum = stream_backend->stream_crc_calculate(0,
         bps.source_data, bps.source_length);
#else
   return PATCH_PATCH_CHECKSUM_INVALID;
#endif

   bps.target_checksum = ~bps.target_checksum;

   if (bps.source_checksum != modify_source_checksum)
      return PATCH_SOURCE_CHECKSUM_INVALID;
   if (bps.target_checksum != modify_target_checksum)
      return PATCH_TARGET_CHECKSUM_INVALID;
   if (checksum != modify_modify_checksum)
      return PATCH_PATCH_CHECKSUM_INVALID;

   *target_length = modify_target_size;

   return PATCH_SUCCESS;
}

struct ups_data
{
   const uint8_t *patch_data, *source_data; 
   uint8_t *target_data;
   unsigned patch_length, source_length, target_length;
   unsigned patch_offset, source_offset, target_offset;
   unsigned patch_checksum, source_checksum, target_checksum;
};

static uint8_t ups_patch_read(struct ups_data *data) 
{
#ifdef HAVE_ZLIB
   const struct file_archive_file_backend *stream_backend = 
      file_archive_get_default_file_backend();
#endif

   if (data && data->patch_offset < data->patch_length) 
   {
      uint8_t n = data->patch_data[data->patch_offset++];
#ifdef HAVE_ZLIB
      data->patch_checksum = 
         ~stream_backend->stream_crc_calculate(~data->patch_checksum, &n, 1);
#endif
      return n;
   }
   return 0x00;
}

static uint8_t ups_source_read(struct ups_data *data) 
{
#ifdef HAVE_ZLIB
   const struct file_archive_file_backend *stream_backend = 
      file_archive_get_default_file_backend();
#endif

   if (data && data->source_offset < data->source_length) 
   {
      uint8_t n = data->source_data[data->source_offset++];
#ifdef HAVE_ZLIB
      data->source_checksum = 
         ~stream_backend->stream_crc_calculate(~data->source_checksum, &n, 1);
#endif
      return n;
   }
   return 0x00;
}

static void ups_target_write(struct ups_data *data, uint8_t n) 
{
#ifdef HAVE_ZLIB
   const struct file_archive_file_backend *stream_backend = 
      file_archive_get_default_file_backend();
#endif

   if (data && data->target_offset < data->target_length) 
   {
      data->target_data[data->target_offset] = n;
#ifdef HAVE_ZLIB
      data->target_checksum = 
         ~stream_backend->stream_crc_calculate(~data->target_checksum, &n, 1);
#endif
   }

   if (data)
      data->target_offset++;
}

static uint64_t ups_decode(struct ups_data *data) 
{
   uint64_t offset = 0, shift = 1;
   while (true) 
   {
      uint8_t x = ups_patch_read(data);
      offset   += (x & 0x7f) * shift;

      if (x & 0x80) 
         break;
      shift <<= 7;
      offset += shift;
   }
   return offset;
}

static enum patch_error ups_apply_patch(
      const uint8_t *patchdata, size_t patchlength,
      const uint8_t *sourcedata, size_t sourcelength,
      uint8_t *targetdata, size_t *targetlength)
{
   size_t i;
   unsigned source_read_length, target_read_length;
   uint32_t patch_read_checksum = 0, source_read_checksum = 0,
            target_read_checksum = 0, patch_result_checksum;
   struct ups_data data = {0};

   data.patch_data      = patchdata;
   data.source_data     = sourcedata;
   data.target_data     = targetdata;
   data.patch_length    = patchlength;
   data.source_length   = sourcelength;
   data.target_length   = *targetlength;
   data.patch_checksum  = ~0;
   data.source_checksum = ~0;
   data.target_checksum = ~0;

   if (data.patch_length < 18) 
      return PATCH_PATCH_INVALID;
   if (ups_patch_read(&data) != 'U') 
      return PATCH_PATCH_INVALID;
   if (ups_patch_read(&data) != 'P') 
      return PATCH_PATCH_INVALID;
   if (ups_patch_read(&data) != 'S') 
      return PATCH_PATCH_INVALID;
   if (ups_patch_read(&data) != '1') 
      return PATCH_PATCH_INVALID;

   source_read_length = ups_decode(&data);
   target_read_length = ups_decode(&data);

   if (data.source_length != source_read_length
         && data.source_length != target_read_length) 
      return PATCH_SOURCE_INVALID;
   *targetlength = (data.source_length == source_read_length ?
         target_read_length : source_read_length);
   if (data.target_length < *targetlength) 
      return PATCH_TARGET_TOO_SMALL;
   data.target_length = *targetlength;

   while (data.patch_offset < data.patch_length - 12) 
   {
      unsigned length = ups_decode(&data);
      while (length--) 
         ups_target_write(&data, ups_source_read(&data));
      while (true) 
      {
         uint8_t patch_xor = ups_patch_read(&data);
         ups_target_write(&data, patch_xor ^ ups_source_read(&data));
         if (patch_xor == 0)
            break;
      }
   }

   while (data.source_offset < data.source_length) 
      ups_target_write(&data, ups_source_read(&data));
   while (data.target_offset < data.target_length) 
      ups_target_write(&data, ups_source_read(&data));


   for (i = 0; i < 4; i++) 
      source_read_checksum |= ups_patch_read(&data) << (i * 8);
   for (i = 0; i < 4; i++) 
      target_read_checksum |= ups_patch_read(&data) << (i * 8);

   patch_result_checksum = ~data.patch_checksum;
   data.source_checksum  = ~data.source_checksum;
   data.target_checksum  = ~data.target_checksum;

   for (i = 0; i < 4; i++) 
      patch_read_checksum |= ups_patch_read(&data) << (i * 8);

   if (patch_result_checksum != patch_read_checksum) 
      return PATCH_PATCH_INVALID;

   if (data.source_checksum == source_read_checksum
         && data.source_length == source_read_length) 
   {
      if (data.target_checksum == target_read_checksum
            && data.target_length == target_read_length) 
         return PATCH_SUCCESS;
      return PATCH_TARGET_INVALID;
   } 
   else if (data.source_checksum == target_read_checksum
         && data.source_length == target_read_length) 
   {
      if (data.target_checksum == source_read_checksum
            && data.target_length == source_read_length) 
         return PATCH_SUCCESS;
      return PATCH_TARGET_INVALID;
   } 

   return PATCH_SOURCE_INVALID;
}

static enum patch_error ips_apply_patch(
      const uint8_t *patchdata, size_t patchlen,
      const uint8_t *sourcedata, size_t sourcelength,
      uint8_t *targetdata, size_t *targetlength)
{
   uint32_t offset = 5;

   if (patchlen < 8 ||
         patchdata[0] != 'P' ||
         patchdata[1] != 'A' ||
         patchdata[2] != 'T' ||
         patchdata[3] != 'C' ||
         patchdata[4] != 'H')
      return PATCH_PATCH_INVALID;

   memcpy(targetdata, sourcedata, sourcelength);

   *targetlength = sourcelength;

   for (;;)
   {
      uint32_t address;
      unsigned length;

      if (offset > patchlen - 3)
         break;

      address  = patchdata[offset++] << 16;
      address |= patchdata[offset++] << 8;
      address |= patchdata[offset++] << 0;

      if (address == 0x454f46) /* EOF */
      {
         if (offset == patchlen)
            return PATCH_SUCCESS;
         else if (offset == patchlen - 3)
         {
            uint32_t size = patchdata[offset++] << 16;
            size |= patchdata[offset++] << 8;
            size |= patchdata[offset++] << 0;
            *targetlength = size;
            return PATCH_SUCCESS;
         }
      }

      if (offset > patchlen - 2)
         break;

      length  = patchdata[offset++] << 8;
      length |= patchdata[offset++] << 0;

      if (length) /* Copy */
      {
         if (offset > patchlen - length)
            break;

         while (length--)
            targetdata[address++] = patchdata[offset++];
      }
      else /* RLE */
      {
         if (offset > patchlen - 3)
            break;

         length  = patchdata[offset++] << 8;
         length |= patchdata[offset++] << 0;

         if (length == 0) /* Illegal */
            break;

         while (length--)
            targetdata[address++] = patchdata[offset];

         offset++;
      }

      if (address > *targetlength)
         *targetlength = address;
   }

   return PATCH_PATCH_INVALID;
}

static bool apply_patch_content(uint8_t **buf,
      ssize_t *size, const char *patch_desc, const char *patch_path,
      patch_func_t func)
{
   size_t target_size;
   ssize_t patch_size;
   void *patch_data         = NULL;
   enum patch_error err     = PATCH_UNKNOWN;
   bool success             = false;
   uint8_t *patched_content = NULL;
   ssize_t ret_size         = *size;
   uint8_t *ret_buf         = *buf;
   
   if (!path_is_valid(patch_path))
      return false;
   if (!filestream_read_file(patch_path, &patch_data, &patch_size))
      return false;
   if (patch_size < 0)
      return false;

   if (!path_file_exists(patch_path))
      return false;

   RARCH_LOG("Found %s file in \"%s\", attempting to patch ...\n",
         patch_desc, patch_path);

   target_size = ret_size * 4; /* Just to be sure. */

   patched_content = (uint8_t*)malloc(target_size);

   if (!patched_content)
   {
      RARCH_ERR("Failed to allocate memory for patched content ...\n");
      goto error;
   }

   err = func((const uint8_t*)patch_data, patch_size, ret_buf,
         ret_size, patched_content, &target_size);

   if (err == PATCH_SUCCESS)
   {
      RARCH_LOG("Content patched successfully (%s).\n", patch_desc);
      success = true;
   }
   else
      RARCH_ERR("Failed to patch %s: Error #%u\n", patch_desc,
            (unsigned)err);

   if (success)
   {
      free(ret_buf);
      *buf = patched_content;
      *size = target_size;
   }

   free(patch_data);
   return true;

error:
   *buf = ret_buf;
   *size = ret_size;
   free(patch_data);

   return false;
}

static bool try_bps_patch(uint8_t **buf, ssize_t *size)
{
   global_t *global = global_get_ptr();
   bool allow_bps   = !global->patch.ups_pref && !global->patch.ips_pref;

   if (!allow_bps || string_is_empty(global->name.bps))
      return false;

   return apply_patch_content(buf, size, "BPS", global->name.bps,
         bps_apply_patch);
}

static bool try_ups_patch(uint8_t **buf, ssize_t *size)
{
   global_t *global = global_get_ptr();
   bool allow_ups   = !global->patch.bps_pref && !global->patch.ips_pref;

   if (!allow_ups || string_is_empty(global->name.ups))
      return false;

   return apply_patch_content(buf, size, "UPS", global->name.ups,
         ups_apply_patch);
}

static bool try_ips_patch(uint8_t **buf, ssize_t *size)
{
   global_t *global = global_get_ptr();
   bool allow_ips   = !global->patch.ups_pref && !global->patch.bps_pref;

   if (!allow_ips || string_is_empty(global->name.ips))
      return false;

   return apply_patch_content(buf, size, "IPS", global->name.ips,
         ips_apply_patch);
}

/**
 * patch_content:
 * @buf          : buffer of the content file.
 * @size         : size   of the content file.
 *
 * Apply patch to the content file in-memory.
 *
 **/
void patch_content(uint8_t **buf, ssize_t *size)
{
   global_t *global = global_get_ptr();

   if (    global->patch.ips_pref 
         + global->patch.bps_pref 
         + global->patch.ups_pref > 1)
   {
      RARCH_WARN("Several patches are explicitly defined, ignoring all ...\n");
      return;
   }

   if (     !try_ips_patch(buf, size) 
         && !try_bps_patch(buf, size) 
         && !try_ups_patch(buf, size))
   {
      RARCH_LOG("Did not find a valid content patch.\n");
   }
}