/* sane - Scanner Access Now Easy.

   Copyright (C) 2018 Stanislav Yuzvinsky
   Based on the work done by viruxx

   This file is part of the SANE package.

   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 <https://www.gnu.org/licenses/>.

   As a special exception, the authors of SANE give permission for
   additional uses of the libraries contained in this release of SANE.

   The exception is that, if you link a SANE library with other files
   to produce an executable, this does not by itself cause the
   resulting executable to be covered by the GNU General Public
   License.  Your use of that executable is in no way restricted on
   account of linking the SANE library code into it.

   This exception does not, however, invalidate any other reasons why
   the executable file might be covered by the GNU General Public
   License.

   If you submit changes to SANE to the maintainers to be included in
   a subsequent release, you agree by submitting the changes that
   those changes may be distributed with this exception intact.

   If you write modifications of your own for SANE, it is your choice
   whether to permit this exception to apply to your modifications.
   If you do not wish that, delete this exception notice.
*/

#include "../include/sane/config.h"

#include <assert.h>
#include <stdlib.h>

#include "../include/sane/sanei_debug.h"

typedef struct ricoh2_buffer
{
  /* lifetime constants */
  SANE_Byte *data;
  SANE_Int   size;
  SANE_Int   pixels_per_line;
  SANE_Int   info_size;
  SANE_Bool  is_rgb;

  /* state */
  SANE_Int   current_position;
  SANE_Int   remain_in_line;

}
ricoh2_buffer;

static ricoh2_buffer *
ricoh2_buffer_create (SANE_Int  size,
                      SANE_Int  pixels_per_line,
                      SANE_Int  info_size,
                      SANE_Bool is_rgb)
{
  ricoh2_buffer *self;
  assert (size > 0);
  assert (pixels_per_line > 0);
  assert (info_size >= 0);

  self = malloc (sizeof (ricoh2_buffer));
  if (!self)
    return NULL;

  self->data = malloc (size);
  if (!self->data)
    {
      free (self);
      return NULL;
    }

  self->size = size;
  self->pixels_per_line = pixels_per_line;
  self->info_size = info_size;
  self->is_rgb = is_rgb;

  self->current_position = 0;
  self->remain_in_line = pixels_per_line;


  DBG (192,
       "size = %d pixels_per_line = %d info_size = %d rgb? = %d pos = %d\n",
       self->size,
       self->pixels_per_line,
       self->info_size,
       self->is_rgb,
       self->current_position);

  return self;
}

/* destructor */
static void
ricoh2_buffer_dispose (ricoh2_buffer *self)
{
  assert (self);
  free (self->data);
  free (self);
}

static SANE_Byte *
ricoh2_buffer_get_internal_buffer (ricoh2_buffer *self)
{
  assert (self);
  DBG (192, "engaging a buffer of size %d\n", self->size);

  self->current_position = 0;
  self->remain_in_line = self->pixels_per_line;

  DBG (192, "remain in line = %d\n", self->remain_in_line);

  return self->data;
}

static SANE_Int
ricoh2_buffer_get_bytes_remain (ricoh2_buffer *self)
{
  assert (self);

  DBG (192,
       "bytes remain in the buffer %d\n",
       self->size - self->current_position);

  return self->size - self->current_position;
}

inline static SANE_Int
min (SANE_Int v1, SANE_Int v2)
{
  return v1 < v2 ? v1 : v2;
}

static SANE_Int
ricoh2_buffer_get_data (ricoh2_buffer *self,
                        SANE_Byte     *dest,
                        SANE_Int       dest_size)
{
  SANE_Int actually_copied = 0;
  SANE_Int pixels_to_copy;
  SANE_Int bytes_per_pixel;
  SANE_Int bytes_per_color;
  SANE_Byte *src;
  SANE_Byte *end;

  assert (self);
  assert (dest);
  assert (self->size > self->current_position);

  bytes_per_pixel = self->is_rgb ? 3 : 1;
  bytes_per_color = self->pixels_per_line + self->info_size;

  DBG (192,
       "trying to get %d bytes from the buffer, "
       "while %d bytes in the line\n",
       dest_size,
       self->remain_in_line);

  for (pixels_to_copy =
       min (dest_size / bytes_per_pixel, self->remain_in_line);
       pixels_to_copy && self->size > self->current_position;
       pixels_to_copy =
       min (dest_size / bytes_per_pixel, self->remain_in_line))
    {

      DBG (192,
           "providing %d bytes to the user (until the end of the line), "
           "position in buffer is %d\n",
           pixels_to_copy * bytes_per_pixel,
           self->current_position);

      for (src = self->data + self->current_position,
           end = src + pixels_to_copy;
           src < end;
           ++src)
        {
          *(dest++) = *(src);
          if (bytes_per_pixel == 3)
            {
              *(dest++) = *(src + bytes_per_color);
              *(dest++) = *(src + 2 * bytes_per_color);
            }
        }

      dest_size -= pixels_to_copy * bytes_per_pixel;
      actually_copied += pixels_to_copy * bytes_per_pixel;
      self->current_position += pixels_to_copy;
      self->remain_in_line -= pixels_to_copy;

      // move to the next line
      if (!self->remain_in_line)
        {
          self->current_position += self->info_size;
          if (self->is_rgb)
            self->current_position += 2 * bytes_per_color;
          self->remain_in_line = self->pixels_per_line;
          DBG (192,
               "Line feed, new position is %d\n",
               self->current_position);
        }

      DBG (192,
           "left in the buffer: %d\n",
           self->size - self->current_position);
    }

  /* invariant */
  assert (self->size >= self->current_position);

  return actually_copied;
}