/* lexmark_x2600.c: SANE backend for Lexmark x2600 scanners.

   (C) 2023 "Benoit Juin" <benoit.juin@gmail.com>

   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 "lexmark_x2600.h"

#define BUILD 1
#define LEXMARK_X2600_CONFIG_FILE "lexmark_x2600.conf"
#define MAX_OPTION_STRING_SIZE 255
static SANE_Int transfer_buffer_size = 32768;
static Lexmark_Device *first_device = 0;
static SANE_Int num_devices = 0;
static const SANE_Device **devlist = 0;

static SANE_Bool initialized = SANE_FALSE;

// first value is the size of the wordlist!
static SANE_Int dpi_list[] = {
  4, 100, 200, 300, 600
};
static SANE_Int dpi_list_size = sizeof(dpi_list) / sizeof(dpi_list[0]);

static SANE_String_Const mode_list[] = {
  SANE_VALUE_SCAN_MODE_COLOR,
  SANE_VALUE_SCAN_MODE_GRAY,
  NULL
};

static SANE_Range x_range = {
  0,				/* minimum */
  5078,				/* maximum */
  1				/* quantization */
};

static SANE_Range y_range = {
  0,				/* minimum */
  7015,				/* maximum */
  1				/* quantization */
};

static SANE_Byte command1_block[] = {
  0xA5, 0x00, 0x19, 0x10, 0x01, 0x83, 0xAA, 0xBB,
  0xCC, 0xDD, 0x02, 0x00, 0x1B, 0x53, 0x03, 0x00,
  0x00, 0x00, 0x80, 0x00, 0xAA, 0xBB, 0xCC, 0xDD,
  0xAA, 0xBB, 0xCC, 0xDD};
static SANE_Int command1_block_size = sizeof(command1_block);

static SANE_Byte command2_block[] = {
  0xA5, 0x00, 0x19, 0x10, 0x01, 0x83, 0xAA, 0xBB,
  0xCC, 0xDD, 0x02, 0x00, 0x1B, 0x53, 0x04, 0x00,
  0x00, 0x00, 0x80, 0x00, 0xAA, 0xBB, 0xCC, 0xDD,
  0xAA, 0xBB, 0xCC, 0xDD};
static SANE_Int command2_block_size = sizeof(command2_block);

static SANE_Byte command_with_params_block[] = {
  0xA5, 0x00, 0x31, 0x10, 0x01, 0x83, 0xAA, 0xBB,
  0xCC, 0xDD, 0x02, 0x00, 0x1B, 0x53, 0x05, 0x00,
  0x18, 0x00, 0x80, 0x00, 0xFF, 0x00, 0x00, 0x02,
  0xFF, 0xFF, 0x00, 0x00, 0xFF, 0xFF, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
  0xFF, 0xFF, 0xFF, 0xFF, 0xAA, 0xBB, 0xCC, 0xDD,
  0xAA, 0xBB, 0xCC, 0xDD};
static SANE_Int command_with_params_block_size = sizeof(command_with_params_block);

static SANE_Byte command_cancel1_block[] = {
  0xa5, 0x00, 0x19, 0x10, 0x01, 0x83, 0xaa, 0xbb,
  0xcc, 0xdd, 0x02, 0x00, 0x1b, 0x53, 0x0f, 0x00,
  0x00, 0x00, 0x00, 0x00, 0xaa, 0xbb, 0xcc, 0xdd,
  0xaa, 0xbb, 0xcc, 0xdd};
static SANE_Byte command_cancel2_block[] = {
  0xa5, 0x00, 0x19, 0x10, 0x01, 0x83, 0xaa, 0xbb,
  0xcc, 0xdd, 0x02, 0x00, 0x1b, 0x53, 0x06, 0x00,
  0x00, 0x00, 0x80, 0x00, 0xaa, 0xbb, 0xcc, 0xdd,
  0xaa, 0xbb, 0xcc, 0xdd};
static SANE_Int command_cancel_size = sizeof(command_cancel1_block);

static SANE_Byte empty_line_data_packet[] = {
  0x1b, 0x53, 0x02, 0x00, 0x01, 0x00, 0x00, 0x00,
  0x00};
static SANE_Int empty_line_data_packet_size = sizeof(empty_line_data_packet);

static SANE_Byte last_data_packet[] = {
  0x1b, 0x53, 0x02, 0x00, 0x01, 0x00, 0x00, 0x00,
  0x01};
static SANE_Int last_data_packet_size = sizeof(last_data_packet);

static SANE_Byte cancel_packet[] = {
  0x1b, 0x53, 0x02, 0x00, 0x01, 0x00, 0x00, 0x00,
  0x03};
static SANE_Int cancel_packet_size = sizeof(cancel_packet);

static SANE_Byte linebegin_data_packet[] = {
  0x1b, 0x53, 0x02, 0x00};
static SANE_Int linebegin_data_packet_size = sizeof(linebegin_data_packet);

static SANE_Byte unknown_a_data_packet[] = {
  0x1b, 0x53, 0x01, 0x00, 0x01, 0x00, 0x80, 0x00};
static SANE_Int unknown_a_data_packet_size = sizeof(unknown_a_data_packet);

static SANE_Byte unknown_b_data_packet[] = {
  0x1b, 0x53, 0x04, 0x00, 0x00, 0x00, 0x80, 0x00};
static SANE_Int unknown_b_data_packet_size = sizeof(unknown_b_data_packet);

static SANE_Byte unknown_c_data_packet[] = {
  0x1b, 0x53, 0x04, 0x00, 0x00, 0x00, 0x84, 0x00};
static SANE_Int unknown_c_data_packet_size = sizeof(unknown_c_data_packet);

static SANE_Byte unknown_d_data_packet[] = {
  0x1b, 0x53, 0x05, 0x00, 0x00, 0x00};
static SANE_Int unknown_d_data_packet_size = sizeof(unknown_d_data_packet);

static SANE_Byte unknown_e_data_packet[] = {
  0xa5, 0x00, 0x06, 0x10, 0x01, 0xaa, 0xbb, 0xcc,
  0xdd};
static SANE_Int unknown_e_data_packet_size = sizeof(unknown_e_data_packet);

/* static SANE_Byte not_ready_data_packet[] = { */
/*   0x1b, 0x53, 0x01, 0x00, 0x01, 0x00, 0x84, 0x00}; */
/* static SANE_Int not_ready_data_packet_size = sizeof(not_ready_data_packet); */


static SANE_Int line_header_length = 9;


//static SANE_Byte empty_data_packet[8] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};

SANE_Status
clean_and_copy_data(const SANE_Byte * source, SANE_Int source_size,
                    SANE_Byte * destination, SANE_Int * destination_length,
                    SANE_Int mode, SANE_Int max_length, SANE_Handle dev)
{
  DBG (10, "clean_and_copy_data\n");
  // if source doesnt start with 1b 53 02, then it is a continuation packet
  // SANE_Int k = 0;
  // SANE_Int bytes_written = 0;
  // BW    1b 53 02 00 21 00 00 00 00  |   32 |   21 ->    33 (segmentlng=   32)
  // BW    1b 53 02 00 41 00 00 00 00  |   64 |   41 ->    65 (segmentlng=   64)
  // COLOR 1b 53 02 00 c1 00 00 00 00  |   64 |   c1 ->   193 (segmentlng=  192)
  // COLOR 1b 53 02 00 01 06 00 00 00  |  512 |  601 ->  1537 (segmentlng= 1536)
  // COLOR 1b 53 02 00 99 3a 00 00 00  | 5000 | 3a99 -> 15001 (segmentlng=15000)
  // COLOR 1b 53 02 00 f7 0f 00        | 1362 | 0ff7 ->  4087 <- limit where sane_read can a read a line at e time, more that 1362 and then the rest
  //                                                             of the line will be available in the next sane_read call
  // COLOR 1b 53 02 00 fa 0f 00        |      | 0ffa ->  4090 <- in that case the line doesnt fit, clean_and_copy_data will be called again with the rest of the data


  // edge case segment doesn(t feet in the packet size
  /* if(segment_length > source_size - 9) */
  /*   segment_length = source_size - 9; */

  // the scanner sends series of 8 lines function param source
  // every lines has prefix see linebegin_data_packet
  // the source parameter as a limited length :function param source_size
  // so the serie og 8 lines can be splited
  // in such case, in the next call of this function, source contain the end of the
  // broken segment.
  // Here is the way data is read:
  // 1 - check that source begin with a linebegin_data_packet signature
  //     if this is the case the source[4] & source[5] contains how much data
  //     can be read before onother header is reach (linebegin_data_packet)

  Lexmark_Device * ldev = (Lexmark_Device * ) dev;
  SANE_Int i = 0;
  SANE_Int bytes_read = 0;
  SANE_Byte tmp = 0;
  SANE_Int source_read_cursor = 0;
  SANE_Int block_pixel_data_length = 0;
  SANE_Int size_to_realloc = 0;


  if(!ldev->eof){

    // does source start with linebegin_data_packet?
    if (memcmp(linebegin_data_packet, source, linebegin_data_packet_size) == 0){
      // extract the number of bytes we can read befor new header is reached
      // store it in the device in case of continuation packet
      ldev->read_buffer->linesize = (source[4] + ((source[5] << 8) & 0xFF00)) - 1;
      ldev->read_buffer->last_line_bytes_read = ldev->read_buffer->linesize;
      DBG (10, "    this is the begining of a line linesize=%ld\n",
           ldev->read_buffer->linesize);
    } else {
      DBG (10, "    this is not a new line packet, continue to fill the read buffer\n");
      //return;
    }

    if(ldev->read_buffer->linesize == 0){
      DBG (10, "    linesize=0 something went wrong, lets ignore that USB packet\n");
      return SANE_STATUS_CANCELLED;
    }


    // loop over source buffer
    while(i < source_size){
      // last line was full
      if(ldev->read_buffer->last_line_bytes_read == ldev->read_buffer->linesize){
        // if next block fit in the source
        if(i + line_header_length + (SANE_Int) ldev->read_buffer->linesize <= source_size){
          ldev->read_buffer->image_line_no += 1;
          source_read_cursor = i + line_header_length;
          block_pixel_data_length = ldev->read_buffer->linesize;
          ldev->read_buffer->last_line_bytes_read = block_pixel_data_length;
          size_to_realloc = ldev->read_buffer->image_line_no *
            ldev->read_buffer->linesize * sizeof(SANE_Byte);
          bytes_read = block_pixel_data_length + line_header_length;
        }
        // next block cannot be read fully because source_size is too small
        // (USB packet fragmentation)
        else{
          ldev->read_buffer->image_line_no += 1;
          source_read_cursor = i + line_header_length;
          block_pixel_data_length = source_size - i - line_header_length;
          ldev->read_buffer->last_line_bytes_read = block_pixel_data_length;
          size_to_realloc = ((ldev->read_buffer->image_line_no-1) *
            ldev->read_buffer->linesize + block_pixel_data_length) * sizeof(SANE_Byte);
          bytes_read = block_pixel_data_length + line_header_length;
        }
      }
      // last line was not full lets extract what is left
      // this is du to USB packet fragmentation
      else{
        // the last line was not full so no increment
        ldev->read_buffer->image_line_no += 0;
        source_read_cursor = i;
        block_pixel_data_length = ldev->read_buffer->linesize -
          ldev->read_buffer->last_line_bytes_read;
        // we completed the last line with missing bytes so new the line is full
        ldev->read_buffer->last_line_bytes_read = ldev->read_buffer->linesize;
        size_to_realloc = ldev->read_buffer->image_line_no *
          ldev->read_buffer->linesize * sizeof(SANE_Byte);
        bytes_read = block_pixel_data_length;
      }

      DBG (20, "    size_to_realloc=%d i=%d image_line_no=%d\n",
           size_to_realloc, i, ldev->read_buffer->image_line_no);
      // do realoc memory space for our buffer
      SANE_Byte* alloc_result = realloc(ldev->read_buffer->data, size_to_realloc);
      if(alloc_result == NULL){
        // TODO allocation was not possible
        DBG (20, "    REALLOC failed\n");
        return SANE_STATUS_NO_MEM;
      }
      // point data to our new memary space
      ldev->read_buffer->data = alloc_result;
      // reposition writeptr and readptr to the correct memory adress
      // to do that use write_byte_counter and read_byte_counter
      ldev->read_buffer->writeptr =
        ldev->read_buffer->data + ldev->read_buffer->write_byte_counter;
      // copy new data
      memcpy(
             ldev->read_buffer->writeptr,
             source + source_read_cursor,
             block_pixel_data_length
      );

      // store how long is the buffer
      ldev->read_buffer->write_byte_counter += block_pixel_data_length;

      i += bytes_read;
    }
  }

  // reposition our readptr
  ldev->read_buffer->readptr =
    ldev->read_buffer->data + ldev->read_buffer->read_byte_counter;


  // read our buffer to fill the destination buffer
  // mulitple call so read may has been already started
  // length already read is stored in ldev->read_buffer->read_byte_counter

  SANE_Int available_bytes_to_read =
    ldev->read_buffer->write_byte_counter - ldev->read_buffer->read_byte_counter;

  DBG (20, "    source read done now sending to destination \n");

  // we will copy image data 3 bytes by 3 bytes if color mod to allow color swap
  // this avoid error on color channels swapping
  if (mode == SANE_FRAME_RGB){

    // get max chunk
    SANE_Int data_chunk_size = max_length;
    if(data_chunk_size > available_bytes_to_read){
      data_chunk_size = available_bytes_to_read;
    }
    data_chunk_size = data_chunk_size / 3;
    data_chunk_size = data_chunk_size * 3;

    // we have to invert color channels
    SANE_Byte * color_swarp_ptr = ldev->read_buffer->readptr;
    for(SANE_Int j=0; j < data_chunk_size;j += 3){
      // DBG (20, "  swapping RGB <- BGR j=%d\n", j);
      tmp = *(color_swarp_ptr + j);
      *(color_swarp_ptr + j) = *(color_swarp_ptr + j + 2);
      *(color_swarp_ptr + j + 2) = tmp;
    }

    memcpy (destination,
            ldev->read_buffer->readptr,
            data_chunk_size);

    ldev->read_buffer->read_byte_counter += data_chunk_size;
    *destination_length = data_chunk_size;

  }
  // gray mode copy until max_length
  else{

    SANE_Int data_chunk_size = max_length;
    if(data_chunk_size > available_bytes_to_read){
      data_chunk_size = available_bytes_to_read;
    }
    memcpy (
      destination,
      ldev->read_buffer->readptr,
      data_chunk_size
    );
    ldev->read_buffer->read_byte_counter += data_chunk_size;;
    *destination_length = data_chunk_size;

  }

  DBG (20, "    done destination_length=%d available_bytes_to_read=%d\n",
       *destination_length, available_bytes_to_read);

  if(available_bytes_to_read > 0){
    return SANE_STATUS_GOOD;
  }else{
    ldev->eof = 0;
    return SANE_STATUS_EOF;
  }

}

SANE_Status
usb_write_then_read (Lexmark_Device * dev, SANE_Byte * cmd, size_t cmd_size)
{
  size_t buf_size = 256;
  SANE_Byte buf[buf_size];
  SANE_Status status;

  DBG (10, "usb_write_then_read: %d\n", dev->devnum);
  sanei_usb_set_endpoint(dev->devnum, USB_DIR_OUT|USB_ENDPOINT_TYPE_BULK, 0x02);
  DBG (10, "    endpoint set: %d\n", dev->devnum);

  /* status = sanei_usb_read_bulk (dev->devnum, buf, &buf_size); */
  /* DBG (10, "    readdone: %d\n", dev->devnum); */
  /* if (status != SANE_STATUS_GOOD && status != SANE_STATUS_EOF) */
  /*   { */
  /*     DBG (1, "USB READ IO Error in usb_write_then_read, fail devnum=%d\n", */
  /*          dev->devnum); */
  /*     return status; */
  /*   } */

  DBG (10, "    attempting to write...: %d\n", dev->devnum);
  status = sanei_usb_write_bulk (dev->devnum, cmd, &cmd_size);
  DBG (10, "    writedone: %d\n", dev->devnum);
  if (status != SANE_STATUS_GOOD)
    {
      DBG (1, "USB WRITE IO Error in usb_write_then_read, launch fail: %d\n",
           status);
      return status;
    }

  debug_packet(cmd, cmd_size, WRITE);

  DBG (10, "    attempting to read...: %d\n", dev->devnum);
  status = sanei_usb_read_bulk (dev->devnum, buf, &buf_size);
  DBG (10, "    readdone: %d\n", dev->devnum);
  if (status != SANE_STATUS_GOOD && status != SANE_STATUS_EOF)
    {
      DBG (1, "USB READ IO Error in usb_write_then_read, fail devnum=%d\n",
           dev->devnum);
      return status;
    }
  debug_packet(buf, buf_size, READ);
  return SANE_STATUS_GOOD;
}

void
build_packet(Lexmark_Device * dev, SANE_Byte packet_id, SANE_Byte * buffer){
  memcpy(buffer, command_with_params_block, command_with_params_block_size);
  // protocole related... "ID?"
  buffer[14] = packet_id;

  // mode
  if (memcmp(dev->val[OPT_MODE].s, "Color", 5) == 0 )
    buffer[20] = 0x03;
  else
    buffer[20] = 0x02;

  // pixel width (swap lower byte -> higher byte)
  buffer[24] = dev->val[OPT_BR_X].w & 0xFF;
  buffer[25] = (dev->val[OPT_BR_X].w >> 8) & 0xFF;

  // pixel height (swap lower byte -> higher byte)
  buffer[28] = dev->val[OPT_BR_Y].w & 0xFF;
  buffer[29] = (dev->val[OPT_BR_Y].w >> 8) & 0xFF;

  // dpi x (swap lower byte -> higher byte)
  buffer[40] = dev->val[OPT_RESOLUTION].w & 0xFF;
  buffer[41] = (dev->val[OPT_RESOLUTION].w >> 8) & 0xFF;

  // dpi y (swap lower byte -> higher byte)
  buffer[42] = dev->val[OPT_RESOLUTION].w & 0xFF;
  buffer[43] = (dev->val[OPT_RESOLUTION].w >> 8) & 0xFF;
}

SANE_Status
init_options (Lexmark_Device * dev)
{

  SANE_Option_Descriptor *od;

  DBG (2, "init_options: dev = %p\n", (void *) dev);

  /* number of options */
  od = &(dev->opt[OPT_NUM_OPTS]);
  od->name = SANE_NAME_NUM_OPTIONS;
  od->title = SANE_TITLE_NUM_OPTIONS;
  od->desc = SANE_DESC_NUM_OPTIONS;
  od->type = SANE_TYPE_INT;
  od->unit = SANE_UNIT_NONE;
  od->size = sizeof (SANE_Word);
  od->cap = SANE_CAP_SOFT_DETECT;
  od->constraint_type = SANE_CONSTRAINT_NONE;
  od->constraint.range = 0;
  dev->val[OPT_NUM_OPTS].w = NUM_OPTIONS;

  /* mode - sets the scan mode: Color / Gray */
  od = &(dev->opt[OPT_MODE]);
  od->name = SANE_NAME_SCAN_MODE;
  od->title = SANE_TITLE_SCAN_MODE;
  od->desc = SANE_DESC_SCAN_MODE;;
  od->type = SANE_TYPE_STRING;
  od->unit = SANE_UNIT_NONE;
  od->size = MAX_OPTION_STRING_SIZE;
  od->cap = SANE_CAP_SOFT_DETECT | SANE_CAP_SOFT_SELECT;
  od->constraint_type = SANE_CONSTRAINT_STRING_LIST;
  od->constraint.string_list = mode_list;
  dev->val[OPT_MODE].s = malloc (od->size);
  if (!dev->val[OPT_MODE].s)
    return SANE_STATUS_NO_MEM;
  strcpy (dev->val[OPT_MODE].s, SANE_VALUE_SCAN_MODE_COLOR);

  /* resolution */
  od = &(dev->opt[OPT_RESOLUTION]);
  od->name = SANE_NAME_SCAN_RESOLUTION;
  od->title = SANE_TITLE_SCAN_RESOLUTION;
  od->desc = SANE_DESC_SCAN_RESOLUTION;
  od->type = SANE_TYPE_INT;
  od->unit = SANE_UNIT_DPI;
  od->size = sizeof (SANE_Int);
  od->cap = SANE_CAP_SOFT_DETECT | SANE_CAP_SOFT_SELECT;
  od->constraint_type = SANE_CONSTRAINT_WORD_LIST;
  od->constraint.word_list = dpi_list;
  dev->val[OPT_RESOLUTION].w = 200;

  /* preview mode */
  od = &(dev->opt[OPT_PREVIEW]);
  od->name = SANE_NAME_PREVIEW;
  od->title = SANE_TITLE_PREVIEW;
  od->desc = SANE_DESC_PREVIEW;
  od->size = sizeof (SANE_Word);
  od->cap = SANE_CAP_INACTIVE;
  od->type = SANE_TYPE_BOOL;
  od->constraint_type = SANE_CONSTRAINT_NONE;
  dev->val[OPT_PREVIEW].w = SANE_FALSE;

  /* "Geometry" group: */
  od = &(dev->opt[OPT_GEOMETRY_GROUP]);
  od->name = "";
  od->title = SANE_I18N ("Geometry");
  od->desc = "";
  od->type = SANE_TYPE_GROUP;
  od->cap = SANE_CAP_SOFT_DETECT | SANE_CAP_SOFT_SELECT;
  od->size = 0;
  od->constraint_type = SANE_CONSTRAINT_NONE;
  //

  /* top-left x */
  od = &(dev->opt[OPT_TL_X]);
  od->name = SANE_NAME_SCAN_TL_X;
  od->title = SANE_TITLE_SCAN_TL_X;
  od->desc = SANE_DESC_SCAN_TL_X;
  od->type = SANE_TYPE_INT;
  od->cap = SANE_CAP_INACTIVE;
  od->size = sizeof (SANE_Word);
  od->unit = SANE_UNIT_PIXEL;
  od->constraint_type = SANE_CONSTRAINT_RANGE;
  od->constraint.range = &x_range;
  dev->val[OPT_TL_X].w = 0;

  /* top-left y */
  od = &(dev->opt[OPT_TL_Y]);
  od->name = SANE_NAME_SCAN_TL_Y;
  od->title = SANE_TITLE_SCAN_TL_Y;
  od->desc = SANE_DESC_SCAN_TL_Y;
  od->type = SANE_TYPE_INT;
  od->cap = SANE_CAP_INACTIVE;
  od->size = sizeof (SANE_Word);
  od->unit = SANE_UNIT_PIXEL;
  od->constraint_type = SANE_CONSTRAINT_RANGE;
  od->constraint.range = &y_range;
  dev->val[OPT_TL_Y].w = 0;

  /* bottom-right x */
  od = &(dev->opt[OPT_BR_X]);
  od->name = SANE_NAME_SCAN_BR_X;
  od->title = SANE_TITLE_SCAN_BR_X;
  od->desc = SANE_DESC_SCAN_BR_X;
  od->type = SANE_TYPE_INT;
  od->size = sizeof (SANE_Word);
  od->cap = SANE_CAP_SOFT_DETECT | SANE_CAP_SOFT_SELECT;
  od->unit = SANE_UNIT_PIXEL;
  od->constraint_type = SANE_CONSTRAINT_RANGE;
  od->constraint.range = &x_range;
  dev->val[OPT_BR_X].w = 1654;

  /* bottom-right y */
  od = &(dev->opt[OPT_BR_Y]);
  od->name = SANE_NAME_SCAN_BR_Y;
  od->title = SANE_TITLE_SCAN_BR_Y;
  od->desc = SANE_DESC_SCAN_BR_Y;
  od->type = SANE_TYPE_INT;
  od->size = sizeof (SANE_Word);
  od->cap = SANE_CAP_SOFT_DETECT | SANE_CAP_SOFT_SELECT;
  od->unit = SANE_UNIT_PIXEL;
  od->constraint_type = SANE_CONSTRAINT_RANGE;
  od->constraint.range = &y_range;
  dev->val[OPT_BR_Y].w = 2339;

  return SANE_STATUS_GOOD;
}

/* callback function for sanei_usb_attach_matching_devices
*/
static SANE_Status
attach_one (SANE_String_Const devname)
{
  Lexmark_Device *lexmark_device;

  DBG (2, "attach_one: attachLexmark: devname=%s first_device=%p\n",
       devname, (void *)first_device);

  for (lexmark_device = first_device; lexmark_device;
       lexmark_device = lexmark_device->next){
    /* already attached devices */

    if (strcmp (lexmark_device->sane.name, devname) == 0){
      lexmark_device->missing = SANE_FALSE;
      return SANE_STATUS_GOOD;
    }
  }

  lexmark_device = (Lexmark_Device *) malloc (sizeof (Lexmark_Device));
  if (lexmark_device == NULL)
    return SANE_STATUS_NO_MEM;

  lexmark_device->sane.name = strdup (devname);
  if (lexmark_device->sane.name == NULL)
    return SANE_STATUS_NO_MEM;
  lexmark_device->sane.vendor = "Lexmark";
  lexmark_device->sane.model = "X2600 series";
  lexmark_device->sane.type = "flat bed";

  /* init transfer_buffer */
  lexmark_device->transfer_buffer = malloc (transfer_buffer_size);
  if (lexmark_device->transfer_buffer == NULL)
    return SANE_STATUS_NO_MEM;

  /* Make the pointer to the read buffer null here */
  lexmark_device->read_buffer = malloc (sizeof (Read_Buffer));
  if (lexmark_device->read_buffer == NULL)
    return SANE_STATUS_NO_MEM;

  /* mark device as present */
  lexmark_device->missing = SANE_FALSE;
  lexmark_device->device_cancelled = SANE_FALSE;
  /* insert it a the start of the chained list */
  lexmark_device->next = first_device;
  first_device = lexmark_device;
  num_devices++;
  DBG (2, "    first_device=%p\n", (void *)first_device);

  return SANE_STATUS_GOOD;
}

SANE_Status
scan_devices(void){
  DBG (2, "scan_devices\n");
  SANE_Char config_line[PATH_MAX];
  FILE *fp;
  const char *lp;
  num_devices = 0;

  // -- free existing device we are doning a full re-scan
  while (first_device){
    Lexmark_Device *this_device = first_device;
    first_device = first_device->next;
    DBG (2, "    free first_device\n");
    free(this_device);
  }

  fp = sanei_config_open (LEXMARK_X2600_CONFIG_FILE);
  if (!fp)
    {
      DBG (2, "    No config no prob...(%s)\n", LEXMARK_X2600_CONFIG_FILE);
      return SANE_STATUS_GOOD;
    }
  while (sanei_config_read (config_line, sizeof (config_line), fp))
    {
      if (config_line[0] == '#')
    continue;		/* ignore line comments */

      lp = sanei_config_skip_whitespace (config_line);
      /* skip empty lines */
      if (*lp == 0)
    continue;

      DBG (4, "    attach_matching_devices(%s)\n", config_line);
      sanei_usb_init();
      sanei_usb_attach_matching_devices (config_line, attach_one);
    }

  fclose (fp);
  return SANE_STATUS_GOOD;
}

SANE_Status
sane_init (SANE_Int *version_code, SANE_Auth_Callback authorize)
{
  DBG_INIT ();
  DBG (2, "sane_init: version_code %s 0, authorize %s 0\n",
       version_code == 0 ? "=" : "!=", authorize == 0 ? "=" : "!=");
  DBG (1, "    SANE lexmark_x2600 backend version %d.%d.%d from %s\n",
       SANE_CURRENT_MAJOR, SANE_CURRENT_MINOR, BUILD, PACKAGE_STRING);

  if (version_code)
    *version_code = SANE_VERSION_CODE (SANE_CURRENT_MAJOR, SANE_CURRENT_MINOR, BUILD);


  SANE_Status status = scan_devices();
  initialized = SANE_TRUE;
  return status;
}

SANE_Status
sane_get_devices (const SANE_Device ***device_list, SANE_Bool local_only)
{
  SANE_Int index;
  Lexmark_Device *lexmark_device;

  DBG (2, "sane_get_devices: device_list=%p, local_only=%d num_devices=%d\n",
       (void *) device_list, local_only, num_devices);

  //sanei_usb_scan_devices ();
  SANE_Status status = scan_devices();

  if (devlist)
    free (devlist);

  devlist = malloc ((num_devices + 1) * sizeof (devlist[0]));
  if (!devlist)
    return (SANE_STATUS_NO_MEM);

  index = 0;
  lexmark_device = first_device;
  while (lexmark_device != NULL)
    {
      DBG (2, "    lexmark_device->missing:%d\n",
           lexmark_device->missing);
      if (lexmark_device->missing == SANE_FALSE)
    {

      devlist[index] = &(lexmark_device->sane);
      index++;
    }
      lexmark_device = lexmark_device->next;
    }
  devlist[index] = 0;

  *device_list = devlist;

  return status;
}

SANE_Status
sane_open (SANE_String_Const devicename, SANE_Handle * handle)
{
  Lexmark_Device *lexmark_device;
  SANE_Status status;

  DBG (2, "sane_open: devicename=\"%s\", handle=%p\n", devicename,
       (void *) handle);

  /* walk the linked list of scanner device until there is a match
   * with the device name */
  for (lexmark_device = first_device; lexmark_device;
       lexmark_device = lexmark_device->next)
    {
      DBG (10, "    devname from list: %s\n",
       lexmark_device->sane.name);
      if (strcmp (devicename, "") == 0
      || strcmp (devicename, "lexmark") == 0
      || strcmp (devicename, lexmark_device->sane.name) == 0)
    break;
    }

  *handle = lexmark_device;

  status = init_options (lexmark_device);
  if (status != SANE_STATUS_GOOD)
    return status;

  DBG(2, "    device `%s' opening devnum: '%d'\n",
      lexmark_device->sane.name, lexmark_device->devnum);
  status = sanei_usb_open (lexmark_device->sane.name, &(lexmark_device->devnum));
  if (status != SANE_STATUS_GOOD)
    {
      DBG (1, "     couldn't open device `%s': %s\n",
           lexmark_device->sane.name,
       sane_strstatus (status));
      return status;
    }
  else
    {
      DBG (2, "    device `%s' successfully opened devnum: '%d'\n",
           lexmark_device->sane.name, lexmark_device->devnum);
    }

  return status;
}

const SANE_Option_Descriptor *
sane_get_option_descriptor (SANE_Handle handle, SANE_Int option)
{
  Lexmark_Device *lexmark_device;

  //DBG (2, "sane_get_option_descriptor: handle=%p, option = %d\n",
  //     (void *) handle, option);

  /* Check for valid option number */
  if ((option < 0) || (option >= NUM_OPTIONS))
    return NULL;

  for (lexmark_device = first_device; lexmark_device;
       lexmark_device = lexmark_device->next)
    {
      if (lexmark_device == handle)
    break;
    }

  if (!lexmark_device)
    return NULL;

  if (lexmark_device->opt[option].name)
    {
      //DBG (2, "    name=%s\n",
      //     lexmark_device->opt[option].name);
    }

  return &(lexmark_device->opt[option]);
}

SANE_Status
sane_control_option (SANE_Handle handle, SANE_Int option, SANE_Action action,
                     void * value, SANE_Word * info)
{
  Lexmark_Device *lexmark_device;
  SANE_Status status;
  SANE_Word w;
  SANE_Int res_selected;

  DBG (2, "sane_control_option: handle=%p, opt=%d, act=%d, val=%p, info=%p\n",
       (void *) handle, option, action, (void *) value, (void *) info);

  for (lexmark_device = first_device; lexmark_device;
       lexmark_device = lexmark_device->next){
    if (lexmark_device == handle)
      break;
  }


  if (value == NULL)
    return SANE_STATUS_INVAL;

  switch (action){
  case SANE_ACTION_SET_VALUE:
    if (!SANE_OPTION_IS_SETTABLE (lexmark_device->opt[option].cap)){
      return SANE_STATUS_INVAL;
    }
    /* Make sure boolean values are only TRUE or FALSE */
    if (lexmark_device->opt[option].type == SANE_TYPE_BOOL){
      if (!
          ((*(SANE_Bool *) value == SANE_FALSE)
           || (*(SANE_Bool *) value == SANE_TRUE)))
        return SANE_STATUS_INVAL;
    }

    /* Check range constraints */
    if (lexmark_device->opt[option].constraint_type ==
        SANE_CONSTRAINT_RANGE){
      status =
        sanei_constrain_value (&(lexmark_device->opt[option]), value,
                               info);
      if (status != SANE_STATUS_GOOD){
        DBG (2, "    SANE_CONTROL_OPTION: Bad value for range\n");
        return SANE_STATUS_INVAL;
      }
    }
    switch (option){
    case OPT_NUM_OPTS:
    case OPT_RESOLUTION:
      res_selected = *(SANE_Int *) value;
      // first value is the size of the wordlist!
      for(int i=1; i<dpi_list_size; i++){
        DBG (10, "    posible res=%d selected=%d\n", dpi_list[i], res_selected);
        if(res_selected == dpi_list[i]){
          lexmark_device->val[option].w = *(SANE_Word *) value;
        }
      }
      break;
    case OPT_TL_X:
    case OPT_TL_Y:
    case OPT_BR_X:
    case OPT_BR_Y:
      DBG (2, "    Option value set to %d (%s)\n", *(SANE_Word *) value,
           lexmark_device->opt[option].name);
      lexmark_device->val[option].w = *(SANE_Word *) value;
      if (lexmark_device->val[OPT_TL_X].w >
          lexmark_device->val[OPT_BR_X].w){
        w = lexmark_device->val[OPT_TL_X].w;
        lexmark_device->val[OPT_TL_X].w =
          lexmark_device->val[OPT_BR_X].w;
        lexmark_device->val[OPT_BR_X].w = w;
        if (info)
          *info |= SANE_INFO_RELOAD_PARAMS;
      }
      if (lexmark_device->val[OPT_TL_Y].w >
          lexmark_device->val[OPT_BR_Y].w){
        w = lexmark_device->val[OPT_TL_Y].w;
        lexmark_device->val[OPT_TL_Y].w =
          lexmark_device->val[OPT_BR_Y].w;
        lexmark_device->val[OPT_BR_Y].w = w;
        if (info)
          *info |= SANE_INFO_RELOAD_PARAMS;
      }
      break;
    case OPT_MODE:
      strcpy (lexmark_device->val[option].s, value);
      if (info)
        *info |= SANE_INFO_RELOAD_PARAMS | SANE_INFO_RELOAD_OPTIONS;
      return SANE_STATUS_GOOD;
    }


    if (info != NULL)
      *info |= SANE_INFO_RELOAD_PARAMS;

    break;
  case SANE_ACTION_GET_VALUE:
    switch (option){
    case OPT_NUM_OPTS:
    case OPT_RESOLUTION:
    case OPT_PREVIEW:
    case OPT_TL_X:
    case OPT_TL_Y:
    case OPT_BR_X:
    case OPT_BR_Y:
      *(SANE_Word *) value = lexmark_device->val[option].w;
      //DBG (2, "    Option value = %d (%s)\n", *(SANE_Word *) value,
      //     lexmark_device->opt[option].name);
      break;
    case OPT_MODE:
      strcpy (value, lexmark_device->val[option].s);
      break;
    }
    break;

  default:
    return SANE_STATUS_INVAL;
  }

  return SANE_STATUS_GOOD;
}

SANE_Status
sane_get_parameters (SANE_Handle handle, SANE_Parameters * params)
{
  Lexmark_Device *lexmark_device;
  SANE_Parameters *device_params;
  SANE_Int width_px;

  DBG (2, "sane_get_parameters: handle=%p, params=%p\n", (void *) handle,
       (void *) params);

  for (lexmark_device = first_device; lexmark_device;
       lexmark_device = lexmark_device->next)
    {
      if (lexmark_device == handle)
    break;
    }

  if (!lexmark_device)
    return SANE_STATUS_INVAL;

  // res = lexmark_device->val[OPT_RESOLUTION].w;
  device_params = &(lexmark_device->params);

  width_px =
    lexmark_device->val[OPT_BR_X].w - lexmark_device->val[OPT_TL_X].w;

  /* 24 bit colour = 8 bits/channel for each of the RGB channels */
  device_params->pixels_per_line = width_px;
  device_params->format = SANE_FRAME_RGB; // SANE_FRAME_GRAY
  device_params->depth = 8;
  device_params->bytes_per_line =
    (SANE_Int) (3 * device_params->pixels_per_line);

  if (strcmp (lexmark_device->val[OPT_MODE].s, SANE_VALUE_SCAN_MODE_COLOR)
      != 0)
    {
      device_params->format = SANE_FRAME_GRAY;
      device_params->bytes_per_line =
        (SANE_Int) (device_params->pixels_per_line);
    }

  /* geometry in pixels */
  device_params->last_frame = SANE_TRUE;
  device_params->lines = -1;//lexmark_device->val[OPT_BR_Y].w;

  DBG (2, "    device_params->pixels_per_line=%d\n",
       device_params->pixels_per_line);
  DBG (2, "    device_params->bytes_per_line=%d\n",
       device_params->bytes_per_line);
  DBG (2, "    device_params->depth=%d\n",
       device_params->depth);
  DBG (2, "    device_params->format=%d\n",
       device_params->format);
  DBG (2, "      SANE_FRAME_GRAY: %d\n",
       SANE_FRAME_GRAY);
  DBG (2, "      SANE_FRAME_RGB: %d\n",
       SANE_FRAME_RGB);

  if (params != 0)
    {
      params->format = device_params->format;
      params->last_frame = device_params->last_frame;
      params->lines = device_params->lines;
      params->depth = device_params->depth;
      params->pixels_per_line = device_params->pixels_per_line;
      params->bytes_per_line = device_params->bytes_per_line;
    }
  return SANE_STATUS_GOOD;
}

SANE_Status
sane_start (SANE_Handle handle)
{
  Lexmark_Device * lexmark_device;
  SANE_Status status;
  SANE_Byte * cmd = (SANE_Byte *) malloc
    (command_with_params_block_size * sizeof (SANE_Byte));
  if (cmd == NULL)
    return SANE_STATUS_NO_MEM;

  DBG (2, "sane_start: handle=%p initialized=%d\n", (void *) handle, initialized);

  if (!initialized)
    return SANE_STATUS_INVAL;

  for (lexmark_device = first_device; lexmark_device;
       lexmark_device = lexmark_device->next)
    {
      if (lexmark_device == handle)
    break;
    }

  if(lexmark_device == NULL){
    DBG (2, "    Cannot find device\n");
    free(cmd);
    return SANE_STATUS_IO_ERROR;
  }

  lexmark_device->read_buffer->data = NULL;
  lexmark_device->read_buffer->size = 0;
  lexmark_device->read_buffer->last_line_bytes_read = 0;
  lexmark_device->read_buffer->image_line_no = 0;
  lexmark_device->read_buffer->write_byte_counter = 0;
  lexmark_device->read_buffer->read_byte_counter = 0;
  lexmark_device->eof = SANE_FALSE;
  lexmark_device->device_cancelled = SANE_FALSE;

  //launch scan commands
  status = usb_write_then_read(lexmark_device, command1_block,
                               command1_block_size);
  if (status != SANE_STATUS_GOOD){
    free(cmd);
    return status;
  }
  status = usb_write_then_read(lexmark_device, command2_block,
                               command2_block_size);
  if (status != SANE_STATUS_GOOD){
    free(cmd);
    return status;
  }
  build_packet(lexmark_device, 0x05, cmd);
  status = usb_write_then_read(lexmark_device, cmd,
                               command_with_params_block_size);
  if (status != SANE_STATUS_GOOD){
    free(cmd);
    return status;
  }
  build_packet(lexmark_device, 0x01, cmd);;
  status = usb_write_then_read(lexmark_device, cmd,
                               command_with_params_block_size);
  if (status != SANE_STATUS_GOOD){
    free(cmd);
    return status;
  }

  free(cmd);
  return SANE_STATUS_GOOD;
}


void debug_packet(const SANE_Byte * source, SANE_Int source_size, Debug_Packet dp){
  if(dp == READ){
    DBG (10, "source READ <<<  size=%d\n", source_size);
  }else{
    DBG (10, "source WRITE >>>  size=%d\n", source_size);
  }

  DBG (10, "       %02hhx %02hhx %02hhx %02hhx | %02hhx %02hhx %02hhx %02hhx \n",
       source[0], source[1], source[2], source[3], source[4], source[5], source[6], source[7]);
  DBG (10, "       %02hhx %02hhx %02hhx %02hhx | %02hhx %02hhx %02hhx %02hhx \n",
       source[8], source[9], source[10], source[11], source[12], source[13], source[14], source[15]);
  int debug_offset = 4092;
  if(source_size > debug_offset){
    DBG (10, "       %02hhx %02hhx %02hhx %02hhx | %02hhx %02hhx %02hhx %02hhx \n",
         source[source_size-16-debug_offset],
         source[source_size-15-debug_offset],
         source[source_size-14-debug_offset],
         source[source_size-13-debug_offset],
         source[source_size-12-debug_offset],
         source[source_size-11-debug_offset],
         source[source_size-10-debug_offset],
         source[source_size-9-debug_offset]);
    DBG (10, "       %02hhx %02hhx %02hhx %02hhx | %02hhx %02hhx %02hhx %02hhx \n",
         source[source_size-8-debug_offset],
         source[source_size-7-debug_offset],
         source[source_size-6-debug_offset],
         source[source_size-5-debug_offset],
         source[source_size-4-debug_offset],
         source[source_size-3-debug_offset],
         source[source_size-2-debug_offset],
         source[source_size-1-debug_offset]);
  }
  return;
}

SANE_Status
sane_read (SANE_Handle handle, SANE_Byte * data,
       SANE_Int max_length, SANE_Int * length)
{
  Lexmark_Device * lexmark_device;
  SANE_Status status;
  size_t size = transfer_buffer_size;
  //SANE_Byte buf[size];
  DBG (1, "\n");
  DBG (1, "sane_read max_length=%d:\n", max_length);

  for (lexmark_device = first_device; lexmark_device;
       lexmark_device = lexmark_device->next)
    {
      if (lexmark_device == handle)
    break;
    }

  if (lexmark_device->device_cancelled == SANE_TRUE) {
      DBG (10, "device_cancelled=True \n");
      usb_write_then_read(lexmark_device, command_cancel1_block,
                          command_cancel_size);
      usb_write_then_read(lexmark_device, command_cancel2_block,
                          command_cancel_size);
      usb_write_then_read(lexmark_device, command_cancel1_block,
                          command_cancel_size);
      usb_write_then_read(lexmark_device, command_cancel2_block,
                          command_cancel_size);
      // to empty buffers
      status = sanei_usb_read_bulk (
          lexmark_device->devnum, lexmark_device->transfer_buffer, &size);
      if(status == SANE_STATUS_GOOD){
        status = sanei_usb_read_bulk (
            lexmark_device->devnum, lexmark_device->transfer_buffer, &size);
      }
      if(status == SANE_STATUS_GOOD){
        status = sanei_usb_read_bulk (
            lexmark_device->devnum, lexmark_device->transfer_buffer, &size);
      }

      return status;
  }

  //status = sanei_usb_read_bulk (lexmark_device->devnum, buf, &size);
  if(!lexmark_device->eof){
      DBG (1, "    usb_read\n");
      status = sanei_usb_read_bulk (
          lexmark_device->devnum, lexmark_device->transfer_buffer, &size);
      if (status != SANE_STATUS_GOOD && status != SANE_STATUS_EOF)
        {
          DBG (1, "    USB READ Error in sanei_usb_read_bulk, cannot read devnum=%d status=%d size=%ld\n",
               lexmark_device->devnum, status, size);
          return status;
        }
      DBG (1, "    usb_read done size=%ld\n", size);
      debug_packet(lexmark_device->transfer_buffer, size, READ);
  }else{
    DBG (1, "    no usb_read eof reached\n");
  }

  // is last data packet ?
  if (!lexmark_device->eof && memcmp(last_data_packet, lexmark_device->transfer_buffer, last_data_packet_size) == 0){

    // we may still have data left to send in our buffer device->read_buffer->data
    //length = 0;
    //return SANE_STATUS_EOF;
    lexmark_device->eof = SANE_TRUE;
    DBG (1, "    EOF PACKET no more data from scanner\n");

    return SANE_STATUS_GOOD;
  }
  // cancel packet received?
  if (memcmp(cancel_packet, lexmark_device->transfer_buffer, cancel_packet_size) == 0){
    length = 0;
    return SANE_STATUS_CANCELLED;
  }
  if (memcmp(empty_line_data_packet, lexmark_device->transfer_buffer, empty_line_data_packet_size) == 0){
    return SANE_STATUS_GOOD;
  }
  if (memcmp(unknown_a_data_packet, lexmark_device->transfer_buffer, unknown_a_data_packet_size) == 0){
    return SANE_STATUS_GOOD;
  }
  if (memcmp(unknown_b_data_packet, lexmark_device->transfer_buffer, unknown_b_data_packet_size) == 0){
    return SANE_STATUS_GOOD;
  }
  if (memcmp(unknown_c_data_packet, lexmark_device->transfer_buffer, unknown_c_data_packet_size) == 0){
    return SANE_STATUS_GOOD;
  }
  if (memcmp(unknown_d_data_packet, lexmark_device->transfer_buffer, unknown_d_data_packet_size) == 0){
    return SANE_STATUS_GOOD;
  }
  if (memcmp(unknown_e_data_packet, lexmark_device->transfer_buffer, unknown_e_data_packet_size) == 0){
    return SANE_STATUS_GOOD;
  }

  status = clean_and_copy_data(
      lexmark_device->transfer_buffer,
      size,
      data,
      length,
      lexmark_device->params.format,
      max_length,
      handle);

  return status;
}

SANE_Status
sane_set_io_mode (SANE_Handle handle, SANE_Bool non_blocking)
{
  DBG (2, "sane_set_io_mode: handle = %p, non_blocking = %d\n",
       (void *) handle, non_blocking);

  if (non_blocking)
    return SANE_STATUS_UNSUPPORTED;

  return SANE_STATUS_GOOD;
}

SANE_Status
sane_get_select_fd (SANE_Handle handle, SANE_Int * fd)
{
  DBG (2, "sane_get_select_fd: handle = %p, fd %s 0\n", (void *) handle,
       fd ? "!=" : "=");

  return SANE_STATUS_UNSUPPORTED;
}

void
sane_cancel (SANE_Handle handle)
{
  Lexmark_Device * lexmark_device;

  DBG (2, "sane_cancel: handle = %p\n", (void *) handle);

  for (lexmark_device = first_device; lexmark_device;
       lexmark_device = lexmark_device->next)
    {
      if (lexmark_device == handle)
    break;
    }
  sanei_usb_reset (lexmark_device->devnum);
  lexmark_device->device_cancelled = SANE_TRUE;
}

void
sane_close (SANE_Handle handle)
{
  Lexmark_Device * lexmark_device;

  DBG (2, "sane_close: handle=%p\n", (void *) handle);

  for (lexmark_device = first_device; lexmark_device;
       lexmark_device = lexmark_device->next)
    {
      if (lexmark_device == handle)
    break;
    }

  sanei_usb_close (lexmark_device->devnum);
}

void
sane_exit (void)
{
  Lexmark_Device *lexmark_device, *next_lexmark_device;

  DBG (2, "sane_exit\n");

  if (!initialized)
    return;

  for (lexmark_device = first_device; lexmark_device;
       lexmark_device = next_lexmark_device)
    {
      next_lexmark_device = lexmark_device->next;
      free (lexmark_device->transfer_buffer);
      free (lexmark_device->read_buffer);
      free (lexmark_device);
    }

  if (devlist)
    free (devlist);

  sanei_usb_exit();
  initialized = SANE_FALSE;

}