/*
 * Based on example code found in the libjpeg archive
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif /* HAVE_CONFIG_H */

#ifdef HAVE_JPEGLIB

#include <stdio.h>
#include <setjmp.h>
#include <string.h>
#include <stdlib.h>

/* This define is also used in the public jpeglib headers. Ugh.*/
#undef HAVE_STDLIB_H


/* The geniuses that made the libjpeg forgot to add this wrapper
   around the header file. */
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
#include <jpeglib.h>
#ifdef __cplusplus
}
#endif

#include "simage_jpeg_reader.icc"
#include "simage_jpeg_writer.icc"


#define ERR_NO_ERROR      0
#define ERR_OPEN          1
#define ERR_MEM           2
#define ERR_JPEGLIB       3
#define ERR_OPEN_WRITE    4
#define ERR_JPEGLIB_WRITE 5

static int jpegerror = ERR_NO_ERROR;

int
simage_jpeg_error(char * buffer, int buflen)
{
  switch (jpegerror) {
  case ERR_OPEN:
    strncpy(buffer, "JPEG loader: Error opening file", buflen);
    break;
  case ERR_MEM:
    strncpy(buffer, "JPEG loader: Out of memory error", buflen);
    break;
  case ERR_JPEGLIB:
    strncpy(buffer, "JPEG loader: Illegal jpeg file", buflen);
    break;
  case ERR_OPEN_WRITE:
    strncpy(buffer, "JPEG saver: Error opening file", buflen);
    break;
  case ERR_JPEGLIB_WRITE:
    strncpy(buffer, "JPEG saver: Internal libjpeg error", buflen);    
    break;
  }
  return jpegerror;
}

struct my_error_mgr {
  struct jpeg_error_mgr pub;    /* "public" fields */

  jmp_buf setjmp_buffer;        /* for return to caller */
};


typedef struct my_error_mgr * my_error_ptr;

static void 
my_error_exit (j_common_ptr cinfo)
{
  /* cinfo->err really points to a my_error_mgr struct, so coerce pointer */
  my_error_ptr myerr = (my_error_ptr) cinfo->err;

  /* Always display the message. */
  /* We could postpone this until after returning, if we chose. */
  /*(*cinfo->err->output_message) (cinfo);*/

  /* FIXME: get error messahe from jpeglib */

  /* Return control to the setjmp point */
  longjmp(myerr->setjmp_buffer, 1);
}

int 
simage_jpeg_identify(const char * ptr,
		     const unsigned char *header,
		     int headerlen)
{
  static unsigned char jpgcmp[] = {'J', 'F', 'I', 'F' };
  static unsigned char jpgcmp2[] = {'E', 'x', 'i', 'f' };
  if (headerlen < 10) return 0;
  if (memcmp((const void*)&header[6], 
	     (const void*)jpgcmp, 4) == 0) return 1;
  if (memcmp((const void*)&header[6], 
	     (const void*)jpgcmp2, 4) == 0) return 1;
  return 0;
}


static unsigned char*
copyScanline(unsigned char *currPtr, unsigned char *from, int cnt)
{
  memcpy((void*)currPtr, (void*)from, cnt);
  currPtr -= cnt;
  return currPtr;
}

unsigned char *
simage_jpeg_load(const char *filename,
		 int *width_ret,
		 int *height_ret,
		 int *numComponents_ret)
{
  int width;
  int height;
  unsigned char *currPtr;
  int format;
  unsigned char *buffer;
  /* This struct contains the JPEG decompression parameters and pointers to
   * working space (which is allocated as needed by the JPEG library).
   */
  struct jpeg_decompress_struct cinfo;
  /* We use our private extension JPEG error handler.
   * Note that this struct must live as long as the main JPEG parameter
   * struct, to avoid dangling-pointer problems.
   */
  struct my_error_mgr jerr;
  /* More stuff */
  FILE * infile;                /* source file */
  JSAMPARRAY rowbuffer;            /* Output row buffer */
  int row_stride;               /* physical row width in output buffer */

  jpegerror = ERR_NO_ERROR;

  /* In this example we want to open the input file before doing anything else,
   * so that the setjmp() error recovery below can assume the file is open.
   * VERY IMPORTANT: use "b" option to fopen() if you are on a machine that
   * requires it in order to read binary files.
   */

  if ((infile = fopen(filename, "rb")) == NULL) {
    jpegerror = ERR_OPEN;
    return NULL;
  }

  /* Step 1: allocate and initialize JPEG decompression object */

  buffer = NULL;

  /* We set up the normal JPEG error routines, then override error_exit. */
  cinfo.err = jpeg_std_error(&jerr.pub);
  jerr.pub.error_exit = my_error_exit;
  /* Establish the setjmp return context for my_error_exit to use. */
  if (setjmp(jerr.setjmp_buffer)) {
    /* If we get here, the JPEG code has signaled an error.
     * We need to clean up the JPEG object, close the input file, and return.
     */
    jpegerror = ERR_JPEGLIB;
    jpeg_destroy_decompress(&cinfo);
    fclose(infile);
    if (buffer) free(buffer);
    return NULL;
  }
  /* Now we can initialize the JPEG decompression object. */
  jpeg_create_decompress(&cinfo);

  /* Step 2: specify data source */

  simage_jpeg_src_init(&cinfo, infile);

  /* Step 3: read file parameters with jpeg_read_header() */

  (void) jpeg_read_header(&cinfo, TRUE);
  /* We can ignore the return value from jpeg_read_header since
   *   (a) suspension is not possible with the stdio data source, and
   *   (b) we passed TRUE to reject a tables-only JPEG file as an error.
   * See libjpeg.doc for more info.
   */

  /* Step 4: set parameters for decompression */
  /* In this example, we don't need to change any of the defaults set by
   * jpeg_read_header(), so we do nothing here.
   */

  /* Step 5: Start decompressor */
  if (cinfo.jpeg_color_space == JCS_GRAYSCALE) {
    format = 1;
    cinfo.out_color_space = JCS_GRAYSCALE;
  }
  else { /* use rgb */
    format = 3;
    cinfo.out_color_space = JCS_RGB;
  }
  
  (void) jpeg_start_decompress(&cinfo);
  /* We can ignore the return value since suspension is not possible
   * with the stdio data source.
   */

  /* We may need to do some setup of our own at this point before reading
   * the data.  After jpeg_start_decompress() we have the correct scaled
   * output image dimensions available, as well as the output colormap
   * if we asked for color quantization.
   * In this example, we need to make an output work buffer of the right size.
   */
  /* JSAMPLEs per row in output buffer */
  row_stride = cinfo.output_width * cinfo.output_components;
  /* Make a one-row-high sample array that will go away when done with image */
  rowbuffer = (*cinfo.mem->alloc_sarray)
    ((j_common_ptr) &cinfo, JPOOL_IMAGE, row_stride, 1);
  width = cinfo.output_width;
  height = cinfo.output_height;
  buffer = currPtr = (unsigned char*) 
    malloc(width*height*cinfo.output_components);
  
  /* Step 6: while (scan lines remain to be read) */
  /*           jpeg_read_scanlines(...); */

  /* Here we use the library's state variable cinfo.output_scanline as the
   * loop counter, so that we don't have to keep track ourselves.
   */
  
  /* flip image upside down */
  if (buffer) {
    currPtr = buffer + row_stride * (cinfo.output_height-1);  
    
    while (cinfo.output_scanline < cinfo.output_height) {
      /* jpeg_read_scanlines expects an array of pointers to scanlines.
       * Here the array is only one element long, but you could ask for
       * more than one scanline at a time if that's more convenient.
       */
      (void) jpeg_read_scanlines(&cinfo, rowbuffer, 1);
      /* Assume put_scanline_someplace wants a pointer and sample count. */
      currPtr = copyScanline(currPtr, rowbuffer[0], row_stride);
    }
  }
  /* Step 7: Finish decompression */

  (void) jpeg_finish_decompress(&cinfo);
  /* We can ignore the return value since suspension is not possible
   * with the stdio data source.
   */

  /* Step 8: Release JPEG decompression object */

  /* This is an important step since it will release a good deal of memory. */
  jpeg_destroy_decompress(&cinfo);

  /* After finish_decompress, we can close the input file.
   * Here we postpone it until after no more JPEG errors are possible,
   * so as to simplify the setjmp error logic above.  (Actually, I don't
   * think that jpeg_destroy can do an error exit, but why assume anything...)
   */
  fclose(infile);

  /* At this point you may want to check to see whether any corrupt-data
   * warnings occurred (test whether jerr.pub.num_warnings is nonzero).
   */

  /* And we're done! */
  if (buffer) {
    *width_ret = width;
    *height_ret = height;
    *numComponents_ret = format;
  }
  else {
    jpegerror = ERR_MEM;
  }
  return buffer;
}

int 
simage_jpeg_save(const char * filename,
                 const unsigned char * bytes,
                 int width,
                 int height,
                 int numcomponents)
{
  /* This struct contains the JPEG compression parameters and pointers to
   * working space (which is allocated as needed by the JPEG library).
   * It is possible to have several such structures, representing multiple
   * compression/decompression processes, in existence at once.  We refer
   * to any one struct (and its associated working data) as a "JPEG object".
   */
  struct jpeg_compress_struct cinfo;

  /* We use our private extension JPEG error handler.
   * Note that this struct must live as long as the main JPEG parameter
   * struct, to avoid dangling-pointer problems.
   */
  struct my_error_mgr jerr;

  /* More stuff */
  FILE * outfile;               /* target file */
  JSAMPROW row_pointer[1];      /* pointer to JSAMPLE row[s] */

  int quality;
  unsigned char * tmpbytes;
  int bytesperrow;
  
  quality = 90;
  tmpbytes = NULL;

  /* Step 1: allocate and initialize JPEG compression object */

  /* We have to set up the error handler first, in case the initialization
   * step fails.  (Unlikely, but it could happen if you are out of memory.)
   * This routine fills in the contents of struct jerr, and returns jerr's
   * address which we place into the link field in cinfo.
   */
  cinfo.err = jpeg_std_error(&jerr.pub);
  /* Now we can initialize the JPEG compression object. */
  jpeg_create_compress(&cinfo);

  /* Step 2: specify data destination (eg, a file) */
  /* Note: steps 2 and 3 can be done in either order. */

  /* Here we use the library-supplied code to send compressed data to a
   * stdio stream.  You can also write your own code to do something else.
   * VERY IMPORTANT: use "b" option to fopen() if you are on a machine that
   * requires it in order to write binary files.
   */

  if ((outfile = fopen(filename, "wb")) == NULL) {
    /* FIXME: should store error message somewhere for the client app
       to read. 20020820 mortene. */
    /*fprintf(stderr, "can't open %s for writing\n", filename);*/
    jpeg_destroy_compress(&cinfo);
    jpegerror = ERR_OPEN_WRITE;
    return 0;
  }

  /* We set up the normal JPEG error routines, then override error_exit. */
  cinfo.err = jpeg_std_error(&jerr.pub);
  jerr.pub.error_exit = my_error_exit;
  /* Establish the setjmp return context for my_error_exit to use. */
  if (setjmp(jerr.setjmp_buffer)) {
    /* If we get here, the JPEG code has signaled an error.
     * We need to clean up the JPEG object, close the input file, and return.
     */
    jpeg_destroy_compress(&cinfo);
    fclose(outfile);
    if (tmpbytes) free(tmpbytes);
    jpegerror = ERR_JPEGLIB_WRITE;
    return 0;
  }

  simage_jpeg_dest_init(&cinfo, outfile);


  /*
   * alpha channel is not supported for jpeg. strip it.
   */
  
  if (numcomponents == 4) {
    unsigned char * dst;
    const unsigned char * src;
    int i, n = width * height;
    dst = tmpbytes = (unsigned char *) malloc(n*3);
    src = bytes;
    for (i = 0; i < n; i++) {
      *dst++ = *src++; 
      *dst++ = *src++; 
      *dst++ = *src++;
      src++;
    }
    numcomponents = 3;
  }
  else if (numcomponents == 2) {
    unsigned char * dst;
    const unsigned char * src;
    int i, n = width * height;
    dst = tmpbytes = (unsigned char *) malloc(n*3);
    src = bytes;
    for (i = 0; i < n; i++) {
      *dst++ = *src++; 
      src++;
    }
    numcomponents = 1;
  }

  /* Step 3: set parameters for compression */

  /* First we supply a description of the input image.
   * Four fields of the cinfo struct must be filled in:
   */
   
  cinfo.image_width = width;         /* image width and height, in pixels */
  cinfo.image_height = height;
  cinfo.input_components = numcomponents;  /* # of color components per pixel */
  cinfo.in_color_space = numcomponents == 3 ? JCS_RGB : JCS_GRAYSCALE;  /* colorspace of input image */
  /* Now use the library's routine to set default compression parameters.
   * (You must set at least cinfo.in_color_space before calling this,
   * since the defaults depend on the source color space.)
   */
  jpeg_set_defaults(&cinfo);
  /* Now you can set any non-default parameters you wish to.
   * Here we just illustrate the use of quality (quantization table) scaling:
   */
  jpeg_set_quality(&cinfo, quality, TRUE /* limit to baseline-JPEG values */);

  /* Step 4: Start compressor */

  /* TRUE ensures that we will write a complete interchange-JPEG file.
   * Pass TRUE unless you are very sure of what you're doing.
   */
  jpeg_start_compress(&cinfo, TRUE);

  /* Step 5: while (scan lines remain to be written) */
  /*           jpeg_write_scanlines(...); */

  /* Here we use the library's state variable cinfo.next_scanline as the
   * loop counter, so that we don't have to keep track ourselves.
   * To keep things simple, we pass one scanline per call; you can pass
   * more if you wish, though.
   */

  bytesperrow = width * numcomponents;
  if (tmpbytes) bytes = tmpbytes; /* more convenient */

  while (cinfo.next_scanline < cinfo.image_height) {
    /* jpeg_write_scanlines expects an array of pointers to scanlines.
     * Here the array is only one element long, but you could pass
     * more than one scanline at a time if that's more convenient.
     */
    row_pointer[0] = (JSAMPROW) bytes + bytesperrow * (height-cinfo.next_scanline-1);
    (void) jpeg_write_scanlines(&cinfo, row_pointer, 1);
  }
  if (tmpbytes) free(tmpbytes);

  /* Step 6: Finish compression */

  jpeg_finish_compress(&cinfo);

  /* Step 7: release JPEG compression object */

  /* This is an important step since it will release a good deal of memory. */
  jpeg_destroy_compress(&cinfo);

  /* After finish_compress, we can close the output file. */
  fclose(outfile);

  /* And we're done! */
  return 1;
}

#endif /* HAVE_JPEGLIB */