#include "JPEGLoader.h"

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

#include <jpeglib.h>
#include <jerror.h>

#include "ifilesystem.h"

#include "stream/ScopedArchiveBuffer.h"
#include "RGBAImage.h"

typedef unsigned char byte;

/* Expanded data source object for stdio input */

typedef struct {
    struct jpeg_source_mgr pub;	/* public fields */

    int src_size;
    JOCTET* src_buffer;

    JOCTET* buffer;		/* start of buffer */
    boolean start_of_file;	/* have we gotten any data yet? */
} my_source_mgr;

typedef my_source_mgr* my_src_ptr;

#define INPUT_BUF_SIZE  4096	/* choose an efficiently fread'able size */


/*
 * Initialize source --- called by jpeg_read_header
 * before any data is actually read.
 */

static void my_init_source(j_decompress_ptr cinfo)
{
    my_src_ptr src = (my_src_ptr)cinfo->src;

    /* We reset the empty-input-file flag for each image,
     * but we don't clear the input buffer.
     * This is correct behavior for reading a series of images from one source.
     */
    src->start_of_file = TRUE;
}


/*
 * Fill the input buffer --- called whenever buffer is emptied.
 *
 * In typical applications, this should read fresh data into the buffer
 * (ignoring the current state of next_input_byte & bytes_in_buffer),
 * reset the pointer & count to the start of the buffer, and return TRUE
 * indicating that the buffer has been reloaded.  It is not necessary to
 * fill the buffer entirely, only to obtain at least one more byte.
 *
 * There is no such thing as an EOF return.  If the end of the file has been
 * reached, the routine has a choice of ERREXIT() or inserting fake data into
 * the buffer.  In most cases, generating a warning message and inserting a
 * fake EOI marker is the best course of action --- this will allow the
 * decompressor to output however much of the image is there.  However,
 * the resulting error message is misleading if the real problem is an empty
 * input file, so we handle that case specially.
 *
 * In applications that need to be able to suspend compression due to input
 * not being available yet, a FALSE return indicates that no more data can be
 * obtained right now, but more may be forthcoming later.  In this situation,
 * the decompressor will return to its caller (with an indication of the
 * number of scanlines it has read, if any).  The application should resume
 * decompression after it has loaded more data into the input buffer.  Note
 * that there are substantial restrictions on the use of suspension --- see
 * the documentation.
 *
 * When suspending, the decompressor will back up to a convenient restart point
 * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
 * indicate where the restart point will be if the current call returns FALSE.
 * Data beyond this point must be rescanned after resumption, so move it to
 * the front of the buffer rather than discarding it.
 */

static boolean my_fill_input_buffer(j_decompress_ptr cinfo)
{
    my_src_ptr src = (my_src_ptr)cinfo->src;
    size_t nbytes;

    if (src->src_size > INPUT_BUF_SIZE)
        nbytes = INPUT_BUF_SIZE;
    else
        nbytes = src->src_size;

    memcpy(src->buffer, src->src_buffer, nbytes);
    src->src_buffer += nbytes;
    src->src_size -= static_cast<int>(nbytes);

    if (nbytes <= 0) {
        if (src->start_of_file)	/* Treat empty input file as fatal error */
            ERREXIT(cinfo, JERR_INPUT_EMPTY);
        WARNMS(cinfo, JWRN_JPEG_EOF);
        /* Insert a fake EOI marker */
        src->buffer[0] = (JOCTET)0xFF;
        src->buffer[1] = (JOCTET)JPEG_EOI;
        nbytes = 2;
    }

    src->pub.next_input_byte = src->buffer;
    src->pub.bytes_in_buffer = nbytes;
    src->start_of_file = FALSE;

    return TRUE;
}


/*
 * Skip data --- used to skip over a potentially large amount of
 * uninteresting data (such as an APPn marker).
 *
 * Writers of suspendable-input applications must note that skip_input_data
 * is not granted the right to give a suspension return.  If the skip extends
 * beyond the data currently in the buffer, the buffer can be marked empty so
 * that the next read will cause a fill_input_buffer call that can suspend.
 * Arranging for additional bytes to be discarded before reloading the input
 * buffer is the application writer's problem.
 */

static void my_skip_input_data(j_decompress_ptr cinfo, long num_bytes)
{
    my_src_ptr src = (my_src_ptr)cinfo->src;

    /* Just a dumb implementation for now.  Could use fseek() except
     * it doesn't work on pipes.  Not clear that being smart is worth
     * any trouble anyway --- large skips are infrequent.
     */
    if (num_bytes > 0) {
        while (num_bytes > (long)src->pub.bytes_in_buffer) {
            num_bytes -= (long)src->pub.bytes_in_buffer;
            (void)my_fill_input_buffer(cinfo);
            /* note we assume that fill_input_buffer will never return FALSE,
             * so suspension need not be handled.
             */
        }
        src->pub.next_input_byte += (size_t)num_bytes;
        src->pub.bytes_in_buffer -= (size_t)num_bytes;
    }
}


/*
 * An additional method that can be provided by data source modules is the
 * resync_to_restart method for error recovery in the presence of RST markers.
 * For the moment, this source module just uses the default resync method
 * provided by the JPEG library.  That method assumes that no backtracking
 * is possible.
 */


 /*
  * Terminate source --- called by jpeg_finish_decompress
  * after all data has been read.  Often a no-op.
  *
  * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
  * application must deal with any cleanup that should happen even
  * for error exit.
  */

static void my_term_source(j_decompress_ptr cinfo)
{
    /* no work necessary here */
}


/*
 * Prepare for input from a stdio stream.
 * The caller must have already opened the stream, and is responsible
 * for closing it after finishing decompression.
 */

static void jpeg_buffer_src(j_decompress_ptr cinfo, void* buffer, int bufsize)
{
    my_src_ptr src;

    /* The source object and input buffer are made permanent so that a series
     * of JPEG images can be read from the same file by calling jpeg_stdio_src
     * only before the first one.  (If we discarded the buffer at the end of
     * one image, we'd likely lose the start of the next one.)
     * This makes it unsafe to use this manager and a different source
     * manager serially with the same JPEG object.  Caveat programmer.
     */
    if (cinfo->src == NULL) {	/* first time for this JPEG object? */
        cinfo->src = (struct jpeg_source_mgr*)
            (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT,
                sizeof(my_source_mgr));
        src = (my_src_ptr)cinfo->src;
        src->buffer = (JOCTET*)
            (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_PERMANENT,
                INPUT_BUF_SIZE * sizeof(JOCTET));
    }

    src = (my_src_ptr)cinfo->src;
    src->pub.init_source = my_init_source;
    src->pub.fill_input_buffer = my_fill_input_buffer;
    src->pub.skip_input_data = my_skip_input_data;
    src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
    src->pub.term_source = my_term_source;
    src->src_buffer = (JOCTET*)buffer;
    src->src_size = bufsize;
    src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
    src->pub.next_input_byte = NULL; /* until buffer loaded */
}

// =============================================================================

static char errormsg[JMSG_LENGTH_MAX];

typedef struct my_jpeg_error_mgr
{
    struct jpeg_error_mgr pub;  // "public" fields
    jmp_buf setjmp_buffer;      // for return to caller
} bt_jpeg_error_mgr;

static void my_jpeg_error_exit(j_common_ptr cinfo)
{
    my_jpeg_error_mgr* myerr = (bt_jpeg_error_mgr*)cinfo->err;

    (*cinfo->err->format_message) (cinfo, errormsg);

    longjmp(myerr->setjmp_buffer, 1);
}

// stash a scanline
static void j_putRGBScanline(unsigned char* jpegline, int widthPix, unsigned char* outBuf, int row)
{
    int offset = row * widthPix * 4;
    int count;

    for (count = 0; count < widthPix; count++)
    {
        unsigned char iRed, iBlu, iGrn;
        unsigned char* oRed, * oBlu, * oGrn, * oAlp;

        iRed = *(jpegline + count * 3 + 0);
        iGrn = *(jpegline + count * 3 + 1);
        iBlu = *(jpegline + count * 3 + 2);

        oRed = outBuf + offset + count * 4 + 0;
        oGrn = outBuf + offset + count * 4 + 1;
        oBlu = outBuf + offset + count * 4 + 2;
        oAlp = outBuf + offset + count * 4 + 3;

        *oRed = iRed;
        *oGrn = iGrn;
        *oBlu = iBlu;
        *oAlp = 255;
    }
}

// stash a scanline
static void j_putRGBAScanline(unsigned char* jpegline, int widthPix, unsigned char* outBuf, int row)
{
    int offset = row * widthPix * 4;
    int count;

    for (count = 0; count < widthPix; count++)
    {
        unsigned char iRed, iBlu, iGrn, iAlp;
        unsigned char* oRed, * oBlu, * oGrn, * oAlp;

        iRed = *(jpegline + count * 4 + 0);
        iGrn = *(jpegline + count * 4 + 1);
        iBlu = *(jpegline + count * 4 + 2);
        iAlp = *(jpegline + count * 4 + 3);

        oRed = outBuf + offset + count * 4 + 0;
        oGrn = outBuf + offset + count * 4 + 1;
        oBlu = outBuf + offset + count * 4 + 2;
        oAlp = outBuf + offset + count * 4 + 3;

        *oRed = iRed;
        *oGrn = iGrn;
        *oBlu = iBlu;

        //!\todo fix jpeglib, it leaves alpha channel uninitialised
#if 1
        iAlp = 255;
#endif
        *oAlp = iAlp;
    }
}

// stash a gray scanline
static void j_putGrayScanlineToRGB(unsigned char* jpegline, int widthPix, unsigned char* outBuf, int row)
{
    int offset = row * widthPix * 4;
    int count;

    for (count = 0; count < widthPix; count++)
    {
        unsigned char iGray;
        unsigned char* oRed, * oBlu, * oGrn, * oAlp;

        // get our grayscale value
        iGray = *(jpegline + count);

        oRed = outBuf + offset + count * 4;
        oGrn = outBuf + offset + count * 4 + 1;
        oBlu = outBuf + offset + count * 4 + 2;
        oAlp = outBuf + offset + count * 4 + 3;

        *oRed = iGray;
        *oGrn = iGray;
        *oBlu = iGray;
        *oAlp = 255;
    }
}

static image::RGBAImagePtr LoadJPGBuff_(const void* src_buffer, int src_size)
{
    struct jpeg_decompress_struct cinfo;
    struct my_jpeg_error_mgr jerr;

    cinfo.err = jpeg_std_error(&jerr.pub);
    jerr.pub.error_exit = my_jpeg_error_exit;

    if (setjmp(jerr.setjmp_buffer)) //< TODO: use c++ exceptions instead of setjmp/longjmp to handle errors
    {
        rError() << "WARNING: JPEG library error: " << errormsg << "\n";
        jpeg_destroy_decompress(&cinfo);
        return {};
    }

    jpeg_create_decompress(&cinfo);
    jpeg_buffer_src(&cinfo, const_cast<void*>(src_buffer), src_size);
    jpeg_read_header(&cinfo, TRUE);
    jpeg_start_decompress(&cinfo);

    int row_stride = cinfo.output_width * cinfo.output_components;

    image::RGBAImagePtr image(new image::RGBAImage(cinfo.output_width, cinfo.output_height));

    JSAMPARRAY buffer = (*cinfo.mem->alloc_sarray) ((j_common_ptr)&cinfo, JPOOL_IMAGE, row_stride, 1);

    while (cinfo.output_scanline < cinfo.output_height)
    {
        jpeg_read_scanlines(&cinfo, buffer, 1);

        if (cinfo.out_color_components == 4)
            j_putRGBAScanline(buffer[0], cinfo.output_width, image->getPixels(), cinfo.output_scanline - 1);
        else if (cinfo.out_color_components == 3)
            j_putRGBScanline(buffer[0], cinfo.output_width, image->getPixels(), cinfo.output_scanline - 1);
        else if (cinfo.out_color_components == 1)
            j_putGrayScanlineToRGB(buffer[0], cinfo.output_width, image->getPixels(), cinfo.output_scanline - 1);
    }

    jpeg_finish_decompress(&cinfo);
    jpeg_destroy_decompress(&cinfo);

    return image;
}

namespace image
{

ImagePtr JPEGLoader::load(ArchiveFile& file) const
{
    archive::ScopedArchiveBuffer buffer(file);
    return LoadJPGBuff_(buffer.buffer, static_cast<int>(buffer.length));
}

ImageTypeLoader::Extensions JPEGLoader::getExtensions() const
{
    Extensions extensions;
    extensions.push_back("jpg");
    extensions.push_back("jpeg");
    return extensions;
}

}
