/*
    This file is part of "scramble", a filter plugin for Adobe Photoshop
    Copyright (C) 2006-9 Toby Thain, toby@telegraphics.com.au

    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, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#include "world.h"

#include <stdlib.h>

#include "scramble.h"

OSErr process(FilterRecordPtr pb, struct params *p){
	long t, ticks = TICKCOUNT();
	int j,
		ncols = pb->outRect.right - pb->outRect.left,
		nrows = pb->outRect.bottom - pb->outRect.top,
		htiles, vtiles;
	unsigned long ntiles, dst, src;

	if(!p || p->tilew <= 0 || p->tilew > ncols
	      || p->tileh <= 0 || p->tileh > nrows){
		//dbg("bad tile size");
		return filterBadParameters;
	}else{
		char *buf = malloc(p->tilew*pb->planes), *out = pb->outData;
		htiles = ncols/p->tilew;
		vtiles = nrows/p->tileh;
		ntiles = htiles*vtiles;

		srand(ticks);

		// loop through each tile of the image, top to bottom, left to right
		for(dst = 0; dst < ntiles; ++dst){
			int strip = p->tilew*pb->planes;
			// pick a random tile to swap with
			// FIXME: this produces visibly poor results if using Windows'
			//        15-bit RNG and relatively large tile counts.
			src = dst + (unsigned long)rand() % (ntiles-dst);

			if(src != dst){
				int srccol = p->tilew*(src % htiles), srcrow = p->tileh*(src / htiles),
				    dstcol = p->tilew*(dst % htiles), dstrow = p->tileh*(dst / htiles);
				// swap tile
				for(j = p->tileh; j--;){
					// move source tile to our current tile
					memcpy(buf, out + pb->outRowBytes*(dstrow+j) + dstcol*pb->planes, strip);
					memcpy(out + pb->outRowBytes*(dstrow+j) + dstcol*pb->planes,
						   out + pb->outRowBytes*(srcrow+j) + srccol*pb->planes, strip);
					// copy the original current tile where the source came from
					memcpy(out + pb->outRowBytes*(srcrow+j) + srccol*pb->planes, buf, strip);
				}
			}

			if((t = TICKCOUNT()) > ticks){
				ticks = t + TICKS_SEC/4; /* check every 1/4 sec */
				/* allow user to cancel */
				if (pb->abortProc())
					return userCanceledErr;
				else /* report progress */
					pb->progressProc(dst, ntiles);
			}
		}

		free(buf);
	}

	return noErr;
}