/*********

Order1 SB : context-code MSB position like order1+1 ,
	then code residual bits.

	(o1_sb is good on 'circles' and golf data;
	competitive with bitplane and order2)

S+P (512) Lossless :

			Lena	Zelda	Kuha	Checa(256)
Order1 	:	4.250	3.948	3.534	3.406
Order1+1:	4.207	3.911	3.517	3.310
Order1sb:	4.216	3.920	3.510	3.305

We seem to beat 1+1 on the very-compressible files, while
we lose on the less compressible files (though this is not
a uniform trend; for example we have identical performance
on Barbara at 4.678 bpp)

SB seams to always beat 1+1 slightly on non-lossless packing,
but this is a moot point because BitPlane stomps them both
for lossy; (bitplane is behind even plain order1 for lossless;
very strange)

(bitplane on the lossy and order1+1 on the deltas is the best
for lossy+delta , but that's again moot because S+P stomps
on lossy+delta).

**********/

#include <stdio.h>
#include <stdlib.h>
#include <crblib/inc.h>
#include <crblib/arithc.h>
#include <crblib/scontext.h>
#include <crblib/intmath.h>

extern int tune_param;

#define ORDER1_TOTMAX		10000
#define ORDER1_INC			30
#define ORDER1_RAWS			2
#define ORDER1_ALPHABET		(16 + ORDER1_RAWS)	/** # of bits **/

#define CN_MAX_PREV			4
#define CN_MAX_PARENT		4
#define CODE_CONTEXTS 		(1 + CN_MAX_PREV + (CN_MAX_PREV+1)*CN_MAX_PARENT)

#define ORDER0_TOTMAX		16000	/** totally irrelevant **/
#define ORDER0_ALPHABET		2		/** binary **/
#define ORDER0_INC			10

// #define CODER_ADAPT	/** doesn't help **/

#include "coder.h"

void coderO1_SB_encodeBand(coder *me,int *band,int w,int h,int fullw,int *parent);
void coderO1_SB_decodeBand(coder *me,int *band,int w,int h,int fullw,int *parent);

typedef struct {
	scontext * o0;
	scontext * sign_sc[3];
	scontext ** o1;
	arithInfo *ari;
} myInfo;

void coderO1_SB_init(coder *c)
{
myInfo *d;
int i;

	if ( (d = new(myInfo)) == NULL )
		errexit("ozero init failed");

	c->data = d;
	d->ari = c->arith;

	if ( (d->o0 = scontextCreate(c->arith,ORDER0_ALPHABET,0,
			ORDER0_TOTMAX,ORDER0_INC,true)) == NULL )
		errexit("ozero init failed");

	for(i=0;i<3;i++) {
		if ( (d->sign_sc[i] = scontextCreate(c->arith,2,0,1000,10,true)) == NULL )
			errexit("sign ozero init failed");
	}

	if ( (d->o1 = newarray(void *,CODE_CONTEXTS)) == NULL )
		errexit("Order1_Init failed!");

	for(i=0;i<CODE_CONTEXTS;i++) {
		if ( (d->o1[i] = scontextCreate(c->arith,ORDER1_ALPHABET,0,
				ORDER1_TOTMAX,ORDER1_INC,true)) == NULL )
			errexit("context creation failed!");
	}
}

void coderO1_SB_free(coder *c)
{
	if ( c->data ) {
		myInfo *d; int i;

		d = c->data;
		if ( d->o0 ) scontextFree(d->o0);
		for(i=0;i<3;i++) {
			if ( d->sign_sc[i] ) scontextFree(d->sign_sc[i]);
		}
		if ( d->o1 ) {
			for(i=0;i<CODE_CONTEXTS;i++) {
				if ( d->o1[i] ) scontextFree(d->o1[i]);
			}
		}
		free(d);
		c->data = NULL;
	}
}

coder coderO1_SB = {
		"SigBit",
		coderO1_SB_init,
		coderO1_SB_free,
		coderO1_SB_encodeBand,
		coderO1_SB_decodeBand
	};

static void mcontext(int *cur_ptr,int parent,int x,int y,int width,int height,int fullw,
	int *cntx_ptr,int *sign_ptr)
{
int neighbors;

	/** cur_ptr[0] is about to be coded **/

	if ( x==0 ) {
		if ( y == 0 ) {
			neighbors = 0;
		} else {
			neighbors = (cur_ptr[-fullw] + cur_ptr[-fullw+1]) >> 1;
		}
	} else if ( y == 0 ) {
		neighbors = cur_ptr[-1];
	} else if ( x == (width-1) ) {
		neighbors = (cur_ptr[-1] + cur_ptr[-fullw] + cur_ptr[-fullw] + cur_ptr[-fullw-1]) >> 2;
	} else {
		neighbors = (cur_ptr[-1] + cur_ptr[-fullw] + cur_ptr[-fullw+1] + cur_ptr[-fullw-1]) >> 2;
	}

if ( neighbors == 0 ) *sign_ptr = 2;
else if ( isneg(neighbors) ) *sign_ptr = 1;
else *sign_ptr = 0;

parent = abs(parent);
neighbors = abs(neighbors);
parent = intlog2(parent+1);
neighbors = intlog2(neighbors);

*cntx_ptr = min(CN_MAX_PREV,neighbors) + (CN_MAX_PREV+1)*(min(CN_MAX_PARENT,parent));
}

static void encode_val(myInfo *mi,int sym,int context)
{
	if ( sym < ORDER1_RAWS ) {
		scontextEncode(mi->o1[context],sym);
	} else {
		int bits,msb;
		sym -= (ORDER1_RAWS-1); 	/** can't use zero **/
		bits = intlog2(sym);
		msb = (1<<bits);
		sym -= msb;
		scontextEncode(mi->o1[context],bits+ORDER1_RAWS);

		/** sym < msb now **/
		msb>>=1;
		for(;msb>=1;msb>>=1) {
			scontextEncode(mi->o0,(sym&msb)?1:0);
		}
	}
}

static int decode_val(myInfo *mi,int bits,int context)
{
	if ( bits < ORDER1_RAWS ) {
		return bits;
	} else {
		int msb,sym,top;
		bits -= ORDER1_RAWS;
		msb = 1<<bits;
		sym = 0;
		for(top = msb>>1;top>=1;top>>=1) {
			if ( scontextDecode(mi->o0) ) sym += top;
		}
		sym += msb + ORDER1_RAWS - 1;
		return sym;
	}
}

static void coder_scaledown(myInfo *mi)
{
int i;
	scontextHalve(mi->o0);
	for(i=0;i<3;i++) 
		scontextHalve(mi->sign_sc[i]);
	for(i=0;i<CODE_CONTEXTS;i++) 
		scontextHalve(mi->o1[i]);
}

void coderO1_SB_encodeBand(coder *me,int *band,int width,int height,int fullw,int *parent)
{
int x,y,val,cntx,sign,sign_cntx;
int *dp,*pp,*dpp,*ppp;
myInfo *mi = ((myInfo *)me->data);
scontext **sign_sc = ((myInfo *)me->data)->sign_sc;
scontext **o1 = ((myInfo *)me->data)->o1;

#ifdef CODER_ADAPT
	coder_scaledown(mi);
#endif

	dp = band;
	pp = parent;
	for(y=0;y<height;y++) {
		dpp = dp; ppp = pp;
		if ( coder_timetostop(me) ) { coder_didstop(me,y); return; }
		for(x=0;x<width;x++) {
			mcontext(dpp,*ppp,x,y,width,height,fullw,&cntx,&sign_cntx);

			val = *dpp++;	if ( x&1 ) ppp++;

			if ( val == 0 ) {
				scontextEncode(o1[cntx],0);
				continue;
			} else if ( val < 0 ) { sign = 1; val = -val;
			} else { sign = 0;
			}

			encode_val(mi,val,cntx);
			scontextEncode(sign_sc[sign_cntx],sign);
		}
		if ( y & 1 ) pp += fullw;
		dp += fullw;
	}
}

void coderO1_SB_decodeBand(coder *me,int *band,int width,int height,int fullw,int *parent)
{
int x,y,val,cntx,sign_cntx;
int *dp,*pp,*dpp,*ppp;
myInfo *mi = ((myInfo *)me->data);
scontext **sign_sc = ((myInfo *)me->data)->sign_sc;
scontext **o1 = ((myInfo *)me->data)->o1;

#ifdef CODER_ADAPT
	coder_scaledown(mi);
#endif

	dp = band;
	pp = parent;
	for(y=0;y<height;y++) {
		dpp = dp; ppp = pp;
		if ( coder_timetostopd(me,y) ) return;
		for(x=0;x<width;x++) {
			mcontext(dpp,*ppp,x,y,width,height,fullw,&cntx,&sign_cntx);

			if ( x&1 ) ppp++;

			val = scontextDecode(o1[cntx]);
			if ( val == 0 ) {
				*dpp++ = 0;
				continue;
			}
			val = decode_val(mi,val,cntx);

			if ( scontextDecode(sign_sc[sign_cntx]) ) val = -val;

			*dpp++ = val;
		}
		if ( y & 1 ) pp += fullw;
		dp += fullw;
	}
}