/* -=- sraRegion.c
 * Copyright (c) 2001 James "Wez" Weatherall, Johannes E. Schindelin
 *
 * A general purpose region clipping library
 * Only deals with rectangular regions, though.
 */

#include "rfb.h"
#include "sraRegion.h"

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

/* -=- Internal Span structure */

struct sraRegion;

typedef struct sraSpan {
  struct sraSpan *_next;
  struct sraSpan *_prev;
  int start;
  int end;
  struct sraRegion *subspan;
} sraSpan;

typedef struct sraRegion {
  sraSpan front;
  sraSpan back;
} sraSpanList;

/* -=- Span routines */

sraSpanList *sraSpanListDup(const sraSpanList *src);
void sraSpanListDestroy(sraSpanList *list);

sraSpan *
sraSpanCreate(int start, int end, const sraSpanList *subspan) {
  sraSpan *item = (sraSpan*)malloc(sizeof(sraSpan));
  item->_next = item->_prev = NULL;
  item->start = start;
  item->end = end;
  item->subspan = sraSpanListDup(subspan);
  return item;
}

sraSpan *
sraSpanDup(const sraSpan *src) {
  sraSpan *span;
  if (!src) return NULL;
  span = sraSpanCreate(src->start, src->end, src->subspan);
  return span;
}

void
sraSpanInsertAfter(sraSpan *newspan, sraSpan *after) {
  newspan->_next = after->_next;
  newspan->_prev = after;
  after->_next->_prev = newspan;
  after->_next = newspan;
}

void
sraSpanInsertBefore(sraSpan *newspan, sraSpan *before) {
  newspan->_next = before;
  newspan->_prev = before->_prev;
  before->_prev->_next = newspan;
  before->_prev = newspan;
}

void
sraSpanRemove(sraSpan *span) {
  span->_prev->_next = span->_next;
  span->_next->_prev = span->_prev;
}

void
sraSpanDestroy(sraSpan *span) {
  if (span->subspan) sraSpanListDestroy(span->subspan);
  xfree(span);
}

void
sraSpanCheck(const sraSpan *span, const char *text) {
  // Check the span is valid!
  if (span->start == span->end) {
    printf(text); 
    printf(":%d-%d\n", span->start, span->end);
    exit(0);
  }
}

/* -=- SpanList routines */

void sraSpanPrint(const sraSpan *s);

void
sraSpanListPrint(const sraSpanList *l) {
  sraSpan *curr;
  if (!l) {
	  printf("NULL");
	  return;
  }
  curr = l->front._next;
  printf("[");
  while (curr != &(l->back)) {
    sraSpanPrint(curr);
    curr = curr->_next;
  }
  printf("]");
}

void
sraSpanPrint(const sraSpan *s) {
  printf("(%d-%d)", (s->start), (s->end));
  if (s->subspan)
    sraSpanListPrint(s->subspan);
}

sraSpanList *
sraSpanListCreate() {
  sraSpanList *item = (sraSpanList*)malloc(sizeof(sraSpanList));
  item->front._next = &(item->back);
  item->front._prev = NULL;
  item->back._prev = &(item->front);
  item->back._next = NULL;
  return item;
}

sraSpanList *
sraSpanListDup(const sraSpanList *src) {
  sraSpanList *newlist;
  sraSpan *newspan, *curr;

  if (!src) return NULL;
  newlist = sraSpanListCreate();
  curr = src->front._next;
  while (curr != &(src->back)) {
    newspan = sraSpanDup(curr);
    sraSpanInsertBefore(newspan, &(newlist->back));
    curr = curr->_next;
  }

  return newlist;
}

void
sraSpanListDestroy(sraSpanList *list) {
  sraSpan *curr, *next;
  while (list->front._next != &(list->back)) {
    curr = list->front._next;
    next = curr->_next;
    sraSpanRemove(curr);
    sraSpanDestroy(curr);
    curr = next;
  }
  xfree(list);
}

void
sraSpanListMakeEmpty(sraSpanList *list) {
  sraSpan *curr, *next;
  while (list->front._next != &(list->back)) {
    curr = list->front._next;
    next = curr->_next;
    sraSpanRemove(curr);
    sraSpanDestroy(curr);
    curr = next;
  }
  list->front._next = &(list->back);
  list->front._prev = NULL;
  list->back._prev = &(list->front);
  list->back._next = NULL;
}

int sraMax(int a, int b) {return (a>b)?a:b;};
int sraMin(int a, int b) {return (a<b)?a:b;};

Bool
sraSpanListEqual(const sraSpanList *s1, const sraSpanList *s2) {
  sraSpan *sp1, *sp2;

  if (!s1) {
    if (!s2) {
      return 1;
    } else {
      printf("sraSpanListEqual:incompatible spans (only one NULL!)\n");
      exit(1);
    }
  }

  sp1 = s1->front._next;
  sp2 = s2->front._next;
  while ((sp1 != &(s1->back)) &&
	 (sp2 != &(s2->back))) {
    if ((sp1->start != sp2->start) ||
	(sp1->end != sp2->end) ||
	(!sraSpanListEqual(sp1->subspan, sp2->subspan))) {
      return 0;
    }
    sp1 = sp1->_next;
    sp2 = sp2->_next;
  }

  if ((sp1 == &(s1->back)) && (sp2 == &(s2->back))) {
    return 1;
  } else {
    return 0;
  }    
}

Bool
sraSpanListEmpty(const sraSpanList *list) {
  return (list->front._next == &(list->back));
}

unsigned long
sraSpanListCount(const sraSpanList *list) {
  sraSpan *curr = list->front._next;
  unsigned long count = 0;
  while (curr != &(list->back)) {
    if (curr->subspan) {
      count += sraSpanListCount(curr->subspan);
    } else {
      count += 1;
    }
    curr = curr->_next;
  }
  return count;
}

void
sraSpanMergePrevious(sraSpan *dest) {
  sraSpan *prev = dest->_prev;
  while ((prev->end == dest->start) &&
	 (prev->_prev) &&
	 (sraSpanListEqual(prev->subspan, dest->subspan))) {
    /*
    printf("merge_prev:");
    sraSpanPrint(prev);
    printf(" & ");
    sraSpanPrint(dest);
    printf("\n");
    */
    dest->start = prev->start;
    sraSpanRemove(prev);
    sraSpanDestroy(prev);
    prev = dest->_prev;
  }
}    

void
sraSpanMergeNext(sraSpan *dest) {
  sraSpan *next = dest->_next;
  while ((next->start == dest->end) &&
	 (next->_next) &&
	 (sraSpanListEqual(next->subspan, dest->subspan))) {
/*
	  printf("merge_next:");
    sraSpanPrint(dest);
    printf(" & ");
    sraSpanPrint(next);
    printf("\n");
	*/
    dest->end = next->end;
    sraSpanRemove(next);
    sraSpanDestroy(next);
    next = dest->_next;
  }
}

void
sraSpanListOr(sraSpanList *dest, const sraSpanList *src) {
  sraSpan *d_curr, *s_curr;
  int s_start, s_end;

  if (!dest) {
    if (!src) {
      return;
    } else {
      printf("sraSpanListOr:incompatible spans (only one NULL!)\n");
      exit(1);
    }
  }

  d_curr = dest->front._next;
  s_curr = src->front._next;
  s_start = s_curr->start;
  s_end = s_curr->end;
  while (s_curr != &(src->back)) {

    // - If we are at end of destination list OR
    //   If the new span comes before the next destination one
    if ((d_curr == &(dest->back)) ||
		(d_curr->start >= s_end)) {
      // - Add the span
      sraSpanInsertBefore(sraSpanCreate(s_start, s_end,
					s_curr->subspan),
			  d_curr);
      if (d_curr != &(dest->back))
	sraSpanMergePrevious(d_curr);
      s_curr = s_curr->_next;
      s_start = s_curr->start;
      s_end = s_curr->end;
    } else {

      // - If the new span overlaps the existing one
      if ((s_start < d_curr->end) &&
	  (s_end > d_curr->start)) {

	// - Insert new span before the existing destination one?
	if (s_start < d_curr->start) {
	  sraSpanInsertBefore(sraSpanCreate(s_start,
					    d_curr->start,
					    s_curr->subspan),
			      d_curr);
	  sraSpanMergePrevious(d_curr);
	}

	// Split the existing span if necessary
	if (s_end < d_curr->end) {
	  sraSpanInsertAfter(sraSpanCreate(s_end,
					   d_curr->end,
					   d_curr->subspan),
			     d_curr);
	  d_curr->end = s_end;
	}
	if (s_start > d_curr->start) {
	  sraSpanInsertBefore(sraSpanCreate(d_curr->start,
					    s_start,
					    d_curr->subspan),
			      d_curr);
	  d_curr->start = s_start;
	}

	// Recursively OR subspans
	sraSpanListOr(d_curr->subspan, s_curr->subspan);

	// Merge this span with previous or next?
	if (d_curr->_prev != &(dest->front))
	  sraSpanMergePrevious(d_curr);
	if (d_curr->_next != &(dest->back))
	  sraSpanMergeNext(d_curr);

	// Move onto the next pair to compare
	if (s_end > d_curr->end) {
	  s_start = d_curr->end;
	  d_curr = d_curr->_next;
	} else {
	  s_curr = s_curr->_next;
	  s_start = s_curr->start;
	  s_end = s_curr->end;
	}
      } else {
	// - No overlap.  Move to the next destination span
	d_curr = d_curr->_next;
      }
    }
  }
}

Bool
sraSpanListAnd(sraSpanList *dest, const sraSpanList *src) {
  sraSpan *d_curr, *s_curr, *d_next;

  if (!dest) {
    if (!src) {
      return 1;
    } else {
      printf("sraSpanListAnd:incompatible spans (only one NULL!)\n");
      exit(1);
    }
  }

  d_curr = dest->front._next;
  s_curr = src->front._next;
  while ((s_curr != &(src->back)) && (d_curr != &(dest->back))) {

    // - If we haven't reached a destination span yet then move on
    if (d_curr->start >= s_curr->end) {
      s_curr = s_curr->_next;
      continue;
    }

    // - If we are beyond the current destination span then remove it
    if (d_curr->end <= s_curr->start) {
      sraSpan *next = d_curr->_next;
      sraSpanRemove(d_curr);
      sraSpanDestroy(d_curr);
      d_curr = next;
      continue;
    }

    // - If we partially overlap a span then split it up or remove bits
    if (s_curr->start > d_curr->start) {
      // - The top bit of the span does not match
      d_curr->start = s_curr->start;
    }
    if (s_curr->end < d_curr->end) {
      // - The end of the span does not match
      sraSpanInsertAfter(sraSpanCreate(s_curr->end,
				       d_curr->end,
				       d_curr->subspan),
			 d_curr);
      d_curr->end = s_curr->end;
    }

    // - Now recursively process the affected span
    if (!sraSpanListAnd(d_curr->subspan, s_curr->subspan)) {
      // - The destination subspan is now empty, so we should remove it
		sraSpan *next = d_curr->_next;
      sraSpanRemove(d_curr);
      sraSpanDestroy(d_curr);
      d_curr = next;
    } else {
      // Merge this span with previous or next?
      if (d_curr->_prev != &(dest->front))
	sraSpanMergePrevious(d_curr);

      // - Move on to the next span
      d_next = d_curr;
      if (s_curr->end >= d_curr->end) {
	d_next = d_curr->_next;
      }
      if (s_curr->end <= d_curr->end) {
	s_curr = s_curr->_next;
      }
      d_curr = d_next;
    }
  }

  while (d_curr != &(dest->back)) {
    sraSpan *next = d_curr->_next;
    sraSpanRemove(d_curr);
    sraSpanDestroy(d_curr);
    d_curr=next;
  }

  return !sraSpanListEmpty(dest);
}

Bool
sraSpanListSubtract(sraSpanList *dest, const sraSpanList *src) {
  sraSpan *d_curr, *s_curr;

  if (!dest) {
    if (!src) {
      return 1;
    } else {
      printf("sraSpanListSubtract:incompatible spans (only one NULL!)\n");
      exit(1);
    }
  }

  d_curr = dest->front._next;
  s_curr = src->front._next;
  while ((s_curr != &(src->back)) && (d_curr != &(dest->back))) {

    // - If we haven't reached a destination span yet then move on
    if (d_curr->start >= s_curr->end) {
      s_curr = s_curr->_next;
      continue;
    }

    // - If we are beyond the current destination span then skip it
    if (d_curr->end <= s_curr->start) {
      d_curr = d_curr->_next;
      continue;
    }

    // - If we partially overlap the current span then split it up
    if (s_curr->start > d_curr->start) {
      sraSpanInsertBefore(sraSpanCreate(d_curr->start,
					s_curr->start,
					d_curr->subspan),
			  d_curr);
      d_curr->start = s_curr->start;
    }
    if (s_curr->end < d_curr->end) {
      sraSpanInsertAfter(sraSpanCreate(s_curr->end,
				       d_curr->end,
				       d_curr->subspan),
			 d_curr);
      d_curr->end = s_curr->end;
    }

    // - Now recursively process the affected span
    if ((!d_curr->subspan) || !sraSpanListSubtract(d_curr->subspan, s_curr->subspan)) {
      // - The destination subspan is now empty, so we should remove it
      sraSpan *next = d_curr->_next;
      sraSpanRemove(d_curr);
      sraSpanDestroy(d_curr);
      d_curr = next;
    } else {
      // Merge this span with previous or next?
      if (d_curr->_prev != &(dest->front))
	sraSpanMergePrevious(d_curr);
      if (d_curr->_next != &(dest->back))
	sraSpanMergeNext(d_curr);

      // - Move on to the next span
      if (s_curr->end > d_curr->end) {
	d_curr = d_curr->_next;
      } else {
	s_curr = s_curr->_next;
      }
    }
  }

  return !sraSpanListEmpty(dest);
}

/* -=- Region routines */

sraRegion *
sraRgnCreate() {
  return (sraRegion*)sraSpanListCreate();
}

sraRegion *
sraRgnCreateRect(int x1, int y1, int x2, int y2) {
  sraSpanList *vlist, *hlist;
  sraSpan *vspan, *hspan;

  /* - Build the horizontal portion of the span */
  hlist = sraSpanListCreate();
  hspan = sraSpanCreate(x1, x2, NULL);
  sraSpanInsertAfter(hspan, &(hlist->front));

  /* - Build the vertical portion of the span */
  vlist = sraSpanListCreate();
  vspan = sraSpanCreate(y1, y2, hlist);
  sraSpanInsertAfter(vspan, &(vlist->front));

  sraSpanListDestroy(hlist);

  return (sraRegion*)vlist;
}

sraRegion *
sraRgnCreateRgn(const sraRegion *src) {
  return (sraRegion*)sraSpanListDup((sraSpanList*)src);
}

void
sraRgnDestroy(sraRegion *rgn) {
  sraSpanListDestroy((sraSpanList*)rgn);
}

void
sraRgnMakeEmpty(sraRegion *rgn) {
  sraSpanListMakeEmpty((sraSpanList*)rgn);
}

/* -=- Boolean Region ops */

Bool
sraRgnAnd(sraRegion *dst, const sraRegion *src) {
  return sraSpanListAnd((sraSpanList*)dst, (sraSpanList*)src);
}

void
sraRgnOr(sraRegion *dst, const sraRegion *src) {
  sraSpanListOr((sraSpanList*)dst, (sraSpanList*)src);
}

Bool
sraRgnSubtract(sraRegion *dst, const sraRegion *src) {
  return sraSpanListSubtract((sraSpanList*)dst, (sraSpanList*)src);
}

void
sraRgnOffset(sraRegion *dst, int dx, int dy) {
  sraSpan *vcurr, *hcurr;

  vcurr = ((sraSpanList*)dst)->front._next;
  while (vcurr != &(((sraSpanList*)dst)->back)) {
    vcurr->start += dy;
    vcurr->end += dy;
    
    hcurr = vcurr->subspan->front._next;
    while (hcurr != &(vcurr->subspan->back)) {
      hcurr->start += dx;
      hcurr->end += dx;
      hcurr = hcurr->_next;
    }

    vcurr = vcurr->_next;
  }
}

Bool
sraRgnPopRect(sraRegion *rgn, sraRect *rect, unsigned long flags) {
  sraSpan *vcurr, *hcurr;
  sraSpan *vend, *hend;
  Bool right2left = flags & 2;
  Bool bottom2top = flags & 1;

  // - Pick correct order
  if (bottom2top) {
    vcurr = ((sraSpanList*)rgn)->back._prev;
    vend = &(((sraSpanList*)rgn)->front);
  } else {
    vcurr = ((sraSpanList*)rgn)->front._next;
    vend = &(((sraSpanList*)rgn)->back);
  }

  if (vcurr != vend) {
    rect->y1 = vcurr->start;
    rect->y2 = vcurr->end;

    // - Pick correct order
    if (right2left) {
      hcurr = vcurr->subspan->back._prev;
      hend = &(vcurr->subspan->front);
    } else {
      hcurr = vcurr->subspan->front._next;
      hend = &(vcurr->subspan->back);
    }

    if (hcurr != hend) {
      rect->x1 = hcurr->start;
      rect->x2 = hcurr->end;

      sraSpanRemove(hcurr);
      sraSpanDestroy(hcurr);
      
      if (sraSpanListEmpty(vcurr->subspan)) {
	sraSpanRemove(vcurr);
	sraSpanDestroy(vcurr);
      }

#if 0
      printf("poprect:(%dx%d)-(%dx%d)\n",
	     rect->x1, rect->y1, rect->x2, rect->y2);
#endif
      return 1;
    }
  }

  return 0;
}

unsigned long
sraRgnCountRects(const sraRegion *rgn) {
  unsigned long count = sraSpanListCount((sraSpanList*)rgn);
  return count;
}

Bool
sraRgnEmpty(const sraRegion *rgn) {
  return sraSpanListEmpty((sraSpanList*)rgn);
}

/* iterator stuff */
sraRectangleIterator *sraRgnGetIterator(sraRegion *s)
{
  /* these values have to be multiples of 4 */
#define DEFSIZE 4
#define DEFSTEP 8
  sraRectangleIterator *i =
    (sraRectangleIterator*)malloc(sizeof(sraRectangleIterator));
  if(!i)
    return(0);

  /* we have to recurse eventually. So, the first sPtr is the pointer to
     the sraSpan in the first level. the second sPtr is the pointer to
     the sraRegion.back. The third and fourth sPtr are for the second
     recursion level and so on. */
  i->sPtrs = (sraSpan**)malloc(sizeof(sraSpan*)*DEFSIZE);
  if(!i->sPtrs) {
    free(i);
    return(0);
  }
  i->ptrSize = DEFSIZE;
  i->sPtrs[0] = &(s->front);
  i->sPtrs[1] = &(s->back);
  i->ptrPos = 0;
  i->reverseX = 0;
  i->reverseY = 0;
  return(i);
}

sraRectangleIterator *sraRgnGetReverseIterator(sraRegion *s,Bool reverseX,Bool reverseY)
{
  sraRectangleIterator *i = sraRgnGetIterator(s);
  if(reverseY) {
    i->sPtrs[1] = &(s->front);
    i->sPtrs[0] = &(s->back);
  }
  i->reverseX = reverseX;
  i->reverseY = reverseY;
  return(i);
}

Bool sraReverse(sraRectangleIterator *i)
{
  return( ((i->ptrPos&2) && i->reverseX) ||
     (!(i->ptrPos&2) && i->reverseY));
}

sraSpan* sraNextSpan(sraRectangleIterator *i)
{
  if(sraReverse(i))
    return(i->sPtrs[i->ptrPos]->_prev);
  else
    return(i->sPtrs[i->ptrPos]->_next);
}

Bool sraRgnIteratorNext(sraRectangleIterator* i,sraRect* r)
{
  /* is the subspan finished? */
  while(sraNextSpan(i) == i->sPtrs[i->ptrPos+1]) {
    i->ptrPos -= 2;
    if(i->ptrPos < 0) /* the end */
      return(0);
  }

  i->sPtrs[i->ptrPos] = sraNextSpan(i);

  /* is this a new subspan? */
  while(i->sPtrs[i->ptrPos]->subspan) {
    if(i->ptrPos+2 > i->ptrSize) { /* array is too small */
      i->ptrSize += DEFSTEP;
      i->sPtrs = (sraSpan**)realloc(i->sPtrs, sizeof(sraSpan*)*i->ptrSize);
    }
    i->ptrPos =+ 2;
    if(sraReverse(i)) {
      i->sPtrs[i->ptrPos]   =   i->sPtrs[i->ptrPos-2]->subspan->back._prev;
      i->sPtrs[i->ptrPos+1] = &(i->sPtrs[i->ptrPos-2]->subspan->front);
    } else {
      i->sPtrs[i->ptrPos]   =   i->sPtrs[i->ptrPos-2]->subspan->front._next;
      i->sPtrs[i->ptrPos+1] = &(i->sPtrs[i->ptrPos-2]->subspan->back);
    }
  }

  if((i->ptrPos%4)!=2) {
    fprintf(stderr,"sraRgnIteratorNext: offset is wrong (%d%%4!=2)\n",i->ptrPos);
    exit(-1);
  }

  r->y1 = i->sPtrs[i->ptrPos-2]->start;
  r->y2 = i->sPtrs[i->ptrPos-2]->end;
  r->x1 = i->sPtrs[i->ptrPos]->start;
  r->x2 = i->sPtrs[i->ptrPos]->end;

  return(-1);
}

void sraRgnReleaseIterator(sraRectangleIterator* i)
{
  free(i->sPtrs);
  free(i);
}

void
sraRgnPrint(const sraRegion *rgn) {
	sraSpanListPrint((sraSpanList*)rgn);
}

Bool
sraClipRect(int *x, int *y, int *w, int *h,
	    int cx, int cy, int cw, int ch) {
  if (*x < cx) {
    *w -= (cx-*x);
    *x = cx;
  }
  if (*y < cy) {
    *h -= (cy-*y);
    *y = cy;
  }
  if (*x+*w > cx+cw) {
    *w = (cx+cw)-*x;
  }
  if (*y+*h > cy+ch) {
    *h = (cy+ch)-*y;
  }
  return (*w>0) && (*h>0);
}

/* test */

#ifdef SRA_TEST
/* pipe the output to sort|uniq -u and you'll get the errors. */
int main(int argc, char** argv)
{
  sraRegionPtr region, region1, region2;
  sraRectangleIterator* i;
  sraRect rect;
  Bool b;

  region = sraRgnCreateRect(10, 10, 600, 300);
  region1 = sraRgnCreateRect(40, 50, 350, 200);
  region2 = sraRgnCreateRect(0, 0, 20, 40);

  sraRgnPrint(region);
  printf("\n[(10-300)[(10-600)]]\n\n");

  b = sraRgnSubtract(region, region1);
  printf("%s ",b?"true":"false");
  sraRgnPrint(region);
  printf("\ntrue [(10-50)[(10-600)](50-200)[(10-40)(350-600)](200-300)[(10-600)]]\n\n");

  sraRgnOr(region, region2);
  printf("%ld\n6\n\n", sraRgnCountRects(region));

  i = sraRgnGetIterator(region);
  while(sraRgnIteratorNext(i, &rect))
    printf("%dx%d+%d+%d ",
	   rect.x2-rect.x1,rect.y2-rect.y1,
	   rect.x1,rect.y1);
  sraRgnReleaseIterator(i);
  printf("\n20x10+0+0 600x30+0+10 590x10+10+40 30x150+10+50 250x150+350+50 590x100+10+200\n\n");

  i = sraRgnGetReverseIterator(region,1,0);
  while(sraRgnIteratorNext(i, &rect))
    printf("%dx%d+%d+%d ",
	   rect.x2-rect.x1,rect.y2-rect.y1,
	   rect.x1,rect.y1);
  sraRgnReleaseIterator(i);
  printf("\n20x10+0+0 600x30+0+10 590x10+10+40 250x150+350+50 30x150+10+50 590x100+10+200\n\n");

  i = sraRgnGetReverseIterator(region,1,1);
  while(sraRgnIteratorNext(i, &rect))
    printf("%dx%d+%d+%d ",
	   rect.x2-rect.x1,rect.y2-rect.y1,
	   rect.x1,rect.y1);
  sraRgnReleaseIterator(i);
  printf("\n590x100+10+200 250x150+350+50 30x150+10+50 590x10+10+40 600x30+0+10 20x10+0+0\n\n");

  return(0);
}
#endif