// stb_rect_pack.h - v0.08 - public domain - rectangle packing
// Sean Barrett 2014
//
// Useful for e.g. packing rectangular textures into an atlas.
// Does not do rotation.
//
// Not necessarily the awesomest packing method, but better than
// the totally naive one in stb_truetype (which is primarily what
// this is meant to replace).
//
// Has only had a few tests run, may have issues.
//
// More docs to come.
//
// No memory allocations; uses qsort() and assert() from stdlib.
// Can override those by defining STBRP_SORT and STBRP_ASSERT.
//
// This library currently uses the Skyline Bottom-Left algorithm.
//
// Please note: better rectangle packers are welcome! Please
// implement them to the same API, but with a different init
// function.
//
// Credits
//
//  Library
//    Sean Barrett
//  Minor features
//    Martins Mozeiko
//  Bugfixes / warning fixes
//    Jeremy Jaussaud
//
// Version history:
//
//     0.08  (2015-09-13)  really fix bug with empty rects (w=0 or h=0)
//     0.07  (2015-09-13)  fix bug with empty rects (w=0 or h=0)
//     0.06  (2015-04-15)  added STBRP_SORT to allow replacing qsort
//     0.05:  added STBRP_ASSERT to allow replacing assert
//     0.04:  fixed minor bug in STBRP_LARGE_RECTS support
//     0.01:  initial release
//
// LICENSE
//
//   This software is in the public domain. Where that dedication is not
//   recognized, you are granted a perpetual, irrevocable license to copy,
//   distribute, and modify this file as you see fit.

//////////////////////////////////////////////////////////////////////////////
//
//       INCLUDE SECTION
//

#ifndef STB_INCLUDE_STB_RECT_PACK_H
#define STB_INCLUDE_STB_RECT_PACK_H

#define STB_RECT_PACK_VERSION  1

#ifdef STBRP_STATIC
#define STBRP_DEF static
#else
#define STBRP_DEF extern
#endif

#ifdef __cplusplus
extern "C"
{
#endif

	typedef struct stbrp_context stbrp_context;
	typedef struct stbrp_node stbrp_node;
	typedef struct stbrp_rect stbrp_rect;

#ifdef STBRP_LARGE_RECTS
typedef int            stbrp_coord;
#else
	typedef unsigned short stbrp_coord;
#endif

	STBRP_DEF void stbrp_pack_rects( stbrp_context* context, stbrp_rect* rects, int num_rects );

	// Assign packed locations to rectangles. The rectangles are of type
	// 'stbrp_rect' defined below, stored in the array 'rects', and there
	// are 'num_rects' many of them.
	//
	// Rectangles which are successfully packed have the 'was_packed' flag
	// set to a non-zero value and 'x' and 'y' store the minimum location
	// on each axis (i.e. bottom-left in cartesian coordinates, top-left
	// if you imagine y increasing downwards). Rectangles which do not fit
	// have the 'was_packed' flag set to 0.
	//
	// You should not try to access the 'rects' array from another thread
	// while this function is running, as the function temporarily reorders
	// the array while it executes.
	//
	// To pack into another rectangle, you need to call stbrp_init_target
	// again. To continue packing into the same rectangle, you can call
	// this function again. Calling this multiple times with multiple rect
	// arrays will probably produce worse packing results than calling it
	// a single time with the full rectangle array, but the option is
	// available.

	struct stbrp_rect
	{
		// reserved for your use:
		int id;

		// input:
		stbrp_coord w, h;

		// output:
		stbrp_coord x, y;
		int was_packed; // non-zero if valid packing
	}; // 16 bytes, nominally

	STBRP_DEF void stbrp_init_target( stbrp_context* context, int width, int height, stbrp_node* nodes, int num_nodes );
	// Initialize a rectangle packer to:
	//    pack a rectangle that is 'width' by 'height' in dimensions
	//    using temporary storage provided by the array 'nodes', which is 'num_nodes' long
	//
	// You must call this function every time you start packing into a new target.
	//
	// There is no "shutdown" function. The 'nodes' memory must stay valid for
	// the following stbrp_pack_rects() call (or calls), but can be freed after
	// the call (or calls) finish.
	//
	// Note: to guarantee best results, either:
	//       1. make sure 'num_nodes' >= 'width'
	//   or  2. call stbrp_allow_out_of_mem() defined below with 'allow_out_of_mem = 1'
	//
	// If you don't do either of the above things, widths will be quantized to multiples
	// of small integers to guarantee the algorithm doesn't run out of temporary storage.
	//
	// If you do #2, then the non-quantized algorithm will be used, but the algorithm
	// may run out of temporary storage and be unable to pack some rectangles.

	STBRP_DEF void stbrp_setup_allow_out_of_mem( stbrp_context* context, int allow_out_of_mem );
	// Optionally call this function after init but before doing any packing to
	// change the handling of the out-of-temp-memory scenario, described above.
	// If you call init again, this will be reset to the default (false).

	STBRP_DEF void stbrp_setup_heuristic( stbrp_context* context, int heuristic );

	// Optionally select which packing heuristic the library should use. Different
	// heuristics will produce better/worse results for different data sets.
	// If you call init again, this will be reset to the default.

	enum
	{
		STBRP_HEURISTIC_Skyline_default=0,
		STBRP_HEURISTIC_Skyline_BL_sortHeight = STBRP_HEURISTIC_Skyline_default,
		STBRP_HEURISTIC_Skyline_BF_sortHeight
	};

	//////////////////////////////////////////////////////////////////////////////
	//
	// the details of the following structures don't matter to you, but they must
	// be visible so you can handle the memory allocations for them

	struct stbrp_node
	{
		stbrp_coord x, y;
		stbrp_node* next;
	};

	struct stbrp_context
	{
		int width;
		int height;
		int align;
		int init_mode;
		int heuristic;
		int num_nodes;
		stbrp_node* active_head;
		stbrp_node* free_head;
		stbrp_node extra[2]; // we allocate two extra nodes so optimal user-node-count is 'width' not 'width+2'
	};

#ifdef __cplusplus
}
#endif

#endif

//////////////////////////////////////////////////////////////////////////////
//
//     IMPLEMENTATION SECTION
//

#ifdef STB_RECT_PACK_IMPLEMENTATION
#ifndef STBRP_SORT
#include <stdlib.h>
#define STBRP_SORT qsort
#endif

#ifndef STBRP_ASSERT
#include <assert.h>
#define STBRP_ASSERT assert
#endif

enum
{
	STBRP__INIT_skyline = 1
};

STBRP_DEF void stbrp_setup_heuristic( stbrp_context* context, int heuristic )
{
	switch( context->init_mode )
	{
		case STBRP__INIT_skyline:
			STBRP_ASSERT(heuristic == STBRP_HEURISTIC_Skyline_BL_sortHeight || heuristic == STBRP_HEURISTIC_Skyline_BF_sortHeight);
			context->heuristic = heuristic;
			break;
		default:
			STBRP_ASSERT(0);
	}
}

STBRP_DEF void stbrp_setup_allow_out_of_mem( stbrp_context* context, int allow_out_of_mem )
{
	if( allow_out_of_mem )
	// if it's ok to run out of memory, then don't bother aligning them;
	// this gives better packing, but may fail due to OOM (even though
	// the rectangles easily fit). @TODO a smarter approach would be to only
	// quantize once we've hit OOM, then we could get rid of this parameter.
		context->align = 1;
	else
	{
		// if it's not ok to run out of memory, then quantize the widths
		// so that num_nodes is always enough nodes.
		//
		// I.e. num_nodes * align >= width
		//                  align >= width / num_nodes
		//                  align = ceil(width/num_nodes)

		context->align = ( context->width + context->num_nodes - 1 ) / context->num_nodes;
	}
}

STBRP_DEF void stbrp_init_target( stbrp_context* context, int width, int height, stbrp_node* nodes, int num_nodes )
{
	int i;
#ifndef STBRP_LARGE_RECTS
	STBRP_ASSERT(width <= 0xffff && height <= 0xffff);
#endif

	for( i = 0; i < num_nodes - 1; ++i )
		nodes[ i ].next = &nodes[ i + 1 ];
	nodes[ i ].next = NULL;
	context->init_mode = STBRP__INIT_skyline;
	context->heuristic = STBRP_HEURISTIC_Skyline_default;
	context->free_head = &nodes[ 0 ];
	context->active_head = &context->extra[ 0 ];
	context->width = width;
	context->height = height;
	context->num_nodes = num_nodes;
	stbrp_setup_allow_out_of_mem( context, 0 );

	// node 0 is the full width, node 1 is the sentinel (lets us not store width explicitly)
	context->extra[ 0 ].x = 0;
	context->extra[ 0 ].y = 0;
	context->extra[ 0 ].next = &context->extra[ 1 ];
	context->extra[ 1 ].x = ( stbrp_coord ) width;
#ifdef STBRP_LARGE_RECTS
   context->extra[1].y = (1<<30);
#else
	context->extra[ 1 ].y = 65535;
#endif
	context->extra[ 1 ].next = NULL;
}

// find minimum y position if it starts at x1
static int stbrp__skyline_find_min_y( stbrp_context* c, stbrp_node* first, int x0, int width, int* pwaste )
{
	( void )c;
	stbrp_node* node = first;
	int x1 = x0 + width;
	int min_y, visited_width, waste_area;
	STBRP_ASSERT(first->x <= x0);

#if 0
	// skip in case we're past the node
   while (node->next->x <= x0)
      ++node;
#else
	STBRP_ASSERT(node->next->x > x0); // we ended up handling this in the caller for efficiency
#endif

	STBRP_ASSERT(node->x <= x0);

	min_y = 0;
	waste_area = 0;
	visited_width = 0;
	while( node->x < x1 )
	{
		if( node->y > min_y )
		{
			// raise min_y higher.
			// we've accounted for all waste up to min_y,
			// but we'll now add more waste for everything we've visted
			waste_area += visited_width * ( node->y - min_y );
			min_y = node->y;
			// the first time through, visited_width might be reduced
			if( node->x < x0 )
				visited_width += node->next->x - x0;
			else
				visited_width += node->next->x - node->x;
		}
		else
		{
			// add waste area
			int under_width = node->next->x - node->x;
			if( under_width + visited_width > width )
				under_width = width - visited_width;
			waste_area += under_width * ( min_y - node->y );
			visited_width += under_width;
		}
		node = node->next;
	}

	*pwaste = waste_area;
	return min_y;
}

typedef struct
{
	int x, y;
	stbrp_node** prev_link;
} stbrp__findresult;

static stbrp__findresult stbrp__skyline_find_best_pos( stbrp_context* c, int width, int height )
{
	int best_waste = ( 1 << 30 ), best_x, best_y = ( 1 << 30 );
	stbrp__findresult fr;
	stbrp_node **prev, *node, *tail, **best = NULL;

	// align to multiple of c->align
	width = ( width + c->align - 1 );
	width -= width % c->align;
	STBRP_ASSERT(width % c->align == 0);

	node = c->active_head;
	prev = &c->active_head;
	while( node->x + width <= c->width )
	{
		int y, waste;
		y = stbrp__skyline_find_min_y( c, node, node->x, width, &waste );
		if( c->heuristic == STBRP_HEURISTIC_Skyline_BL_sortHeight )
		{ // actually just want to test BL
			// bottom left
			if( y < best_y )
			{
				best_y = y;
				best = prev;
			}
		}
		else
		{
			// best-fit
			if( y + height <= c->height )
			{
				// can only use it if it first vertically
				if( y < best_y || ( y == best_y && waste < best_waste ) )
				{
					best_y = y;
					best_waste = waste;
					best = prev;
				}
			}
		}
		prev = &node->next;
		node = node->next;
	}

	best_x = ( best == NULL ) ? 0 : ( *best )->x;

	// if doing best-fit (BF), we also have to try aligning right edge to each node position
	//
	// e.g, if fitting
	//
	//     ____________________
	//    |____________________|
	//
	//            into
	//
	//   |                         |
	//   |             ____________|
	//   |____________|
	//
	// then right-aligned reduces waste, but bottom-left BL is always chooses left-aligned
	//
	// This makes BF take about 2x the time

	if( c->heuristic == STBRP_HEURISTIC_Skyline_BF_sortHeight )
	{
		tail = c->active_head;
		node = c->active_head;
		prev = &c->active_head;
		// find first node that's admissible
		while( tail->x < width )
			tail = tail->next;
		while( tail )
		{
			int xpos = tail->x - width;
			int y, waste;
			STBRP_ASSERT(xpos >= 0);
			// find the left position that matches this
			while( node->next->x <= xpos )
			{
				prev = &node->next;
				node = node->next;
			}
			STBRP_ASSERT(node->next->x > xpos && node->x <= xpos);
			y = stbrp__skyline_find_min_y( c, node, xpos, width, &waste );
			if( y + height < c->height )
			{
				if( y <= best_y )
				{
					if( y < best_y || waste < best_waste || ( waste == best_waste && xpos < best_x ) )
					{
						best_x = xpos;
						STBRP_ASSERT(y <= best_y);
						best_y = y;
						best_waste = waste;
						best = prev;
					}
				}
			}
			tail = tail->next;
		}
	}

	fr.prev_link = best;
	fr.x = best_x;
	fr.y = best_y;
	return fr;
}

static stbrp__findresult stbrp__skyline_pack_rectangle( stbrp_context* context, int width, int height )
{
	// find best position according to heuristic
	stbrp__findresult res = stbrp__skyline_find_best_pos( context, width, height );
	stbrp_node *node, *cur;

	// bail if:
	//    1. it failed
	//    2. the best node doesn't fit (we don't always check this)
	//    3. we're out of memory
	if( res.prev_link == NULL || res.y + height > context->height || context->free_head == NULL )
	{
		res.prev_link = NULL;
		return res;
	}

	// on success, create new node
	node = context->free_head;
	node->x = ( stbrp_coord ) res.x;
	node->y = ( stbrp_coord ) ( res.y + height );

	context->free_head = node->next;

	// insert the new node into the right starting point, and
	// let 'cur' point to the remaining nodes needing to be
	// stiched back in

	cur = *res.prev_link;
	if( cur->x < res.x )
	{
		// preserve the existing one, so start testing with the next one
		stbrp_node* next = cur->next;
		cur->next = node;
		cur = next;
	}
	else
	{
		*res.prev_link = node;
	}

	// from here, traverse cur and free the nodes, until we get to one
	// that shouldn't be freed
	while( cur->next && cur->next->x <= res.x + width )
	{
		stbrp_node* next = cur->next;
		// move the current node to the free list
		cur->next = context->free_head;
		context->free_head = cur;
		cur = next;
	}

	// stitch the list back in
	node->next = cur;

	if( cur->x < res.x + width )
		cur->x = ( stbrp_coord ) ( res.x + width );

#ifdef _DEBUG
	cur = context->active_head;
	while( cur->x < context->width )
	{
		STBRP_ASSERT(cur->x < cur->next->x);
		cur = cur->next;
	}
	STBRP_ASSERT(cur->next == NULL);

	{
		stbrp_node *L1 = NULL, *L2 = NULL;
		int count = 0;
		cur = context->active_head;
		while( cur )
		{
			L1 = cur;
			cur = cur->next;
			++count;
		}
		cur = context->free_head;
		while( cur )
		{
			L2 = cur;
			cur = cur->next;
			++count;
		}
		STBRP_ASSERT(count == context->num_nodes+2);
	}
#endif

	return res;
}

static int rect_height_compare( const void* a, const void* b )
{
	stbrp_rect* p = ( stbrp_rect * ) a;
	stbrp_rect* q = ( stbrp_rect * ) b;
	if( p->h > q->h )
		return -1;
	if( p->h < q->h )
		return 1;
	return ( p->w > q->w ) ? -1 : ( p->w < q->w );
}

static int rect_width_compare( const void* a, const void* b )
{
	stbrp_rect* p = ( stbrp_rect * ) a;
	stbrp_rect* q = ( stbrp_rect * ) b;
	if( p->w > q->w )
		return -1;
	if( p->w < q->w )
		return 1;
	return ( p->h > q->h ) ? -1 : ( p->h < q->h );
}

static int rect_original_order( const void* a, const void* b )
{
	stbrp_rect* p = ( stbrp_rect * ) a;
	stbrp_rect* q = ( stbrp_rect * ) b;
	return ( p->was_packed < q->was_packed ) ? -1 : ( p->was_packed > q->was_packed );
}

#ifdef STBRP_LARGE_RECTS
#define STBRP__MAXVAL  0xffffffff
#else
#define STBRP__MAXVAL  0xffff
#endif

STBRP_DEF void stbrp_pack_rects( stbrp_context* context, stbrp_rect* rects, int num_rects )
{
	int i;

	// we use the 'was_packed' field internally to allow sorting/unsorting
	for( i = 0; i < num_rects; ++i )
	{
		rects[ i ].was_packed = i;
#ifndef STBRP_LARGE_RECTS
		STBRP_ASSERT(rects[i].w <= 0xffff && rects[i].h <= 0xffff);
#endif
	}

	// sort according to heuristic
	STBRP_SORT( rects, num_rects, sizeof( rects[ 0 ] ), rect_height_compare );

	for( i = 0; i < num_rects; ++i )
	{
		if( rects[ i ].w == 0 || rects[ i ].h == 0 )
		{
			rects[ i ].x = rects[ i ].y = 0; // empty rect needs no space
		}
		else
		{
			stbrp__findresult fr = stbrp__skyline_pack_rectangle( context, rects[ i ].w, rects[ i ].h );
			if( fr.prev_link )
			{
				rects[ i ].x = ( stbrp_coord ) fr.x;
				rects[ i ].y = ( stbrp_coord ) fr.y;
			}
			else
			{
				rects[ i ].x = rects[ i ].y = STBRP__MAXVAL;
			}
		}
	}

	// unsort
	STBRP_SORT( rects, num_rects, sizeof( rects[ 0 ] ), rect_original_order );

	// set was_packed flags
	for( i = 0; i < num_rects; ++i )
		rects[ i ].was_packed = !( rects[ i ].x == STBRP__MAXVAL && rects[ i ].y == STBRP__MAXVAL );
}
#endif
