#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <err.h>
#include <math.h>

#include "ugui.h"
#include "def_style.h"


#define SALT         0xbabb0cac
#define DEF_SCALE    1.0
#define DEF_PPI      96.0
#define STACK_STEP   64
#define SLICE_STEP   128

#define RESIZEALL     (                                                        \
                      UG_CNT_RESIZE_RIGHT  |                                   \
                      UG_CNT_RESIZE_BOTTOM |                                   \
                      UG_CNT_RESIZE_LEFT   |                                   \
                      UG_CNT_RESIZE_TOP                                        \
                      )

#define BTN_ANY       (                                                        \
                      UG_BTN_LEFT   |                                          \
                      UG_BTN_RIGHT  |                                          \
                      UG_BTN_MIDDLE |                                          \
                      UG_BTN_4      |                                          \
                      UG_BTN_5                                                 \
                      )

#define CNT_STATE_ALL (                                                        \
                      CNT_STATE_NONE     |                                     \
                      CNT_STATE_MOVING   |                                     \
		      CNT_STATE_RESIZE_T |                                     \
                      CNT_STATE_RESIZE_B |                                     \
                      CNT_STATE_RESIZE_L |                                     \
                      CNT_STATE_RESIZE_R |                                     \
                      CNT_STATE_RESIZE_D                                       \
                      )

#define PPI_PPM(ppi, scale)  (ppi * scale * 0.03937008)
#define PPI_PPD(ppi, scale)  (PPI_PPM(ppi, scale) * 0.3528)
#define IS_VALID_UNIT(u)     (u==UG_UNIT_PX||u==UG_UNIT_MM||u==UG_UNIT_PT)
#define UG_ERR(...)          err(errno, "__FUNCTION__: " __VA_ARGS__)
#define BETWEEN(x, min, max) (x <= max && x >= min)
#define INTERSECTS(v, r)     (BETWEEN(v.x, r.x, r.x+r.w) && BETWEEN(v.y, r.y, r.y+r.h))
#define TEST(f, b)           (f & (b))
#define MAX(a, b)            (a > b ? a : b)
#define R_MARGIN(r, b) (r.x + r.w - b)
#define L_MARGIN(r, b) (r.x + b)
#define T_MARGIN(r, b) (r.y + b)
#define B_MARGIN(r, b) (r.y + r.h - b)
// check if ra is outside of rb
#define OUTSIDE(ra, ba, rb, bb) (L_MARGIN(ra, ba) > R_MARGIN(rb, bb) ||        \
                                 T_MARGIN(ra, ba) > B_MARGIN(rb, bb) ||        \
				 R_MARGIN(ra, ba) < L_MARGIN(rb, bb) ||        \
				 B_MARGIN(ra, ba) < T_MARGIN(rb, bb))


static ug_style_t style_cache = {0};


/*=============================================================================*
 *                          Common Functions                                   *
 *=============================================================================*/


// grow a stack
#define GROW_STACK(S)                                                          \
{                                                                              \
	S.items = realloc(S.items, (S.size+STACK_STEP)*sizeof(*(S.items)));    \
	if(!S.items)                                                           \
		UG_ERR("Could not allocate stack #S: %s", strerror(errno));    \
	memset(&(S.items[S.size]), 0, STACK_STEP*sizeof(*(S.items)));          \
	S.size += STACK_STEP;                                                  \
}


#define GET_FROM_STACK(S, c)                                                   \
{                                                                              \
	if (S.idx >= S.size)                                                   \
		GROW_STACK(S);                                                 \
	c = &(S.items[S.idx++]);                                               \
}


// delete all items that have the same id from the stack, also shrink it if the total
// number of items is less than a third of the capacity
#define DELETE_FROM_STACK(S, c)                                                     \
{                                                                                   \
	for (int i = 0; i < S.idx; i++) {                                           \
		if (c->id != S.items[i].id)                                         \
			continue;                                                   \
		memmove(&S.items[i], &S.items[i+1], (S.idx-i)*sizeof(S.items[0]));  \
		memset(&S.items[S.idx--], 0, sizeof(S.items[0]));                   \
	}                                                                           \
	if (S.size > STACK_STEP && S.idx*3 < S.size) {                              \
		S.items = realloc(S.items, (S.size-STACK_STEP)*sizeof(*(S.items))); \
		if(!S.items)                                                        \
			UG_ERR("Could not allocate stack #S: %s", strerror(errno)); \
		S.size -= STACK_STEP;                                               \
	}                                                                           \
}                                                                                   \


// FIXME: is it really  necessary to clear (memset) the stack
#define RESET_STACK(S)                                                         \
{                                                                              \
	memset(S.items, 0, S.idx*sizeof(*(S.items)));                          \
	S.idx = 0;                                                             \
}


#define MOUSEDOWN(ctx, btn) (~(ctx->mouse.hold & btn) & (ctx->mouse.update & btn))
#define MOUSEUP(ctx, btn)   ((ctx->mouse.hold & btn)  & (ctx->mouse.update & btn))
#define MOUSEHELD(ctx, btn) (ctx->mouse.hold & btn)


// https://en.wikipedia.org/wiki/Jenkins_hash_function
static ug_id_t hash(const void *data, unsigned int size)
{
	if (!size)
		return 0;
	ug_id_t hash = SALT;
	unsigned char *v = (unsigned char *)data;

	for (; size; size--) {
		hash += v[size-1];
		hash += hash << 10;
		hash ^= hash >> 6;
	}
	hash += hash << 3;
  	hash ^= hash >> 11;
  	hash += hash << 15;

	return hash;
}


int size_to_px(ug_ctx_t *ctx, ug_size_t s)
{
	switch (s.unit) {
	case UG_UNIT_MM: return roundf(s.size.f * ctx->ppm);
	case UG_UNIT_PT: return roundf(s.size.f * ctx->ppd);
	case UG_UNIT_PX: return s.size.i;
	default: return 0;
	}
}

ug_rect_t div_to_rect(ug_ctx_t *ctx, ug_div_t *div)
{
	ug_rect_t r;
	r.x = size_to_px(ctx, div->x);
	r.y = size_to_px(ctx, div->y);
	r.w = size_to_px(ctx, div->w);
	r.h = size_to_px(ctx, div->h);
	return r;
}


// update the style cache with the correct sizes in pixels and colors
static void update_style_cache(ug_ctx_t *ctx)
{
	const ug_style_t *s = ctx->style;
	// FIME: use the correct units and convert, for now assume default style
	style_cache = *s;
}


void scale_rect(ug_ctx_t *ctx, ug_rect_t *rect)
{
	if (ctx->ppi != ctx->last_ppi) {
		// if the scale has been updated than we need to scale the container
		// as well
		float scale = ctx->ppi / ctx->last_ppi;
		rect->x = roundf(rect->x * scale);
		rect->y = roundf(rect->y * scale);
		rect->w = roundf(rect->w * scale);
		rect->h = roundf(rect->h * scale);
	}
}


int crop_rect(ug_rect_t *ra, ug_rect_t *rb)
{
	int cropped = 0;
	if (L_MARGIN((*ra), 0) < L_MARGIN((*rb), 0)) {
		ra->w -= L_MARGIN((*rb), 0) - L_MARGIN((*ra), 0);
		ra->x = rb->x;
		cropped = 1;
	}
	if (R_MARGIN((*ra), 0) > R_MARGIN((*rb), 0)) {
		ra->w -= R_MARGIN((*ra), 0) - R_MARGIN((*rb), 0);
		cropped = 1;
	}
	if (T_MARGIN((*ra), 0) < T_MARGIN((*rb), 0)) {
		ra->h -= T_MARGIN((*rb), 0) - T_MARGIN((*ra), 0);
		ra->y = rb->y;
		cropped = 1;
	}
	if (B_MARGIN((*ra), 0) > B_MARGIN((*rb), 0)) {
		ra->h -= B_MARGIN((*ra), 0)- B_MARGIN((*rb), 0);
		cropped = 1;
	}
	return cropped;
}


/*=============================================================================*
 *                          Command Operations                                 *
 *=============================================================================*/


// TODO: when pushing onto the stack calculate the incremental hash of the whole
//       stack instead of calculating it at the end, this saves us one last scroll
//       trought the draw stack
static void push_rect_command(ug_ctx_t *ctx, const ug_rect_t *rect, ug_color_t color)
{
	ug_cmd_t *c;
	GET_FROM_STACK(ctx->cmd_stack, c);
	c->type       = UG_CMD_RECT;
	c->rect.x     = rect->x;
	c->rect.y     = rect->y;
	c->rect.w     = rect->w;
	c->rect.h     = rect->h;
	c->rect.color = color;
}


// pushes a text command to the render command stack, str is a pointer to a valid
// string offered by the user, it must be valid at least until rendering is done
static void push_text_command(ug_ctx_t *ctx, ug_vec2_t pos, int size, ug_color_t color, const char *str)
{
	ug_cmd_t *c;
	GET_FROM_STACK(ctx->cmd_stack, c);
	c->type       = UG_CMD_TEXT;
	c->text.x     = pos.x;
	c->text.y     = pos.y;
	c->text.size  = size;
	c->text.color = color;
	c->text.str   = str;
}


ug_cmd_t *ug_cmd_next(ug_ctx_t *ctx)
{
	if(!ctx)
		return NULL;
	if (ctx->cmd_it < ctx->cmd_stack.idx)
		return &ctx->cmd_stack.items[ctx->cmd_it++];
	return NULL;
}


/*=============================================================================*
 *                          Context Operations                                 *
 *=============================================================================*/


// creates a new context, fills with default values, ctx is ready for ug_start()
ug_ctx_t *ug_ctx_new(void)
{
	ug_ctx_t *ctx = malloc(sizeof(ug_ctx_t));
	if (!ctx)
		err(errno, "__FUNCTION__:" "Could not allocate context: %s", strerror(errno));
	memset(ctx, 0, sizeof(ug_ctx_t));

	ctx->style     = &default_style;
	ctx->style_px  = &style_cache;
	// NOTE: this fixes a bug where for the first frame the container stack
	//       doesn't get sorted, but it is kind of a botch
	ctx->last_active_cnt = 1;
	ug_ctx_set_displayinfo(ctx, DEF_SCALE, DEF_PPI);

	// TODO: allocate stacks
	return ctx;
}


void ug_ctx_free(ug_ctx_t *ctx)
{
	if (!ctx) {
		warn("__FUNCTION__:" "Trying to free a null context");
		return;
	}

	free(ctx->cmd_stack.items);
	free(ctx->cnt_stack.items);

	free(ctx);

	// NOTE: do not free style since the default style is statically allocated,
	// let the user take care of it instead
}


// TODO: add error codes
#define TEST_CTX(ctx) { if (!ctx) return -1; }
#define TEST_STR(s)   { if (!s || !s[0]) return -1; }


int ug_ctx_set_displayinfo(ug_ctx_t *ctx, float scale, float ppi)
{
	TEST_CTX(ctx);
	if (scale <= 0 || ppi < 20.0)
		return -1;

	ctx->last_ppi = ctx->ppi;
	ctx->last_ppm = ctx->ppd;
	ctx->last_ppd = ctx->ppm;

	ctx->ppm   = PPI_PPM(scale, ppi);
	ctx->ppd   = PPI_PPM(scale, ppi);
	ctx->ppi   = ppi;

	update_style_cache(ctx);

	return 0;
}


int ug_ctx_set_drawableregion(ug_ctx_t *ctx, ug_vec2_t size)
{
	TEST_CTX(ctx);
	if (size.w <= 0 || size.h <= 0)
		return -1;

	ctx->size.w = size.w;
	ctx->size.h = size.h;

	return 0;
}


int ug_ctx_set_style(ug_ctx_t *ctx, const ug_style_t *style)
{
	TEST_CTX(ctx);
	if (!style)
		return -1;
	// TODO: validate style

	ctx->style = style;
	update_style_cache(ctx);

	return 0;
}


/*=============================================================================*
 *                          Container Operations                               *
 *=============================================================================*/

#define STATEIS(cnt, f) ((cnt->flags & CNT_STATE_ALL) == f)

/*
 * Container style: rca stands for absolute rectangle, it delimits the total
 * drawable area, as such it does not include borders
 *
 *   rca                  v Border Top v
 * +-v--------------------------------------------------------+
 * | +------------------------------------------------------+ |
 * | |                  Titlebar                            | |
 * | +------------------------------------------------------+ |
 * | +------------------------------------------------------+ |
 * | |\.................................................... | |
 * | | \                  ^ Border Top ^                  . | |
 * | | .\_ rect(0,0)                                      . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | . < Border Left                                    . | |
 * | | .   + Margin                         Border Right >. | |
 * | | .                                     + Margin     . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .                                                  . | |
 * | | .................................................... | |
 * | +------------------------------------------------------+ |
 * +----------------------------------------------------------+
 *                  ^ Border Bottom ^
 */


// search a container by id int the stack and get it's address
static ug_container_t *search_container(ug_ctx_t *ctx, ug_id_t id)
{
	ug_container_t *c = NULL;
	for (int i = 0; i < ctx->cnt_stack.idx; i++) {
		if (ctx->cnt_stack.items[i].id == id) {
			c = &(ctx->cnt_stack.items[i]);
			break;
		}
	}
	return c;
}


// get a new or existing container handle
static ug_container_t *get_container(ug_ctx_t *ctx, ug_id_t id)
{
	ug_container_t *c = search_container(ctx, id);
	// if the container was not already there allocate a new one
	if (!c) {
		GET_FROM_STACK(ctx->cnt_stack, c);
		ctx->cnt_stack.sorted = 0;
	}

	return c;
}


// sort the conatiner stack so that floating conatiners always stay on top and
// the active floating conatiner i son top of everything
static void sort_containers(ug_ctx_t *ctx)
{
	if (ctx->cnt_stack.sorted)
		return;
	int tot = ctx->cnt_stack.idx;
	if (!tot)
		return;

	for (int i = 0; i < tot; i++) {
		ug_container_t *cnt = &ctx->cnt_stack.items[i];
		// move floating containers to the top
		// FIXME: this is really shit
		if (TEST(cnt->flags, UG_CNT_FLOATING)) {
			int y = tot;

			ug_container_t *s = ctx->cnt_stack.items;
			ug_container_t c = *cnt;

			if (ctx->active_cnt != c.id)
				for (; y > 0 && TEST(s[y-1].flags, UG_CNT_FLOATING); y--);

			if (i >= y)
				continue;

			memmove(&s[i], &s[i+1], (y - i) * sizeof(ug_container_t));
			s[y-1] = c;
		}
	}
	ctx->cnt_stack.sorted = 1;
}


// update the container position in the context area
// TODO: can we generalize position_container and position_element into one or
//       more similar functions
static int position_container(ug_ctx_t *ctx, ug_container_t *cnt)
{
	if (!TEST(cnt->flags, UG_CNT_FLOATING)) {
		// if there is no space left propagate the error
		if (ctx->origin.w <= 0 || ctx->origin.h <= 0)
			return -1;
	}

	ug_rect_t *rect, *rca;
	rect = &(cnt->rect);
	rca  = &(cnt->rca);
	scale_rect(ctx, rect);

	*rca = *rect;

	const ug_style_t *s = ctx->style_px;
	int b  = SZ_INT(s->border.size);
	int hh = SZ_INT(s->title.height);
	ug_rect_t c = {
		.x = ctx->origin.x + b,
		.y = ctx->origin.y + b,
		.w = ctx->origin.w - 2*b,
		.h = ctx->origin.h - 2*b
	};

	// handle relative sizes
	if (rect->w == 0) rca->w = c.w;
	if (rect->h == 0) rca->h = c.h;
	else if (TEST(cnt->flags, UG_CNT_MOVABLE)) rca->h += hh + b;

	// handle borders, only draw borders on sides which can be used to resize
	//if (TEST(cnt->flags, UG_CNT_RESIZE_LEFT)) {
	//	rca->w += b;
	//}
	//if (TEST(cnt->flags, UG_CNT_RESIZE_RIGHT)) {
	//	rca->w += b;
	//}
	//if (TEST(cnt->flags, UG_CNT_RESIZE_TOP)) {
	//	rca->h += b;
	//}
	//if (TEST(cnt->flags, UG_CNT_RESIZE_BOTTOM)) {
	//	rca->h += b;
	//}
	//if (TEST(cnt->flags, UG_CNT_MOVABLE)) {
	//	rca->h += b;
	//}

	// if the container is not fixed than it can have positions outside of the
	// main window, thus negative
	if (!TEST(cnt->flags, UG_CNT_FLOATING)) {
		// <0 -> relative to the right margin
		if (rect->x < 0) rca->x = R_MARGIN(c, 0) - R_MARGIN((*rca), -1);
		else rca->x = L_MARGIN(c, 0);
		if (rect->y < 0) rca->y = B_MARGIN(c, 0) - B_MARGIN((*rca), -1);
		else rca->y = T_MARGIN(c, 0);

		// if the container is fixed than update the available space in
		// the context
		if (rect->w) {
			if (rect->x >= 0)
				ctx->origin.x = R_MARGIN((*rca), -b);
			ctx->origin.w -= rca->w;
		} else if (rect->h) {
			if (rect->y >= 0)
				ctx->origin.y = B_MARGIN((*rca), -b);
			ctx->origin.h -= rca->h;
		} else {
			// width and height zero means fill everything
			ctx->origin.w = ctx->origin.h = 0;
		}
	}

	// set the correct element origin
	cnt->c_orig.x = cnt->r_orig.x = cnt->space.x = L_MARGIN((*rca), 0);
	cnt->c_orig.y = cnt->r_orig.y = cnt->space.y = T_MARGIN((*rca), 0);
	if (TEST(cnt->flags, UG_CNT_MOVABLE)) {
		cnt->c_orig.y += hh + SZ_INT(s->border.size);
		cnt->r_orig.y += hh + SZ_INT(s->border.size);
		cnt->space.y  += hh + SZ_INT(s->border.size);
	}

	return 0;
}


// TODO: make a set of fixed return values for the different states
// handle moving and resizing, return 1 if it had focus, 0 otherwise, negative
// return values represent errors
static int handle_container(ug_ctx_t *ctx, ug_container_t *cnt)
{
	// if we are not the currently active container than definately we are not
	// being moved or resized
	if (ctx->active_cnt != cnt->id) {
		cnt->flags &= ~CNT_STATE_ALL;
		return 0;
	}

	// mouse pressed handle resize, for simplicity containers can only
	// be resized from the bottom and right border
	// TODO: change return value to indicate this case
	if (!MOUSEHELD(ctx, UG_BTN_LEFT) ||
	    !TEST(cnt->flags, (RESIZEALL | UG_CNT_MOVABLE)))
		return 1;

	ug_rect_t *rect, *rca;
	rect = &cnt->rect;
	rca  = &cnt->rca;

	const ug_style_t *s = ctx->style_px;
	int b = SZ_INT(s->border.size);
	int m  = SZ_INT(s->margin);
	int hh = SZ_INT(s->title.height);

	ug_vec2_t mpos = ctx->mouse.pos;
	ug_rect_t clip;

	// handle movable windows
	if (TEST(cnt->flags, UG_CNT_MOVABLE)) {
		clip = (ug_rect_t){
			.x = L_MARGIN((*rca), 0),
			.y = T_MARGIN((*rca), 0),
			.w = rca->w,
			.h = hh,
		};
		if (STATEIS(cnt, CNT_STATE_MOVING) ||
		    (STATEIS(cnt, 0) && INTERSECTS(mpos, clip))) {
			cnt->flags |= CNT_STATE_MOVING;
			rect->x += ctx->mouse.delta.x;
			rect->y += ctx->mouse.delta.y;
			rca->x  += ctx->mouse.delta.x;
			rca->y  += ctx->mouse.delta.y;
		}
	}

	// lower diagonal resize
	if (TEST(cnt->flags, UG_CNT_RESIZE_BOTTOM) && TEST(cnt->flags, UG_CNT_RESIZE_RIGHT)) {
		clip = (ug_rect_t){
			.x = R_MARGIN((*rca), m),
			.y = B_MARGIN((*rca), m),
			.w = b + m,
			.h = b + m,
		};
		if (STATEIS(cnt, CNT_STATE_RESIZE_D) ||
		    (STATEIS(cnt, 0) && INTERSECTS(mpos, clip))) {
			cnt->flags |= CNT_STATE_RESIZE_D;
			rect->h = MAX(10, rect->h + ctx->mouse.delta.y);
			rca->h  = MAX(10, rca->h + ctx->mouse.delta.y);
			rect->w = MAX(10, rect->w + ctx->mouse.delta.x);
			rca->w  = MAX(10, rca->w + ctx->mouse.delta.x);
		}
	}

	// right border resize
	if (TEST(cnt->flags, UG_CNT_RESIZE_RIGHT)) {
		clip = (ug_rect_t){
			.x = R_MARGIN((*rca), m),
			.y = T_MARGIN((*rca), 0),
			.w = b + m,
			.h = rca->h,
		};
		if (STATEIS(cnt, CNT_STATE_RESIZE_R) ||
		    (STATEIS(cnt, 0) && INTERSECTS(mpos, clip))) {
			cnt->flags |= CNT_STATE_RESIZE_R;
			rect->w = MAX(10, rect->w + ctx->mouse.delta.x);
			rca->w  = MAX(10, rca->w + ctx->mouse.delta.x);
		}
	}

	// left border resize
	if (TEST(cnt->flags, UG_CNT_RESIZE_LEFT)) {
		clip = (ug_rect_t){
			.x = L_MARGIN((*rca), -b),
			.y = T_MARGIN((*rca), 0),
			.w = b + m,
			.h = rca->h,
		};
		if (STATEIS(cnt, CNT_STATE_RESIZE_L) ||
		    (STATEIS(cnt, 0) && INTERSECTS(mpos, clip))){
			cnt->flags |= CNT_STATE_RESIZE_L;

			if (rect->w - ctx->mouse.delta.x >= 10) {
				rect->w -= ctx->mouse.delta.x;
				if (TEST(cnt->flags, UG_CNT_MOVABLE))
					rect->x += ctx->mouse.delta.x;
			}
			if (rca->w - ctx->mouse.delta.x >= 10) {
				rca->w  -= ctx->mouse.delta.x;
				rca->x  += ctx->mouse.delta.x;
			}
		}
	}

	// bottom border resize
	if (TEST(cnt->flags, UG_CNT_RESIZE_BOTTOM)) {
		clip = (ug_rect_t){
			.x = L_MARGIN((*rca), 0),
			.y = B_MARGIN((*rca), m),
			.w = rca->w,
			.h = b + m,
		};
		if (STATEIS(cnt, CNT_STATE_RESIZE_B) ||
		    (STATEIS(cnt, 0) && INTERSECTS(mpos, clip))) {
			cnt->flags |= CNT_STATE_RESIZE_B;
			rect->h = MAX(10, rect->h + ctx->mouse.delta.y);
			rca->h  = MAX(10, rca->h + ctx->mouse.delta.y);
		}
	}

	// top border resize
	if (TEST(cnt->flags, UG_CNT_RESIZE_TOP)) {
		clip = (ug_rect_t){
			.x = L_MARGIN((*rca), 0),
			.y = T_MARGIN((*rca), -b),
			.w = rca->w,
			.h = b + m,
		};
		if (STATEIS(cnt, CNT_STATE_RESIZE_T) ||
		    (STATEIS(cnt, 0) && INTERSECTS(mpos, clip))) {
			cnt->flags |= CNT_STATE_RESIZE_T;

			if (rect->h - ctx->mouse.delta.y >= 10) {
				rect->h -= ctx->mouse.delta.y;
				if (TEST(cnt->flags, UG_CNT_MOVABLE))
					rect->y += ctx->mouse.delta.y;
			}
			if (rca->h - ctx->mouse.delta.y >= 10) {
				rca->h  -= ctx->mouse.delta.y;
				rca->y  += ctx->mouse.delta.y;
			}
		}
	}

	// if we were not resized but we are still active it means we are doing
	// something to the contained elements, as such set state to none
	if (STATEIS(cnt, 0))
		cnt->flags |= CNT_STATE_NONE;

	// TODO: what if I want to close a floating container?
	//       Maybe add a UG_CNT_CLOSABLE flag?

	// TODO: what about scrolling? how do we know if we need to draw
	//       a scroll bar? Maybe add that information inside the
	//       container structure
	return 1;
}

#define EXPAND(r, b) {r.x-=b,r.y-=b,r.w+=2*b,r.h+=2*b;}

static void draw_container(ug_ctx_t *ctx, ug_container_t *cnt, const char *text)
{
	ug_rect_t rect;
	const ug_style_t *s = ctx->style_px;
	int b  = SZ_INT(s->border.size);
	int hh = SZ_INT(s->title.height);
	int ts = SZ_INT(s->title.font_size);

	// push main body
	rect = cnt->rca;
	EXPAND(rect, b);
	push_rect_command(ctx, &rect, s->color.bg);

	// push outline
	if (TEST(cnt->flags, UG_CNT_RESIZE_LEFT)) {
		rect = cnt->rca;
		rect.x -= b;
		rect.y -= b,
		rect.h += 2*b;
		rect.w = b;
		push_rect_command(ctx, &rect, s->border.color);
	}
	if (TEST(cnt->flags, UG_CNT_RESIZE_RIGHT)) {
		rect = cnt->rca;
		rect.x += rect.w;
		rect.y -= b;
		rect.h += 2*b;
		rect.w = b;
		push_rect_command(ctx, &rect, s->border.color);
	}
	if (TEST(cnt->flags, UG_CNT_RESIZE_TOP)) {
		rect = cnt->rca;
		rect.y -= b;
		rect.x -= b;
		rect.h = b;
		rect.w += 2*b;
		push_rect_command(ctx, &rect, s->border.color);
	}
	if (TEST(cnt->flags, UG_CNT_RESIZE_BOTTOM)) {
		rect = cnt->rca;
		rect.x -= b;
		rect.y += rect.h;
		rect.h = b;
		rect.w += 2*b;
		push_rect_command(ctx, &rect, s->border.color);
	}
	// titlebar
	if (TEST(cnt->flags, UG_CNT_MOVABLE)) {
		// titlebar area
		rect = cnt->rca;
		rect.h = hh;
		push_rect_command(ctx, &rect, s->title.color.bg);
		// titlebar border
		rect.y += hh;
		rect.h  = b;
		push_rect_command(ctx, &rect, s->border.color);
		if (text) {
			// TODO: center text
			push_text_command(ctx,
			                 (ug_vec2_t){.x = rect.x, .y = rect.y},
					 ts, s->title.color.fg, text);
		}
	}
}


// a floating container can be placed anywhere and can be resized, acts like a
// window inside another window
int ug_container_floating(ug_ctx_t *ctx, const char *name, ug_div_t div)
{
	TEST_CTX(ctx);
	TEST_STR(name);
	// TODO: verify div

	ug_id_t id = hash(name, strlen(name));
	ug_container_t *cnt = get_container(ctx, id);

	// maybe the name address was changed so always overwrite it
	cnt->name = name;
	if (cnt->id) {
		// nothing? maybe we can skip updating all dimensions and stuff
	} else {
		cnt->id = id;
		cnt->rect = div_to_rect(ctx, &div);
		cnt->flags = UG_CNT_FLOATING | RESIZEALL | UG_CNT_MOVABLE |
			     UG_CNT_SCROLL_X | UG_CNT_SCROLL_Y;
	}

	// TODO:  what about error codes and meaning?
	if (position_container(ctx, cnt)) {
		DELETE_FROM_STACK(ctx->cnt_stack, cnt);
		return -1;
	}

	// Select current conatiner
	ctx->selected_cnt = id;

	return handle_container(ctx, cnt);
}


int ug_container_popup(ug_ctx_t *ctx, const char *name, ug_div_t div)
{
	TEST_CTX(ctx);
	TEST_STR(name);
	// TODO: verify div

	ug_id_t id = hash(name, strlen(name));
	ug_container_t *cnt = get_container(ctx, id);

	// maybe the name address was changed so always overwrite it
	cnt->name = name;
	if (cnt->id) {
		// nothing? maybe we can skip updating all dimensions and stuff
	} else {
		cnt->id = id;
		cnt->rect = div_to_rect(ctx, &div);
		cnt->flags = UG_CNT_FLOATING;
	}

	// TODO:  what about error codes and meaning?
	if (position_container(ctx, cnt)) {
		DELETE_FROM_STACK(ctx->cnt_stack, cnt);
		return -1;
	}

	// Select current conatiner
	ctx->selected_cnt = id;

	return handle_container(ctx, cnt);
}


int ug_container_sidebar(ug_ctx_t *ctx, const char *name, ug_size_t size, int side)
{
	TEST_CTX(ctx);
	TEST_STR(name);

	ug_id_t id = hash(name, strlen(name));
	ug_container_t *cnt = get_container(ctx, id);

	// maybe the name address was changed so always overwrite it
	cnt->name = name;
	if (cnt->id) {
		// nothing? maybe we can skip updating all dimensions and stuff
	} else {
		cnt->id = id;
		cnt->flags = UG_CNT_SCROLL_X | UG_CNT_SCROLL_Y;
		ug_rect_t rect = {0};
		switch (side) {
		case UG_SIDE_BOTTOM:
			cnt->flags |= UG_CNT_RESIZE_TOP;
			rect.y = -1;
			rect.h = size_to_px(ctx, size);
			break;
		case UG_SIDE_TOP:
			cnt->flags |= UG_CNT_RESIZE_BOTTOM;
			rect.h = size_to_px(ctx, size);
			break;
		case UG_SIDE_RIGHT:
			cnt->flags |= UG_CNT_RESIZE_LEFT;
			rect.x = -1;
			rect.w = size_to_px(ctx, size);
			break;
		case UG_SIDE_LEFT:
			cnt->flags |= UG_CNT_RESIZE_RIGHT;
			rect.w = size_to_px(ctx, size);
			break;
		default: return -1;
		}
		cnt->rect = rect;
	}

	if (position_container(ctx, cnt)) {
		DELETE_FROM_STACK(ctx->cnt_stack, cnt);
		return -1;
	}

	// Select current conatiner
	ctx->selected_cnt = id;

	return handle_container(ctx, cnt);
}

int ug_container_menu_bar(ug_ctx_t *ctx, const char *name, ug_size_t height)
{
	TEST_CTX(ctx);
	TEST_STR(name);

	ug_id_t id = hash(name, strlen(name));
	ug_container_t *cnt = get_container(ctx, id);

	// maybe the name address was changed so always overwrite it
	cnt->name = name;
	if (cnt->id) {
		// nothing? maybe we can skip updating all dimensions and stuff
	} else {
		cnt->id = id;
		cnt->flags = 0;
		ug_rect_t rect = {
			.x = 0, .y = 0,
			.w = 0, .h = size_to_px(ctx, height),
		};
		cnt->rect = rect;
	}

	if (position_container(ctx, cnt)) {
		DELETE_FROM_STACK(ctx->cnt_stack, cnt);
		return -1;
	}

	// Select current conatiner
	ctx->selected_cnt = id;

	return handle_container(ctx, cnt);
}


int ug_container_body(ug_ctx_t *ctx, const char *name)
{
	TEST_CTX(ctx);
	TEST_STR(name);

	ug_id_t	id = hash(name, strlen(name));
	ug_container_t *cnt = get_container(ctx, id);

	// maybe the name address was changed so always overwrite it
	cnt->name = name;
	if (cnt->id) {
		// nothing? maybe we can skip updating all dimensions and stuff
	} else {
		cnt->id = id;
		cnt->flags = 0;
		cnt->rect = (ug_rect_t){0};
	}

	if (position_container(ctx, cnt)) {
		DELETE_FROM_STACK(ctx->cnt_stack, cnt);
		return -1;
	}

	// Select current conatiner
	ctx->selected_cnt = id;

	return handle_container(ctx, cnt);
}


// TODO: return an error indicating that no container exists with that name
int ug_container_remove(ug_ctx_t *ctx, const char *name)
{
	TEST_CTX(ctx);

	ug_id_t id = ctx->selected_cnt;
	if (name)
		id = hash(name, strlen(name));

	ug_container_t *c = search_container(ctx, id);
	if (c) {
		c->flags |= CNT_STATE_DELETE;
		return 0;
	} else return -1;
}


ug_rect_t ug_container_get_rect(ug_ctx_t *ctx, const char *name)
{
	ug_rect_t r = {0};
	if(!ctx)
		return r;

	ug_id_t id = ctx->selected_cnt;
	if (name)
		id = hash(name, strlen(name));

	ug_container_t *c = search_container(ctx, id);
	if (c)
		r = c->rca;
	return r;
}


/*=============================================================================*
 *                            Frame Handling                                   *
 *=============================================================================*/


// At the beginning of a frame assume that all input has been passed to the context
// update the mouse delta and reset the command stack
int ug_frame_begin(ug_ctx_t *ctx)
{
	TEST_CTX(ctx);

	// update mouse delta
	ctx->mouse.delta.x = ctx->mouse.pos.x - ctx->mouse.last_pos.x;
	ctx->mouse.delta.y = ctx->mouse.pos.y - ctx->mouse.last_pos.y;

	// clear command stack
	RESET_STACK(ctx->cmd_stack);

	// update the origin
	ctx->origin.x = 0;
	ctx->origin.y = 0;
	ctx->origin.w = ctx->size.w;
	ctx->origin.h = ctx->size.h;

	// update hover index
	printf("Container Stack: active %x\n", ctx->active_cnt);
	ug_vec2_t v = ctx->mouse.pos;
	for (int i = 0; i < ctx->cnt_stack.idx; i++) {
		ug_container_t *c = &ctx->cnt_stack.items[i];

		printf("[%d]: %x\n", i, c->id);
		if (TEST(c->flags, CNT_STATE_DELETE)) {
			DELETE_FROM_STACK(ctx->cnt_stack, c);
			// FIXME: this should be fine since all elements in the
			//        stack are moved back and c now points to the
			//        container that would be next
		}

		ug_rect_t r = c->rca;
		EXPAND(r, SZ_INT(ctx->style_px->border.size));
		if (INTERSECTS(v, r)) {
			ctx->hover_cnt = c->id;
			// update element hover for the hovered container
			for (int i = 0; i < c->elem_stack.idx; i++) {
				ug_element_t *e = &c->elem_stack.items[i];
				if (INTERSECTS(ctx->mouse.pos, e->rca)) {
					c->hover_elem = e->id;
					break;
				}
			}
		}
	}
	printf("\n");

	if (ctx->last_active_cnt && ctx->active_cnt != ctx->last_active_cnt)
		ctx->cnt_stack.sorted = 0;

	// update active container
	if (MOUSEDOWN(ctx, UG_BTN_LEFT)) {
		ctx->active_cnt = ctx->hover_cnt;
	} else if (MOUSEUP(ctx, UG_BTN_LEFT)) {
		ctx->last_active_cnt = ctx->active_cnt;
		ctx->active_cnt = 0;
	}

	return 0;
}

// FIXME: reoreder code such that this prototype is not needed
void draw_elements(ug_ctx_t *, ug_container_t *);

// At the end of a frame reset inputs
int ug_frame_end(ug_ctx_t *ctx)
{
	TEST_CTX(ctx);

	// before drawing floating contaners need to be drawn on top of the others
	sort_containers(ctx);
	for (int i = 0; i < ctx->cnt_stack.idx; i++) {
		ug_container_t *c = &ctx->cnt_stack.items[i];
		// draw containers
		draw_container(ctx, c, c->name);
		// TODO: add a debug flag
		// debug draw space used by elements
		push_rect_command(ctx, &c->space, (ug_color_t)RGBA_FORMAT(0x0000abf0));
		// draw elements
		draw_elements(ctx, c);
		// reset the hover element
		c->hover_elem = 0;
		// reset the layout to row
		c->flags &= ~(CNT_LAYOUT_COLUMN);
		// reset used space
		c->space = (ug_rect_t){0};
	}

	ctx->input_text[0]      = '\0';
	ctx->key.update         = 0;
	ctx->mouse.hold        ^= ctx->mouse.update;
	ctx->mouse.update       = 0;
	ctx->mouse.scroll_delta = (ug_vec2_t){0};
	ctx->mouse.last_pos     = ctx->mouse.pos;

	// reset hover, it has to be calculated at frame beginning
	// FIXME: reeeeeally?
	//ctx->hover_cnt       = 0;

	ctx->last_ppi = ctx->ppi;
	ctx->last_ppm = ctx->ppm;
	ctx->last_ppd = ctx->ppd;

	ctx->frame++;

	// deselect container
	ctx->selected_cnt = 0;

	ctx->cmd_it = 0;

	return 0;
}


/*=============================================================================*
 *                                Layouting                                    *
 *=============================================================================*/


/*
 * Container layout:
 * A partition in the space taken up by the conglomerate of elements in
 * between calls to new_row or new_column (no backing state, just an idea)
 * +--------------------------------------------------------+
 * |                             .<- r_orig                 |
 * |                             .                          |
 * |   previous element          .                          |
 * |                             .                          |
 * |..............................                          |
 * |^                                                       |
 * |c_orig                                                  |
 * |                                                        |
 * |                                                        |
 * |                                                        |
 * |                                                        |
 * |                                                        |
 * +--------------------------------------------------------+
 *
 * Element Style:
 *
 *   rca             margin
 * +-v--------------+<--->+----------------+
 * | +------------+ |     | +------------+ |
 * | |            | |     | |            | |
 * | |            | |     | |            | |
 * | |            | |     | |            | |
 * | +------------+ |     | +------------+ |
 * +----------------+     +----------------+
 * <->
 *  border
*/


#define GET_SELECTED_CONTAINER(ctx, cp)                                        \
{                                                                              \
	cp = search_container(ctx, ctx->selected_cnt);                         \
	if (!cp)                                                               \
		return -1;                                                     \
}


// set the layout to row
int ug_layout_row(ug_ctx_t *ctx)
{
	TEST_CTX(ctx);

	ug_container_t *cp;
	GET_SELECTED_CONTAINER(ctx, cp);
	cp->flags &= ~CNT_LAYOUT_COLUMN;
	return 0;
}


// set the layout to column
int ug_layout_column(ug_ctx_t *ctx)
{
	TEST_CTX(ctx);

	ug_container_t *cp;
	GET_SELECTED_CONTAINER(ctx, cp);
	cp->flags |= CNT_LAYOUT_COLUMN;
	return 0;
}


int ug_layout_next_row(ug_ctx_t *ctx)
{
	TEST_CTX(ctx);

	ug_container_t *cp;
	GET_SELECTED_CONTAINER(ctx, cp);

	cp->c_orig.x = cp->r_orig.x = L_MARGIN(cp->space, 0);
	cp->c_orig.y = cp->r_orig.y = B_MARGIN(cp->space, 0);

	return 0;
}


int ug_layout_next_column(ug_ctx_t *ctx)
{
	TEST_CTX(ctx);

	ug_container_t *cp;
	GET_SELECTED_CONTAINER(ctx, cp);

	cp->c_orig.x = cp->r_orig.x = R_MARGIN(cp->space, 0);
	cp->c_orig.y = cp->r_orig.y = T_MARGIN(cp->space, 0);

	return 0;
}


/*=============================================================================*
 *                                Elements                                     *
 *=============================================================================*/

// search an element by id in the container's element stack and get it's address
static ug_element_t *search_element(ug_container_t *cnt, ug_id_t id)
{
	ug_element_t *e = NULL;
	for (int i = 0; i < cnt->elem_stack.idx; i++) {
		if (cnt->elem_stack.items[i].id == id) {
			e = &(cnt->elem_stack.items[i]);
			break;
		}
	}
	return e;
}


// get a new or existing container handle
static ug_element_t *get_element(ug_container_t *cnt, ug_id_t id)
{
	ug_element_t *e = search_element(cnt, id);
	if (!e) {
		GET_FROM_STACK(cnt->elem_stack, e);
		cnt->elem_stack.sorted = 0;
	}
	return e;
}


// update the element's position in the container area
static int position_element(ug_ctx_t *ctx, ug_container_t *cnt, ug_element_t *elem)
{

	// if there is no space then return
	if (TEST(cnt->flags, CNT_LAYOUT_COLUMN)) {
		if (cnt->space.w >= cnt->rca.w)
			return -1;
	} else {
		if (cnt->space.h >= cnt->rca.h)
			return -1;
	}


	ug_rect_t *rect, *rca;
	rect = &(elem->rect);
	rca  = &(elem->rca);
	scale_rect(ctx, rect);

	*rca = *rect;

	const ug_style_t *s = ctx->style_px;
	int b  = SZ_INT(s->border.size);
	int m  = SZ_INT(s->margin);
	int cx, cy, cw, ch;
	int eb = 0;

	switch (elem->type) {
	case UG_ELEM_BUTTON: eb = SZ_INT(s->btn.border); break;
	default: break;
	}

	// FIXME: this does not work
	cw = MAX(cnt->rca.w - cnt->space.w, 0);
	ch = MAX(cnt->rca.h - cnt->space.h, 0);
	if (TEST(cnt->flags, CNT_LAYOUT_COLUMN)) {
		cx = cnt->c_orig.x;
		cy = cnt->c_orig.y;
	} else {
		cx = cnt->r_orig.x;
		cy = cnt->r_orig.y;
	}

	// handle relative sizes
	if (rect->w == 0) rca->w = cw - 2*eb;
	if (rect->h == 0) rca->h = ch - 2*eb;
	// for elements x and y are offsets
	rca->x = cx + rect->x + eb + m;
	rca->y = cy + rect->y + eb + m;

	// if the element was put outside of the container return, this can happen
	// because of the element offset
	if (OUTSIDE((*rca), 0, cnt->rca, b))
		return -1;

	elem->flags &= ~(ELEM_CLIPPED);
	if (crop_rect(rca, &cnt->rca))
		elem->flags |= ELEM_CLIPPED;

	if (TEST(cnt->flags, CNT_LAYOUT_COLUMN)) {
		cnt->c_orig.y = B_MARGIN((*rca), 0) + eb;
		cnt->r_orig.x = R_MARGIN((*rca), 0) + eb;
		cnt->r_orig.y = T_MARGIN((*rca), 0) + eb;

	} else {
		cnt->r_orig.x = R_MARGIN((*rca), 0) + eb;
		cnt->c_orig.x = L_MARGIN((*rca), 0) + eb;
		cnt->c_orig.y = B_MARGIN((*rca), 0) + eb;
	}

	// expand used space
	if (R_MARGIN(cnt->space, 0) < R_MARGIN((*rca), -eb))
		cnt->space.w = R_MARGIN((*rca), -eb) - L_MARGIN(cnt->space, 0);
	if (B_MARGIN(cnt->space, 0) < B_MARGIN((*rca), -eb))
		cnt->space.h = B_MARGIN((*rca), -eb) - T_MARGIN(cnt->space, 0);

	return 0;
}


// TODO: have a map of function pointers for each element type instead of this
//       generic function
int handle_element(ug_ctx_t *ctx, ug_container_t *cnt, ug_element_t *elem)
{
	// if the contaniner is not the current hover then do nothing, think about
	// floating cont. over bodies
	if (ctx->hover_cnt != cnt->id)
		return 0;
	// if the element is not selected nor hovered then do nothing
	if (cnt->hover_elem != elem->id && cnt->selected_elem != elem->id)
		return 0;

	if (cnt->hover_elem == elem->id) {
		if (MOUSEDOWN(ctx, BTN_ANY))
			cnt->selected_elem = elem->id;
	} else {
		if (cnt->selected_elem != elem->id)
			return 0;
	}
	// TODO: handle different types of elements

	// TODO: return which button was held
	return 1;
}


void draw_elements(ug_ctx_t *ctx, ug_container_t *cnt)
{
	const ug_style_t *s = ctx->style_px;

	for (int i = 0; i < cnt->elem_stack.idx; i++) {
		ug_element_t *e = &(cnt->elem_stack.items[i]);
		ug_color_t col = RGB_FORMAT(0), bcol = RGB_FORMAT(0);
		ug_color_t txtcol = RGB_FORMAT(0);
		ug_rect_t r = e->rca;
		int eb = 0, ts = 0;
		unsigned char draw_br = 0, draw_fg = 0, draw_txt = 0;

		switch (e->type) {
		case UG_ELEM_BUTTON:
			col  = cnt->hover_elem == e->id ? s->btn.color.act : s->btn.color.bg;
			bcol = cnt->selected_elem == e->id && ctx->hover_cnt == cnt->id ? s->btn.color.sel : s->btn.color.br;
			txtcol = s->btn.color.fg;
			ts = SZ_INT(s->btn.font_size);
			eb = SZ_INT(ctx->style_px->btn.border);
			draw_br = draw_fg = draw_txt = 1;
			break;
		case UG_ELEM_TXTBTN:
			ts = SZ_INT(s->btn.font_size);
			txtcol = s->color.fg;
			draw_txt = 1;
		default: break;
		}

		if (draw_br) {
			r = (ug_rect_t){
				.x = e->rca.x - eb,
				.y = e->rca.y - eb,
				.w = e->rca.w + 2*eb,
				.h = e->rca.h + 2*eb,
			};
			if (TEST(e->flags, ELEM_CLIPPED))
				crop_rect(&r, &cnt->rca);
			push_rect_command(ctx, &r, bcol);
		}
		if (draw_fg) {
			r = e->rca;
			push_rect_command(ctx, &r, col);
		}
		if (draw_txt) {
			push_text_command(ctx,
			                 (ug_vec2_t){
						.x = e->rca.x+eb,
						.y = e->rca.y+eb+e->rca.h/2
					 },
					 ts,
					 txtcol,
					 e->btn.txt);
		}
	}
}


int ug_element_button(ug_ctx_t *ctx, const char *name, const char *txt, ug_div_t dim)
{
	TEST_CTX(ctx);
	TEST_STR(name);

	ug_container_t *cp;
	GET_SELECTED_CONTAINER(ctx, cp);

	ug_id_t id = hash(name, strlen(name));
	ug_element_t *elem = get_element(cp, id);

	// FIXME: we don't always need to do everything
	elem->id      = id;
	elem->type    = UG_ELEM_BUTTON;
	elem->rect    = div_to_rect(ctx, &dim);
	elem->name    = name;
	elem->btn.txt = txt;

	// FIXME: what about error codes?
	if (position_element(ctx, cp, elem)) {
		DELETE_FROM_STACK(cp->elem_stack, elem);
		return -1;
	}

	return handle_element(ctx, cp, elem);
}


// text-only button
int ug_element_textbtn(ug_ctx_t *ctx, const char *name, const char *txt, ug_div_t dim)
{
	TEST_CTX(ctx);
	TEST_STR(name);
	TEST_STR(txt);

	ug_container_t *cp;
	GET_SELECTED_CONTAINER(ctx, cp);

	ug_id_t id = hash(name, strlen(name));
	ug_element_t *elem = get_element(cp, id);

	// FIXME: we don't always need to do everything
	elem->id      = id;
	elem->type    = UG_ELEM_TXTBTN;
	elem->rect    = div_to_rect(ctx, &dim);
	elem->name    = name;
	elem->btn.txt = txt;

	// FIXME: what about error codes?
	if (position_element(ctx, cp, elem)) {
		DELETE_FROM_STACK(cp->elem_stack, elem);
		return -1;
	}

	return handle_element(ctx, cp, elem);
}