/*
 *  Copyright (C) 2018  Vito Caputo - <vcaputo@pengaru.com>
 *
 *  This program is free software: you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License version 3 as published
 *  by the Free Software Foundation.
 *
 *  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, see <http://www.gnu.org/licenses/>.
 */

#include <SDL.h>

#include "list.h"
#include "stage.h"

typedef struct v2f_t {
	float	x, y;
} v2f_t;

typedef struct aabb_t {
	v2f_t	min, max;
} aabb_t;

typedef struct stage_cached_t {
	int		width, height;
	SDL_Texture	*texture;
} stage_cached_t;

struct stage_node_t {
	list_head_t		nodes;
	char			name[STAGE_NODE_NAME_MAX];
	stage_cached_t		cached;
	aabb_t			aabb;		/* node coordinates expressed in the space of -1.0...1.0 */
	v2f_t			position;	/* position of node, optionally used to move aabb as a whole */
	float			alpha;		/* alpha for the texture when composited */
	double			angle;		/* angle for the texture when composited */
	unsigned		active:1;	/* node is active */
	unsigned		locked:1;	/* node is locked */

	stage_render_func_t	render;		/* render object into a texture */
	stage_free_func_t	free;		/* free object */
	void			*object;	/* object */
};

struct stage_t {
	list_head_t	layers[STAGE_LAYERS_MAX];
	SDL_Renderer	*renderer;		/* target renderer */
	float		aspect_ratio;		/* width/height ratio of stage, -1.0...1.0 range of node coordinates map to this ratio. */
};


/* minimally initialize a node to carry an object */
static void node_init(stage_node_t *node, const char *name, void *object, stage_render_func_t render_func, stage_free_func_t free_func)
{
	strncpy(node->name, name, sizeof(node->name));
	node->render = render_func;
	node->free = free_func;
	node->object = object;
}


/* allocate a node, no list manipulation occurs, this purely creates a node in isolation and assigns its associated name, object and functions */
static stage_node_t * node_new(const char *name, void *object, stage_render_func_t render_func, stage_free_func_t free_func)
{
	stage_node_t	*node;

	node = calloc(1, sizeof(stage_node_t));
	if (!node)
		return NULL;

	node_init(node, name, object, render_func, free_func);

	return node;
}


/* free a node, no list manipulation occurs, this is purely cleanup of the node and its associated texture and object */
static void node_free(stage_node_t *node)
{
	if (node->free)
		node->free(node->object);
	if (node->cached.texture)
		SDL_DestroyTexture(node->cached.texture);
	free(node);
}


/* returns a new node installed at the specified layer */
stage_node_t * stage_node_new(stage_t *stage, int layer, const char *name, void *object, stage_render_func_t render_func, stage_free_func_t free_func)
{
	stage_node_t	*node;

	node = node_new(name, object, render_func, free_func);
	if (!node)
		return NULL;

	list_add_tail(&node->nodes, &stage->layers[layer]);

	return node;
}


/* replace a given node's object only - retain render/free hooks and everything else, invalidates cache  - DOES NOT FREE OLD OBJECT */
/* FIXME: this is being used as a kludge to swap frames in an svg - 
 * eliminate this bullshit and add support for animations or at least frames,
 * the stage really shouldn't have anything to do with it, we can dick with
 * the svg behind its back.  I just don't currently have the helpers for creating
 * svg nodes actually giving out the bare svg handle currently, so the stage_node_t
 * is all I have to dick with at the moment.  Next time!  This really dicks with
 * the resource lifecycle - if the stage frees the node, which object was active
 * at the time and which object still needs to be freed because it wasn't in
 * the stage when the node was killed?  It's totally shitty, and I'm aware.
 */
void stage_node_set_object(const stage_t *stage, stage_node_t *node, void *object)
{
	if (node->cached.texture) {
		SDL_DestroyTexture(node->cached.texture);
		node->cached.texture = NULL;
	}

	node->object = object;
}

/* FIXME: GROSS fuck me */
void stage_node_get_object(const stage_t *stage, stage_node_t *node, void **res_object)
{
	*res_object = node->object;
}


/* replaces a given node's object-related properties but otherwise keeping the existing state */
void stage_node_replace(const stage_t *stage, stage_node_t *node, const char *name, void *object, stage_render_func_t render_func, stage_free_func_t free_func)
{
	if (node->free)
		node->free(node->object);

	if (node->cached.texture) {
		SDL_DestroyTexture(node->cached.texture);
		node->cached.texture = NULL;
	}

	node_init(node, name, object, render_func, free_func);
}


/* frees a given node removing it from the stage */
stage_node_t * stage_node_free(stage_t *stage, stage_node_t *node)
{
	if (node) {
		list_del(&node->nodes);
		node_free(node);
	}

	return NULL;
}


/* set the alpha on a node */
void stage_node_set_alpha(const stage_t *stage, stage_node_t *node, float alpha)
{
	/* TODO: this should probably mark something dirty for when we stop always recomposing everything */
	node->alpha = alpha;
}


/* set the aabb for a node */
void stage_node_set_aabb(const stage_t *stage, stage_node_t *node, const aabb_t *aabb)
{
	node->aabb = *aabb;
}


/* get the aabb for a node */
void stage_node_get_aabb(const stage_t *stage, stage_node_t *node, aabb_t *res_aabb)
{
	*res_aabb = node->aabb;
}


/* set the position for a node */
void stage_node_set_position(const stage_t *stage, stage_node_t *node, float x, float y)
{
	node->position.x = x;
	node->position.y = y;
}


/* get the position for a node */
void stage_node_get_position(const stage_t *stage, stage_node_t *node, float *res_x, float *res_y)
{
	*res_x = node->position.x;
	*res_y = node->position.y;
}


/* set a node to active (participates in rendering) */
void stage_node_set_active(const stage_t *stage, stage_node_t *node)
{
	node->active = 1;
}


/* set a node to inactive (doesn't participate in rendering) */
void stage_node_set_inactive(const stage_t *stage, stage_node_t *node)
{
	/* TODO: should this discard the potentially cached texture? */
	node->active = 0;
}


/* set a node to locked (doesn't get freed by clears) */
void stage_node_set_locked(const stage_t *stage, stage_node_t *node)
{
	node->locked = 1;
}


/* set a node to unlocked (default, gets freed by clears) */
void stage_node_set_unlocked(const stage_t *stage, stage_node_t *node)
{
	node->locked = 0;
}


/* set a node's layer */
void stage_node_set_layer(stage_t *stage, stage_node_t *node, int layer)
{
	/* TODO: assert layer sanity */
	list_del(&node->nodes);
	list_add_tail(&node->nodes, &stage->layers[layer]);
}


void stage_node_set_angle(const stage_t *stage, stage_node_t *node, double angle)
{
	node->angle = angle;
}


void stage_node_get_angle(const stage_t *stage, stage_node_t *node, double *res_angle)
{
	*res_angle = node->angle;
}


/* create a new stage with the given aspect ratio */
stage_t * stage_new(SDL_Renderer *renderer, float aspect_ratio)
{
	stage_t	*stage;
	int	i;

	stage = calloc(1, sizeof(stage_t));
	if (!stage)
		return NULL;

	for (i = 0; i < STAGE_LAYERS_MAX; i++)
		INIT_LIST_HEAD(&stage->layers[i]);

	stage->renderer = renderer;
	stage->aspect_ratio = aspect_ratio;

	return stage;
}

static void _stage_clear(stage_t *stage, int force)
{
	stage_node_t	*node, *_node;
	int		i;

	for (i = 0; i < STAGE_LAYERS_MAX; i++) {
		list_for_each_entry_safe(node, _node, &stage->layers[i], nodes) {
			if (force || !node->locked)
				stage_node_free(stage, node);
		}
	}
}

/* free everything in the stage, but keep the stage around */
/* probably good hygiene to clear everything when there's no intention of
 * reusing nodes at the start of a new context, in case something is left
 * around unintentionally. */
void stage_clear(stage_t *stage)
{
	_stage_clear(stage, 0);
}


/* free the supplied stage and all associated textures and objects */
stage_t * stage_free(stage_t *stage)
{

	if (stage) {
		_stage_clear(stage, 1);
		free(stage);
	}

	return NULL;
}


/* fit a stage to the supplied dimensions, returns the fitted dimensions in the result pointers */
/* the idea is this can be used in a window resize hook to enforce the stage's aspect ratio */
void stage_fit(const stage_t *stage, int width, int height, int *res_width, int *res_height)
{
	float	full_width = stage->aspect_ratio * ((float)height);

	if (full_width == width) {
		/* perfect fit */
		*res_width = width;
		*res_height = height;
	} else if (full_width > width) {
		/* height is too large */
		*res_height = (1.0f / stage->aspect_ratio) * ((float)width);
		*res_width = width;
	} else {
		/* width is too large */
		*res_width = full_width;
		*res_height = height;
	}
}


static void aabb_to_rect(const aabb_t *aabb, const v2f_t *pos, const SDL_Rect *stage_rect, SDL_Rect *res_rect)
{
	float	half_w = ((float)stage_rect->w) * .5f, half_h = ((float)stage_rect->h) * .5f;	/* FIXME silly to recompute this repeatedly... */

	res_rect->x = stage_rect->x;
	res_rect->y = stage_rect->y;
	res_rect->x += ((float)aabb->min.x + pos->x) * half_w + half_w;
	res_rect->y += stage_rect->h - (((float)aabb->max.y + pos->y) * half_h + half_h);

	res_rect->w = (aabb->max.x - aabb->min.x) * half_w;
	res_rect->h = (aabb->max.y - aabb->min.y) * half_h;
}


static void render_nodes(list_head_t *head, SDL_Renderer *renderer, SDL_Rect *dest_rect)
{
	stage_node_t	*node;

	list_for_each_entry(node, head, nodes) {
		SDL_Rect	node_rect;

		if (!node->active)
			continue;

		/* scale the node's aabb stage coordinates to destination renderer coordinates */
		aabb_to_rect(&node->aabb, &node->position, dest_rect, &node_rect);

		/* if we have a cached texture, see if the dimensions changed */
		if (node->cached.texture &&
		    (node_rect.w != node->cached.width ||
		     node_rect.h != node->cached.height)) {
			SDL_DestroyTexture(node->cached.texture);
			node->cached.texture = NULL;
		}

		/* Tell the node to draw its cached texture */
		/* The draw function may either use the existing texture when non-NULL or destroy and create a new one,
		 * whatever is most convenient for it.
		 * If the texture is NULL, a create & render must be performed, and 1 returned.
		 * If the texture is non-NULL, and there's no animation or anything to be done, 0 may simply be returned.
		 * Otherwise, if supplied a non-NULL texture and it's modified, 1 must be returned.
		 */
		/* XXX: at this time, the return value is ignored (it always composites the stage even when unchanged) */
		node->render(renderer, node->object, node_rect.w, node_rect.h, &node->cached.texture);
		node->cached.width = node_rect.w;
		node->cached.height = node_rect.h;
		SDL_SetTextureAlphaMod(node->cached.texture, ((float)node->alpha * 255.0f));

		/* copy the texture to renderer */
		if (node->angle == 0)
			SDL_RenderCopy(renderer, node->cached.texture, NULL, &node_rect);
		else
			SDL_RenderCopyEx(renderer, node->cached.texture, NULL, &node_rect, node->angle, NULL, SDL_FLIP_NONE);
	}
}


/* XXX: ANOTHER KLUDGE FIXME */
/* we shouldn't need to let this out of the stage, but for the mouse aiming
 * it was easier this way for now.
 */
void stage_get_output_size(stage_t *stage, int *res_width, int *res_height)
{
	SDL_GetRendererOutputSize(stage->renderer, res_width, res_height);
}


/* render the supplied stage into the supplied renderer */
/* the aspect_ratio of the stage will be enforced in filling the logical size
 * of the renderer.  Unless the aspect ratio matches precisely, stage_render()
 * will center the rendering and leave blank borders on the edges left empty.
 * The renderer may be sized precisely by first calling stage_fit().
 */
void stage_render(stage_t *stage)
{
	SDL_Rect	rect;
	int		i, width, height;

	/* XXX TODO: investigate renderer viewports and scale factors */
	SDL_GetRendererOutputSize(stage->renderer, &width, &height);

	stage_fit(stage, width, height, &rect.w, &rect.h);
	rect.x = (width - rect.w) / 2;
	rect.y = (height - rect.h) / 2;

	SDL_RenderClear(stage->renderer);	/* TODO: handle -1 on error */

	for (i = 0; i < STAGE_LAYERS_MAX; i++)
		render_nodes(&stage->layers[i], stage->renderer, &rect);
}


/* lookup a node from a name */
stage_node_t * stage_node_lookup_name(const stage_t *stage, const char *name)
{
	stage_node_t	*node;
	int		i;

	for (i = 0; i < STAGE_LAYERS_MAX; i++) {
		list_for_each_entry(node, &stage->layers[i], nodes) {
			if (!strncmp(node->name, name, sizeof(node->name)))
				return node;
		}
	}

	return NULL;
}


/* lookup a node from a cartesian renderer coordinate */
stage_node_t * stage_node_lookup_cartesian(const stage_t *stage, int x, int y)
{
	stage_node_t	*node;
	SDL_Rect	rect;
	int		i, width, height;

	/* FIXME: copy-pasta with render, factor out */
	SDL_GetRendererOutputSize(stage->renderer, &width, &height);

	stage_fit(stage, width, height, &rect.w, &rect.h);
	rect.x = (width - rect.w) / 2;
	rect.y = (height - rect.h) / 2;

	/* this is currently very simple: find the first top-most node
	 * including the specified coordinate.
	 */
	for (i = STAGE_LAYERS_MAX - 1; i >= 0; i--) {
		list_for_each_entry(node, &stage->layers[i], nodes) {
			SDL_Rect	node_rect;

			if (!node->active)
				continue;

			aabb_to_rect(&node->aabb, &node->position, &rect, &node_rect);
			if (x >= node_rect.x && x < node_rect.x + node_rect.w &&
			    y >= node_rect.y && y < node_rect.y + node_rect.h)
				return node;
		}
	}

	return NULL;
}