#include <math.h>
#include <stdlib.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>

#include "til.h"
#include "til_fb.h"

#include "draw.h"

/* Copyright (C) 2020 Philip J. Freeman <elektron@halo.nu> */

/*

Spirograph Emulator

  refs:

    - https://en.wikipedia.org/wiki/Spirograph#Mathematical_basis
    - https://en.wikipedia.org/wiki/Unit_circle#Trigonometric_functions_on_the_unit_circle
*/

typedef struct spiro_context_t {
	float r;
	int r_dir;
	float p;
	int p_dir;
} spiro_context_t;


static void * spiro_create_context(unsigned seed, unsigned ticks, unsigned n_cpus, til_setup_t *setup)
{
	spiro_context_t *ctxt;
	float		z;

	ctxt = malloc(sizeof(spiro_context_t));
	if (!ctxt)
		return NULL;

	ctxt->r=.25f+(rand()/(float)RAND_MAX)*.5f;
	if(ctxt->r>.5f)
		ctxt->r_dir=-1;
	else
		ctxt->r_dir=1;
	ctxt->p=(rand()/(float)RAND_MAX)*ctxt->r;
	ctxt->p_dir=ctxt->r_dir*-1;
#ifdef DEBUG
	printf("spiro: initial context: r=%f, dir=%i, p=%f, dir=%i\n", ctxt->r, ctxt->r_dir, ctxt->p, ctxt->p_dir);
#endif
	return ctxt;
}

static void spiro_destroy_context(void *context)
{
	spiro_context_t *ctxt = context;

	free(context);
}


static void spiro_render_fragment(void *context, unsigned ticks, unsigned cpu, til_fb_fragment_t *fragment)
{
	spiro_context_t	*ctxt = context;

	int		width = fragment->width, height = fragment->height;

	int display_R, display_origin_x, display_origin_y;

	/* Based on the fragment's dimensions, calculate the origin and radius of the fixed outer
	circle, C0. */

	if(width>=height) {			 // landscape or square aspect ratio
		display_R=(height-1)*0.5f;
		display_origin_x=((width-height)*.5f)+display_R;
		display_origin_y=display_R;
	} else {				// portrait
		display_R=(width-1)*.5f;
		display_origin_x=display_R;
		display_origin_y=((height-width)*.5f)+display_R;
	}

	/* blank the fragment */
	til_fb_fragment_clear(fragment);

	/* plot one spirograph run */
	float l=ctxt->p/ctxt->r;
	float k=ctxt->r;
	for(float t=0.f; t<128*2*M_PI; t+= M_PI/display_R) {
		float my_x=((1.f-k)*cosf(t))+(l*k*cosf(((1.f-k)/k)*t));
		float my_y=((1.f-k)*sinf(t))-(l*k*sinf(((1.f-k)/k)*t));
		int pos_x=display_origin_x+(my_x*display_R);
		int pos_y=display_origin_y+(my_y*display_R);
		til_fb_fragment_put_pixel_unchecked(fragment, TIL_FB_DRAW_FLAG_TEXTURABLE, pos_x, pos_y,
			makergb(sinf(M_1_PI*t)*127+128,
				sinf(M_1_PI*t+(2*M_PI*.333333333333f))*127+128,
				sinf(M_1_PI*t+(4*M_PI*.333333333333f))*127+128,
				0.76));
	}

#ifdef DEBUG
	/* plot the origin point */
	til_fb_fragment_put_pixel_unchecked(fragment, 0, display_origin_x, display_origin_y,
		makergb(0xFF, 0xFF, 0x00, 1));

	/* plot the fixed outer circle C0 */
	for(float a=0.f; a<2*M_PI; a+= M_PI_2/display_R) {
		int pos_x=display_origin_x+(cosf(a)*display_R);
		int pos_y=display_origin_y+(sinf(a)*display_R);
		til_fb_fragment_put_pixel_unchecked(fragment, 0, pos_x, pos_y,
			makergb(0xFF, 0xFF, 0x00, 1));
	}

	/* plot inner circle Ci */
	til_fb_fragment_put_pixel_unchecked(fragment, 0, display_origin_x+display_R-(ctxt->r*display_R),
		display_origin_y, makergb(0xFF, 0xFF, 0x00, 1));

	for(float a=0.f; a<2*M_PI; a+= M_PI_2/display_R) {
		int pos_x=display_origin_x+display_R-(ctxt->r*display_R)+
			(cosf(a)*ctxt->r*display_R);
		int pos_y=display_origin_y+(sinf(a)*ctxt->r*display_R);
		til_fb_fragment_put_pixel_unchecked(fragment, 0, pos_x, pos_y,
			makergb(0xFF, 0xFF, 0x00, 1));
	}

	/* plot p */
	til_fb_fragment_put_pixel_unchecked(fragment, 0, display_origin_x+display_R-(ctxt->r*display_R)+
		(ctxt->p*display_R), display_origin_y, makergb(0xFF, 0xFF, 0x00, 1));
#endif

	/* check bounds and increment r & p */
	float next_r=ctxt->r+(.00001f*ctxt->r_dir);
	if(next_r >= 1.f || next_r <= 0.f || next_r <= ctxt->p)
		ctxt->r_dir=ctxt->r_dir*-1;
	else
		ctxt->r=ctxt->r+(.00001f*ctxt->r_dir);

	float next_p=ctxt->p+(.0003f*ctxt->p_dir);
	if(next_p >= ctxt->r || next_p <= 0)
		ctxt->p_dir=ctxt->p_dir*-1;
	else
		ctxt->p=ctxt->p+(.0003f*ctxt->p_dir);

}

til_module_t	spiro_module = {
	.create_context  = spiro_create_context,
	.destroy_context = spiro_destroy_context,
	.render_fragment = spiro_render_fragment,
	.name = "spiro",
	.description = "Spirograph emulator",
	.author = "Philip J Freeman <elektron@halo.nu>",
	.flags = TIL_MODULE_OVERLAYABLE,
};