#include <stdio.h>
#include <allegro5/allegro5.h>
#include <math.h>
#include <allegro5/a5_iio.h>

static ALLEGRO_COLOR aa_color(ALLEGRO_COLOR c, ALLEGRO_COLOR bg, float percent)
{
	ALLEGRO_COLOR ret;

	ret = al_map_rgba(
		(int)(c.r*(1-percent)*255),// + (int)(bg.r*(1-percent)*255),
		(int)(c.g*(1-percent)*255),// + (int)(bg.g*(1-percent)*255),
		(int)(c.b*(1-percent)*255),// + (int)(bg.b*(1-percent)*255),
		(int)(c.a*255)
	);

	return ret;
}

static void m_put_aa_pixel(float x, float y, ALLEGRO_COLOR color)
{
	ALLEGRO_BITMAP *target = al_get_target_bitmap();

	float frac1 = x - (int)x;
	float frac2 = y - (int)y;

	if (frac1 != 0.0f && frac2 != 0.0f) {
		// Touching 4 pixels
		float p1 = (1 - frac1) * (1 - frac2);
		float p2 = frac1 * (1 - frac2);
		float p3 = frac2 * (1 - frac1);
		float p4 = frac2 * frac1;
		int x1 = (int)x;
		int x2 = (int)x + 1;
		int y1 = (int)y;
		int y2 = (int)y + 1;
		al_draw_pixel(x1, y1, aa_color(color, al_get_pixel(target, x1, y1), p1));
		al_draw_pixel(x2, y1, aa_color(color, al_get_pixel(target, x2, y1), p2));
		al_draw_pixel(x1, y2, aa_color(color, al_get_pixel(target, x1, y2), p3));
		al_draw_pixel(x2, y2, aa_color(color, al_get_pixel(target, x2, y2), p4));
	}
	else if (frac1 != 0.0f) {
		// Touching two pixels, horizontal
		float p1 = (1 - frac1);
		float p2 = frac1;
		int x1 = (int)x;
		int x2 = (int)x + 1;
		al_draw_pixel(x1, y, aa_color(color, al_get_pixel(target, x1, y), p1));
		al_draw_pixel(x2, y, aa_color(color, al_get_pixel(target, x2, y), p2));
	}
	else if (frac2 != 0.0f) {
		// Touching two pixel, vertical
		float p1 = (1 - frac2);
		float p2 = frac2;
		int y1 = (int)y;
		int y2 = (int)y + 1;
		al_draw_pixel(x, y1, aa_color(color, al_get_pixel(target, x, y1), p1));
		al_draw_pixel(x, y2, aa_color(color, al_get_pixel(target, x, y2), p2));
	}
	else {
		// Touching one pixel
		al_draw_pixel(x, y, color);
	}
}

float interpolate(float f1, float f2, float p)
{
	return (f1 * (1 - p)) + (f2 * p);
}

void draw_bolt_1(float a)
{
	int radius = 5;
	int dest_x = 120;
	int dest_y = 110;
	float px = dest_x, py = dest_y;
	float dx = cos(a);
	float dy = sin(a);
	float lx = cos(a+M_PI/2);
	float ly = -sin(a+M_PI/2);
	int i = 0;
	float step = 1.0f / radius;

	while (py > 0 && px > 0 && px < 240) {
		for (float f = 0; f < 1.0f; f += step) {
			ALLEGRO_COLOR color;
			if (f < 0.5f) {
				color = al_map_rgba(interpolate(255, 0, f*2),
					interpolate(255, 0, f),
					255, 255);
			}
			else {
				color = al_map_rgba(0, 0, 255, 255*(1-(f-0.5f)*2));
			}
			float a = lx * radius * f;
			float b = ly * radius * f;

			m_put_aa_pixel(px+a, py+b, color);
			m_put_aa_pixel(px-a, py-b, color);
		}
		px += (rand() % 5 - 2) + dx;
		py -= dy;
	}
}

int main(void)
{
	al_init();
	al_iio_init();

	ALLEGRO_DISPLAY *display = al_create_display(720, 480);

	const int FRAMES = 16;
	
	ALLEGRO_BITMAP *b = al_create_bitmap(240, 110);

	for (int i = 0; i < FRAMES; i++) {
		float diff = M_PI/2;
		float a = (M_PI/2+M_PI/4) - ((float)i/FRAMES*diff);
		al_set_target_bitmap(b);
		al_clear(al_map_rgba(0, 100, 0, 255));
		draw_bolt_1(a);
		char name[100];
		sprintf(name, "Bolt2_%d.png", i);
		al_iio_save(name, b);
		printf("i=%d done\n", i);
	}

	return 0;
}
END_OF_MAIN()