#include <SDL2/SDL.h>

#include <assert.h>
#include <stdlib.h>

#include "maths.cpp"

struct Shrinkwrap {
	v2f* points;
	int count;
	v2f p0;
	Shrinkwrap(v2f* src, int src_count):
		count(0), p0(INFINITY, INFINITY) {
		int i, top = 0;
		int stack_size = src_count;
		v2f* stack = (v2f*)malloc(stack_size * sizeof *stack);
		points = (v2f*)malloc(src_count * sizeof *points);
		auto push = [&](v2f p) {
			assert(top < stack_size);
			stack[top++] = p;
		};
		auto pop = [&]() {
			assert(top > 0);
			return stack[--top];
		};
		auto peek = [&](int i) {
			assert(top - 1 - i >= 0);
			return stack[top - 1 - i];
		};
		auto ccw = [](v2f a, v2f b, v2f c) {
    	float angle =
    		(b.y - a.y) * (c.x - b.x) -
    		(b.x - a.x) * (c.y - b.y);
    	return angle > -0.00001f;
		};
		for (i = 0; i < src_count; i++) {
			v2f p = src[i];
			if (p.y < p0.y || (fabsf(p.y - p0.y) < 0.0001f && p.x < p0.x))
				p0 = p;
		}
		std::sort(
			src,
			src + src_count,
			[this](const v2f& f, const v2f& s) {
    		float a =
    			(f.y - p0.y) * (s.x - f.x) -
    			(f.x - p0.x) * (s.y - f.y);
    		bool colinear = fabsf(a - 0.0f) < 0.001f;
    		if (colinear)
    			return v2f::mag(p0 - s) >= v2f::mag(p0 - f);
    		return a < 0.0f;
			}
		);
		for (i = 0; i < src_count; i++) {
			v2f p = src[i];
			while (top > 1 && ccw(peek(1), peek(0), p))
				pop();
			push(p);
		}
		while (top)
			points[count++] = pop();
		free(stack);
	}
};

int main(int argc, const char** argv) {
	int r = 1;
	float rot = 3.5f;
	SDL_Window* window;
	SDL_Renderer* ren;
	SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_JOYSTICK);
	SDL_CreateWindowAndRenderer(
		800,
		800,
		0,
		&window,
		&ren
	);
	v2f points[] = {
		{ 129.0f, 148.0f },
		{ 178.0f, 178.0f },
		{ 146.0f, 146.0f },
		{ 163.0f, 172.0f },
		{ 129.0f, 159.0f },
		{ 102.0f, 151.0f },
		{ 167.0f, 122.0f }
	};
	float rots[] = {
		0.0f,
		1.0f,
		1.0f,
		1.0f,
		0.0f,
		1.0f,
		0.0f,
	};
	constexpr int point_count = sizeof points / sizeof *points;
	v2f points2[point_count];
	while (r) {
		int i;
		SDL_Event e;
		while (SDL_PollEvent(&e)) {
			switch (e.type) {
				case SDL_QUIT:
					r = 0;
					break;
			}
		}
		for (i = 0; i < point_count; i++) {
			v2f p = points[i];
			points2[i] = v2f(
				p.x * 2 + (sinf(rot * rots[i]) * p.x - cosf(rot * rots[i]) * p.y),
				p.y * 2 + (sinf(rot * rots[i]) * p.x + cosf(rot * rots[i]) * p.y)
			);
		}
		Shrinkwrap s(points2, point_count);
		SDL_SetRenderDrawColor(ren, 0x00, 0x00, 0x00, 0x00);
		SDL_RenderClear(ren);
		for (int i = 0; i < s.count; i++) {
			v2f a = s.points[i];
			v2f b = s.points[(i + 1) % s.count];
			v2f e = a - b;
			v2f h = e * 0.5f;
			v2f n = v2f(e.y, -e.x);
			n = v2f::normalised(n);
			SDL_SetRenderDrawColor(ren, 0x00, 0x00, 0xff, 0xff);
			SDL_RenderDrawLine(ren, (int)a.x, (int)a.y, (int)b.x, (int)b.y);
			SDL_SetRenderDrawColor(ren, 0xff, 0x00, 0xff, 0xff);
			SDL_RenderDrawLine(
				ren,
				(int)(a.x - h.x),
				(int)(a.y - h.y),
				(int)((a.x - h.x) + n.x * 32.0f),
				(int)((a.y - h.y) + n.y * 32.0f)
			);
		}
		SDL_SetRenderDrawColor(ren, 0xff, 0x00, 0x00, 0xff);
		for (i = 0; i < point_count; i++) {
			v2f p = points2[i];
			SDL_RenderDrawPoint(ren, (int)p.x, (int)p.y);
		}
		SDL_SetRenderDrawColor(ren, 0x00, 0xff, 0x00, 0xff);
		SDL_RenderDrawPoint(ren, (int)s.p0.x, (int)s.p0.y);
		SDL_RenderPresent(ren);
		free(s.points);
		rot += 0.0003f;
	}
	SDL_DestroyRenderer(ren);
	SDL_DestroyWindow(window);
	SDL_Quit();
	return 0;
}