#pragma once

#include <array>
#include <cassert>
#include <cstdint>

namespace kel {
namespace impl {
struct ico_surface_helper {
	/**
	 * On each triangle we assume a ccw order and we start on the top-left part of the
	 * triangle. The orientation of the triangle is determined by the horizontal line
	 * (on the 2D foldout of the icosahedron) which is the down direction.  
	 */
	static constexpr std::array<std::array<uint8_t,3u>, 20u> neighbour_map {{
		{1,4,5},//0
		{2,0,6},//1
		{3,1,7},//2
		{4,2,8},//3
		{0,3,9},//4
		{14,10,0},//5
		{10,11,1},//6
		{11,12,2},//7
		{12,13,3},//8
		{13,14,4},//9
		{6,5,15},//10
		{7,6,16},//11
		{8,7,17},//12
		{9,8,18},//13
		{5,9,19},//14
		{19,16,10},//15
		{15,17,11},//16
		{16,18,12},//17
		{17,19,13},//18
		{18,15,14} //19
	}};
};
}

template<uint64_t SubD>
class ico_addr {
private:
	std::array<uint8_t, SubD> vals_;
public:
	uint8_t& at(uint64_t i){
		return vals_[i];
	}

	const uint8_t& at(uint64_t i) const {
		return vals_[i];
	}

	constexpr uint64_t size() const {
		return SubD;
	}

	bool is_equal(const ico_addr<SubD>& rhs) const {
		bool eq = true;

		for(uint64_t i = 0u; i < size(); ++i){
			eq &= (at(i) == rhs.at(i));
		}

		return eq;
	}

	bool has_zero() const {
		uint64_t z_ctr = 0u;
		for(uint64_t i = 1u; i < size(); ++i){
			z_ctr += (at(i) == 0u ? 1u : 0u);
		}
		return (z_ctr > 0u);
	}

	std::array<uint64_t,4u> count_groups() const {
		std::array<uint64_t,4u> grps{0,0,0,0};

		for(uint64_t i = 1u; i < size(); ++i){
			auto& addr_i = vals_[i];
			assert(addr_i < 4);

			++grps[addr_i];
		}

		return grps;
	}

	uint64_t count_non_zero_groups() const {
		auto ctr = count_groups();

		uint64_t grp_ctr = 0u;
		for(uint64_t i = 1u; i < ctr.size(); ++i){
			grp_ctr += (ctr[i] > 0u ? 1u : 0u);
		}
		return grp_ctr;
	}

	bool has_all_non_zero_groups() const {
		auto ctr = count_non_zero_groups();
		return (ctr == 3u);
	}

	ico_addr<SubD> go_to(uint8_t dir_i){
		ico_addr<SubD> cpy_addr;
		cpy_addr.vals_ = vals_;

		if(at(size() - 1u) == 0u){
			cpy_addr.at(size() - 1u) = dir_i + 1u;
		}
		if(at(size() - 1u) == (dir_i + 1u)){
			cpy_addr.at(size() - 1u) = 0u;
		}

		return cpy_addr;
	}

	bool borders_root() const {
		return not (has_all_non_zero_groups() or has_zero());
	}
};

template<typename T, uint64_t D>
class ico_triangle {
private:
	std::array<ico_triangle<T,D-1u>,4u> subdivs_;
public:

	ico_triangle<T,D-1u>& at(uint8_t i){
		return subdivs_[i];
	}

	template<uint64_t AddrOrigLen>
	ico_triangle<T,0u> at(const ico_addr<AddrOrigLen>& addr, uint64_t next_i){
		auto& addr_i = addr[next_i];

		auto& sub_triangle = subdivs_[addr_i];
		if constexpr ( D == 1u){
			return sub_triangle;
		}
		return sub_triangle.at(addr,next_i+1u);
	}
};

template<typename T>
class ico_triangle<T,0u> final {
private:
	T val_;
public:
};

namespace impl {
}

template<typename T, uint64_t SubD>
class icosahedron final {
private:
	std::array<ico_triangle<T,SubD>,20u> surfaces_;
public:

	template<uint64_t AddrD>
	ico_triangle<T,SubD+1u-AddrD> at(const ico_addr<AddrD>& addr){
		static_assert(AddrD <= (SubD+1u), "Addr length to large.");
		static_assert(AddrD > 0u, "Addr length to small.");

		auto& root_addr = addr[0u];
		auto& root_triangle = surfaces_[root_addr];
		return root_triangle.at(addr, 1u);
	}
};
}