From 5ca778dba2fa6fa89fbea0fe76a3d1fbba6bc143 Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Mon, 2 Nov 2026 21:22:23 +0100
Subject: Restructure

---
 app/c++/ico.hpp | 170 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 170 insertions(+)
 create mode 100644 app/c++/ico.hpp

(limited to 'app/c++/ico.hpp')

diff --git a/app/c++/ico.hpp b/app/c++/ico.hpp
new file mode 100644
index 0000000..5dc00a0
--- /dev/null
+++ b/app/c++/ico.hpp
@@ -0,0 +1,170 @@
+#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);
+	}
+};
+}
+}
-- 
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