#include <cmath>
#include <fstream>
#include <iostream>
#include <set>
#include <string>
#include <unistd.h>
#include <vector>

void ApplyMovement(std::pair<int, int> &head,
                   std::pair<int, int> &tail)
{
	const int x_diff = head.first - tail.first;
	const int y_diff = head.second - tail.second;
	if(std::abs(x_diff) > 1) // 2 away
	{
		tail.first += (head.first - tail.first) / 2;
		if(std::abs(y_diff) > 1) // 2 away due to diagonally following!!!
			tail.second += (head.second - tail.second) / 2;
		else
			// snap to axis since you're already on it or you're one away
			tail.second = head.second;
	}
	if(std::abs(y_diff) > 1) // 2 away
	{
		tail.second += (head.second - tail.second) / 2;
		if(std::abs(x_diff) > 1) // 2 away due to diagonally following!!!
			tail.first += (head.first - tail.first) / 2;
		else
			// snap to axis since you're already on it or you're one away
			tail.first = head.first;
	}
}

void DebugPrint(std::vector<std::pair<int, int> > &points,
                std::set<std::pair<int, int> > &visited_positions,
                std::set<std::pair<int, int> > &visited_positions_part2)
{
	int x_min = points[0].first;
	int y_min = points[0].second;
	int x_max = points[0].first;
	int y_max = points[0].second;

	for(auto &pos : visited_positions)
	{
		x_min = std::min(x_min, pos.first);
		x_max = std::max(x_max, pos.first);
		y_min = std::min(y_min, pos.second);
		y_max = std::max(y_max, pos.second);
	}
	for(auto &pos : visited_positions_part2)
	{
		x_min = std::min(x_min, pos.first);
		x_max = std::max(x_max, pos.first);
		y_min = std::min(y_min, pos.second);
		y_max = std::max(y_max, pos.second);
	}

	for(auto i = 0; i < 50; ++i)
		std::cout << std::endl;
	std::cout << "X: " << x_min << " - " << x_max << std::endl;
	std::cout << "Y: " << y_min << " - " << y_max << std::endl;
	std::cout << std::endl;

	for(auto y = y_min; y <= y_max; ++y)
	{
		for(auto x = x_min; x <= x_max; ++x)
		{
			if(points[0].first == x && points[0].second == y)
				std::cout << "\033[1;30mH"; // head
			else if(points[1].first == x && points[1].second == y)
				std::cout << "\033[1;25m1"; // tail
			else if(points[2].first == x && points[2].second == y)
				std::cout << "\033[1;25m2"; // tail
			else if(points[3].first == x && points[3].second == y)
				std::cout << "\033[1;25m3"; // tail
			else if(points[4].first == x && points[4].second == y)
				std::cout << "\033[1;25m4"; // tail
			else if(points[5].first == x && points[5].second == y)
				std::cout << "\033[1;25m5"; // tail
			else if(points[6].first == x && points[6].second == y)
				std::cout << "\033[1;25m6"; // tail
			else if(points[7].first == x && points[7].second == y)
				std::cout << "\033[1;25m7"; // tail
			else if(points[8].first == x && points[8].second == y)
				std::cout << "\033[1;25m8"; // tail
			else if(points[9].first == x && points[9].second == y)
				std::cout << "\033[1;25m9"; // tail
			else if(visited_positions.contains({x, y}))
				std::cout << "\033[1;31mX"; // red
			else if(visited_positions_part2.contains({x, y}))
				std::cout << "\033[1;20mY"; // ??
			else
				std::cout << "\033[0m-"; // default white
		}
		std::cout << std::endl;
	}
	std::cout << "\033[0m"; // default white
}

int main()
{
	std::ifstream ifs("data.txt");
	if(!ifs.is_open())
	{
		std::cerr << "Missing data.txt." << std::endl;
		return -1;
	}

	unsigned long total = 0;
	unsigned long total_pt2 = 0;

	std::set<std::pair<int, int> > visited_positions;
	std::set<std::pair<int, int> > visited_positions_part2;

	std::vector<std::pair<int, int> > points;
	for(auto i = 0; i < 10; ++i)
		points.push_back({0,0});

	char dir;
	int amt;

	for(std::string line; std::getline(ifs, line); )
	{
		if(line == "")
			continue;

		dir = line[0];
		amt = std::atoi(line.substr(2).c_str());

		for(auto i = 0; i < amt; ++i)
		{
			// Move head:
			switch(dir)
			{
			case 'U':
				points[0].second--;
				break;
			case 'D':
				points[0].second++;
				break;
			case 'L':
				points[0].first--;
				break;
			case 'R':
				points[0].first++;
				break;
			}

			// Follow with tail:
			for(auto i = 0; i < points.size() - 1; ++i)
				ApplyMovement(points[i], points[i+1]);

			visited_positions.insert(points[1]);
			visited_positions_part2.insert(points.back());

			DebugPrint(points, visited_positions, visited_positions_part2);
			usleep(100000);
		}
	}

	DebugPrint(points, visited_positions, visited_positions_part2);
	total = visited_positions.size();
	total_pt2 = visited_positions_part2.size();

	std::cout << "    Total: " <<     total << std::endl;
	std::cout << "PT2 Total: " << total_pt2 << std::endl;

	return 0;
}