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

void DebugPrint(std::pair<int, int> &head, std::pair<int, int> &tail,
                std::set<std::pair<int, int> > &visited_positions)
{
	int x_min = head.first;
	int y_min = head.second;
	int x_max = head.first;
	int y_max = head.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 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(head.first == x && head.second == y)
				std::cout << "\033[1;30mH"; // head
			else if(tail.first == x && tail.second == y)
				std::cout << "\033[1;25mT"; // head
			else if(visited_positions.contains({x, y}))
				std::cout << "\033[1;31mX"; // red
			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::pair<int, int> head = {0,0};
	std::pair<int, int> tail = {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':
				head.second--;
				break;
			case 'D':
				head.second++;
				break;
			case 'L':
				head.first--;
				break;
			case 'R':
				head.first++;
				break;
			}

			// Follow with 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(y_diff)
				{
					int to_change = std::ceil(std::abs(head.second - tail.second) / 2.0);
					if(y_diff < 0)
						tail.second -= to_change;
					else
						tail.second += to_change;
				}
			}
			if(std::abs(y_diff) > 1) // 2 away
			{
				tail.second += (head.second - tail.second) / 2;
				if(x_diff)
				{
					int to_change = std::ceil(std::abs(head.first - tail.first) / 2.0);
					if(x_diff < 0)
						tail.first -= to_change;
					else
						tail.first += to_change;
				}
			}

			visited_positions.insert(tail);
			// DebugPrint(head, tail, visited_positions);
			// usleep(1000000);
		}
	}

	DebugPrint(head, tail, visited_positions);
	total = visited_positions.size();

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

	return 0;
}