#include "common/aoc.h"

namespace y2016::day17
{
  REGISTER_DAY(2016, Day17, std::string, std::string);

  REGISTER_TEST_EXAMPLE(2016, Day17, ExampleInput, 1, "DRURDRUDDLLDLUURRDULRLDUUDDDRR");
  REGISTER_TEST(2016, Day17, Input, 1, "DUDDRLRRRD");
  REGISTER_TEST_EXAMPLE(2016, Day17, ExampleInput, 2, "830");
  REGISTER_TEST(2016, Day17, Input, 2, "578");

  READ_INPUT(input)
  {
    std::vector<int> vec;
    std::string str;
    getline(input, str);
    return str;
  }

  struct State
  {
    std::string str{""};
    int x{0};
    int y{0};
  };

  bool IsOpen(char c)
  {
    return c >= 'b' && c <= 'f';
  }

  void Branch(const State& state, std::queue<State>& queue)
  {
    std::string hash = Md5::Hash(state.str);
    if (state.y > 0 && IsOpen(hash[0]))
      queue.emplace(State{state.str + "U", state.x, state.y - 1});
    if (state.y < 3 && IsOpen(hash[1]))
      queue.emplace(State{state.str + "D", state.x, state.y + 1});
    if (state.x > 0 && IsOpen(hash[2]))
      queue.emplace(State{state.str + "L", state.x - 1, state.y});
    if (state.x < 3 && IsOpen(hash[3]))
      queue.emplace(State{state.str + "R", state.x + 1, state.y});
  }

  bool IsGoal(const State& state)
  {
    return state.x == 3 && state.y == 3;
  }

  OUTPUT1(input)
  {
    std::queue<State> queue;
    queue.emplace(State{input, 0, 0});
    while (!queue.empty())
    {
      State state = queue.front();
      queue.pop();
      if (IsGoal(state))
        return state.str.substr(input.size());
      Branch(state, queue);
    }

    return "";
  }

  OUTPUT2(input)
  {
    std::queue<State> queue;
    queue.emplace(State{input, 0, 0});
    int longest = 0;
    while (!queue.empty())
    {
      State state = queue.front();
      queue.pop();
      if (IsGoal(state))
      {
        longest = state.str.size() - input.size();
        continue;
      }
      Branch(state, queue);
    }

    return std::to_string(longest);
  }
}