#ifndef DIRECTION_H_AB66A90E
#define DIRECTION_H_AB66A90E

#include <cmath>
#include <string>
#include <stdexcept>
#include "vector.h"

enum class Direction {
  up,
  up_right,
  right,
  down_right,
  down,
  down_left,
  left,
  up_left
};

inline Direction directionFromString(std::string_view str) {
  if (str == "up") return Direction::up;
  if (str == "up_right") return Direction::up_right;
  if (str == "right") return Direction::right;
  if (str == "down_right") return Direction::down_right;
  if (str == "down") return Direction::down;
  if (str == "down_left") return Direction::down_left;
  if (str == "left") return Direction::left;
  if (str == "up_left") return Direction::up_left;
  throw std::invalid_argument("Invalid direction: " + std::string(str));
}

inline vec2i unitVecInDirection(Direction dir) {
  switch (dir) {
    case Direction::up: return { 0, -1 };
    case Direction::up_right: return { 1, -1 };
    case Direction::right: return { 1, 0 };
    case Direction::down_right: return { 1, 1 };
    case Direction::down: return { 0, 1 };
    case Direction::down_left: return { -1, 1 };
    case Direction::left: return { -1, 0 };
    case Direction::up_left: return { -1, -1 };
  }
}

inline bool dirHasDir(Direction value, Direction inner) {
  switch (inner) {
    case Direction::up: return value == Direction::up_left || value == Direction::up || value == Direction::up_right;
    case Direction::down: return value == Direction::down_left || value == Direction::down || value == Direction::down_right;
    case Direction::left: return value == Direction::up_left || value == Direction::left || value == Direction::down_left;
    case Direction::right: return value == Direction::up_right || value == Direction::right || value == Direction::down_right;
    default: return value == inner;
  }
}

inline Direction oppositeDirection(Direction value) {
  switch (value) {
    case Direction::up: return Direction::down;
    case Direction::up_right: return Direction::down_left;
    case Direction::right: return Direction::left;
    case Direction::down_right: return Direction::up_left;
    case Direction::down: return Direction::up;
    case Direction::down_left: return Direction::up_right;
    case Direction::left: return Direction::right;
    case Direction::up_left: return Direction::down_right;
  }
}

inline Direction directionMirroredVertically(Direction value) {
  switch (value) {
    case Direction::up: return Direction::down;
    case Direction::up_right: return Direction::down_right;
    case Direction::right: return Direction::right;
    case Direction::down_right: return Direction::up_right;
    case Direction::down: return Direction::up;
    case Direction::down_left: return Direction::up_left;
    case Direction::left: return Direction::left;
    case Direction::up_left: return Direction::down_left;
  }
}

inline Direction directionFacingPoint(vec2i point) {
  double theta = atan2(-point.y(), point.x());
  theta /= M_PI;

  if (theta < -7.0/8.0) {
    return Direction::left;
  } else if (theta < -5.0/8.0) {
    return Direction::down_left;
  } else if (theta < -3.0/8.0) {
    return Direction::down;
  } else if (theta < -1.0/8.0) {
    return Direction::down_right;
  } else if (theta < 1.0/8.0) {
    return Direction::right;
  } else if (theta < 3.0/8.0) {
    return Direction::up_right;
  } else if (theta < 5.0/8.0) {
    return Direction::up;
  } else if (theta < 7.0/8.0) {
    return Direction::up_left;
  } else {
    return Direction::left;
  }
}

inline Direction cardinalDirectionFacingPoint(vec2i point) {
  double theta = atan2(-point.y(), point.x());
  theta /= M_PI;

  if (theta < -3.0/4.0) {
    return Direction::left;
  } else if (theta < -1.0/4.0) {
    return Direction::down;
  } else if (theta < 1.0/4.0) {
    return Direction::right;
  } else if (theta < 3.0/4.0) {
    return Direction::up;
  } else {
    return Direction::left;
  }
}

inline bool isCardinalDirection(Direction dir) {
  return (dir == Direction::left || dir == Direction::right || dir == Direction::up || dir == Direction::down);
}

#endif /* end of include guard: DIRECTION_H_AB66A90E */