path: root/dungeon/src/pos.rs

//! The `pos` module contains structures for representation an
//! entity or objects position and facing direction inside the
//! dungeon grid.

use strum::IntoEnumIterator;
use strum_macros::EnumIter;

use rand::{
	Rng,
	distr::{Distribution, StandardUniform},
};

use std::{
	fmt::Display,
	ops::{AddAssign, SubAssign},
};

use crate::{MAP_SIZE_USIZE, map::MAP_SIZE};

macro_rules! downcast {
	($usize:expr, $type:ty) => {
		if $usize > <$type>::MAX as usize {
			None
		} else {
			#[expect(clippy::cast_possible_truncation)]
			Some($usize as $type)
		}
	};
}

#[macro_export]
macro_rules! const_pos {
	($x:expr, $y:expr) => {{
		const CONST_POS: Pos = Pos::new_unchecked($x, $y);
		CONST_POS
	}};
}

/// The `Direction` type represents a direction an entity
/// or any position object is facing inside the dungeon map.
/// Since the dungeon lives on a grid, there are only four
/// possible directions.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, EnumIter)]
pub enum Direction {
	North,
	South,
	East,
	West,
}
impl Direction {
	/// Returns an iterator over all possible directions
	pub fn values() -> impl Iterator<Item = Self> {
		Self::iter()
	}

	pub fn get_random_dir() -> Self {
		rand::random()
	}
}
impl Display for Direction {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
		match self {
			Self::North => write!(f, "NORTH"),
			Self::South => write!(f, "SOUTH"),
			Self::East => write!(f, "EAST"),
			Self::West => write!(f, "WEST"),
		}
	}
}

impl Distribution<Direction> for StandardUniform {
	fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Direction {
		// match rng.gen_range(0, 3) { // rand 0.5, 0.6, 0.7
		match rng.random_range(0..=3) {
			0 => Direction::North,
			1 => Direction::East,
			2 => Direction::South,
			_ => Direction::West,
		}
	}
}

/// The `Pos` type represents a 2D position inside the dungeon grid.
///
/// The max size for the dungeon map is set by the `MAP_SIZE` constant
/// and therefore the x and y positions can be between 0 and `MAP_SIZE - 1`.
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Pos(u16, u16);
impl Pos {
	/// Creates a new position from a given x and y position.
	///
	/// Returns `None` if the position goes out of the map.
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::Pos;
	///
	/// let pos = Pos::new(0,0);
	/// assert!(pos.is_some());
	/// ```
	///
	/// ```
	/// use dungeon::{Pos, MAP_SIZE};
	///
	/// let pos = Pos::new(MAP_SIZE, MAP_SIZE);
	/// assert!(pos.is_none())
	/// ```
	#[must_use]
	pub const fn new(x: u16, y: u16) -> Option<Self> {
		if x >= MAP_SIZE || y >= MAP_SIZE {
			None
		} else {
			Some(Self(x, y))
		}
	}

	/// Creates a new position from a given x and y position.
	///
	/// Bounds checks are asserted at runtime and will panic if out of bounds.
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::Pos;
	///
	/// let pos = Pos::new_unchecked(1, 1);
	/// assert_eq!(pos.xy(), (1,1));
	/// ```
	#[must_use]
	pub const fn new_unchecked(x: u16, y: u16) -> Self {
		assert!(x < MAP_SIZE, "Positions must be smaller then MAP_SIZE");
		assert!(y < MAP_SIZE, "Positions must be smaller then MAP_SIZE");
		Self(x, y)
	}

	/// Returns the x and y positions of `Pos`.
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::Pos;
	///
	/// let pos = Pos::new(5,7).unwrap();
	/// let (x,y) = pos.xy();
	/// assert_eq!(x, 5);
	/// assert_eq!(y, 7);
	/// ```
	#[must_use]
	pub const fn xy(self) -> (u16, u16) {
		(self.0, self.1)
	}

	/// Returns the x component of `Pos`
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::Pos;
	///
	/// let pos = Pos::new(5,7).unwrap();
	/// assert_eq!(pos.x(), 5);
	/// ```
	#[must_use]
	pub const fn x(&self) -> u16 {
		self.0
	}

	/// Returns the y component of `Pos`
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::Pos;
	///
	/// let pos = Pos::new(5,7).unwrap();
	/// assert_eq!(pos.y(), 7);
	/// ```
	#[must_use]
	pub const fn y(&self) -> u16 {
		self.1
	}

	/// Converts the x and y positions into an index of a continous list.
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::{Pos, MAP_SIZE_USIZE};
	///
	/// let pos = Pos::new(1,2).unwrap();
	/// let idx = pos.idx();
	/// assert_eq!(idx, 1 + 2 * MAP_SIZE_USIZE);
	/// ```
	#[must_use]
	pub const fn idx(self) -> usize {
		let (x, y) = (self.x() as usize, self.y() as usize);
		x + y * MAP_SIZE_USIZE
	}

	/// Converse an index into a possible x and y position
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::{Pos, MAP_SIZE_USIZE};
	///
	/// let idx_pos = Pos::from_idx(MAP_SIZE_USIZE);
	/// let pos = Pos::new(0, 1);
	///
	/// assert_eq!(idx_pos, pos);
	/// ```
	///
	/// ```
	/// use dungeon::{Pos, MAP_SIZE_USIZE};
	///
	/// let idx_pos = Pos::from_idx(MAP_SIZE_USIZE * 70 + 1);
	/// let pos = Pos::new(70, 1);
	///
	/// assert_eq!(idx_pos, pos);
	/// ```
	#[must_use]
	pub const fn from_idx(idx: usize) -> Option<Self> {
		let x = downcast!(idx % MAP_SIZE_USIZE, u16);
		let y = downcast!(idx / MAP_SIZE_USIZE, u16);
		match (x, y) {
			(Some(a), Some(b)) => Self::new(a, b),
			_ => None,
		}
	}

	/// Steps `Pos` one space in the `Direction` `dir`.
	///
	/// Returns `None` if the position goes out of the map.
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::{Direction, Pos};
	///
	/// let pos = Pos::new(0, 1).unwrap();
	/// let new_pos = pos.step(Direction::North);
	/// assert_eq!(new_pos, Pos::new(0, 0));
	/// ```
	///
	/// ```
	/// use dungeon::{Direction, Pos};
	///
	/// let pos = Pos::new(0, 1).unwrap();
	/// let new_pos = pos.step(Direction::West);
	/// assert!(new_pos.is_none());
	/// ```
	#[must_use]
	pub const fn step(self, dir: Direction) -> Option<Self> {
		self.step_by(dir, 1)
	}

	/// Steps `Pos` a given ammount in the `Direction` `dir`.
	///
	/// Returns `None` if the position goes out of the map.
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::{Direction, Pos};
	///
	/// let pos = Pos::new(0, 1).unwrap();
	/// let new_pos = pos.step_by(Direction::South, 3);
	/// assert_eq!(new_pos, Pos::new(0, 4));
	/// ```
	///
	/// ```
	/// use dungeon::{Direction, Pos};
	///
	/// let pos = Pos::new(1, 1).unwrap();
	/// let new_pos = pos.step_by(Direction::West, 2);
	/// assert!(new_pos.is_none());
	/// ```
	#[must_use]
	pub const fn step_by(self, dir: Direction, amt: u16) -> Option<Self> {
		let (x, y) = self.xy();
		if amt > MAP_SIZE {
			return None;
		}
		match dir {
			Direction::North if y >= amt => Self::new(x, y - amt),
			Direction::South => Self::new(x, y + amt),
			Direction::East => Self::new(x + amt, y),
			Direction::West if x >= amt => Self::new(x - amt, y),
			_ => None,
		}
	}

	/// Computes the absolute difference between to positions
	///
	/// Both values are gurenteed to be less than MAP_SIZE
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::Pos;
	///
	/// let pos1 = Pos::new(2,7).unwrap();
	/// let pos2 = Pos::new(1,17).unwrap();
	/// let diff = pos1.abs_diff(pos2);
	/// assert_eq!(diff.xy(), (1, 10));
	/// ```
	///
	#[must_use]
	pub const fn abs_diff(self, other: Self) -> Self {
		let x = self.0.abs_diff(other.0);
		let y = self.1.abs_diff(other.1);
		Self(x, y)
	}

	/// Returns the manhattan distance between `self` and `other`
	pub fn manhattan(self, other: Self) -> u16 {
		let abs_diff = Self::abs_diff(self, other);
		abs_diff.0 + abs_diff.1
	}

	/// Returns of the given position is on the border of the map
	///
	/// ```
	/// use dungeon::{Pos, MAP_SIZE};
	///
	/// // Assuming MAP_SIZE is at least 2
	///
	/// let pos1 = Pos::new(0, MAP_SIZE - 1).unwrap();
	/// let pos2 = Pos::new(1, MAP_SIZE - 2).unwrap();
	/// let pos3 = Pos::new(MAP_SIZE - 1, MAP_SIZE - 1).unwrap();
	/// let pos4 = Pos::new(MAP_SIZE - 1, MAP_SIZE - 1).unwrap();
	/// let pos5 = Pos::new(MAP_SIZE - 1, 0).unwrap();
	///
	/// assert!(pos1.is_border());
	/// assert!(!pos2.is_border());
	/// assert!(pos3.is_border());
	/// assert!(pos4.is_border());
	/// assert!(pos5.is_border());
	/// ```
	#[must_use]
	pub const fn is_border(&self) -> bool {
		self.0 == 0 || self.0 == MAP_SIZE - 1 || self.1 == 0 || self.1 == MAP_SIZE - 1
	}

	/// Returns the cardinal neighbors of this positions
	pub fn neighbors(&self) -> impl Iterator<Item = Self> {
		Direction::values().filter_map(|dir| self.step(dir))
	}

	/// Returns an iterator over all possible `Pos`
	pub fn values() -> impl Iterator<Item = Self> {
		(0..MAP_SIZE).flat_map(|y| (0..MAP_SIZE).filter_map(move |x| Self::new(x, y)))
	}
}
impl Default for Pos {
	/// Returns a default postion at the origin (0,0)
	///
	/// ```
	/// use dungeon::Pos;
	///
	/// let pos = Pos::default();
	///
	/// assert_eq!(pos.xy(), (0, 0));
	/// ```
	///
	fn default() -> Self {
		const_pos!(0, 0)
	}
}
impl TryFrom<usize> for Pos {
	type Error = ();

	fn try_from(value: usize) -> Result<Self, Self::Error> {
		Self::from_idx(value).ok_or(())
	}
}

/// The `FPos` type represents a floating 2D (temp) position.
///
/// This position is not gurenteed to be inside the dungeon grid. FPos exists to
/// tween between two different `Pos`. All bounds checks should be done in `Pos` before updating
/// the underlying Floating Position.
#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
pub struct FPos(f32, f32);
impl FPos {
	/// Creates a new position from a given floating x and y position.
	///
	/// Returns `None` if the position goes out of the map.
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::FPos;
	///
	/// let fpos = FPos::new(5.4,6.7);
	/// ```
	#[must_use]
	pub const fn new(x: f32, y: f32) -> Self {
		Self(x, y)
	}

	/// Creates a new `FPos` using the checked/fixed `Pos`.
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::{Pos, FPos};
	///
	/// let pos = Pos::new(1, 1).unwrap();
	/// let fpos = FPos::from_pos(pos);
	/// ```
	#[must_use]
	pub const fn from_pos(pos: Pos) -> Self {
		let (x, y) = pos.xy();
		Self(x as f32, y as f32)
	}

	/// Returns the x and y positions of `FPos`.
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::FPos;
	///
	/// let fpos = FPos::new(5.0,7.2);
	/// let (x,y) = fpos.xy();
	/// assert_eq!(x, 5.0);
	/// assert_eq!(y, 7.2);
	/// ```
	#[must_use]
	pub const fn xy(self) -> (f32, f32) {
		(self.0, self.1)
	}

	/// Returns the x component of `FPos`
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::FPos;
	///
	/// let fpos = FPos::new(5.0,7.2);
	/// assert_eq!(fpos.x(), 5.0);
	/// ```
	#[must_use]
	pub const fn x(&self) -> f32 {
		self.0
	}

	/// Returns the y component of `FPos`
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::FPos;
	///
	/// let fpos = FPos::new(5.0,7.2);
	/// assert_eq!(fpos.y(), 7.2);
	/// ```
	#[must_use]
	pub const fn y(&self) -> f32 {
		self.1
	}

	/// Steps `FPos` a given floating amount in the `Direction` `dir`.
	///
	/// Returns `None` if the floating position wraps.
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::{Direction, FPos};
	///
	/// let fpos = FPos::new(0.0, 1.0);
	/// let new_fpos = fpos.step_by(Direction::North, 0.3);
	/// assert!(new_fpos.is_some());
	/// ```
	///
	/// ```
	/// use dungeon::{Direction, FPos};
	///
	/// let fpos = FPos::new(0.0, 0.0);
	/// let new_fpos = fpos.step_by(Direction::North, 5.0);
	/// assert!(new_fpos.is_none());
	/// ```
	#[must_use]
	pub fn step_by(self, dir: Direction, amt: f32) -> Option<Self> {
		use Direction as D;
		let (mut x, mut y) = self.xy();
		match dir {
			D::North if y >= amt => y.sub_assign(amt),
			D::South => y.add_assign(amt),
			D::East => x.add_assign(amt),
			D::West if x >= amt => x.sub_assign(amt),
			_ => return None,
		};
		Some(Self(x, y))
	}

	/// Computes the absolute difference between to positions
	///
	/// # Examples
	///
	/// ```
	/// use dungeon::FPos;
	///
	/// let fpos1 = FPos::new(1.0,0.0);
	/// let fpos2 = FPos::new(0.0,1.0);
	/// let diff = fpos1.abs_diff(fpos2);
	/// assert_eq!(diff.xy(), (1.0, 1.0));
	/// ```
	///
	#[must_use]
	pub fn abs_diff(self, other: Self) -> Self {
		let x = (self.0 - other.0).abs();
		let y = (self.1 - other.1).abs();
		Self(x, y)
	}

	pub fn manhattan(self, other: Self) -> f32 {
		let abs_diff = Self::abs_diff(self, other);
		abs_diff.0 + abs_diff.1
	}
}
impl Default for FPos {
	/// Returns a default postion at the origin (0,0)
	///
	/// ```
	/// use dungeon::FPos;
	///
	/// let fpos = FPos::default();
	///
	/// assert_eq!(fpos.xy(), (0.0, 0.0));
	/// ```
	///
	fn default() -> Self {
		Self::new(0.0, 0.0)
	}
}
impl From<Pos> for FPos {
	fn from(value: Pos) -> Self {
		Self::from_pos(value)
	}
}