dungeon: add hash to to check if it has been changed

1 files changed, 47 insertions, 8 deletions

diff --git a/dungeon/src/map.rs b/dungeon/src/map.rs
index d9a4323..a2cdd9a 100644
--- a/dungeon/src/map.rs
+++ b/dungeon/src/map.rs
@@ -2,6 +2,11 @@
 //! including the current `Floor`, and map `Tile`.
 
 use crate::wfc::Wfc;
+use std::{
+	cell::RefCell,
+	hash::{DefaultHasher, Hash, Hasher},
+};
+
 use crate::{const_pos, pos::Pos};
 
 /// `MAP_SIZE` is the size of the size of the dungeon grid.
@@ -37,7 +42,7 @@ impl Tile {
 /// The `Floor` type represents the current playing
 /// grid of the dungeon. It contains the tiles of the
 /// grid, and the starting position of the player.
-#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(Clone, Debug, PartialEq, Eq)]
 pub struct Floor {
 	/// The dungeon grid
 	tiles: Box<[Tile; TILE_COUNT]>,
@@ -45,8 +50,23 @@ pub struct Floor {
 	player_start: Pos,
 	/// The seed used when generating the dungeon grid
 	seed: u64,
+	/// The computed hash of the tile map
+	hash: RefCell<u64>,
+	/// If the tiles are dirty (hash needs to be recomputed)
+	dirty: RefCell<bool>,
 }
 impl Floor {
+	/// Internal constructor for `Floor`
+	fn new(tiles: Box<[Tile; TILE_COUNT]>, player_start: Pos, seed: u64) -> Self {
+		Self {
+			tiles,
+			player_start,
+			seed,
+			hash: RefCell::new(0),
+			dirty: RefCell::new(true),
+		}
+	}
+
 	/// Generates a dungeon `Floor` using wave function collapse.
 	///
 	/// # Examples
@@ -107,7 +127,8 @@ impl Floor {
 
 	/// Returns a multable reference to a `Tile` on the dungeon grid at `Pos`.
 	#[must_use]
-	pub const fn get_mut(&mut self, pos: Pos) -> &mut Tile {
+	pub fn get_mut(&mut self, pos: Pos) -> &mut Tile {
+		*self.dirty.get_mut() = true;
 		let idx = pos.idx();
 		&mut self.tiles[idx]
 	}
@@ -122,9 +143,31 @@ impl Floor {
 	/// Returns a mutable reference to all tiles in the `Floor`.
 	/// The size of this lise will always be `TILE_COUNT` long.
 	#[must_use]
-	pub const fn tiles_mut(&mut self) -> &mut [Tile] {
+	pub fn tiles_mut(&mut self) -> &mut [Tile] {
+		*self.dirty.get_mut() = true;
 		&mut *self.tiles
 	}
+
+	/// Computes the hash of the tile map
+	#[must_use]
+	pub fn hash(&self) -> u64 {
+		// initial (immutable) dirty check
+		let dirty = self.dirty.borrow();
+		if *dirty {
+			return *self.hash.borrow();
+		}
+		drop(dirty);
+
+		// recompute hash
+		let mut dirty = self.dirty.borrow_mut();
+		let mut hash = self.hash.borrow_mut();
+		let mut s = DefaultHasher::new();
+		self.tiles.hash(&mut s);
+		*hash = s.finish();
+
+		*dirty = false;
+		*hash
+	}
 }
 impl Default for Floor {
 	/// Returns a floor with a single set of walls on the map border
@@ -139,10 +182,6 @@ impl Default for Floor {
 			}
 		}
 
-		Self {
-			tiles,
-			player_start,
-			seed,
-		}
+		Self::new(tiles, player_start, seed)
 	}
 }