From c80ba7f72596437b28540f463b952e6dcbce6295 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Tomas=20Wenstr=C3=B6m?= <tomas.wenstrom@gmail.com>
Date: Sun, 24 Jan 2021 18:57:13 +0100
Subject: [PATCH] Delete smaller wall regions and leave only one room

---
 src/core/game.rs  |  3 +++
 src/core/level.rs | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/src/core/game.rs b/src/core/game.rs
index 1bdaa8d..3e017b1 100644
--- a/src/core/game.rs
+++ b/src/core/game.rs
@@ -57,6 +57,9 @@ impl AppState for GameState {
 	    Event::KeyDown { keycode: Some(Keycode::KpMinus), .. } => {
 		self.world.level.decrease_iteration();
 	    }
+	    Event::KeyDown { keycode: Some(Keycode::KpEnter), .. } => {
+		self.world.level.filter_regions();
+	    }
 	    _ => {}
 	}
     }
diff --git a/src/core/level.rs b/src/core/level.rs
index bab89e0..65e74ff 100644
--- a/src/core/level.rs
+++ b/src/core/level.rs
@@ -34,6 +34,10 @@ impl Level {
 	println!("iterate {} time(s)", self.iterations);
     }
 
+    pub fn filter_regions(&mut self) {
+	self.grid.filter_regions();
+    }
+
     pub fn render(&mut self, renderer: &mut Renderer, _sprites: &SpriteManager) {
 	let w = renderer.viewport().0 as i32;
 
@@ -189,4 +193,77 @@ impl Grid {
 	    cells
 	}
     }
+
+    fn find_regions(&self) -> Vec<Region> {
+	let mut regions = vec!();
+	let mut marked = vec!(vec!(false; self.height); self.width);
+	for x in 0..self.width {
+	    for y in 0..self.height {
+		if !marked[x][y] {
+		    regions.push(self.get_region_at_point(x, y, &mut marked));
+		}
+	    }
+	}
+	regions
+    }
+
+    fn get_region_at_point(&self, x: usize, y: usize, marked: &mut Vec<Vec<bool>>) -> Region {
+	let value = self.cells[x][y];
+	let mut cells = vec!();
+	let mut queue = vec!((x, y));
+	marked[x][y] = true;
+
+	while let Some(p) = queue.pop() {
+	    cells.push(p);
+	    for i in &[(-1, 0), (1, 0), (0, -1), (0, 1)] {
+		let ip = (p.0 as isize + i.0, p.1 as isize + i.1);
+		if ip.0 >= 0 && ip.0 < self.width as isize && ip.1 >= 0 && ip.1 < self.height as isize {
+		    let up = (ip.0 as usize, ip.1 as usize);
+		    if self.cells[up.0][up.1] == value && !marked[up.0][up.1] {
+			marked[up.0][up.1] = true;
+			queue.push(up);
+		    }
+		}
+	    }
+	}
+
+	Region { value, cells }
+    }
+
+    fn delete_region(&mut self, region: &Region) {
+	for c in &region.cells {
+	    self.cells[c.0][c.1] = !region.value;
+	}
+    }
+
+    pub fn filter_regions(&mut self) {
+	let min_wall_size = 0.0015;
+	println!("grid size: ({}, {}) = {} cells", self.width, self.height, self.width * self.height);
+	println!("min wall size: {}", (self.width * self.height) as f64 * min_wall_size);
+
+	// delete all smaller wall regions
+	for r in self.find_regions().iter().filter(|r| r.value) {
+	    let percent = r.cells.len() as f64 / (self.width * self.height) as f64;
+	    if percent < min_wall_size {
+		println!("delete wall region of size {}", r.cells.len());
+		self.delete_region(r);
+	    }
+	}
+
+	// delete all rooms but the largest
+	let regions = self.find_regions(); // check again, because if a removed room contains a removed wall, the removed wall will become a room
+	let mut rooms: Vec<&Region> = regions.iter().filter(|r| !r.value).collect();
+	rooms.sort_by_key(|r| r.cells.len());
+	rooms.reverse();
+	while rooms.len() > 1 {
+	    self.delete_region(rooms.pop().unwrap());
+	}
+    }
+}
+
+////////// REGION //////////////////////////////////////////////////////////////
+
+struct Region {
+    value: bool,
+    cells: Vec<(usize, usize)>,
 }
-- 
2.11.0