IntervalSpawningSystem{} (% chance for monster creation each turn)

src/map/interval_spawning_system.rs

@@ -0,0 +1,60 @@
+use crate::{gamelog, raws, spawner, Clock, Map, RandomNumberGenerator, TakingTurn};
+use specs::prelude::*;
+
+const TRY_SPAWN_CHANCE: i32 = 70;
+
+pub fn try_spawn_interval(ecs: &mut World) {
+    let mut try_spawn = false;
+    // Scope for borrow checker (ECS)
+    {
+        let map = ecs.fetch::<Map>();
+        // Difficulty 0 maps shouldn't have respawning hostile mobs.
+        if map.difficulty == 0 {
+            return;
+        }
+        let clock = ecs.read_storage::<Clock>();
+        let turns = ecs.read_storage::<TakingTurn>();
+        let mut rng = ecs.write_resource::<rltk::RandomNumberGenerator>();
+        for (_c, _t) in (&clock, &turns).join() {
+            if rng.roll_dice(1, TRY_SPAWN_CHANCE) == 1 {
+                rltk::console::log("Trying spawn.");
+                try_spawn = true;
+            }
+        }
+    }
+    if try_spawn {
+        spawn_random_mob_in_free_nonvisible_tile(ecs);
+    }
+}
+
+fn spawn_random_mob_in_free_nonvisible_tile(ecs: &mut World) {
+    let map = ecs.fetch::<Map>();
+    let available_tiles = populate_unblocked_nonvisible_tiles(&map);
+    let difficulty = (map.difficulty + gamelog::get_event_count("player_level")) / 2;
+    if available_tiles.len() == 0 {
+        return;
+    }
+    let mut rng = ecs.write_resource::<RandomNumberGenerator>();
+    let idx = get_random_idx_from_possible_tiles(&mut rng, available_tiles);
+    let key = spawner::mob_table(difficulty).roll(&mut rng);
+    let x = idx as i32 % map.width;
+    let y = idx as i32 / map.width;
+    std::mem::drop(map);
+    std::mem::drop(rng);
+    raws::spawn_named_entity(&raws::RAWS.lock().unwrap(), ecs, &key, raws::SpawnType::AtPosition { x, y }, difficulty);
+}
+
+fn populate_unblocked_nonvisible_tiles(map: &Map) -> Vec<usize> {
+    let mut tiles: Vec<usize> = Vec::new();
+    for (i, _tile) in map.tiles.iter().enumerate() {
+        if !map.blocked[i] && !map.visible_tiles[i] {
+            tiles.push(i);
+        }
+    }
+    return tiles;
+}
+
+fn get_random_idx_from_possible_tiles(rng: &mut rltk::RandomNumberGenerator, area: Vec<usize>) -> usize {
+    let idx = if area.len() == 1 { 0usize } else { (rng.roll_dice(1, area.len() as i32) - 1) as usize };
+    return idx;
+}

src/map/mod.rs

@@ -6,6 +6,8 @@ pub mod colours;
 mod glyphs;
 mod tiletype;
 pub use tiletype::{tile_cost, tile_opaque, tile_walkable, TileType};
+mod interval_spawning_system;
+pub use interval_spawning_system::try_spawn_interval;
 pub mod themes;
 
 // FIXME: If the map size gets too small, entities stop being rendered starting from the right.