From 385ca6511a8de0a4cc1dca774a3c743422c3d6be Mon Sep 17 00:00:00 2001
From: jjanzen <jjanzen@jjanzen.ca>
Date: Tue, 21 Jan 2025 22:39:11 -0600
Subject: refactor ecs for better genericism

---
 src/ecs/ecs.zig | 40 ++++++++++++++++++++++------------------
 1 file changed, 22 insertions(+), 18 deletions(-)

(limited to 'src/ecs/ecs.zig')

diff --git a/src/ecs/ecs.zig b/src/ecs/ecs.zig
index 919587a..d1341bf 100644
--- a/src/ecs/ecs.zig
+++ b/src/ecs/ecs.zig
@@ -8,6 +8,12 @@ pub const EntityComponentSystem = struct {
     available_ids: std.ArrayList(usize),
     next_id: usize,
 
+    fn nullEntity(self: *EntityComponentSystem, entity: usize) void {
+        inline for (std.enums.valuesFromFields(ComponentType, std.meta.fields(ComponentType))) |comp| {
+            self.componentRemoveEntity(comp, entity);
+        }
+    }
+
     pub fn init(allocator: std.mem.Allocator) EntityComponentSystem {
         return EntityComponentSystem{
             .allocator = allocator,
@@ -23,16 +29,13 @@ pub const EntityComponentSystem = struct {
     }
 
     pub fn createEntity(self: *EntityComponentSystem) !usize {
-        const reuse_id = self.available_ids.popOrNull();
-        if (reuse_id != null and reuse_id.? < self.components.items(.component_stub).len) {
-            return reuse_id.?;
-        }
-
-        const id = self.next_id;
-        try self.components.append(self.allocator, .{
-            .component_stub = null,
-        });
-        self.next_id += 1;
+        const id = self.available_ids.popOrNull() orelse noroom: {
+            const id = self.next_id;
+            try self.components.append(self.allocator, undefined);
+            self.next_id += 1;
+            break :noroom id;
+        };
+        self.nullEntity(id);
         return id;
     }
 
@@ -48,23 +51,24 @@ pub const EntityComponentSystem = struct {
     }
 
     pub fn deleteEntity(self: *EntityComponentSystem, entity: usize) !void {
-        inline for (std.enums.valuesFromFields(ComponentType, std.meta.fields(ComponentType))) |comp| {
-            self.componentRemoveEntity(comp, entity);
-        }
+        self.nullEntity(entity);
         try self.available_ids.append(entity);
     }
 
+    fn componentRemoveEntityGeneric(comp: anytype, entity: usize) void {
+        var fixed_comp = comp[entity] orelse return;
+        fixed_comp.deinit();
+        comp[entity] = null;
+    }
+
     pub fn componentRemoveEntity(
         self: *EntityComponentSystem,
         comp: component.ComponentType,
         entity: usize,
     ) void {
+        var components = self.components;
         switch (comp) {
-            ComponentType.component_stub => {
-                var comp_opt = self.components.items(.component_stub)[entity];
-                if (comp_opt != null) comp_opt.?.deinit();
-                self.components.items(.component_stub)[entity] = null;
-            },
+            ComponentType.component_stub => componentRemoveEntityGeneric(components.items(.component_stub), entity),
         }
     }
 };
-- 
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