added on_order handler to entities and components, added visibility map

lib/visiblity_map.rb

@@ -0,0 +1,36 @@
+class IMICRTS
+  class VisibilityMap
+    attr_reader :width, :height, :tile_size
+
+    def initialize(width:, height:, tile_size:)
+      @width = width
+      @height = height
+      @tile_size = tile_size
+
+      @map = Array.new(width * height, false)
+    end
+
+    def visible?(x, y)
+      @map.dig(index_at(x, y))
+    end
+
+    def index_at(x, y)
+      ((y.clamp(0, @height - 1) * @width) + x.clamp(0, @width - 1))
+    end
+
+    def update(entity)
+      range = entity.sight_radius
+      pos = entity.position.clone / @tile_size
+      pos.x = pos.x.ceil - range
+      pos.y = pos.y.ceil - range
+
+      (range * 2).times do |y|
+        (range * 2).times do |x|
+          if not visible?(pos.x + x, pos.y + y).nil?
+            @map[index_at(pos.x + x, pos.y + y)] = true
+          end
+        end
+      end
+    end
+  end
+end