2 files changed, 55 insertions, 0 deletions
diff --git a/src/simulation/postprocess.js b/src/simulation/postprocess.js
new file mode 100644
index 0000000..d50839e
--- /dev/null
+++ b/src/simulation/postprocess.js
@@ -0,0 +1,18 @@
+'use strict';
+
+export const postprocess = [
+  (world) => ({
+    ...world,
+    agents: world.agents.map(a => {
+      const {x, y} = a;
+      if (
+        world.lattice[y][x].type === 'mutable' ||
+        world.lattice[y][x].type === 'active'
+    ) {
+        return { ...a, flags: {...a.flags, frozen: true } };
+      } else {
+        return a;
+      }
+    }),
+  }),
+];
diff --git a/src/simulation/postprocess.test.js b/src/simulation/postprocess.test.js
new file mode 100644
index 0000000..dc77c6a
--- /dev/null
+++ b/src/simulation/postprocess.test.js
@@ -0,0 +1,37 @@
+'use strict';
+
+import { world_update } from '../world/world.js';
+import { postprocess } from './postprocess.js';
+
+test("agents freeze when finishing on a mutable or active", () => {
+  const agent = {
+    id: 1,
+    net: { compute: () => [[1], null] },
+    state: null,
+    x: 0, y: 0,
+    flags: {},
+  };
+
+  const lattice = [[{ type: 'empty', flags: {} }]];
+  
+  const world = {
+    lattice,
+    lattice_rules: { empty: ()=>{}, active: ()=>{}, mutable: ()=>{} },
+    agents: [agent],
+    senses: [],
+    actions: [],
+    validity: [],
+  };
+
+  expect(world_update(world, postprocess).agents[0]).toEqual(agent);
+  world.lattice[0][0].type = 'mutable';
+  expect(world_update(world, postprocess).agents[0]).toEqual({
+    ...agent,
+    flags: { frozen: true },
+  });
+  world.lattice[0][0].type = 'active';
+  expect(world_update(world, postprocess).agents[0]).toEqual({
+    ...agent,
+    flags: { frozen: true },
+  });
+});