1 files changed, 32 insertions, 0 deletions
diff --git a/Homework/cs5410/bbiy/src/systems/undo.js b/Homework/cs5410/bbiy/src/systems/undo.js
new file mode 100644
index 0000000..086d6b4
--- /dev/null
+++ b/Homework/cs5410/bbiy/src/systems/undo.js
@@ -0,0 +1,32 @@
+game.system.Undo = (entitiesGrid, logicSystem, gridSystem) => {
+  const states = [];
+
+  const update = (elapsedTime, entities, changedIds) => {
+    if (changedIds.size) {
+      const state = {};
+      for (let id in entities) {
+        if (entities[id].hasComponent("gridPosition")) {
+          state[id] = JSON.parse(JSON.stringify(entities[id].components));
+        }
+      }
+      states.push(state);
+    }
+    return new Set();
+  };
+
+  const undo = (entities) => {
+    let state = states.slice(0, -1).pop();
+    if (states.length > 1) {
+      states.pop();
+    }
+    for (let id in state) {
+      for (let componentName in state[id]) {
+        entities[id].addComponent({name: componentName, ...state[id][componentName]});
+      }
+    }
+    gridSystem.update(0, entities, new Set());
+    logicSystem.parseRules(entities);
+  };
+
+  return { update, undo };
+};