1 files changed, 43 insertions, 6 deletions

diff --git a/Museum.cpp b/Museum.cpp
index 4a12038..d389602 100644
--- a/Museum.cpp
+++ b/Museum.cpp
@@ -20,22 +20,39 @@ void Museum::update() {
 	this->canvas.update();
 	this->collision.update();
 	this->tick++;
+
+	unsigned long long next_snapshot = this->snapshot_ticks;
+	if (!this->history.empty()) next_snapshot += this->history.top().tick;
+	if (next_snapshot > this->tick) return;
+	this->history.push(this->save_snapshot());
+	printf("saved snapshot at tick %llu\n", this->tick);
 }
 
 void Museum::skip_forward() {
-	this->jump += this->snapshot_ticks;
+	this->jump++;
 }
-
 void Museum::skip_backward() {
-
+	this->jump--;
 }
 
 void Museum::work() {
 	while (this->working) {
-		// immediately process forward jumps, even if paused
+		// immediately process jumps, even if paused
 		if (this->jump > 0) {
-			for (; this->jump != 0; this->jump--)
-				this->update();
+			// forward jump
+			for (; this->jump != 0; this->jump--) {
+				printf("jumping forward %u ticks\n", this->snapshot_ticks);
+				for (size_t i = 0; i < this->snapshot_ticks; i++)
+					this->update();
+			}
+		} else if (this->jump < 0) {
+			// backward jump
+			for (; this->jump != 0; this->jump++) {
+				if (this->history.empty()) continue;
+				printf("restoring snapshot from tick %llu\n", this->history.top().tick);
+				this->restore_snapshot(this->history.top());
+				this->history.pop();
+			}
 		}
 
 		// wait with regular update if paused
@@ -48,3 +65,23 @@ void Museum::work() {
 	}
 }
 
+static void memories_concat(Memories & a, Memories b) {
+	a.insert(a.end(), make_move_iterator(b.begin()), make_move_iterator(b.end()));
+}
+
+Museum::Snapshot Museum::save_snapshot() {
+	Snapshot snapshot = {
+		.tick = this->tick,
+		.memories = {},
+	};
+	memories_concat(snapshot.memories, this->canvas.save());
+	memories_concat(snapshot.memories, this->people.save());
+	return snapshot;
+}
+
+void Museum::restore_snapshot(const Snapshot & snapshot) {
+	this->tick = snapshot.tick;
+	this->canvas.restore(snapshot.memories);
+	this->people.restore(snapshot.memories);
+}
+