1 files changed, 69 insertions, 0 deletions
diff --git a/kscurses/history_stack.jai b/kscurses/history_stack.jai
new file mode 100644
index 0000000..3f73df4
--- /dev/null
+++ b/kscurses/history_stack.jai
@@ -0,0 +1,69 @@
+History_Stack :: struct(
+	Action_Type : Type,
+	destructor : (obj : Action_Type) = default_destructor
+){
+	BUF_SIZE :: 100;
+	buffer : [BUF_SIZE]Action_Type;
+ 	offset, current, saved : int;
+}
+
+deinit :: (using history_stack : *History_Stack) {
+	guard(history);
+
+	for i : 0..saved-1 {
+		j := (i + offset) % BUF_SIZE;		
+		destructor(buffer[offset]);
+	}
+	offset, current, saved = 0;
+}
+
+write :: (using history : *History_Stack, action : Edit_Action) {
+	guard(history);
+
+	for i : current..saved-1 {
+		j := (i + offset) % BUF_SIZE;
+		destructor(buffer[j]);
+	}
+
+	i0 := (offset + current) % BUF_SIZE;
+	if current == BUF_SIZE {
+		destructor(buffer[offset]);
+		saved = current;
+		offset = (offset + 1) % BUF_SIZE;
+	} else {
+		current += 1;
+		saved = current;
+	}
+	i1 := (offset + current) % BUF_SIZE;
+	assert(i0 == i1);
+	buffer[i0] = action;
+}
+
+
+undo :: (using history : *History) -> bool, Action_Type {
+	guard(history);
+	action : Action_Type = ---;   
+	if current == 0 return false, action;
+	current -= 1;
+	action = buffer[(current + offset) % BUF_SIZE];
+	return true, action;
+}
+redo :: (using history : *History) -> bool, Action_Type {
+	guard(history);
+	action : Action_Type = ---;
+	if current == saved return false, action;
+	action = buffer[(current + offset) % BUF_SIZE];
+	current += 1;
+	return true, action;
+}
+
+#scope_file
+default_destructor :: (obj : $T) { }
+
+guard :: (using history : *History) #expand {
+	check :: (using history : *History) {
+		assert(0 <= current && current <= saved && saved <= BUF_SIZE);
+		assert(0 <= offset && offset <= BUF_SIZE);		
+	}
+	check(history); defer check(history);
+}
+\ No newline at end of file