[feat]: Filter (#18)

closes #16

Reviewed-on: #18

inc/FilterFactory.h

@@ -0,0 +1,29 @@
+#pragma once
+#include "Filter.h"
+#include "LowPassFilter.h"
+#include "BandPassFilter.h"
+#include "HighPassFilter.h"
+
+struct FilterFactory {
+    static Filter* CreateFilter(Filter* old_filter, FilterType new_type) {
+        Filter* new_filter;
+        switch (new_type) {
+        case LowPass:
+            new_filter = new LowPassFilter(old_filter);
+            break;
+        case BandPass:
+            new_filter = new BandPassFilter(old_filter);
+            break;
+        case HighPass:
+            new_filter = new HighPassFilter(old_filter);
+            break;
+        default:
+            break;
+        }
+        return new_filter;
+    }
+
+    static Filter* GetDefaultFilter() {
+        return new LowPassFilter();
+    }
+};