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lib/chesstrainer/cache/evict.ex

@@ -0,0 +1,29 @@
+defmodule Chesstrainer.Cache.Evict do
+  @moduledoc """
+  Eviction functions for LRU cache
+  """
+
+  # O(n) time, not efficient
+  def maybe_evict_oldest(table, max_size) do
+    if :ets.info(table, :size) > max_size do
+      case find_oldest_entry(table) do
+        {oldest_key, _} -> :ets.delete(table, oldest_key)
+        _ -> :ok
+      end
+    end
+  end
+
+  defp find_oldest_entry(table) do
+    :ets.foldl(
+      fn {k, _v, t}, acc ->
+        case acc do
+          nil -> {k, t}
+          {_, oldest_t} when t < oldest_t -> {k, t}
+          _ -> acc
+        end
+      end,
+      nil,
+      table
+    )
+  end
+end