2 files changed, 77 insertions, 11 deletions
diff --git a/lib/plugins/link/html.ex b/lib/plugins/link/html.ex
index bef9640..78f3192 100644
--- a/lib/plugins/link/html.ex
+++ b/lib/plugins/link/html.ex
@@ -30,7 +30,7 @@ defmodule Nola.Plugins.Link.HTML do
   defp generate_text_from_opengraph(url, html, opengraph) do
     itemprops = collect_itemprops(html)
     prefix = collect_prefix_and_site_name(url, opengraph, itemprops)
-    description = collect_description(opengraph, itemprops, 500)
+    description = collect_description(opengraph, itemprops, 400)
 
     [clean_text("#{prefix}#{Map.get(opengraph, "title")}")] ++ description
   end
@@ -138,7 +138,7 @@ defmodule Nola.Plugins.Link.HTML do
   defp transform_description(nil, _), do: nil
 
   defp transform_description(string, length) when is_binary(string) do
-    if String.length(string) >= length, do: String.truncate(string, length), else: string
+    if String.length(string) > length, do: "#{String.slice(string, 0..length)}…", else: string
   end
 
   defp clean_text(text) do
diff --git a/lib/plugins/link/store.ex b/lib/plugins/link/store.ex
index ea43070..4e2aa58 100644
--- a/lib/plugins/link/store.ex
+++ b/lib/plugins/link/store.ex
@@ -1,29 +1,95 @@
 defmodule Nola.Plugins.Link.Store do
+  alias DialyxirVendored.Warnings.Apply
+  use GenServer
+  require Logger
   require Record
   import Ex2ms
 
   @type url() :: String.t()
 
-  Record.defrecord(:link, link: nil, at: nil)
-  @type link :: record(:link, link: String.t(), at: nil)
+  Record.defrecord(:link, link: nil, result: nil, at: nil)
+  @type link :: record(:link, link: url(), result: any(), at: nil)
 
-  Record.defrecord(:link_entry, key: nil, at: nil)
-  @type link_entry :: record(:link_entry, key: {url(), String.t()}, at: nil)
+  Record.defrecord(:link_seen, key: nil, at: nil)
+
+  @doc "A `link_seen` record represents a link that has been seen at a specific time in a given context."
+  @type link_seen :: record(:link_seen, key: {url(), String.t()}, at: nil)
 
   def setup do
     :ets.new(:links, [:set, :public, :named_table, keypos: 2])
+    :ets.new(:links_witness, [:set, :public, :named_table, keypos: 2])
   end
 
-  @spec insert_link(url()) :: true
-  def insert_link(url) do
-    :ets.insert(:links, link(link: url, at: NaiveDateTime.utc_now() |> NaiveDateTime.to_unix()))
+  @spec insert_link(url(), any()) :: true
+  def insert_link(url, result) do
+    :ets.insert(
+      :links,
+      link(link: url, result: result, at: DateTime.utc_now() |> DateTime.to_unix())
+    )
   end
 
-  @spec get_link(url()) :: String.t() | nil
+  @spec get_link(url()) :: any() | nil
   def get_link(url) do
     case :ets.lookup(:links, url) do
-      [link] -> link
+      [link(result: result)] -> result
       [] -> nil
     end
   end
+
+  @spec witness_link(url(), String.t()) :: boolean()
+  def inhibit_link?(url, key) do
+    case :ets.lookup(:links_witness, {url, key}) do
+      [_] -> true
+      [] -> false
+    end
+  end
+
+  @spec witness_link(url(), String.t()) :: :ok | :inhibit
+  def witness_link(url, key) do
+    if inhibit_link?(url, key) do
+      :inhibit
+    else
+      :ets.insert(
+        :links_witness,
+        link_seen(key: {url, key}, at: DateTime.utc_now() |> DateTime.to_unix())
+      )
+
+      :ok
+    end
+  end
+
+  def start_link(), do: GenServer.start_link(__MODULE__, [], name: __MODULE__)
+
+  @doc false
+  @impl true
+  def init(_) do
+    setup()
+    env = Keyword.fetch!(Application.get_env(:nola, Nola.Plugins.Link, []), :store)
+    :erlang.send_after(env[:interval], self(), :expire)
+    {:ok, nil}
+  end
+
+  @doc false
+  @impl true
+  def handle_info(:expire, state) do
+    env = Keyword.fetch!(Application.get_env(:nola, Nola.Plugins.Link, []), :store)
+    :erlang.send_after(env[:interval], self(), :expire)
+    ttl = env[:ttl] / 1000
+    inhibit = env[:inhibit] / 1000
+    now = DateTime.utc_now() |> DateTime.to_unix()
+
+    links_evicted =
+      :ets.select_delete(:links, [
+        {{:_, :_, :_, :"$1"}, [{:<, :"$1", now - ttl}], [true]}
+      ])
+
+    witness_evicted =
+      :ets.select_delete(:links_witness, [
+        {{:_, :_, :"$1"}, [{:<, :"$1", now - inhibit}], [true]}
+      ])
+
+    Logger.debug("evicted #{links_evicted} links and #{witness_evicted} witnesses")
+
+    {:noreply, state}
+  end
 end