irc_plugin util: tempref

1 files changed, 95 insertions, 0 deletions

diff --git a/lib/irc/plugin/temp_ref.ex b/lib/irc/plugin/temp_ref.ex
new file mode 100644
index 0000000..84b41bb
--- /dev/null
+++ b/lib/irc/plugin/temp_ref.ex
@@ -0,0 +1,95 @@
+defmodule Irc.Plugin.TempRef do
+  @moduledoc """
+  This module allows to easily implement local temporary simple references for easy access from IRC.
+
+  For example, your plugin output could be acted on, and instead of giving the burden for the user to
+  write or copy that uuid, you could give them a small alphanumeric reference to use instead.
+
+  You can configure how many and for how long the references are kept.
+
+  ## Usage
+
+  `import Irc.Plugin.TempRef`
+
+  ```elixir
+  defmodule Irc.MyPlugin do
+    defstruct [:temprefs]
+
+    def init(_) do
+      # …
+      {:ok, %__MODULE__{temprefs: new_temp_refs()}
+    end
+  end
+  ```
+  """
+
+  defstruct [:refs, :max, :expire, :build_fun, :build_increase_fun, :build_options]
+
+  defmodule SimpleAlphaNumericBuilder do
+    def build(options) do
+      length = Keyword.get(options, :length, 3)
+      for _ <- 1..length, into: "", do: <<Enum.random('bcdfghjkmpqtrvwxy2346789')>>
+    end
+ 
+    def increase(options) do
+      Keyword.put(options, :length, Keyword.get(options, :length, 3) + 1)
+    end
+  end
+
+  def new_temp_refs(options \\ []) do
+    %__MODULE__{
+      refs: Keyword.get(options, :init_refs, []),
+      max: Keyword.get(options, :max, []),
+      expire: Keyword.get(options, :expire, :infinity),
+      build_fun: Keyword.get(options, :build_fun, &__MODULE__.SimpleAlphaNumericBuilder.build/1),
+      build_increase_fun: Keyword.get(options, :build_increase_fun, &__MODULE__.SimpleAlphaNumericBuilder.increase/1),
+      build_options: Keyword.get(options, :build_options, [length: 3])
+    }
+  end
+
+  def janitor_refs(state = %__MODULE__{}) do
+    if length(state.refs) > state.max do
+      %__MODULE__{refs: state.refs |> Enum.reverse() |> tl() |> Enum.reverse()}
+    else
+      state
+    end
+  end
+
+  def put_temp_ref(data, state = %__MODULE__{}) do
+    state = janitor_refs(state)
+    key = new_nonexisting_key(state)
+    if key do
+      ref = {key, DateTime.utc_now(), data}
+      {key, %__MODULE__{state | refs: [ref | state.refs]}}
+    else
+      {nil, state}
+    end
+  end
+
+  def lookup_temp_ref(key, state, default \\ nil) do
+    case List.keyfind(state.refs, key, 0) do
+      {_, _, data} -> data
+      _ -> nil
+    end
+  end
+
+  defp new_nonexisting_key(state, i) when i > 50 do
+    nil
+  end
+
+  defp new_nonexisting_key(state = %__MODULE__{refs: refs}, i \\ 1) do
+    build_options = if rem(i, 5) == 0 do
+      state.build_increase_fun.(state.build_options)
+    else
+      state.build_options
+    end
+    
+    key = state.build_fun.(state.build_options)
+    if !List.keymember?(refs, key, 0) do
+      key
+    else
+      new_nonexisting_key(state, i + 1)
+    end
+  end
+
+end