defmodule Plug.Session.Redis do
  @moduledoc """
  Stores the session in an in-memory data structure store: Redis.
  """

  def init(_) do
    opts = Application.get_env(:plug_session_redis_store, :redis, [])
    {:ok, conn} = Redix.start_link(opts)
    conn
  end

  def get(_conn, sid, store) do
    duration = Application.get_env(:plug_session_redis_store, :duration, 86_400)

    encoder =
      Application.get_env(
        :plug_session_redis_store,
        :encoder,
        PlugSessionRedisStore.Encoder.Binary
      )

    case Redix.command(store, ["GET", sid]) do
      {:ok, nil} ->
        {nil, %{}}

      {:ok, data} ->
        case Redix.command(store, ["EXPIRE", sid, duration]) do
          {:ok, 1} -> {sid, encoder.decode(data)}
          {:error, _error} -> {nil, %{}}
        end

      {:error, _error} ->
        {nil, %{}}
    end
  end

  def put(conn, nil, data, store) do
    genetator =
      Application.get_env(
        :plug_session_redis_store,
        :sid_generator,
        PlugSessionRedisStore.Generator.StrongRandBytes
      )

    sid = genetator.generate()
    put(conn, sid, data, store)
  end

  def put(_conn, sid, data, store) do
    duration = Application.get_env(:plug_session_redis_store, :duration, 86_400)

    encoder =
      Application.get_env(
        :plug_session_redis_store,
        :encoder,
        PlugSessionRedisStore.Encoder.Binary
      )

    case Redix.command(store, ["SETEX", sid, duration, encoder.encode(data)]) do
      {:ok, "OK"} -> sid
      {:error, _error} -> {nil, %{}}
    end
  end

  def delete(_conn, sid, store) do
    case Redix.command(store, ["DEL", sid]) do
      {:ok, _} -> :ok
      _ -> {nil, %{}}
    end
  end
end