exkad

defmodule Exkad.Store do
  use GenServer


  def start_link(opts) do
    GenServer.start_link(__MODULE__, opts)
  end

  def init(_opts) do
    {:ok, %{values: %{}, meta: %{}}}
  end


  def put(server, value) do
    GenServer.call(server, {:put, value})
  end

  def put_meta(server, term, ptr) do
    GenServer.call(server, {:put_meta, term, ptr})
  end

  def search(server, key) do
    GenServer.call(server, {:get_meta, key})
  end

  def get(server, key) do
    GenServer.call(server, {:get, key})
  end

  #Streaming hash
  # def hash(s) do 
  #   ctx = :crypto.hash_init(:md5)
  #   ctx = Enum.reduce(s, ctx, fn chunk, acc -> 
  #     :crypto.hash_update(acc, chunk)
  #   end)
  #   :crypto.hash_final(ctx)
  #     |> :erlang.bitstring_to_list
  #     |> Enum.map(&(:io_lib.format("~2.16.0b", [&1]))) 
  #     |> List.flatten
  #     |> :erlang.list_to_bitstring
  # end

  def hash(bin) do
    :crypto.hash(:md5, bin)
      |> :erlang.bitstring_to_list
      |> Enum.map(&(:io_lib.format("~2.16.0b", [&1]))) 
      |> List.flatten
      |> :erlang.list_to_bitstring
  end

  def handle_call({:put_meta, term, ptr}, _from, state) do
    key = hash(term)
    ptrs = case state.meta[key] do
      nil -> [ptr]
      existing -> [ptr | existing]
    end

    meta = Dict.put(state.meta, key, ptrs)
    state = Enum.into(%{meta: meta}, state)
    {:reply, {:ok, key}, state}
  end

  def handle_call({:get_meta, key}, _from, state) do
    res = Dict.get(state.meta, key, [])
    {:reply, {:ok, res}, state}
  end

  def handle_call({:put, value}, _from, state) do
    key = hash(value)
    values = Dict.put(state.values, key, value)
    state = Enum.into(%{values: values}, state)

    {:reply, {:ok, key}, state}
  end

  def handle_call({:get, key}, _from, state) do
    res = case state.values[key] do
      nil -> {:error, :not_found}
      val -> {:ok, val}
    end
    {:reply, res, state}
  end

end