defmodule SApp.Identity do
  use GenServer

  require Logger

  defmodule Manifest do
    defstruct [:pk]
  end

  defmodule State do
    defstruct [:info, :rev, :signed]
  end

  defimpl Shard.Manifest, for: Manifest do
    def start(m) do
      DynamicSupervisor.start_child(Shard.DynamicSupervisor, {SApp.Identity, m.pk})
    end
  end

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

  def init(pk) do
    manifest = %Manifest{pk: pk}
    id = SData.term_hash manifest

    case Shard.Manager.register(id, manifest, self()) do
      :ok ->
        Shard.Manager.dispatch_to(id, nil, self())
        state = case Shard.Manager.load_state(id) do
          nil ->
            info = %{nick: default_nick(pk)}
            SData.SignRev.new info
          st ->
            st
        end
        GenServer.cast(self(), :init_pull)
        {:ok, %{pk: pk, id: id, state: state}}
      :redundant ->
        exit(:redundant)
    end
  end

  def default_nick(pk) do
    nick_suffix = pk
                  |> binary_part(0, 4)
                  |> Base.encode16
                  |> String.downcase
    "Anon" <> nick_suffix
  end

  def find_proc(pk) do
    manifest = %Manifest{pk: pk}
    id = SData.term_hash manifest
    Shard.Manager.find_proc id
  end

  def handle_call(:manifest, _from, state) do
    {:replyl, state.manifest, state}
  end

  def handle_call(:get_info, _from, state) do
    {:reply, SData.SignRev.get(state.state), state}
  end

  def handle_call({:set_info, new_info}, _from, state) do
    case SData.SignRev.set(state.state, new_info, state.pk) do
      {:ok, st2} ->
        Shard.Manager.save_state(state.id, st2)
        state = put_in(state.state, st2)
        bcast_state(state)
        {:reply, :ok, state}
      err ->
        {:reply, err, state}
    end
  end

  def handle_cast(:init_pull, state) do
    for {_, pid, _, _} <- Shard.Manager.list_peers do
      GenServer.cast(pid, {:send_msg, {:interested, [state.id]}})
    end
    {:noreply, state}
  end

  def handle_cast({:interested, peer_id}, state) do
    Shard.Manager.send(peer_id, {state.id, nil, {:update, SData.SignRev.signed(state.state)}})
  end

  def handle_cast({:msg, peer_id, _shard_id, nil, msg}, state) do
    state = case msg do
      {:update, signed} ->
        case SData.SignRev.merge(state.state, signed, state.pk) do
          {true, st2} ->
            Shard.Manager.save_state(state.id, st2)
            state = put_in(state.state, st2)
            bcast_state(state, [peer_id])
            state
          {false, _} ->
            state
        end
    end
    {:noreply, state}
  end

  def bcast_state(state, exclude \\ []) do
    for peer_id <- Shard.Manager.get_shard_peers(state.id) do
      if not Enum.member? exclude, peer_id do
        Shard.Manager.send(peer_id, {state.id, nil, {:update, SData.SignRev.signed(state.state)}})
      end
    end
  end
end