# Copyright 2016 Apcera Inc. All rights reserved.
defmodule Nats.Client do
  use GenServer
  require Logger

  @default_host "127.0.0.1"
  @default_port 4222
  @default_timeout 5000

  @default_opts %{ tls_required: false,
                   auth: %{}, # "user" => "user", "pass" => "pass"},
                   verbose: false,
                   timeout: @default_timeout,
                   host: @default_host, port: @default_port,
                   socket_opts: [:binary, active: true],
                   ssl_opts: []}
  @start_state %{ conn: nil, opts: %{}, status: :starting, why: nil,
                  subs_by_pid: %{},
                  subs_by_sid: %{},
                  next_sid: 0}

  def start_link(opts \\ %{}) do
    GenServer.start_link(__MODULE__, Map.merge(@default_opts, opts))
  end

  def init(opts) do
#    IO.puts "init! #{inspect(opts)}"
    state = @start_state
    opts = Map.merge(state.opts, opts)
    parent = self()
    case Nats.Connection.start_link(parent, opts) do
      {:ok, x}  when is_pid(x) ->
        receive do
          {:connected, ^x } ->
            {:ok, %{state | conn: x, status: :connected, opts: opts}}
        after opts.timeout -> {:stop, "timeout connecting to NATS"}
        end
      other -> {:error, "unable to start connection link", other}
    end
  end

  def handle_info({:msg, subject, sid, reply, what},
                  state = %{ subs_by_sid: subs_by_sid,
                             status: client_status})
  when client_status != :closed do
    pid = Map.get(subs_by_sid, sid)
    if pid, do: send pid, {:msg, subject, reply, what}
    {:noreply, state}
  end
  def handle_info({:msg, _subject, _sid, _reply, _what}, state) do
    # ignore messages we get after being closed...
    {:noreply, state}
  end
  def handle_cast(_command, state) do
#    IO.puts "handle_cast #{inspect(command)}"
    {:noreply, state}
  end
  def handle_call({:sub, who, subject, queue}, _from,
                  state = %{subs_by_sid: subs_by_sid,
                            subs_by_pid: subs_by_pid,
                            next_sid: next_sid,
                            status: client_status})
  when client_status != :closed do
    m = Map.get(subs_by_pid, who, %{})
    found = Map.get(m, subject)
    if found do
      {:error, "#{inspect(who)} already subjscribed to #{subject}"}
    else
      sid = "@#{next_sid}"
      m = Map.put(m, subject, sid)
      subs_by_pid = Map.put(subs_by_pid, who, m)
      subs_by_sid = Map.put(subs_by_sid, sid, who)
      state = %{state |
                subs_by_sid: subs_by_sid,
                subs_by_pid: subs_by_pid,
                next_sid: next_sid + 1}
      send state.conn, {:sub, subject, queue, sid}
#      IO.puts "subscribed!! #{inspect(state)}" 
      {:reply, :ok, state}
    end
  end
  def handle_call({:sub, _who, _subject, _queue}, _from, _state) do
    {:error, "connection closed"}
  end
  def handle_call(request, _from, state) do
#    IO.puts "handle_call #{inspect(request)}"
    send state.conn, request
    {:reply, :ok, state}
  end
 
  def pub(self, subject, what) do pub(self, subject, nil, what) end
  def pub(self, subject, reply, what) do
    GenServer.call(self, {:pub, subject, reply, what})
  end

  def subscribe(self, who, subject), do: subscribe(self, who, subject, nil)
  def subscribe(self, who, subject, queue),
    do: GenServer.call(self, {:sub, who, subject, queue})
end