chromecast

defmodule Chromecast do
    require Logger
    use GenServer
    use Protobuf, from: Path.expand("../proto/cast_channel.proto", __DIR__)

    @ping "PING"
    @pong "PONG"
    @receiver_status "RECEIVER_STATUS"
    @media_status "MEDIA_STATUS"


    defmodule State do
        defstruct media_session: nil,
            session: nil,
            destination_id: "receiver-0",
            ssl: nil,
            ip: nil,
            request_id: 0,
            receiver_status: %{},
            media_status: %{}
    end

    @namespace %{
        :con => "urn:x-cast:com.google.cast.tp.connection",
        :receiver => "urn:x-cast:com.google.cast.receiver",
        :cast => "urn:x-cast:com.google.cast.media",
        :heartbeat =>  "urn:x-cast:com.google.cast.tp.heartbeat",
        :message => "urn:x-cast:com.google.cast.player.message",
        :media => "urn:x-cast:com.google.cast.media",
        :youtube => "urn:x-cast:com.google.youtube.mdx",
    }

    def start_link(ip \\ {192,168,1,15}) do
        GenServer.start_link(__MODULE__, ip)
    end

    def play(device) do
        GenServer.call(device, :play)
    end

    def pause(device) do
        GenServer.call(device, :pause)
    end

    def set_volume(device, level) do
        GenServer.call(device, {:set_volume, level})
    end

    def state(device) do
        GenServer.call(device, :state)
    end

    def create_message(namespace, payload, destination) when payload |> is_map do
        Chromecast.CastMessage.new(
            protocol_version: :CASTV2_1_0,
            source_id: "sender-0",
            destination_id: destination,
            payload_type: :STRING,
            namespace: @namespace[namespace],
            payload_utf8: Poison.encode!(payload)
        )
    end

    def connect_channel(namespace, state) do
        con = create_message(:con, %{:type => "CONNECT", :origin => %{}, :requestId => state.request_id}, state.destination_id)
        state = send_msg(state.ssl, con, state)
        status = create_message(namespace, %{:type => "GET_STATUS", :requestId => state.request_id}, state.destination_id)
        state = send_msg(state.ssl, status, state)
    end

    def send_msg(ssl, msg, state) do
        case :ssl.send(ssl, encode(msg)) do
            :ok ->
                cond do
                    state.request_id > 2000 -> %State{state | :request_id => 0}
                    true -> %State{state | :request_id => state.request_id + 1}
                end
            {:error, reason} ->
                Logger.error "SSL Send Error: #{inspect reason}"
                state
        end
    end

    def connect(ip) do
        {:ok, ssl} = :ssl.connect(ip, 8009, [:binary, {:reuseaddr, true}], :infinity)
    end

    def init(ip) do
        {:ok, ssl} = connect(ip)
        state = %State{:ssl => ssl, :ip => ip}
        state = connect_channel(:receiver, state)
        {:ok, state}
    end

    def handle_call(:state, _from, state) do
        {:reply, state, state}
    end

    def handle_call(:play, _from, state) do
        msg = create_message(:media, %{
            :mediaSessionId => state.media_session,
            :requestId => state.request_id,
            :type => "PLAY"
        }, state.destination_id)
        {:reply, :ok, send_msg(state.ssl, msg, state)}
    end

    def handle_call(:pause, _from, state) do
        msg = create_message(:media, %{
            :mediaSessionId => state.media_session,
            :requestId => state.request_id,
            :type => "PAUSE"
        }, state.destination_id)
        {:reply, :ok, send_msg(state.ssl, msg, state)}
    end

    def handle_call({:set_volume, level}, _from, state) do
        msg = create_message(:media, %{
            :mediaSessionId => state.media_session,
            :requestId => state.request_id,
            :type => "VOLUME",
            :Volume => %{:level => level, :muted => 0}
        }, state.destination_id)
        {:reply, :ok, send_msg(state.ssl, msg, state)}
    end

    def handle_info({:ssl_closed, _}, {:sslsocket, _, state}) do
        Logger.debug("SSL Connection Closed. Re-opening...")
        {:ok, ssl} = connect(state.ip)
        state = %State{state | :ssl => ssl}
        state = connect_channel(:receiver, state)
        {:noreply, state}
    end

    def handle_info({:ssl, {sslsocket, new_ssl, _}, data}, state) do
        msg = decode(data)
        new_state =
            cond do
                msg.payload_utf8 != nil ->
                    payload = Poison.Parser.parse!(msg.payload_utf8)
                    new_state = handle_payload(payload, state)
                true -> state
            end
        {:noreply, new_state}
    end

    def handle_payload(%{"type" => @ping} = payload, state) do
        msg = create_message(:heartbeat, %{:type => @pong}, "receiver-0")
        state = send_msg(state.ssl, msg, state)
    end

    def handle_payload(%{"type" => @receiver_status} = payload, state) do
        case payload["status"]["applications"] do
            nil -> state
            other ->
                app = Enum.at(other, 0)
                cond do
                    app["transportId"] != state.destination_id ->
                        state = %State{state | :destination_id => app["transportId"], :session => app["sessionId"]}
                        state = connect_channel(:media, state)
                        %State{state | :receiver_status => payload}
                    true -> state
                end
        end
    end

    def handle_payload(%{"type" => @media_status} = payload, state) do
        status = Enum.at(payload["status"], 0)
        status = Map.merge(state.media_status, status)
        %State{state | :media_status => status, :media_session => status["mediaSessionId"]}
    end

    def handle_payload(%{"backendData" => status} = payload, state) do
        %State{state | :media_status => payload}
    end

    def handle_payload(%{} = payload, state) do
        Logger.debug "Unknown Payload: #{inspect payload}"
        state
    end

    def encode(msg) do
        m = Chromecast.CastMessage.encode(msg)
        << byte_size(m)::big-unsigned-integer-size(32) >> <> m
    end

    def decode(<< length::big-unsigned-integer-size(32), rest::binary >> = msg) when length < 102400 do
        Chromecast.CastMessage.decode(rest)
    end

    def decode(<< length::big-unsigned-integer-size(32), rest::binary >> = msg) do
        Chromecast.CastMessage.decode(msg)
    end
end