74 lines
2.1 KiB
Elixir
74 lines
2.1 KiB
Elixir
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defmodule Player do
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use GenServer
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# Client API
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def start_link(arg \\ nil) do
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GenServer.start_link(__MODULE__, arg, name: __MODULE__)
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end
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def set_schedule(schedule) do
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GenServer.call(__MODULE__, {:set_schedule, schedule})
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end
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def play do
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GenServer.call(__MODULE__, :play)
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end
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# Server callbacks
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@impl true
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def init(_arg) do
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{:ok, synth} = MIDISynth.start_link([])
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epoch = Timex.epoch() |> Timex.to_datetime()
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{:ok, %{timer: nil, schedule: [], schedule_left: [], start_time: epoch, synth: synth}}
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end
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@impl true
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def handle_call({:set_schedule, schedule}, _from, state) do
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{:reply, :ok, %{state | schedule: schedule, schedule_left: schedule}}
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end
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def handle_call(:play, _from, %{schedule_left: schedule_left} = state) do
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start_time = Timex.now()
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state = %{state | start_time: start_time}
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timer = start_timer(schedule_left, start_time)
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{:reply, :ok, %{state | timer: timer}}
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end
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@impl true
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def handle_info(
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:play,
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%{schedule_left: schedule_left, start_time: start_time, synth: synth} = state
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) do
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schedule_left = play_next_midi(schedule_left, start_time, synth)
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{:noreply, %{state | schedule_left: schedule_left}}
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end
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defp play_next_midi([], _start_time, _synth), do: []
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defp play_next_midi([{offset, command} | next_schedule] = schedule_left, start_time, synth) do
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next_time = DateTime.add(start_time, offset, :millisecond)
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micro_diff = Timex.diff(next_time, Timex.now(), :microsecond)
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if micro_diff < 500 do
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# Play command, and try to play next command too.
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MIDISynth.midi(synth, command)
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play_next_midi(next_schedule, start_time, synth)
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else
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# Command is too far in the future, schedule next timer.
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delay = ceil(micro_diff / 1000)
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Process.send_after(self(), :play, delay)
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schedule_left
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end
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end
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defp start_timer([], _start_time), do: nil
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defp start_timer([{offset, _command} | _], start_time) do
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next_time = DateTime.add(start_time, offset, :millisecond)
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delay = Timex.diff(next_time, Timex.now(), :millisecond)
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Process.send_after(self(), :play, delay)
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end
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end
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