食事する哲学者の問題 with Cizen ref: https://qiita.com/ryo33/items/3d3fc82cdcb929e0b9ec

file0.txt

mix new cizen_dining_philosophers
cd cizen_dining_philosophers

file1.txt

defp deps do
  [
    {:cizen, "~> 0.14.1"}
  ]
end

file2.txt

defmodule BorrowChopstick do
  defstruct [:chopstick_id]

  use Cizen.Request # to use defresponse/3
  defresponse LendChopstick, :request_id do
    defstruct [:request_id]
  end
end

defmodule ReturnChopstick do
  defstruct [:chopstick_id]
end

file3.txt

defmodule Chopstick do
  use Cizen.Automaton
  defstruct []

  alias Cizen.Effects.{Dispatch, Receive, Subscribe}
  alias Cizen.{Event, Filter}

  @impl true
  def spawn(id, %__MODULE__{}) do
    perform id, %Subscribe{
      event_filter: Filter.any([
        Filter.new(fn %Event{body: %BorrowChopstick{chopstick_id: ^id}} -> true end),
        Filter.new(fn %Event{body: %ReturnChopstick{chopstick_id: ^id}} -> true end)
      ])
    }
    :available
  end

  @impl true
  def yield(id, :available) do
    received = perform id, %Receive{
      event_filter: Filter.new(fn %Event{body: %BorrowChopstick{}} -> true end)
    }

    alias BorrowChopstick.LendChopstick
    perform id, %Dispatch{
      body: %LendChopstick{
        request_id: received.id
      }
    }

    :not_available
  end

  @impl true
  def yield(id, :not_available) do
    perform id, %Receive{
      event_filter: Filter.new(fn %Event{body: %ReturnChopstick{}} -> true end)
    }

    :available
  end
end

file4.txt

defmodule Philosopher do
  use Cizen.Automaton
  defstruct [:name, :left_chopstick, :right_chopstick]

  alias Cizen.Effects.{Request, Dispatch}

  @impl true
  def spawn(_id, struct) do
    {:hungry, struct}
  end

  @impl true
  def yield(id, {:hungry, struct}) do
    %__MODULE__{
      name: name,
      left_chopstick: left_chopstick,
      right_chopstick: right_chopstick
    } = struct

    IO.puts("#{name} is hungry.")

    perform id, %Request{
      body: %BorrowChopstick{
        chopstick_id: left_chopstick
      }
    }

    IO.puts("#{name} has a chopstick in their left hand.")

    perform id, %Request{
      body: %BorrowChopstick{
        chopstick_id: right_chopstick
      }
    }

    IO.puts("#{name} has chopstics in both hands.")

    {:eating, struct}
  end

  @impl true
  def yield(id, {:eating, struct}) do
    %__MODULE__{
      name: name,
      left_chopstick: left_chopstick,
      right_chopstick: right_chopstick
    } = struct

    IO.puts("#{name} is eating.")

    perform id, %Dispatch{
      body: %ReturnChopstick{
        chopstick_id: left_chopstick
      }
    }

    perform id, %Dispatch{
      body: %ReturnChopstick{
        chopstick_id: right_chopstick
      }
    }

    {:hungry, struct}
  end
end

file5.txt

defmodule Dining do
  use Cizen.Effectful # for handle/1 and perform/2

  alias Cizen.Effects.{All, Start}

  def run do
    handle fn id ->
      chopstick_1 = perform id, %Start{saga: %Chopstick{}}
      chopstick_2 = perform id, %Start{saga: %Chopstick{}}
      chopstick_3 = perform id, %Start{saga: %Chopstick{}}
      chopstick_4 = perform id, %Start{saga: %Chopstick{}}
      chopstick_5 = perform id, %Start{saga: %Chopstick{}}

      philosophers = [
        %Philosopher{
          name: "Plato",
          left_chopstick: chopstick_1,
          right_chopstick: chopstick_2
        },
        %Philosopher{
          name: "Konfuzius",
          left_chopstick: chopstick_2,
          right_chopstick: chopstick_3
        },
        %Philosopher{
          name: "Socrates",
          left_chopstick: chopstick_3,
          right_chopstick: chopstick_4
        },
        %Philosopher{
          name: "Voltaire",
          left_chopstick: chopstick_4,
          right_chopstick: chopstick_5
        },
        %Philosopher{
          name: "Descartes",
          left_chopstick: chopstick_5,
          right_chopstick: chopstick_1
        }
      ]

      perform id, %All{
        effects: Enum.map(philosophers, &(%Start{saga: &1}))
      }

      receive do
        _ -> :ok
      end
    end
  end
end

Dining.run

file6.txt

Plato is hungry.
Konfuzius is hungry.
Socrates is hungry.
Voltaire is hungry.
Descartes is hungry.
Plato has a chopstick in their left hand.
Konfuzius has a chopstick in their left hand.
Socrates has a chopstick in their left hand.
Voltaire has a chopstick in their left hand.
Descartes has a chopstick in their left hand.

file7.txt

%Philosopher{
  name: "Descartes",
  left_chopstick: chopstick_1,
  right_chopstick: chopstick_5
}

file8.txt

Plato is hungry.
Konfuzius is hungry.
Socrates is hungry.
Voltaire is hungry.
Descartes is hungry.
Plato has a chopstick in their left hand.
Konfuzius has a chopstick in their left hand.
Socrates has a chopstick in their left hand.
Voltaire has a chopstick in their left hand.
Voltaire has chopstics in both hands.
Voltaire is eating.
Voltaire is hungry.
Socrates has chopstics in both hands.
Socrates is eating.
Socrates is hungry.
Konfuzius has chopstics in both hands.
Konfuzius is eating.
Voltaire has a chopstick in their left hand.
Konfuzius is hungry.
Plato has chopstics in both hands.
Plato is eating.
Plato is hungry.
Socrates has a chopstick in their left hand.
Voltaire has chopstics in both hands.
Voltaire is eating.
Voltaire is hungry.
Descartes has a chopstick in their left hand.
Konfuzius has a chopstick in their left hand.
Socrates has chopstics in both hands.
Socrates is eating.
Socrates is hungry.
Descartes has chopstics in both hands.
Descartes is eating.
Descartes is hungry.
.
.
.