Exercism Elixir exercise on agents done at AlpesCraft 2024

community-garden.exs

defmodule Plot do
  @enforce_keys [:plot_id, :registered_to]
  defstruct [:plot_id, :registered_to]
end

defmodule State do
  @enforce_keyz [:next_id, :registrations]
  defstruct [:next_id, :registrations]
end

defmodule CommunityGarden do
  def start() do
    Agent.start(fn -> %State{next_id: 1, registrations: []} end)
  end

  def list_registrations(pid) do
    Agent.get(pid, fn state -> state.registrations end)
  end

  def register(pid, register_to) do
    Agent.get_and_update(pid, fn state -> register_in_state(state, register_to) end)
  end

  defp register_in_state(state, register_to) do
    new_plot = %Plot{plot_id: state.next_id, registered_to: register_to}
    {new_plot, %State{next_id: state.next_id + 1, registrations: state.registrations ++ [new_plot]}}
  end

  def release(pid, plot_id) do
    Agent.update(pid, fn state -> 
      %State{
        next_id: state.next_id,
        registrations: Enum.filter(state.registrations, fn plot -> plot.plot_id != plot_id end) }
              end)
  end

  def get_registration(pid, plot_id) do
    Agent.get(pid, fn state -> Enum.find(state.registrations, {:not_found, "plot is unregistered"}, fn plot -> plot.plot_id == plot_id end) end)
  end
end