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defmodule Agent.Server do
@moduledoc false
use GenServer
def init(fun) do
_ = initial_call(fun)
{:ok, run(fun, [])}
end
def handle_call({:get, fun}, _from, state) do
{:reply, run(fun, [state]), state}
end
def handle_call({:get_and_update, fun}, _from, state) do
case run(fun, [state]) do
{reply, state} -> {:reply, reply, state}
other -> {:stop, {:bad_return_value, other}, state}
end
end
def handle_call({:update, fun}, _from, state) do
{:reply, :ok, run(fun, [state])}
end
def handle_cast({:cast, fun}, state) do
{:noreply, run(fun, [state])}
end
def code_change(_old, state, fun) do
{:ok, run(fun, [state])}
end
defp initial_call(mfa) do
_ = Process.put(:"$initial_call", get_initial_call(mfa))
:ok
end
defp get_initial_call(fun) when is_function(fun, 0) do
{:module, module} = Function.info(fun, :module)
{:name, name} = Function.info(fun, :name)
{module, name, 0}
end
defp get_initial_call({mod, fun, args}) do
{mod, fun, length(args)}
end
defp run({m, f, a}, extra), do: apply(m, f, extra ++ a)
defp run(fun, extra), do: apply(fun, extra)
end
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