Artilce Demonstration Project

bank.ex

defmodule Bank do
  use GenServer
  alias Bank.Cache
  @moduledoc """
  Documentation for Bank.
  """
# client API
  def start_link(cache_pid) do 
    GenServer.start_link(Bank, cache_pid, name: Bank)
  end
  def init cache_pid do
    balance = Cache.get_balance(cache_pid)
    {:ok, %{current_balance: balance, cache_pid: cache_pid}}
  end
  def get_current_balance() do
    GenServer.call(Bank, :get)
  end
  def show_balance() do
    IO.inspect(get_current_balance(), label: "Available Balance")
  end
  def deposit amount do
    GenServer.cast(Bank, {:credit, amount})
  end
  def with_draw amount do
    transaction = GenServer.call(Bank, {:with_draw, amount})
    case transaction do
      :ok ->
        IO.inspect amount, label: "Amount debitted"
        show_balance()
       {:ok, error}-> 
        IO.inspect error.reason, label: "ERROR:"
        
    end
  end
# Server API
  
  def handle_call(:get, _from, state) do
    {:reply, state.current_balance, state}
  end
  def handle_call({:with_draw, with_draw_amount}, _from, %{current_balance: current_balance } = state) 
  when current_balance > with_draw_amount do
    GenServer.cast(Bank, {:debit, with_draw_amount})
    {:reply, :ok, state}
  end
  def handle_cast({:credit,amount}, %{current_balance: current_balance}=state) do
    new_balance = current_balance + amount
    {:noreply, %{state | current_balance: new_balance } }
  end
  def handle_cast({:debit,amount}, %{current_balance: current_balance} = state) when amount < current_balance do
    new_balance = current_balance - amount
    {:noreply, %{state | current_balance: new_balance } }
  end
  def terminate(_reason, state) do
    Cache.save_balance(state.current_balance, state.cache_pid)
  end
end