-module(bank).

-export([deposit/2, withdraw/2, balance/1]).

-include("bank.hrl").

deposit(Who, X) ->
    fun() ->
	    case mnesia:read({account, Who}) of
		[] ->
		    %% no accout so we make one
		    Entry = #account{name=Who,balance=X},
		    mnesia:write(Entry),
		    X;
		[E] ->
		    Old = E#account.balance,
		    New = Old + X,
		    E1 = E#account{balance=New},
		    mnesia:write(E1),
		    New
	    end
    end.

balance(Who) ->
    fun() ->
	    case mnesia:read({account, Who}) of
		[] ->
		    %% no account
		    {error, no_such_account};
		[E] ->
		    B = E#account.balance,
		    {ok, B}
	    end
    end.

withdraw(Who, X) ->
    fun() ->
	    case mnesia:read({account, Who}) of
		[] ->
		    %% no account
		    {error, no_such_user};
		[E] ->
		    Old = E#account.balance,
		    if 
			Old >= X ->
			    New = Old - X,
			    E1 = E#account{balance=New},
			    mnesia:write(E1),
			    ok;
			Old < X ->
			    {error, not_enough_money}
		    end
	    end
    end.