-module(robust_bank_client).

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

deposit(Who, X)  -> robust_rpc({deposit, Who, X}).
withdraw(Who, X) -> robust_rpc({withdraw, Who, X}).
balance(Who)     -> robust_rpc({balance, Who}).

robust_rpc(X) ->
    Id = make_ref(),
    X1 = {call, Id, X},
    io:format("trying to connect to server 1~n"),
    case gen_tcp:connect("localhost", 3020, 
			 [binary, {packet, 4}]) of
	{ok, Socket} ->
	    io:format("sending to server 1~n"),
	    gen_tcp:send(Socket, [term_to_binary(X1)]),
	    wait_reply1(Socket, Id, X);
	{error, _} ->
	    io:format("cannot connect to server 1~n"),
	    robust_rpc_try_again(Id, X)
    end.

wait_reply1(Socket, Id, X) ->
    receive
 	{tcp, Socket, Bin} ->
 	    case binary_to_term(Bin) of
		{ack, Id, Reply} ->
		    io:format("server 1 replied~n"),
		    B = term_to_binary({delete_tag, Id}),
		    gen_tcp:send(Socket, B),
		    gen_tcp:close(Socket),
		    {ok, {server1, Reply}};
		_ ->
		    robust_rpc_try_again(Id, X)
	    end;
 	{tcp_closed, Socket} ->
	    robust_rpc_try_again(Id, X)
    after 10000 ->
	    io:format("timeout from server 1~n"),
	    gen_tcp:close(Socket),
	    robust_rpc_try_again(Id, X)
    end.

robust_rpc_try_again(Id, X) ->
    io:format("trying to connect to server 2~n"),
    case gen_tcp:connect("localhost", 3030, 
			 [binary, {packet, 4}]) of
	{ok, Socket} ->
	    X1 = {call, Id, X},    
	    io:format("sending to server 2~n"),
	    gen_tcp:send(Socket, [term_to_binary(X1)]),
	    wait_reply2(Socket, Id);
	{error, E} ->
	    io:format("cannot connect to server 2~n"),
	    {error, both_servers_down}
    end.

wait_reply2(Socket, Id) ->
    receive
 	{tcp, Socket, Bin} ->
	    case binary_to_term(Bin) of
		{ack, Id, Reply} ->
		    B =  term_to_binary({delete_tag, Id}),
		    gen_tcp:send(Socket, B),
		    gen_tcp:close(Socket),
		    {ok, {server2, Reply}};
		O ->
		    {error, {unexpect_reply, O}}
	    end;
 	{tcp_closed, Socket} ->
	    {error, server2}
    after 10000 ->
	    io:format("timeout from server 2~n"),
	    gen_tcp:close(Socket),
	    {error, no_reply_sever2}
    end.