client.erl

%% - Client module
%% - The client module creates a parallel process by spawning handler.
%% - The handler does the following:
%%      1/ It makes itself into a system process in order to trap exits.
%%      2/ It creates a window and sets up the prompt and the title.
%%      4/ It waits for connection message (see disconnected).
%%

-module(client).

-import(window, [set_title/2, insert_str/2, set_prompt/2]).

-export([start/1]).

start(Host) ->
  spawn(fun() -> handler(Host) end).

%%%%%%%%%%%%%%%%%%%%%%% INACTIVE CLIENT %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% - The handler starts a window and a connector
handler(Host) ->
  process_flag(trap_exit, true),
  Window = window:start(self()),
  set_title(Window, "Connecting..."),
  set_prompt(Window, "action > "),
  start_connector(Host),
  disconnected(Window).

%% - The window is disconnected until it received a connected meassage from
%% the connector
disconnected(Window) ->
  receive
    {connected, ServerPid} ->
      insert_str(Window, "Connected to the transaction server\n"),
      set_title(Window, "Connected"),
      connected(Window, ServerPid);
    {'Exit', _, _} -> exit(died);
    Other -> io:format("client disconnected unexpected:~p~n",[Other]),
      disconnected(Window)
  end.
%%%%%%%%%%%%%%%%%%%%%%% INACTIVE CLIENT %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%%%%%%%%%%%%%%%%%%%% CONNECTOR %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
start_connector(Host) ->
  S = self(),
  spawn_link(fun() -> try_to_connect(S,Host) end).

try_to_connect(Parent, Host) ->
  %% Parent is the Pid of the process (handler) that spawned this process
  {transaction_server, Host} ! {login, self(), Parent},
  receive
    {ok, ServerPid} -> Parent ! {connected, ServerPid},
      exit(connectorFinished);
    Any -> io:format("Unexpected message~p.~n",[Any])
  after 5000 ->
      io:format("Unable to connect to the transaction server at node~p. Restart the client application later.~n",[Host])
  end,
  exit(serverBusy).
%%%%%%%%%%%%%%%%%%%%%%% CONNECTOR %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%




%%%%%%%%%%%%%%%%%%%%%%% ACTIVE CLIENT %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
connected(Window, ServerPid) ->
  receive
    %% - The user has requested a transaction
    {request, Window, Transaction} ->
      io:format("Client requested the transaction ~p.~n",[Transaction]),
      insert_str(Window, "Processing request...\n"),
      process(Window, ServerPid, Transaction);
    {'EXIT', Window, windowDestroyed} -> end_client(ServerPid);
    {close, ServerPid} -> exit(serverDied);
    Other ->
      io:format("client active unexpected: ~p~n",[Other]),
      connected(Window,ServerPid)
  end.

%% - Asking to process a request
process(Window, ServerPid, Transaction) ->
  ServerPid ! {request, self()}, %% Send a request to server and wait for proceed message
  receive
    {proceed, ServerPid} ->
        send(Window, ServerPid, Transaction); %% received green light send the transaction.
    {close, ServerPid} -> exit(serverDied);
    Other ->
      io:format("client active unexpected: ~p~n",[Other])
  end.

%% - Sending the transaction and waiting for confirmation
send(Window, ServerPid, []) ->
  ServerPid ! {confirm, self()}, %% Once all the list (transaction) items sent, send confirmation
  receive
    {abort, ServerPid} -> insert_str(Window, "Aborted... type run if you want to try again!\n"),
      connected(Window, ServerPid);
    {committed, ServerPid} -> insert_str(Window, "Transaction succeeded!\n"),
      connected(Window, ServerPid);
    {'EXIT', Window, windowDestroyed} -> end_client(ServerPid);
    {close, ServerPid} ->
      exit(serverDied);
    Other ->
      io:format("client active unexpected: ~p~n",[Other])
  end;
send(Window, ServerPid, [H|T]) ->
  sleep(3),
  case loose(6) of
    %% In order to handle losses, think about adding an extra field to the
    %message sent
    false ->
        ServerPid ! {action, self(), H};
    true ->
        io:format("dropped package~n"),
        ok
  end,

  %Stop and wait
  receive
      {ack, ServerPid} ->
          send(Window, ServerPid, T)
  after 1000 ->
          send(Window, ServerPid, [H|T])
  end.
%%%%%%%%%%%%%%%%%%%%%%% Active Window %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%% - Clean end
end_client(ServerPid) ->
  io:format("Client ended communication.~n",[]),
  ServerPid ! {close, self()},
  exit(died).

%% - Blocks a random amount of seconds between 1 and 5.
%% - This simulates latency in the network.
%% - Latency is an integer parameter which can be interpreted as a worst case
%% waiting time in seconds
sleep(Latency) ->
  receive
  after 1000*random:uniform(Latency) ->
      true
  end.

%% - Loses messages randomly
%% - This simulates the fact that the communication media is unreliable
%% - Lossyness is an integer parameter:
%%        - if Lossyness =0 the function will always return true
%%        - if Lossyness >10 the function will always return false
%%        - if lossyness =6 the function will return either values with
%%        probability 1/2
loose(Lossyness) ->
  Val=random:uniform(10),
  if
    Val >= Lossyness -> false;
    true -> true
  end.