%%% Name            :Marcus Näslund
%%% Personal number :9312105118
%%% E-mail          :

-module(dist_erlang).
-record(object, {pid, dbkey, value}).
%% DO NOT CHANGE THE EXPORT STATEMENT!
-export([start/0, init/0, stop/0, store/2, fetch/1, flush/0,
         task/1, dist_task/1, pmap/2, faulty_task/1
        ]).
%% End of no-change area


start() ->
  case whereis(sts) of
    undefined ->
      Pid = spawn(dist_erlang,init,[]),
      register(sts,Pid),
      {ok,Pid};
    Pid ->
      {ok,Pid}
  end.


stop() ->
  case whereis(sts) of
    undefined ->
      already_stopped;
    Pid ->
      true = exit(Pid,stop),
      stopped
  end.


store(Key,Value) ->
  case whereis(sts) of
    undefined ->
      no_server_running;
    Pid ->
      Pid ! {self(),store, Key, Value},
      receive
        Result ->
          Result
      after 1500 ->
        request_timeout
      end
  end.


fetch(Key) ->
  case whereis(sts) of
    undefined ->
      no_server_running;
    Pid ->
      Pid ! {self(),fetch, Key},
      receive
        Result ->
          Result
      after 1500 ->
        reqest_timeout
      end
  end.

flush() ->
  case whereis(sts) of
    undefined ->
      no_server_running;
    Pid ->
      Pid ! {self(),flush},
      receive
        Result ->
          Result
      after 1500 ->
        requet_timeout
      end
  end.

init() ->
  loop([]).

%% Server loop
loop(Db) ->
  receive
    {Pid,fetch,Key} ->
      Pid ! fetch(Pid,Key,Db),
      loop(Db);

    {Pid,store,Key,Value} ->
      case fetch(Pid,Key,Db) of
        {ok,_} ->
          ok, Pid ! {ok,Value};
        {error,not_found} ->
          no_value, Pid ! {ok,no_value}
      end,
      Db2 = [#object{pid=Pid,dbkey=Key,value=Value}|Db],
      loop(Db2);

    {Pid,flush} ->
      NewDb = flush(Pid,Db,[]),
      Pid ! {ok,flushed},
      loop(NewDb)
  end,
  loop(Db).



fetch(Pid,Key,[H|T]) ->
  case H of
    #object{pid=Pid,dbkey=Key} ->
      {ok,H#object.value};
    H ->
      fetch(Pid,Key,T)
  end;

fetch(_,_,[]) ->
  {error,not_found}.


flush(Pid,[H|T],Db) ->
  case H of
    #object{pid=Pid} ->
      flush(Pid,T,Db);
    H ->
      flush(Pid,T,[H|Db])
  end;

flush(_,_,Db) ->
  Db.