Cache based basic Fibonacci Server

Author: immidisa

febonnacy_server.erl

@@ -0,0 +1,168 @@
+%%%-------------------------------------------------------------------
+%%% @author Adinarayana
+%%% @copyright (C) 2019, <COMPANY>
+%%% @doc
+%%%
+%%% @end
+%%% Created : 27. Apr 2019 15:48
+%%%-------------------------------------------------------------------
+-module(febonnacy_server).
+-author("Adinarayana").
+
+-behaviour(gen_server).
+
+%% API
+-export([start_link/0]).
+
+%% gen_server callbacks
+-export([init/1,
+  handle_call/3,
+  handle_cast/2,
+  handle_info/2,
+  terminate/2,
+  code_change/3]).
+
+-define(SERVER, ?MODULE).
+
+-record(state, {}).
+
+%%%===================================================================
+%%% API
+%%%===================================================================
+
+%%--------------------------------------------------------------------
+%% @doc
+%% Starts the server
+%%
+%% @end
+%%--------------------------------------------------------------------
+-spec(start_link() ->
+  {ok, Pid :: pid()} | ignore | {error, Reason :: term()}).
+start_link() ->
+  gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
+
+%%%===================================================================
+%%% gen_server callbacks
+%%%===================================================================
+
+%%--------------------------------------------------------------------
+%% @private
+%% @doc
+%% Initializes the server
+%%
+%% @spec init(Args) -> {ok, State} |
+%%                     {ok, State, Timeout} |
+%%                     ignore |
+%%                     {stop, Reason}
+%% @end
+%%--------------------------------------------------------------------
+-spec(init(Args :: term()) ->
+  {ok, State :: #state{}} | {ok, State :: #state{}, timeout() | hibernate} |
+  {stop, Reason :: term()} | ignore).
+init([]) ->
+  ets:new(feb_result, [set,public, named_table]),
+  {ok, #state{}}.
+
+%%--------------------------------------------------------------------
+%% @private
+%% @doc
+%% Handling call messages
+%%
+%% @end
+%%--------------------------------------------------------------------
+-spec(handle_call(Request :: term(), From :: {pid(), Tag :: term()},
+    State :: #state{}) ->
+  {reply, Reply :: term(), NewState :: #state{}} |
+  {reply, Reply :: term(), NewState :: #state{}, timeout() | hibernate} |
+  {noreply, NewState :: #state{}} |
+  {noreply, NewState :: #state{}, timeout() | hibernate} |
+  {stop, Reason :: term(), Reply :: term(), NewState :: #state{}} |
+  {stop, Reason :: term(), NewState :: #state{}}).
+handle_call(Request, _From, State) ->
+  Result = compute_fibonacci(Request),
+  {reply, Result, State}.
+
+%%--------------------------------------------------------------------
+%% @private
+%% @doc
+%% Handling cast messages
+%%
+%% @end
+%%--------------------------------------------------------------------
+-spec(handle_cast(Request :: term(), State :: #state{}) ->
+  {noreply, NewState :: #state{}} |
+  {noreply, NewState :: #state{}, timeout() | hibernate} |
+  {stop, Reason :: term(), NewState :: #state{}}).
+handle_cast(_Request, State) ->
+  {noreply, State}.
+
+%%--------------------------------------------------------------------
+%% @private
+%% @doc
+%% Handling all non call/cast messages
+%%
+%% @spec handle_info(Info, State) -> {noreply, State} |
+%%                                   {noreply, State, Timeout} |
+%%                                   {stop, Reason, State}
+%% @end
+%%--------------------------------------------------------------------
+-spec(handle_info(Info :: timeout() | term(), State :: #state{}) ->
+  {noreply, NewState :: #state{}} |
+  {noreply, NewState :: #state{}, timeout() | hibernate} |
+  {stop, Reason :: term(), NewState :: #state{}}).
+handle_info(_Info, State) ->
+  {noreply, State}.
+
+%%--------------------------------------------------------------------
+%% @private
+%% @doc
+%% This function is called by a gen_server when it is about to
+%% terminate. It should be the opposite of Module:init/1 and do any
+%% necessary cleaning up. When it returns, the gen_server terminates
+%% with Reason. The return value is ignored.
+%%
+%% @spec terminate(Reason, State) -> void()
+%% @end
+%%--------------------------------------------------------------------
+-spec(terminate(Reason :: (normal | shutdown | {shutdown, term()} | term()),
+    State :: #state{}) -> term()).
+terminate(_Reason, _State) ->
+  ok.
+
+%%--------------------------------------------------------------------
+%% @private
+%% @doc
+%% Convert process state when code is changed
+%%
+%% @spec code_change(OldVsn, State, Extra) -> {ok, NewState}
+%% @end
+%%--------------------------------------------------------------------
+-spec(code_change(OldVsn :: term() | {down, term()}, State :: #state{},
+    Extra :: term()) ->
+  {ok, NewState :: #state{}} | {error, Reason :: term()}).
+code_change(_OldVsn, State, _Extra) ->
+  {ok, State}.
+
+
+
+compute_fibonacci(0) -> 0;
+compute_fibonacci(1) -> 1;
+compute_fibonacci(N) ->
+  Num2 = case ets:lookup(feb_result,N-2) of
+         [] ->
+           Second_Prev =  compute_fibonacci(N-2),
+           ets:insert(feb_result,{N-2, Second_Prev}),
+           Second_Prev;
+         [{_,Second_Prev}] -> Second_Prev
+       end,
+  Num1 = case ets:lookup(feb_result,N-1) of
+         [] ->
+           First_Prev =  compute_fibonacci(N-1),
+           ets:insert(feb_result,{N-1, First_Prev}),
+           First_Prev;
+         [{_,First_Prev}] -> First_Prev
+       end,
+  Num2 + Num1.
+%%%===================================================================
+%%% Internal functions
+%%%===================================================================