distributed_system_coursework/lib/server.ex

defmodule ServerMacros do

  def create_create_loop(name, do: match_exp, else: process_exp) do
    function_name = :"#{name}_loop"

    ast1 = quote do
      {:timeout} -> :timeout
    end
    ast2 = quote do
      value ->
        # TODO check spelling
        log("Disreguarding: #{inspect(value)}")
        # Process.send_after(self(), value, t + 2000)
        unquote(function_name)(v, t)
    end

    ast3 = ast1 ++ match_exp ++ ast2

    quote do
      def unquote(function_name)(v, t) do
        var!(v) = v
        unquote(process_exp)
        receive do
          unquote(ast3)
        after
          t -> :timeout
        end
      end
    end
  end

  def create_create_loop(name, do: exp, else: else_exp) do
    create_create_loop(name, do: exp, else: else_exp)
  end

  def create_create_loop(name, do: exp) do
    create_create_loop(name, do: exp, else: nil)
  end

  defmacro create_loop(name, clauses) do
  	create_create_loop(name, clauses)
  end

  defmacro try_propose(val, do: ready, else: recal_do) do
    ast1 = quote do
      {:timeout} ->  unquote(recal_do)
      {:abort} ->   unquote(recal_do)
    end
    ast2 = quote do
      {:decision, v} ->
        var!(state) = apply_game(var!(state), v)
        unquote(recal_do)

      v ->
        raise "Unknown message on try_propose #{inspect(v)}"
    end

    ast3 = ast1 ++ ready ++ ast2

    quote do
      v = Paxos.propose(var!(state).paxos, var!(state).instance, unquote(val), 1000)
      case v do
        unquote(ast3)
      end
    end
  end

end

defmodule Server do
  require ServerMacros
  import ServerMacros
  require Utils
  import Utils

  create_log 3

  def start(name, participants) do
    log("starting server")

    pid = spawn(Server, :init, [name, participants])
    register_name(name, pid, false)
  end

  def init(name, participants) do
    paxos = Paxos.start(alter_name(name, "_paxos"), Enum.map(participants, fn name -> alter_name(name, "_paxos") end), true)
    state = %{
      name: name,
      procs: participants,
      games: %{},
      paxos: paxos,
      instance: 0,
    }

    run(state)
  end

  runfn do
    {:start_game, participants, pid_to_inform} ->
      {state, game_id} = try_to_create_game(state, participants)
      state = set_modifed(state, game_id)
      safecast(pid_to_inform, {:start_game_ans, game_id})
      state

    {:get_game_state, game_id, pid_to_inform} ->
      get_game_state(state, game_id, pid_to_inform)

    {:make_move, game_id, move, pid_to_inform} ->
      try_to_play_checks(state, game_id, move, pid_to_inform)

  end

  def try_to_play_checks(state, game_id, move, pid_to_inform, repeat \\ false) do
    cond do
      state.games[game_id] == :not_playing_in_game ->
        safecast(pid_to_inform, {:make_move, game_id, :not_playing})
        state

      state.games[game_id] == nil ->
        if repeat do
          safecast(pid_to_inform, {:make_move, game_id, :game_does_not_exist})
          state
        else
          state = qurey_status(state)
          try_to_play_checks(state, game_id, move, pid_to_inform, true)
        end 

      true ->
        state = qurey_status(state)
        game = state.games[game_id]
        cond do
          is_finished(state, game_id) ->
            {_, score} = state.games[game_id]
            safecast(pid_to_inform, {:make_move, game_id, :game_finished, score})
            state
          game.modified ->
            safecast(pid_to_inform, {:make_move, game_id, :player_moved_before, game.game_state, game.hand})
            set_modifed(state, game_id)
          true ->
            try_to_play(state, game_id, move, pid_to_inform)
        end
    end
  end

  def try_to_play(state, game_id, move, pid_to_inform) do
    name = state.name
    new_hand = get_hand_for_game_state(state.games[game_id].game_state)
    try_propose {:make_move, game_id, name, move, new_hand}
    do
      {:decision, {:make_move, ^game_id, ^name, ^move, ^new_hand}} ->
        state = apply_game(state, {:make_move, game_id, name, move, new_hand})

        if is_finished(state, game_id) do
          {_, score} = state.games[game_id]
          safecast(pid_to_inform, {:make_move, game_id, :game_finished, score})
        else
          game = state.games[game_id]
          safecast(pid_to_inform, {:make_move, game_id, game.game_state, game.hand[state.name]})
        end

        set_modifed(state, game_id)

      {:decision, {:make_move, ^game_id, new_name, new_move, new_new_hand}} ->
        state = apply_game(state, {:make_move, game_id, new_name, new_move, new_new_hand})

        if is_finished(state, game_id) do
          {_, score} = state.games[game_id]
          safecast(pid_to_inform, {:make_move, game_id, :game_finished, score})
        else
          game = state.games[game_id]
          safecast(pid_to_inform, {:make_move, game_id, :player_moved_before, game.game_state, game.hand})
        end

        set_modifed(state, game_id)
    else
      try_to_play(state, game_id, move, pid_to_inform)
    end
  end

  def get_game_state(state, game_id, pid_to_inform, repeat \\ false) do
    cond do 
      state.games[game_id] == :not_playing_in_game ->
        safecast(pid_to_inform, {:game_state, game_id, :not_playing})
        state

      state.games[game_id] == nil ->
        if repeat do
          safecast(pid_to_inform, {:game_state, game_id, :game_does_not_exist})
          state
        else
          state = qurey_status(state)
          get_game_state(state, game_id, pid_to_inform, true)
        end

      true ->
        state = qurey_status(state)
        if is_finished(state, game_id) do
          {_, score} = state.games[game_id]
          safecast(pid_to_inform, {:game_state, game_id, :game_finished, score})
        else
          game = state.games[game_id]
          safecast(pid_to_inform, {:game_state, game_id, game.game_state, game.hand[state.name]})
        end
        state
    end
  end

  def get_hand_for_game_state(game_state) do
    r1 = Enum.random(0..100)
    if r1 <= 10 do
      :+
    else
      mx = game_state |> Enum.filter(fn m -> m != :+ end) |> Enum.max()
      mn = max(mx - 20, 1)
      mx = max(mx - 2, 4)
      Enum.random(mn..mx)
    end 
  end

  def try_to_create_game(state, participants) do
    game_ids = Map.keys(state.games)
    latest = Enum.at(Enum.sort(game_ids), length(game_ids) - 1)
    new_game_id = if latest do latest else 0 end + 1

    new_game_state = Enum.to_list(0..Enum.random(3..8)) |> Enum.map(fn _ -> Enum.random(1..4) end)
    hand = Enum.reduce(participants, %{}, fn p, acc -> Map.put(acc, p, get_hand_for_game_state(new_game_state)) end)

    try_propose {:start_game, new_game_id, participants, new_game_state, hand}
    do
      {:decision, {:start_game, ^new_game_id, ^participants, ^new_game_state, ^hand}} ->
        state = apply_game(state, {:start_game, new_game_id, participants, new_game_state, hand})
        {state, new_game_id}
    else
      try_to_create_game(state, participants)
    end
  end

  #
  # Utils
  #
  
  def is_finished(state, game) do
    case state.games[game] do
      {:finished, _} -> true
      _ -> false
    end
  end

  def qurey_status(state) do
    v = Paxos.get_decision(state.paxos, state.instance, 100)
    or_state v != nil do
      state = apply_game(state, v)
      qurey_status(state)
    end
  end

  def set_modifed(state, game, val \\ false) do
    or_state not is_finished(state, game) do
      %{state | games: Map.put(state.games, game, %{state.games[game] | modified: val})}
    end
  end

  #
  # Apply Game States
  #

  def get_index(indexed_game_state, spos, index) do
    index = spos + index
    len = length(indexed_game_state)
    cond do
      index < 0 ->
        len - 1
      index >= len ->
        rem(index, len)
      true ->
        index 
    end
  end

  def simplify_game_state_pluses([], indexed_game_state), do: {false, indexed_game_state}
  def simplify_game_state_pluses([{:+, i} | tl], indexed_game_state) do
    before_i = get_index(indexed_game_state, i, -1)
    after_i = get_index(indexed_game_state, i, 1)

    if before_i != after_i do 
      {b, b_i} = Enum.at(indexed_game_state, before_i)
      {a, a_i} = Enum.at(indexed_game_state, after_i)

      if b == a do
        case b do
          :+ -> simplify_game_state_pluses(tl, indexed_game_state)
          n ->
            list =
              indexed_game_state |>
              Enum.map(fn {x, ti} -> if ti == i, do: {{:merged, n + 1}, i}, else: {x, ti} end) |>
              Enum.filter(fn {x, ti} -> cond do
                  b_i == ti -> false
                  a_i == ti -> false
                  true -> true
                end
              end) |>
              reindex()
            {true, expand_merge(list)}
        end
      else
        simplify_game_state_pluses(tl, indexed_game_state)
      end
    else
        simplify_game_state_pluses(tl, indexed_game_state)
    end
  end

  def is_merged(item) do
    case item do
      {:merged, _} -> true
      _ -> false
    end
  end

  def expand_merge(indexed_game_state) do
    {{:merged, n}, i} = indexed_game_state |> Enum.find(fn {x, _} -> is_merged(x) end)

    b_i = get_index(indexed_game_state, i, - 1)
    a_i = get_index(indexed_game_state, i, + 1)

    if b_i != a_i do
      {b, b_i} = Enum.at(indexed_game_state, b_i)
      {a, a_i} = Enum.at(indexed_game_state, a_i)
      if a == b do
        case b do
          :+ -> indexed_game_state
          {:merged, _} -> indexed_game_state
          _ ->
            indexed_game_state |>
              Enum.map(fn {x, ti} -> if ti == i, do: {{:merged, n + 1}, i}, else: {x, ti} end) |>
              Enum.filter(fn {x, ti} -> cond do
                  b_i == ti -> false
                  a_i == ti -> false
                  true -> true
                end
              end) |>
              reindex() |>
              expand_merge()
        end
      else
        indexed_game_state
      end
    else
      indexed_game_state
    end
  end

  def reindex(list, flat \\ true) do
    list = if flat do
      list |> Enum.map(fn {n, _} -> n end)
    else
      list
    end

    [list, 0..(length(list) - 1)] |> Enum.zip()
  end

  def remove_merged([], rec, _), do: rec

  def remove_merged([{:merged, n} | tl], rec, add) do
    if add do
      remove_merged(tl, rec ++ [n], false)
    else
      remove_merged(tl, rec, false)
    end
  end

  def remove_merged([n | tl], rec, add), do: 
    remove_merged(tl, rec ++ [n], add)

  def remove_merged(list) do
    log("#{inspect(list)}")
    remove_merged(list, [], true)
  end

  def simplify_game_state(game_state) do
    log("game_state: #{inspect(game_state)}")
    indexed_game_state = 
      game_state |>
      reindex(false)

    {repeat, indexed_game_state} =
      indexed_game_state |>
      Enum.filter(fn x -> case x do 
        {:+, _} -> true
        _ -> false
        end
      end) |>
      simplify_game_state_pluses(indexed_game_state)

    log("game_state2: #{inspect(indexed_game_state)}")

    if repeat do
      indexed_game_state |> 
        Enum.map(fn {v, _} -> v end) |>
        remove_merged() |>
        simplify_game_state()
    else
      indexed_game_state |> Enum.map(fn {v, _} -> v end)
    end
  end

  def apply_game(state, {:make_move, game_id, player_name, pos_move, new_hand}) do
    game = state.games[game_id]
    case game do
      {:finished, _} ->
        raise "Game already finished"
      :not_playing_in_game ->
        %{state | instance: state.instance + 1 }
      game ->
        game_state = game.game_state
        {b, e} = Enum.split(game_state, pos_move)
        game_state = b ++ [ game.hand[player_name] ] ++ e
        game_state = simplify_game_state(game_state)
        hand = Map.put(game.hand, player_name, new_hand)
        game = %{game| hand: hand, game_state: game_state }

        if length(game.game_state) > 15 do
          %{state| games: Map.put(state.games, game_id, {:finished, Enum.sum(game.game_state)}), instance: state.instance + 1}
        else
          %{state| games: Map.put(state.games, game_id, game), instance: state.instance + 1}
        end
    end
  end
  
  def apply_game(state, {:start_game, game_id, participants, new_game_state, hand}) do
    cond do
      state.games[game_id] ->
        raise "Game Already Exists"
      state.name in participants ->
        %{state | 
          games: Map.put(state.games, game_id, %{
            game_state: new_game_state,
            participants: participants,
            hand: hand,
            modified: true,
          }),
          instance: state.instance + 1
        }
      true ->
        %{state | 
          games: Map.put(state.games, game_id, :not_playing_in_game),
          instance: state.instance + 1,
        }
    end
  end

  def apply_game(_, _), do: raise "Do not know how to apply game state"

  ############
  # Interface 
  ############

  create_loop :start_game do
     {:start_game_ans, game_id} ->
       log("Started a game #{game_id}")
       {:start_game, game_id}
  end

  def start_game(name, participants) do
    safecast(name, {:start_game, participants, self()})
    start_game_loop(nil, 10000)
  end

  create_loop :get_game_state do
    {:game_state, ^v, :not_playing} ->
      log("Not Playing in that game")
      {:not_playing}
    {:game_state, ^v, game_state, hand} ->
      log("Got game state, #{inspect(game_state)}, hand: #{inspect(hand)}")
      {:state, game_state, hand}
    {:game_state, ^v, :not_playing} ->
      log("Not Playing in that game")
      {:not_playing}
    {:game_state, ^v, :game_finished, score} ->
      log("Game finsihed, #{score}")
      {:game_finished, score}
    {:game_state, ^v, :game_does_not_exist} ->
      log("Got game does not exist")
      {:not_exists}
  end

  def get_game_state(name, game_id) do
    safecast(name, {:get_game_state, game_id, self()})
    get_game_state_loop(game_id, 10000)
  end

  create_loop :make_move do
    {:make_move, ^v, :game_does_not_exist} ->
      log("Got game does not exist")
      {:not_exists}
    {:make_move, ^v, :not_playing} ->
      log("Not Playing in that game")
      {:not_playing}
    {:make_move, ^v, :game_finished, score} ->
      log("Game finsihed, #{score}")
      {:game_finished, score}
    {:make_move, ^v, :player_moved_before, game_state, hand} ->
      log("Player moved_before, #{inspect(game_state)} #{inspect(hand)}")
      {:player_moved_before, game_state, hand}
    {:make_move, ^v, game_state, hand} ->
      log("Got game state, #{inspect(game_state)}, hand: #{inspect(hand)}")
      {:state, game_state, hand}
  end

  def make_move(name, game_id, move) do
    safecast(name, {:make_move, game_id, move, self()})
    make_move_loop(game_id, 10000)
  end


  ############
  # Debug 
  ############

  def spinup(number_of_participants) do
    procs = Enum.to_list(0..number_of_participants) |> Enum.map(fn n -> :"p#{n}" end)
    Enum.map(procs, fn proc -> Server.start(proc, procs) end)
  end

  def kill (pids) do
    pids |> Enum.map(fn m -> Process.exit(m, :kill) end)
  end
end