-module(gilded_rose).

-include("gilded_rose.hrl").

-export([
  update_quality/1
]).

-spec update_quality([#item{}]) -> [#item{}].
update_quality(Items) ->
  lists:map(fun update_item/1, Items).

-spec update_item(#item{}) -> #item{}.
update_item(Item = #item{name = Name}) ->
  Item1 = if
    Name /= "Aged Brie" andalso Name /= "Backstage passes to a TAFKAL80ETC concert" ->
      if
        Item#item.quality > 0 ->
          if
            Name /= "Sulfuras, Hand of Ragnaros" ->
              Item#item{quality = Item#item.quality - 1};
            true ->
              Item
          end;
        true ->
          Item
      end;
    true ->
      if
        Item#item.quality < 50 ->
          Item2 = Item#item{quality = Item#item.quality + 1},
          if
            Name == "Backstage passes to a TAFKAL80ETC concert" ->
              Item3 = if
                Item2#item.sell_in < 11 ->
                  if
                    Item2#item.quality < 50 ->
                      Item2#item{quality = Item2#item.quality + 1};
                    true -> Item2
                  end;
                true -> Item2
              end,
              if
                Item3#item.sell_in < 6 ->
                  if
                    Item3#item.quality < 50 ->
                      Item3#item{quality = Item3#item.quality + 1};
                    true -> Item3
                  end;
                true -> Item3
              end;
            true -> Item2
          end;
        true -> Item
      end
  end,
  Item4 = if
    Name /= "Sulfuras, Hand of Ragnaros" ->
      Item1#item{sell_in = Item1#item.sell_in - 1};
    true -> Item1
  end,
  if
    Item4#item.sell_in < 0 ->
      if
        Name /= "Aged Brie" ->
          if
            Name /= "Backstage passes to a TAFKAL80ETC concert" ->
              if
                Item4#item.quality > 0 ->
                  if
                    Name /= "Sulfuras, Hand of Ragnaros" ->
                      Item4#item{quality = Item4#item.quality - 1};
                    true -> Item4
                  end;
                true -> Item4
              end;
            true -> Item4#item{quality = Item4#item.quality - Item4#item.quality}
          end;
        true ->
          if
            Item4#item.quality < 50 ->
              Item4#item{quality = Item4#item.quality + 1};
            true -> Item4
          end
      end;
    true -> Item4
  end.