module Item = struct
  type t = { name : string; sell_in : int; quality : int } [@@deriving show]

  let v name sell_in quality = { name; sell_in; quality }
end

module Items = struct
  type items = Item.t list [@@deriving show]

  let v ?(items = []) () = items
  let show items : string = show_items items

  let update_quality items =
    let update_quality_items ({ name; sell_in; quality } as item : Item.t) =
      let quality' =
        if
          name <> "Aged Brie"
          && name <> "Backstage passes to a TAFKAL80ETC concert"
        then
          if quality > 0 then
            if name <> "Sulfuras, Hand of Ragnaros" then quality - 1
            else quality
          else quality
        else if quality < 50 then
          quality + 1
          +
          if name = "Backstage passes to a TAFKAL80ETC concert" then
            if sell_in < 11 then
              if quality < 49 then
                1 + if sell_in < 6 then if quality < 48 then 1 else 0 else 0
              else 0
            else 0
          else 0
        else quality
      in
      let sell_in' =
        if name <> "Sulfuras, Hand of Ragnaros" then sell_in - 1 else sell_in
      in
      if sell_in' < 0 then
        if name <> "Aged Brie" then
          if name <> "Backstage passes to a TAFKAL80ETC concert" then
            if quality' > 0 then
              if name <> "Sulfuras, Hand of Ragnaros" then
                { item with sell_in = sell_in'; quality = quality' - 1 }
              else { item with sell_in = sell_in'; quality = quality' }
            else { item with sell_in = sell_in'; quality = quality' }
          else { item with sell_in = sell_in'; quality = quality' - quality' }
        else if quality' < 50 then
          { item with sell_in = sell_in'; quality = quality' + 1 }
        else { item with sell_in = sell_in'; quality = quality' }
      else { item with sell_in = sell_in'; quality = quality' }
    in
    List.map update_quality_items items
end