local table = require("__flib__/table")

local util = require("__CursorEnhancements__/scripts/util")

local function build_subgroups()
  --- @type table<string, string[]>
  local subgroups = {}

  for subgroup_name in pairs(game.item_subgroup_prototypes) do
    local subgroup = {}
    local prototypes = game.get_filtered_item_prototypes({ { filter = "subgroup", subgroup = subgroup_name } })
    for name, item in pairs(prototypes) do
      if name ~= "dummy-steel-axe" and not item.has_flag("spawnable") and not item.has_flag("hidden") then
        subgroup[#subgroup + 1] = name
      end
    end
    subgroups[subgroup_name] = subgroup
  end

  global.subgroups = subgroups
end

--- @param e EventData.CustomInputEvent
--- @param delta integer
local function scroll_item(e, delta)
  local player = game.get_player(e.player_index)
  if not player then
    return
  end
  local item = util.get_cursor_item(player)
  if not item then
    return
  end
  local subgroup_name = game.item_prototypes[item].subgroup.name
  if not subgroup_name then
    return
  end
  local subgroup = global.subgroups[subgroup_name]
  local index = table.find(subgroup, item)
  if not index then
    return
  end
  local new_item = subgroup[index + delta]
  if not new_item then
    return
  end
  util.set_cursor(player, new_item)
end

local scroll_subgroup = {}

scroll_subgroup.on_init = build_subgroups
scroll_subgroup.on_configuration_changed = build_subgroups

scroll_subgroup.events = {
  --- @param e EventData.CustomInputEvent
  ["cen-scroll-next"] = function(e)
    scroll_item(e, 1)
  end,
  --- @param e EventData.CustomInputEvent
  ["cen-scroll-previous"] = function(e)
    scroll_item(e, -1)
  end,
}

return scroll_subgroup