local common = require("scripts.common")

--- @generic T
--- @param array T[]
--- @param pred fun(elem: T): boolean
local function remove_if(array, pred)
  local to_remove = {}
  for i = 1, #array do
    if pred(array[i]) then
      to_remove[#to_remove + 1] = i
    end
  end
  -- Remove from back to front to keep the indices valid
  for i = #to_remove, 1, -1 do
    table.remove(array, to_remove[i])
  end
end

--- @param base LocalisedString
--- @param child LocalisedString
local function append_localised_string(base, child)
  --- @cast base -?

  local len = #base

  if len < 18 then
    base[len + 1] = child
    return
  end

  if len == 18 then
    base[19] = { "" }
  end

  append_localised_string(base[19], child)
end

--- @alias Deltas table<string, {name: string, quality: string, count: integer}>

--- @param deltas Deltas
--- @param name string
--- @param quality string
--- @param count integer
local function add_delta(deltas, name, quality, count)
  local key = name .. "/" .. quality
  local delta = deltas[key]
  if not delta then
    delta = { name = name, quality = quality, count = 0 }
    deltas[key] = delta
  end
  delta.count = delta.count + count
end

--- @param player LuaPlayer
--- @param entity LuaEntity
return function(player, entity)
  if not player.mod_settings["moc-enable-insertion"].value then
    return
  end

  if entity.type == "entity-ghost" then
    return
  end

  local proxy = entity.item_request_proxy
  if not proxy then
    return
  end

  --- @type Deltas
  local deltas = {}

  local entity_insert_plan = proxy.insert_plan
  remove_if(entity_insert_plan, function(insert_plan)
    -- TODO: Equipment grids
    local inventories = insert_plan.items.in_inventory
    if not inventories then
      return false
    end

    -- Despite the docs, these reads are not LuaObjects because insert_plan is a PropertyTree...
    local name = insert_plan.id.name --[[@as string]]
    local quality_name = insert_plan.id.quality or "normal" --[[@as string]]
    local quality = prototypes.quality[quality_name]

    remove_if(inventories, function(inventory_position)
      local inventory = entity.get_inventory(inventory_position.inventory)
      if not inventory then
        return false
      end

      if not inventory_position.count then
        inventory_position.count = 1
      end

      while inventory_position.count > 0 do
        local item = common.get_item(player, name, quality)()
        if not item then
          return false
        end

        -- For some ungodly reason, stack is zero indexed!
        local destination_stack = inventory[inventory_position.stack + 1]
        local to_transfer = math.min(inventory_position.count, item.count)
        assert(destination_stack.transfer_stack(item, to_transfer), "Inventory transfer failed")
        inventory_position.count = inventory_position.count - to_transfer
        -- Negate because the deltas are relative to the player inventory.
        add_delta(deltas, name, quality_name, -to_transfer)
      end

      return inventory_position.count == 0
    end)

    return not next(inventories)
  end)
  proxy.insert_plan = entity_insert_plan

  local entity_removal_plan = proxy.removal_plan
  remove_if(entity_removal_plan, function(removal_plan)
    -- TODO: Equipment grids
    local inventories = removal_plan.items.in_inventory
    if not inventories then
      return false
    end

    -- Despite the docs, these reads are not LuaObjects because removal_plan is a PropertyTree...
    local name = removal_plan.id.name --[[@as string]]
    local item_prototype = prototypes.item[name]
    local quality_name = removal_plan.id.quality or "normal" --[[@as string]]
    local quality = prototypes.quality[quality_name]

    remove_if(inventories, function(inventory_position)
      local inventory = entity.get_inventory(inventory_position.inventory)
      if not inventory then
        return false
      end

      local count_to_remove = inventory_position.count or 1

      -- For some ungodly reason, stack is zero indexed!
      local source_stack = inventory[inventory_position.stack + 1]
      -- This probably can't ever happen.
      if source_stack.count < count_to_remove then
        return false
      end

      local destination_stack_iterator = common.get_item(player, name, quality)
      repeat
        local destination_stack = destination_stack_iterator()
        if not destination_stack then
          return false
        end

        local to_transfer = math.min(inventory_position.count, destination_stack.count)
        assert(destination_stack.transfer_stack(destination_stack, to_transfer), "Inventory transfer failed")
        inventory_position.count = inventory_position.count - to_transfer
        -- Negate because the deltas are relative to the player inventory.
        add_delta(deltas, name, quality_name, -to_transfer)
      until count_to_remove <= 0 or not destination_stack

      return inventory_position.count == 0
    end)

    return not next(inventories)
  end)
  proxy.removal_plan = entity_removal_plan

  table.sort(deltas, function(a, b)
    return a.count > b.count
  end)

  --- @type LocalisedString
  local output = { "" }

  for _, delta in pairs(deltas) do
    if delta.count == 0 then
      goto continue
    end

    player.play_sound({ path = "item-drop/" .. delta.name })
    local delta_string = tostring(delta.count)
    if delta.count > 0 then
      delta_string = "+" .. delta_string
    end
    append_localised_string(output, {
      "",
      delta_string,
      " ",
      "[item=" .. delta.name .. "] ",
      prototypes.item[delta.name].localised_name,
      "\n",
    })

    ::continue::
  end

  player.create_local_flying_text({
    position = entity.position,
    text = output,
  })

  return true
end