local item_to_place = "concrete"
local max_at_once = 20

local current_index = 0
local max_creepers = 0
local tick_multiplier_calculated = 600

local function recalc_multiplier(a)
    max_creepers = max_creepers + (a or 0)
    tick_multiplier_calculated = math.ceil(math.max(1, math.min(1000, 5 * math.max(1, 10 - max_creepers) / 10)) - .5)
end

local function addPort(robo)
    recalc_multiplier(1)
    global.creepers[max_creepers] = {roboport = robo, valid = true, started = false, x = 0, y = 0, dx = 0, dy = -1, t = 0, i = 0}
end

local function init()
    global.creepers = {}
    current_index = 1
    local roboports = game.surfaces[1].find_entities_filtered{type="roboport"}
    for index, port in pairs(roboports) do
        addPort(port)
    end
    init_done = true
end

local function checkRoboport(index)
    local creeper = global.creepers[index]
    if creeper and creeper.valid then
        local roboport = creeper.roboport
        if roboport and roboport.valid then
            local network = roboport.logistic_network
            if network and network.valid then
                local cell = roboport.logistic_cell
                if cell and cell.valid then
                    if network.available_construction_robots > 0 then
                        if not creeper.didTrees then
                            for i, v in pairs(roboport.surface.find_entities_filtered{type = "tree", area={{roboport.position.x - cell.construction_radius + 1, roboport.position.y - cell.construction_radius + 1},{roboport.position.x + cell.construction_radius - 1, roboport.position.y + cell.construction_radius - 1}}}) do
                                v.order_deconstruction(roboport.force)
                            end
                            creeper.didTrees = true
                        end
                        if network.get_item_count(item_to_place) > 0 then
                            local max_rad = cell.construction_radius * 2
                            local maxI = max_rad * max_rad
                            local count = 0
                            for i = creeper.i, maxI do
                                if network.get_item_count(item_to_place) < 1 or network.available_construction_robots < 1 then
                                    return
                                end
                                if ((-max_rad/2 <= creeper.x) and (creeper.x <= max_rad/2) and (-max_rad/2 <= creeper.y) and (creeper.y <= max_rad/2)) then
                                    local tile = roboport.surface.get_tile(roboport.position.x + creeper.x, roboport.position.y + creeper.y)
                                    if not tile.name:find(item_to_place) then
                                        if roboport.surface.can_place_entity{name="tile-ghost", position={roboport.position.x + creeper.x, roboport.position.y + creeper.y}, inner_name=item_to_place, force=roboport.force} then
                                            roboport.surface.create_entity{name="tile-ghost", position={roboport.position.x + creeper.x, roboport.position.y + creeper.y}, inner_name=item_to_place, force=roboport.force}
                                            creeper.i = i
                                            count = count + 1
                                            if count >= max_at_once then
                                                return
                                            end
                                        end
                                    end
                                end
                                if ((creeper.x == creeper.y) or ((creeper.x < 0) and (creeper.x == -creeper.y)) or ((creeper.x > 0) and (creeper.x == 1-creeper.y))) then
                                    creeper.t = creeper.dx
                                    creeper.dx = -creeper.dy
                                    creeper.dy = creeper.t
                                end
                                creeper.x = creeper.x + creeper.dx
                                creeper.y = creeper.y + creeper.dy
                                creeper.i = creeper.i + 1
                            end
                        end
                    end
                end
            end
        else
            table.remove(global.creepers, index)
            recalc_multiplier(-1)
        end
    else
        current_index = 1
    end
end

script.on_event(defines.events.on_built_entity, function(event)
    if global.creepers then
        if event.created_entity and event.created_entity.valid and event.created_entity.type == "roboport" then
            addPort(event.created_entity)
        end
    else
        init()
    end
end)

script.on_event(defines.events.on_tick, function(event)
    if global.creepers then
        if event.tick % tick_multiplier_calculated == 0 then
            if max_creepers == 0 then init() end
            checkRoboport(current_index)
            current_index = current_index + 1
        end
    else
        init()
    end
end)

script.on_configuration_changed(function()
    init()
end)