local area = require("__flib__.area")

local util = require("scripts.util")

-- TODO: fix edge case with curved rails
return function(player, tile_name, fill_gaps, margin)
  local blueprint = util.get_blueprint(player.cursor_stack)
  if not blueprint then return end

  local entities = blueprint.get_blueprint_entities()
  local entity_prototypes = game.entity_prototypes

  local tiles = {}
  local tile_index = 0

  if fill_gaps then
    local TileArea = area.load(area.from_position(entities[1].position))

    -- iterate entities to calculate needed grid size
    for _, entity in pairs(entities) do
      local prototype = entity_prototypes[entity.name]
      if prototype then
        TileArea:expand_to_contain_area(area.center_on(prototype.collision_box, entity.position))
      end
    end

    -- ceil to outside edges and add a margin
    TileArea:ceil():expand(margin)

    -- for the purpose of this function, we don't care about any pre-existing tiles - we will replace all of them
    for position in TileArea:iterate() do
      tile_index = tile_index + 1
      tiles[tile_index] = {
        position = position,
        name = tile_name
      }
    end
  else
    local mapping = {}

    for _, entity in pairs(entities) do
      local prototype = entity_prototypes[entity.name]
      if prototype then
        local EntityArea = area.load(area.center_on(prototype.collision_box, entity.position)):ceil():expand(margin)

        for position in EntityArea:iterate() do
          local add = false

          if mapping[position.x] then
            if not mapping[position.x][position.y] then
              add = true
              mapping[position.x][position.y] = true
            end
          else
            add = true
            mapping[position.x] = {[position.y] = true}
          end

          if add then
            tile_index = tile_index + 1
            tiles[tile_index] = {
              position = position,
              name = tile_name
            }
          end
        end
      end
    end
  end

  blueprint.set_blueprint_tiles(tiles)
end