ComfyFactorio/modules/crawl_into_pipes.lua

--Your character may enter pipes.

local Global = require 'utils.global'
local Event = require 'utils.event'

local math_floor = math.floor

local pipe_crawl = {}
Global.register(
    pipe_crawl,
    function(tbl)
        pipe_crawl = tbl
    end
)

local function get_current_pipe(player)
	local position = {math_floor(player.position.x) + 0.5, math_floor(player.position.y) + 0.5}
	local pipe = player.surface.find_entities_filtered({type = {"pipe", "pipe-to-ground"}, position = position, limit = 1})[1]
	return pipe
end

local function is_pipe_end_piece(pipe)
	local neighbours = pipe.neighbours[1]
	if #neighbours == 1 then return true end
end

local function enter_pipe(player, pipe)
	if not is_pipe_end_piece(pipe) then return end
	
	player.walking_state = {walking = false}
	pipe_crawl[player.name].character = player.character.clone({position = {0,0}, surface = "crawl_into_pipes", force = player.force})
	player.character.destroy()
	player.set_controller({type = defines.controllers.god})
end

local function exit_pipe(player)
	if player.character then return end	
	local saved_character = pipe_crawl[player.name].character
	player.character = saved_character.clone({position = player.position, surface = player.surface, force = player.force})	
	saved_character.destroy()
end
--[[
local function align_position_to_pipe(player, pipe)
	local position = player.position
	local tile_position = {x = math_floor(position.x), y = math_floor(position.y)}
	local inside_position = {x = position.x - tile_position.x, y = position.y - tile_position.y}

end
]]
local function on_player_changed_position(event)
	local player = game.players[event.player_index]
	local pipe = get_current_pipe(player)
	if not pipe then 
		exit_pipe(player) 
		return 
	end
	--[[
	if not player.character then 
		align_position_to_pipe(player, pipe)
		return 
	end
	]]
	if not player.character.valid then return end
	if player.character.driving then return end
	
	enter_pipe(player, pipe)
end

local function on_player_joined_game(event)
	local player = game.players[event.player_index]
	if not pipe_crawl[player.name] then pipe_crawl[player.name] = {} end
end

local function on_init()
	pipe_crawl.players = {}

	game.create_surface(
		"crawl_into_pipes",
		{
			height = 3,
			width = 3,
			["default_enable_all_autoplace_controls"] = false,
			["autoplace_settings"] = {
				["entity"] = {treat_missing_as_default = false},
				["tile"] = {treat_missing_as_default = false},
				["decorative"] = {treat_missing_as_default = false},
			},
		}
	)
end

Event.on_init(on_init)
Event.add(defines.events.on_player_changed_position, on_player_changed_position)
Event.add(defines.events.on_player_joined_game, on_player_joined_game)