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)