refuelbot.lua

local CHEST_NAME = "EnderStorage:enderChest"
local went_up = false

local function is_facing_name(str, matching_chars)
    local success, data = turtle.inspect()
    if not success then
        return false
    end
    if not matching_chars then
        if data.name == str then
            return true
        end
    else
        if string.sub(str, 1, matching_chars) == string.sub(data.name, 1, matching_chars) then
            return true
        end
    end
    return false
end

local function orient()
    local turned = 0
    while not is_facing_name(CHEST_NAME) do
        turtle.turnLeft()
        turned = turned + 1
        if turned >= 4 then
            print("Could not find orientation")
            return -1
        end
    end
    turtle.turnLeft()
    turtle.turnLeft()
    return turned
end

local function is_facing_turtle()
    return is_facing_name("ComputerCraft", 13)
end



local function up()
    if turtle.getFuelLevel() < 2 then
        -- Needs to go down eventually, resupply yourself first
        local turned = orient()
        turtle.turnLeft()
        turtle.turnLeft()
        turtle.suck(1)
        turtle.refuel()
        turtle.drop(1)
        -- Wait for the bucket to be filled
        sleep(60)
    end
    turtle.up()
end

local function down()
    turtle.down()
end

local function get_bucket()
    if went_up then
        down()
    end
    while true do
        turtle.select(1)
        turtle.suck(1)
        if turtle.getItemCount() > 0 then
            if went_up then
                up()
            end
            return
        end
        sleep(1)
    end
end

local function on_found_turtle()
    sleep(60)
    if not is_facing_turtle() then
        print("Turtle not there anymore")
        return
    else
        print("Turtle is still there")
    end

    -- Get rid of the old one
    turtle.suck(1)
    turtle.turnLeft()
    turtle.drop(1)
    turtle.turnLeft()

    -- Grab the new one
    get_bucket()
    turtle.turnLeft()
    turtle.turnLeft()
    turtle.drop(1)

    -- Put the old one in the chest
    if went_up then
        down()
    end
    turtle.turnLeft()
    turtle.suck(1)
    turtle.turnLeft()
    turtle.drop(1)
    turtle.turnLeft()
    turtle.turnLeft()
    if went_up then
        up()
    end
end

local function find_turtles()
    while true do
        sleep(1)
        if is_facing_turtle() then
            print("Found a turtle")
            on_found_turtle()
        end

        if went_up then
            went_up = false
            up()
        else
            went_up = true
            down()
        end
    end
end

local function init()
    if orient() != -1 then
        find_turtles()
    end
end

init()