refuelbot.lua

local CHEST_NAME = "EnderStorage:enderChest"
local y = 0

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(total)
    if turtle.getFuelLevel() < (total *  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)
        for t = 0, turned do
            turtle.turnRight()
        end
    end
    for h = 1, total do
        turtle.up()
    end
end

local function down()
    turtle.down()
end

local function go_all_the_way_down()
    for h = 1, y do
        down()
    end
    local prev_y = y
    y = 0
    return prev_y
end

local function get_bucket()
    local amount_down = go_all_the_way_down()
    while true do
        turtle.select(1)
        turtle.suck(1)
        if turtle.getItemCount() > 0 then
            up(amount_down)
            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
    local amount_down = go_all_the_way_down()
    turtle.turnLeft()
    turtle.suck(1)
    turtle.turnLeft()
    turtle.drop(1)
    turtle.turnLeft()
    turtle.turnLeft()
    up(amount_down)
end

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

        print("Y = ", y)
        if y < 2 then
            y = y + 1
            up(1)
        else
            for l = 1, y do
                down()
            end
            y = 0
        end
    end
end

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

init()