Strip Mine

local FUEL = true
local NUM_STRIPS = 32
local STRIP_DISTANCE = 3
local GRAVEL_FALL_TIME = 0.5
local ENDERCHEST_FAIL_WAIT_TIME = 0.5
local SLOT_ENDERCHEST_ITEMS = 1
local SLOT_ENDERCHEST_FUEL = 2
local SLOT_MINING = 2

local yieldTime -- variable to store the time of the last yield
local function yield()
        if yieldTime then -- check if it already yielded
                if os.clock() - yieldTime > 2 then -- if it were more than 2 seconds since the last yield
                        os.queueEvent("someFakeEvent") -- queue the event
                        os.pullEvent("someFakeEvent") -- pull it
                        yieldTime = nil -- reset the counter
                end
        else
                yieldTime = os.clock() -- store the time
        end
end

function mine1()
    while turtle.detectUp() do
        turtle.digUp()
        sleep(GRAVEL_FALL_TIME)
    end
    while turtle.detect() do
        turtle.dig()
        sleep(GRAVEL_FALL_TIME)
    end
    turtle.digDown()
    while not turtle.forward() do
        turtle.dig()
        sleep(GRAVEL_FALL_TIME)
    end
end

function mine1row()
    for i=1,45 do
        mine1()
        yield()
    end
end

function mine2rows()
    mine1row()
    turtle.turnLeft()
    for i=1,STRIP_DISTANCE do
        mine1()
        yield()
    end
    turtle.turnLeft()
    mine1row()
end

function mineFull(length)
    for i=1,length do
        turtle.select(2)
        turtle.turnRight()
        mine2rows()
        turtle.turnRight()
        if FUEL then
            if turtle.getFuelLevel() < 140 then
                print "Need fuel ..."
            end
            -- Refuel
            while turtle.getFuelLevel() < 140 do
                turtle.select(SLOT_ENDERCHEST_FUEL)
                turtle.digDown() -- Note: Not testing for unmineable blocks.
                turtle.placeDown()
                turtle.suckDown()
                turtle.refuel()
                turtle.digDown()
                sleep(10)
            end
        end
        print("Continuing row ", i)

        for i=1,STRIP_DISTANCE do
            mine1()
            yield()
        end

        turtle.back()
        turtle.select(SLOT_ENDERCHEST_ITEMS)
        while not turtle.place() do -- Place down enderchest
            turtle.dig()
        end
        for j=2,10 do
            turtle.select(j)
            -- Wait if cannot place in enderchest
            while not turtle.drop() and turtle.getItemCount(j) > 0 do
                print "Enderchest full... waiting to empty slots 2-10"
                sleep(ENDERCHEST_FAIL_WAIT_TIME)
            end
            yield()
        end
        sleep(1) -- Allow time to empty enderchest
        for j=11,16 do
            turtle.select(j) -- Place remaining 6 slots into enderchest
            while not turtle.drop() and turtle.getItemCount(j) > 0 do
                print "Enderchest full... waiting to empty slots 11-16"
                sleep(ENDERCHEST_FAIL_WAIT_TIME)
            end
            yield()
        end
        turtle.select(SLOT_ENDERCHEST_ITEMS)
        turtle.dig() -- Pick up enderchest
        while turtle.detect() do
            turtle.dig()
            yield()
        end
        turtle.forward()
        yield()
    end
end

function mineReturn()
    mineFull(NUM_STRIPS)

    turtle.turnRight()
    turtle.turnRight()
    totalDistance = NUM_STRIPS * STRIP_DISTANCE * 2
    for i=1,totalDistance do
        mine1()
        yield()
    end
end