Strip Mining

-- 0.4
-- strip mining

local switch = false
local runsToDo = 5
local fuelPerRun = 65
local fuelNeeded = runsToDo * fuelPerRun
local fuelLevel = turtle.getFuelLevel()
local torchesPerRun = 6
local torchesNeeded = torchesPerRun * runsToDo
local torchesInInv = turtle.getItemCount(16)
local isGravel = false

function digLine()
    compareGravel()
    turtle.dig()
    turtle.forward()
    turtle.digUp()
    turtle.digDown()
end

function compareGravel()
    turtle.select(15)
    isGravel = turtle.compare()

    print("Found gravel? " .. tostring(isGravel))

    if isGravel then dealWithGravel() end
end

function dealWithGravel()
    print("Dealing with gravel!")

    while isGravel do
        turtle.dig()
        compareGravel()
    end
end

function nextLineRight()
    turtle.turnRight()
    digLine()
    digLine()
    digLine()
    turtle.turnRight()
end

function nextLineLeft()
    turtle.turnLeft()
    digLine()
    digLine()
    digLine()
    turtle.turnLeft()
end

function fullRun()
    for i = 0, 19, 1 do
        digLine()

        if i == 3 or i == 11 or i == 18 then
            turtle.select(16)
            turtle.placeDown()
            turtle.select(1)
        end
    end
end

if fuelLevel < fuelNeeded then error("Not enough fuel!") end
if torchesInInv < torchesNeeded then print("Will run out of torches!") end

for i = 1, runsToDo, 1 do
    fullRun()

    if not switch then nextLineRight() else nextLineLeft() end
    switch = not switch

    fullRun()

    if not switch then nextLineRight() else nextLineLeft() end
    switch = not switch
end