Smart Miner

quarrySize = 0
minFuelLevel = 1000
fuelUsed = 0

x = 0 --Standing in positive X direction when starting
y = 0
z = 0
direction = 0

local goHome

function printPosition()
    --print("X: " .. x .. ", Y: " .. y .. ", Z: " .. z .. ", Direction: " .. direction)
end

function checkFullInventory()
    for i = 1, 16, 1 do
        if turtle.getItemCount(i) == 0 then
            return false
        end
    end

    return true
end

function dig(careAboutInventory)
    if careAboutInventory == nil then
        careAboutInventory = true
    end

    if careAboutInventory then
        if not checkFullInventory() then
            turtle.dig()
        else
            goHome()
        end
    else
        turtle.dig()
    end
end
function digDown(careAboutInventory)
    if careAboutInventory == nil then
        careAboutInventory = true
    end

    if careAboutInventory then
        if not checkFullInventory() then
            turtle.digDown()
        else
            goHome()
        end
    else
        turtle.digDown()
    end
end

function digUp(careAboutInventory)
    if careAboutInventory == nil then
        careAboutInventory = true
    end

    if careAboutInventory then
        if not checkFullInventory() then
            turtle.digUp()
        else
            goHome()
        end
    else
        turtle.digUp()
    end
end

function forward(steps, careAboutInventory)
    if careAboutInventory == nil then
        careAboutInventory = true
    end

    if steps == nil then
        steps = 1
    end

    for i = 1, steps, 1 do
        while not turtle.forward() do
            turtle.attack()
            dig(careAboutInventory)
        end

        fuelUsed = fuelUsed + 1

        --Update coordinates
        if direction == 0 then
            x = x + 1
        elseif direction == 1 then
            z = z + 1
        elseif direction == 2 then
            x = x - 1
        elseif direction == 3 then
            z = z - 1
        end
        printPosition()

    end
end

function up(steps, careAboutInventory)
    if careAboutInventory == nil then
        careAboutInventory = true
    end

    if steps == nil then
        steps = 1
    end

    for i = 1, steps, 1 do
        while not turtle.up() do
            turtle.attackUp()
            digUp(careAboutInventory)
        end
        fuelUsed = fuelUsed + 1
        y = y + 1
        printPosition()
    end
end


function down(steps, careAboutInventory)
    if careAboutInventory == nil then
        careAboutInventory = true
    end

    if steps == nil then
        steps = 1
    end

    for i = 1, steps, 1 do
        while not turtle.down() do
            turtle.attackDown()
            digDown(careAboutInventory)
        end
        fuelUsed = fuelUsed + 1
        y = y - 1
        printPosition()
    end
end

function updateDirection(amount)
    direction = direction + amount
    direction = direction % 4
end

function turnLeft(steps)
    if steps == nil then
        steps = 1
    end

    for i = 1, steps, 1 do
        turtle.turnLeft()
        updateDirection(-1)
    end
end

function turnRight(steps)
    if steps == nil then
        steps = 1
    end

    for i = 1, steps, 1 do
        turtle.turnRight()
        updateDirection(1)
    end
end

function turnTo(dir)
    turnLeft((direction - dir) % 4 )
end

function unloadInventory()
    for i = 1, 16, 1 do
        turtle.select(i)
        turtle.drop()
    end
    turtle.select(1)
end

function waitForFuel()
    print("Waiting for fuel..")

    while true do
        fuel = turtle.getFuelLevel()

        print(fuel .. " of " .. minFuelLevel .. " fuel.")

        if fuel >= minFuelLevel then
            return
        end
        sleep(5)
    end
end

function goHome()
    print("Going home...")

    resumeAtX = x
    resumeAtY = y
    resumeAtZ = z
    resumeDirection = direction

    --Go to the home position
    up(-y, false)
    turnTo(2) --X-axis
    forward(x, false)
    turnTo(3) --Z-axis
    forward(z, false)

    print(fuelUsed .. " fuel used.")

    --Unload
    turnTo(2) --Face the chest
    unloadInventory()
    turnTo(0) --Face the quarry again

    waitForFuel()

    --Return where it left off
    turnTo(0) --X-axis
    forward(resumeAtX, false)
    turnTo(1) --Z-axis
    forward(resumeAtZ, false)
    down(-resumeAtY, false)
    turnTo(resumeDirection)
end

function mine()
    digUp()
    digDown()
    dig()
end


function checkArguments(args)
    if #args == 0 then
        print("You have to supply an argument for quarry size.")
        return false
    end
    quarrySize = tonumber(args[1])
    return true
end

function nextRow(left)
    if left then
        turnLeft()
    else
        turnRight()
    end

    mine()
    forward()

    if left then
        turnLeft()
    else
        turnRight()
    end
end

function mineLayer()
    left = false
    for i=1, quarrySize, 1 do
        --For each row
        for j=2, quarrySize, 1 do
            mine()
            forward()
        end

        if i ~= quarrySize then
            nextRow(left)
            left = not left
        else
            if evenSize then
                turnRight()
            else
                turnLeft(2)
            end
        end

        mine()
    end
end

if not checkArguments({...}) then
    return --Exit the program
end

done = false
evenSize = (quarrySize % 2) == 0

waitForFuel()

down(2)

while true do
    mineLayer()
    down(3)
end