computer craft StripMiner

local tArgs = {...}

if #tArgs ~= 2 then
    print("Usage: strip <# of strips> <strip depth>")
    return
end

local stripCount=tonumber(tArgs[1])
local stripDepth=tonumber(tArgs[2])
local heading="forward"
local xPos,zPos=0,0

function faceLeft()
    if heading =="forward" then
        turtle.turnLeft()
    elseif heading=="backward" then
        turtle.turnRight()
    elseif heading=="left" then

    elseif heading=="right" then
        turtle.turnLeft()
        turtle.turnLeft()
    else
        print("error invalid heading fL")
        return
    end
    heading="left"
end

function faceRight()
    if heading=="forward" then
        turtle.turnRight()
    elseif heading=="backward" then
        turtle.turnLeft()
    elseif heading=="left" then
        turtle.turnRight()
        turtle.turnRight()
    elseif heading=="right" then

    else
        print("error invalid heading fR")
        return
    end
    heading="right"
end

function faceForward()
    if heading=="forward" then

    elseif heading=="backward" then
        turtle.turnLeft()
        turtle.turnLeft()
    elseif heading=="left" then
        turtle.turnRight()
    elseif heading=="right" then
        turtle.turnLeft()
    else
        print("error invalid heading fF")
        return
    end
    heading="forward"
end

function faceBackward()
    if heading=="forward" then
        turtle.turnLeft()
        turtle.turnLeft()
    elseif heading=="backward" then

    elseif heading=="left" then
        turtle.turnLeft()
    elseif heading=="right" then
        turtle.turnRight()
    else
        print("error invalid heading fB")
        return
    end
    heading="backward"
end

function canRTH()
    local xDistance=math.abs(xPos)
    local zDistance=math.abs(zPos)
    if (xDistance + zDistance + 2) > turtle.getFuelLevel() then
        return false
    else
        return true
    end
end

function moveForward()
    while not turtle.forward() do
        if turtle.detect() then
            turtle.dig()
            sleep(0.8)
        end
        if turtle.attack() then

        end
    end
end

function goTo(x,z)
    local distanceToTarget = xPos-x+zPos-z

    if canRTH() and distanceToTarget+2<turtle.getFuelLevel() then
        if z>zPos then
            faceForward()
            for i=1,z-zPos do
                if turtle.detect() then
                    turtle.dig()
                end
                moveForward()
                if turtle.detectUp() then
                    turtle.digUp()
                end
                turtle.suck()
                zPos=zPos+1
                print("forwards1")
            end

        end

        if z<zPos then
            faceBackward()

            for i=1,zPos-z do
                if turtle.detect() then
                    turtle.dig()
                end
                moveForward()
                if turtle.detectUp() then
                    turtle.digUp()
                end
                turtle.suck()
                zPos=zPos-1
                print("backwards1")
            end

        end

        if x>xPos then
            faceRight()

            for i=1,x-xPos do
                if turtle.detect() then
                    turtle.dig()
                end
                moveForward()
                if turtle.detectUp() then
                    turtle.digUp()
                end
                turtle.suck()
                xPos=xPos+1
                print("right1")
            end

        end

        if x<xPos then
            faceLeft()

            for i=1,xPos-x do
                if turtle.detect() then
                    turtle.dig()
                end
                    moveForward()
                if turtle.detectUp() then
                    turtle.digUp()
                end
                turtle.suck()
                xPos=xPos-1
                print("left1")
            end

        end
    else
        local lastX,lastZ=xPos,zPos
        returnToHome()
        print("I need fuel in slot 1, then press enter")
        io.read()
        turtle.select(1)
        turtle.refuel()
        print("Resuming..")
        goTo(lastX,lastZ)
    end
end

function returnToHome()
    goTo(0,zPos)
    goTo(0,0)
    faceLeft()
    for i=1,16 do
        turtle.select(i)
        turtle.drop()
    end
    turtle.select(1)
    faceForward()
end

goTo(0,1)
for i=1,stripCount do
    sleep(1)
    goTo(-stripDepth,i*3)
    goTo(0,i*3)
    goTo(stripDepth,i*3)
end

returnToHome()
print("Finished. Mined " .. stripCount .. "strips for " .. stripDepth .. " blocks each.")