Q

-- Davis Cook's myExcavate (Totaly written from scratch)

x=0 --forward
y=0 --down
z=0 --right (Perpendicular to "forward")
lookdir="forward"

function checkFuel()
    fuelLvl = turtle.getFuelLevel()
    --print("Checking Fuel Level...")
    if fuelLvl<100 then
        --print("Needs Fuel, Refueling..")
        turtle.select(16)
        turtle.refuel(2)
    else
        --print("No Fuel Needed.")
    end
end

function left()
    turtle.turnLeft()
end

function right()
    turtle.turnRight()
end

function lookDir(s) -- Options are "forward" "left" "right" "back" --print("Looking " .. s)
    if     ((lookdir=="forward") and (s=="forward")) then
    elseif ((lookdir=="forward") and (s=="right")) then    right()
    elseif ((lookdir=="forward") and (s=="left")) then     left()
    elseif ((lookdir=="forward") and (s=="back")) then     left() left()
    elseif ((lookdir=="right") and (s=="forward")) then    left()
    elseif ((lookdir=="right") and (s=="right")) then
    elseif ((lookdir=="right") and (s=="left")) then       left() left()
    elseif ((lookdir=="right") and (s=="back")) then       right()
    elseif ((lookdir=="left") and (s=="forward")) then     right()
    elseif ((lookdir=="left") and (s=="right")) then       left() left()
    elseif ((lookdir=="left") and (s=="left")) then
    elseif ((lookdir=="left") and (s=="back")) then        left()
    elseif ((lookdir=="back") and (s=="forward")) then     left() left()
    elseif ((lookdir=="back") and (s=="right")) then       left()
    elseif ((lookdir=="back") and (s=="left")) then        right()
    elseif ((lookdir=="back") and (s=="back")) then
    end
    lookdir = s
end

function forward()
    checkFuel()
    while turtle.forward()==false do
        turtle.attack()
        turtle.dig()
    end
    if lookdir=="forward" then x=x+1
    elseif lookdir=="right" then z=z+1
    elseif lookdir=="left" then z=z-1
    elseif lookdir=="back" then x=x-1
    end
end

function up()
    checkFuel()
    while turtle.up()==false do
        turtle.attackUp()
        turtle.digUp()
    end
    y=y+1
end

function down()
    checkFuel()
    while turtle.down()==false do
        turtle.attackDown()
        turtle.digDown()
    end
    y=y-1
end

function reSupply()

    print("Re-Supplying")
    checkFuel()
    savex = x
    savey = y
    savez = z
    savedir=lookdir

    lookDir("back")
    while y~=0 do
        up()
    end
    while x~=0 do
        forward()
    end
    while z~=0 do
        lookDir("left")
        forward()
    end
    print("Grabbing Fuel...")
    while ((turtle.getItemCount(16)<10) and (turtle.getFuelLevel()<300)) do
        turtle.select(16)
        turtle.suckUp()
    end
    lookDir("back")
    print("Emptying Inventory...")
    for slot=1, 15 do
        turtle.select(slot)
        turtle.drop()
    end
    rs.setOutput("front",true)
    sleep(1)
    rs.setOutput("front",false)
    lookDir("forward")
    while x~=savex do
        forward()
    end
    while z~=savez do
        lookDir("right")
        forward()
    end
    while y~=savey do
        down()
    end
    lookDir(savedir)
end

function digupdown()
    turtle.digUp()
    turtle.digDown()
end

function needResupply()
    n=1
    for q=1,15 do
        if ((turtle.getItemCount(q)>0) or ((turtle.getFuelLevel()<100) and (turtle.getItemCount(16)<4))) then
            n=n+1
        end
    end
    if n>13 then reSupply() end
end

function goHome()

    print("Going Home")
    checkFuel()

    lookDir("back")
    while y~=0 do
        up()
    end
    while x~=0 do
        forward()
    end
    while z~=0 do
        lookDir("left")
        forward()
    end
    lookDir("forward")

end

function excavate(length,width,depth)

    checkFuel()
    down()
    down()
    for u=1,(depth/3) do
        for o=1,(width/2) do
            for i=1,(length-1) do
                needResupply()
                digupdown()
                forward()
            end
            digupdown()
            lookDir("right")
            forward()
            lookDir("back")
            for p=2,length do
                needResupply()
                digupdown()
                forward()
            end
            digupdown()
            if o~=(width/2) then
                lookDir("right")
                forward()
                lookDir("forward")
            end
        end
        lookDir("left")
        for r=2,width do
            forward()
        end
        lookDir("forward")
        if u~=(depth/3) then
            down()
            down()
            down()
        end
    end
end

function bedRock()

    print("At Bedrock Level.")
    print("Running Bedrock Code...")
    for h=1,(width/2) do
        for j=2,length do
            checkFuel()
            hole=0
            while turtle.down() do
                y=y-1
                turtle.digDown()
                hole=hole+1
            end
            while hole~=0 do
                up()
                hole=hole-1
            end
            if j~=length then
                forward()
            end
        end
        while turtle.down() do
            y=y-1
            turtle.digDown()
            hole=hole+1
        end
        while hole~=0 do
            up()
            hole=hole-1
        end
        lookDir("right")
        forward()
        lookDir("back")
        for b=2,length do
            checkFuel()
            hole=0
            while turtle.down() do
                y=y-1
                turtle.digDown()
                hole=hole+1
            end
            while hole~=0 do
                up()
                hole=hole-1
            end
            if b~=length then
                forward()
            end
        end
        while turtle.down() do
            y=y-1
            turtle.digDown()
            hole=hole+1
        end
        while hole~=0 do
            up()
            hole=hole-1
        end
        if h~=(width/2) then
            lookDir("right")
            forward()
            lookDir("forward")
        end
    end

end

print("Davis Cook's myExcavate")
print("")
print("Length can Be Anything above 2.")
print("Length?")
length= io.read()
print("Width has to be Even and Above 2.")
print("Width?")
width= io.read()
print("To Go All The Way To Bedrock, do: y_coord-5")
print("Depth?")
depth=io.read()
print("Dig Bellow Bedrock? yes or no")
decision=io.read()
reSupply()
excavate(length,width,(depth))
if decision=="yes" then
    bedRock()
end
goHome()