CC 2-High Cave Digger

-- definitions

function checkLavaAndFuel()
    local fuelLimit = turtle.getFuelLimit()
    if turtle.getFuelLevel() < fuelLimit - 1000 then
        turtle.select(15)
        if turtle.place() then
            if not turtle.refuel() then
                -- we picked up something other than lava (water, etc.)
                turtle.place()
            end
        end
    end
end

function autoRefuel()
    checkLavaAndFuel()
    local fuelLimit = turtle.getFuelLimit()
    while turtle.getFuelLevel() < 80 do
        turtle.select(16)
        if turtle.refuel(0) then
            -- we can refuel using slot 16
            turtle.refuel(1)
        end
    end
end

function isFull()
    if turtle.getItemCount(12) > 0 then
        return true
    else
        return false
    end
end

function dumpAndReturn(p_x, p_y)
    temp_x = p_x
    temp_y = p_y

    -- go to chest
    turtle.turnLeft()
    turtle.turnLeft()
    while temp_y > 0 do
        while turtle.detect() do
            turtle.dig()
        end
        turtle.forward()
        temp_y = temp_y - 1
    end
    turtle.turnLeft()
    turtle.turnLeft()

    turtle.turnRight()
    turtle.turnLeft()
    turtle.turnLeft()
    while temp_x > 0 do
        while turtle.detect() do
            turtle.dig()
        end
        turtle.forward()
        temp_x = temp_x - 1
    end
    turtle.turnLeft()
    turtle.turnLeft()

    -- drop stuff off
    for i=1, 14 do
        turtle.select(i)
        turtle.dropDown()
    end
    turtle.select(1)

    -- return to spot left off
    while temp_x ~= p_x do
        turtle.forward()
        temp_x = temp_x + 1
    end
    turtle.turnLeft()
    while temp_y ~= p_y do
        turtle.forward()
        temp_y = temp_y + 1
    end
end

function finishedDump(p_x, p_y)
    temp_x = p_x
    temp_y = p_y

    -- go to chest
    turtle.turnLeft()
    turtle.turnLeft()
    while temp_y > 0 do
        while turtle.detect() do
            turtle.dig()
        end
        turtle.forward()
        temp_y = temp_y - 1
    end
    turtle.turnLeft()
    turtle.turnLeft()

    turtle.turnRight()
    turtle.turnLeft()
    turtle.turnLeft()
    while temp_x > 0 do
        while turtle.detect() do
            turtle.dig()
        end
        turtle.forward()
        temp_x = temp_x - 1
    end
    turtle.turnLeft()
    turtle.turnLeft()

    -- drop stuff off
    for i=1, 14 do
        turtle.select(i)
        turtle.dropDown()
    end
    turtle.select(1)

    turtle.turnLeft()
end

-- start
print("Enter y size (how far forward):")
y_size = read()
print("Enter x size (how far to the right):")
x_size = read()
print("Starting...")

pos_x = 0
pos_y = 0

for x=2, x_size do
    -- forward
    for y=2, y_size do
        autoRefuel()
        if isFull() then
            dumpAndReturn(pos_x, pos_y)
        end

        while turtle.detect() do
            turtle.dig()
        end
        turtle.forward()
        pos_y = pos_y + 1
        while turtle.detectUp() do
            turtle.digUp()
        end
    end
    -- back
    turtle.turnLeft()
    turtle.turnLeft()
    for y=2, y_size do
        autoRefuel()
        while turtle.detect() do
            turtle.dig()
        end
        turtle.forward()
        pos_y = pos_y - 1
    end
    turtle.turnLeft()
    turtle.turnLeft()

    -- go to next column
    autoRefuel()
    turtle.turnRight()
    while turtle.detect() do
        turtle.dig()
    end
    turtle.forward()
    pos_x = pos_x + 1
    while turtle.detectUp() do
        turtle.digUp()
    end
    turtle.turnLeft()
end

-- one last forward
for y=2, y_size do
    autoRefuel()
    if isFull() then
        dumpAndReturn(pos_x, pos_y)
    end

    while turtle.detect() do
        turtle.dig()
    end
    turtle.forward()
    pos_y = pos_y + 1
    while turtle.detectUp() do
        turtle.digUp()
    end
end

finishedDump(pos_x, pos_y)
print("Finished.")