Excavator Computer Craft Script

print("Conor's excavating program!!")
write("Please enter the length: ")
local length = tonumber(read())

write("Please enter the width: ")
local width = tonumber(read())

write("Please enter the depth: ")
local depth = tonumber(read())

local function checkFuel()
    if turtle.getFuelLevel() < 200 then
        for i = 1, 16 do
            turtle.select(i)
            if turtle.refuel(0) then
                turtle.refuel(1)
            end
        end
    end
end

local function left(currentDepth, depth)
    turtle.turnLeft()
    turtle.dig()

    if currentDepth + 1 < depth then
        turtle.digDown()
    end

    turtle.forward()
    turtle.turnLeft()
end

local function right(currentDepth, depth)
    turtle.turnRight()
    turtle.dig()

    if currentDepth + 1 < depth then
        turtle.digDown()
    end

    turtle.forward()
    turtle.turnRight()
end

local function excavate(length, width, depth)
    if depth > 1 then
        turtle.digDown()
    end

    local i = 0
    local z = 1

    --for i = 1, depth do
    while i < depth do
        for j = 1, width do
            checkFuel()

            for k = 1, length - 1 do
                if i + 1 < depth then
                    turtle.digDown()
                end
                turtle.dig()
                turtle.forward()
            end

            if j < width then
                -- if even width
                if width % 2 == 0 then
                    -- if even depth
                    if z % 2 == 0 then
                        if j % 2 == 0 then
                            right(i, depth)
                        else
                            left(i, depth)
                        end
                    -- if odd depth
                    else
                        if j % 2 == 0 then
                            left(i, depth)
                        else
                            right(i, depth)
                        end
                    end
                -- if odd width
                else
                    if j % 2 == 0 then
                        left(i, depth)
                    else
                        right(i, depth)
                    end
                end
            end
        end

        -- position turtle if more than 0 depth to go
        if i + 1 < depth then
            turtle.turnRight()
            turtle.turnRight()
            turtle.digDown()
            turtle.down()

            if i + 2 < depth then
                turtle.digDown()
                turtle.down()
            end
        end

        if i + 1 < depth then
            i = i + 2
        elseif i < depth then
            i = i + 1
        end

        z = z + 1
    end
end

excavate(length, width, depth)