Layer miner

-- config
local width = 0
local length = 0
local linecount = 0
local dblocks = 0 -- blocks dug so far minus air
local tblocks = 0 -- total blocks in area
local mblocks = 0 -- current line progress
local goneleft = false -- has turtle gone left yet

--functions start

--clear
function clear()
    term.clear()
    term.setCursorPos(1,1)
end

--dig line
local function line()
    mblocks = 0
    while mblocks < length do
        if turtle.dig() == true then
            dblocks = dblocks+1
        end
        while turtle.forward() ~= true do
            os.sleep(0.5)
        end
        mblocks = mblocks+1
    end
    print("dug " .. dblocks .. "/" .. tblocks .. " blocks.")
    linecount = linecount+1
end

-- turn left and dig a line
local function lineleft()
    turtle.turnLeft()
    if turtle.dig() == true then
        dblocks = dblocks+1
    end
    while turtle.forward() ~= true do
        os.sleep(0.5)
    end
    turtle.turnLeft()
    line()
end

-- turn right and dig a line
local function lineright()
    turtle.turnRight()
    if turtle.dig() == true then
        dblocks = dblocks+1
    end
    while turtle.forward() ~= true do
        os.sleep(0.5)
    end
    turtle.turnRight()
    line()
end

--begin code
clear()
print("Place turtle above block at bottom right of area.")
write("Enter Width: ")
width = tonumber(read())
write("Enter Length: ")
length = tonumber(read()-1)
tblocks = ((length+1)*(width))

if turtle.digDown() == true then
    dblocks = dblocks+1
end

turtle.down()
line()

while linecount < width do
    if goneleft == true then
        lineright()
        goneleft = false
    else
        lineleft()
        goneleft = true
    end
end
print("Done. Mined " .. dblocks .. " out of " .. tblocks .. " blocks total.")