rectexc

function move()
    if (turtle.getItemCount(16) ~= 0) then
        dropItems()
    end
    if(turtle.getFuelLevel() == 0) then
        error("Out of fuel")
    end
    while (not turtle.forward()) do
        turtle.dig()
    end
end

function right()
    turtle.turnRight()
end

function left()
    turtle.turnLeft()
end

function down()
    turtle.digDown()
    turtle.down()
end

function outer()
    digside1()
    right()
    digside2()
    right()
    digside1()
    right()
end

function digside1()
    for num = 2, side1 do
        move()
    end
end

function digside2()
    for num = 2, side2 do
        move()
    end
end

function inner()
    peaks = (side2 / 2) - 1
    for num = 1, peaks do
        ascend()
        descend()
    end
    move()
    right()
    if(oddSide) then
        oddSideFix()
    end
end

function ascend()
    move()
    right()
    for num = 3, side1 do
        move()
    end
    left()
end

function descend()
    move()
    left()
    for num = 3, side1 do
        move()
    end
    right()
end

function oddSideFix()
    for num = 3, side1 do
        move()
    end
    left()
    left()
    for num = 3, side1 do
        move()
    end
    right()
    move()
    right()
end

function dropItems()
    right()
    right()
    turtle.select(1)
    while (not turtle.place()) do
        turtle.dig()
    end
    for num = 2, 16 do
        turtle.select(num)
        turtle.drop()
    end
    turtle.select(2)
    left()
    left()
    if(turtle.getItemCount(1) == 0) then
        error("Out of chests")
    end
end

-------------------------

local args = { ... }

side1 = tonumber(args[1])
side2 = tonumber(args[2])
depth = tonumber(args[3])

oddSide = false

if(side2 % 2 == 1) then
    oddSide = true
end

if(turtle.getItemCount(1) == 0) then
    error("Place chests in slot 1 and try again")
end

print(" ")
print("Excavating these dimensions:")
print("Out: " .. side1)
print("Across: " .. side2)
print("Down: " .. depth)
print(" ")

layers = 0
while(layers < depth) do
    outer()
    inner()
    layers = layers + 1
    if(layers < depth) then down() end
    print((100*layers/depth) .. "% complete")
end

print(" ")
print("Done!")