cc: tweaked - petr_axeman - dturtle_extension

local dturtle = {}

function dturtle.gets_lengths (height, width, reversed)
    reversed = reversed or false
    h = height
    w = width - 1
    lengths = {}

    while true do
        if h == 0 then
            return lengths
        end

        if h == height and reversed ~= true then
            lengths[#lengths + 1] = h - 1
        else
            lengths[#lengths + 1] = h
        end
        h = h - 1

        if w == 0 then
            return lengths
        end

        lengths[#lengths + 1] = w
        w = w - 1
    end
end


function dturtle.gets_lengths_reversed (height, width)
    lengths = dturtle.gets_lengths(height, width, true)
    reversed_lengths = {}
    counter = 1
    for i = #lengths,1,-1 do
        if i ~= 1 then
            reversed_lengths[counter] = lengths[i]
        else
            reversed_lengths[counter] = lengths[i] - 1
        end
        counter = counter + 1
    end
    return reversed_lengths
end


function dturtle.gets_face_direction (h, w)
    if h >= w then
        if w % 2 ~= 0 then
            return 1
        else
            return 3
        end
    else
        if h % 2 ~= 0 then
            return 2
        else
            return 4
        end
    end
end


function dturtle.gets_position (h, w)
    if w > h then
        w = h
    end

    if w % 2 == 0 then
        return math.floor(w / 2), math.floor((w / 2) - 1)
    else
        return math.floor((w - 1) / 2), h - math.floor((w - 1) / 2)
    end
end


function dturtle.dig_spiral (turn, lengths)
    for l = 1, #lengths do
        for p = 1, lengths[l] do
            turtle.dig()
            turtle.forward()
        end
        turn()
    end
end


function dturtle.exit_from_center (height, width)
    x_pos, y_pos = dturtle.gets_position(height, width)
    direction = dturtle.gets_face_direction(height, width)
    if direction == 2 then
        turtle.turnLeft()
    elseif direction == 3 then
        turtle.turnLeft()
        turtle.turnLeft()
    elseif direction == 4 then
        turtle.turnRight()
    end

    for i = 1, y_pos do
        turtle.back()
    end
    turtle.turnLeft()
    for i = 1, x_pos do
        turtle.forward()
    end
    turtle.turnRight()
end


function dturtle.dig_area (height, width, depth)
    local state = 1
    turtle.dig()
    turtle.forward()
    for i = 1, depth do
        if i % 2 == 0 then
            lengths = dturtle.gets_lengths_reversed(height, width)
            turtle.turnRight()
            turtle.turnRight()
            dturtle.dig_spiral(turtle.turnLeft, lengths)
            turtle.turnRight()
        else
            lengths = dturtle.gets_lengths(height, width)
            if i ~= 1 then
                turtle.turnRight()
                turtle.turnRight()
            end
            dturtle.dig_spiral(turtle.turnRight, lengths)
            turtle.turnLeft()
        end
        if i ~= depth then
            turtle.digDown()
            turtle.down()
        end
    end
    if depth % 2 ~= 0 then
        dturtle.exit_from_center(height, width, depth)
    end
    if depth ~= 1 then
        for i = 1, depth - 1 do
            turtle.up()
        end
    end
    direction = dturtle.gets_face_direction(height, width)
    if direction == 3 then
        turtle.turnRight()
        turtle.turnRight()
    end
    turtle.back()
end

return dturtle