wart.lua

turtle.up()
turtle.forward()
local rotateright = false
local function turn_around()
    if rotateright then
        turtle.turnRight()
        if turtle.detect() then return 1 end
        turtle.forward()
        turtle.turnRight()
    else
        turtle.turnLeft()
        if turtle.detect() then return 1 end
        turtle.forward()
        turtle.turnLeft()
    end
    rotateright = not rotateright
end
while true do
    local is,data = turtle.inspectDown()
    local justrotated = false
    if is and data.name=="minecraft:nether_wart" then
        if data.state.age>=3 then
            turtle.digDown()
            local success,reason = turtle.placeDown()
            -- (reason == "Cannot place item here" or reason == "No items to place")
            if not success and reason ~= "Cannot place block here" then
                for i=1,16 do
                    if turtle.getItemCount(i)>0 and turtle.getItemDetail(i).name=="minecraft:nether_wart" then
                        turtle.select(i)
                        turtle.placeDown()
                        break
                    end
                end
            end
        end
    end
    if turtle.detect() then
        if turn_around() then break end
        justrotated = true
    elseif not is then
        turtle.back()
        if turn_around() then break end
        justrotated = true
    else
        if not turtle.forward() then
            if turn_around() then break end
            justrotated = true
        end
    end
    if justrotated and not turtle.detectDown() then
        break
    end
end