-- 3 wide bridge v2.0 by SparkVGX

--Variables
distance = 0
blocksPlaced = 0
fuel = 1
torches = 2
spaceCounter = 7

-- Clears screen for instructions or not
function clear(test) -- function to reset screen
        term.clear()
        term.setCursorPos(1,1)
        if test == nil then -- easy way to decide whether to display text or not
                print("Place me on the ground just in front of where you want the bridge.")
                print()
                print("Fuel goes in slot 1, Torches in two, and blocks everywhere else.")
                print()
                print("Press any key to start..")
        end
end

function anyKey()
   while not bEnd do
         local event, key = os.pullEvent("key")
         if (key ~= 1) and (key ~= 42) then
             bEnd = true
         end
   end       
end

-- If I need fuel, I will try use refuel
function checkFuel()
 if turtle.getFuelLevel() <= 5 then
   turtle.select(1) --fuel goes in this slot
   turtle.refuel(1)
 end
end

-- Place torch
function pTorch()
  turtle.select(2)
  turtle.up()
  turtle.place()
  turtle.down()
end

-- Select blocks to place
-- only slots 3-16 should have blocks
function selectBlock()
  for slot=3,16 do
     if turtle.getItemCount(slot)~=0 then
       turtle.select(slot)
       break
     end
  end
end

-- Select blocks and place them if possible, otherwise if out of blocks, wait.
function placeB()
  selectBlock()
  if turtle.detect() == false then
   if turtle.place() == false then
     print("Need blocks")
     sleep(5)
     placeB()
   end
  blocksPlaced = blocksPlaced + 1
    
  end    
end

-- pretty simple.. you turn around
function turnAround()
  turtle.turnLeft()
  turtle.turnLeft()
end

--initial start to get turtle in position
function runOnce()
  checkFuel()
  while turtle.detectDown() == true do
    turtle.forward()
	distance = distance + 1
  end
  turtle.down()
  turtle.turnLeft()
  placeB()
  turnAround()
  placeB()
  turtle.turnRight()
end
-- takes the turtle back where it started
function goHome()
  turtle.up()
  selectBlock()
  turtle.placeDown()
  blocksPlaced = blocksPlaced + 1
  turtle.up()
 
    for i=1,distance do
      turtle.forward()
    end
  turnAround()
  turtle.down()
	print("All done!")
	print("I went " .. distance .. " meters and placed " .. blocksPlaced .. " blocks.")
end

--The main code to run
function start()
runOnce()
--checks fuel, places blocks behind and on the sides.
  while turtle.back() do
    checkFuel()
    placeB()
    turtle.turnLeft()
	placeB()
	turnAround()
	placeB()
	turtle.turnLeft()
	spaceCounter = spaceCounter + 1
	distance = distance + 1
	-- every so often, places a torch and
	-- resets the counter
	if spaceCounter == 8 then
	  pTorch()
	  spaceCounter = 0
	end  
  end
  -- all done? return to start
  goHome()
end

clear()
anyKey()
start()