belts

-- belts
-- Lays down conveyor belts in a rectangular pattern
-- All belts face the forward direction
-- Written by HarvDad, June 2014

args = {...}
nArgs = #args

version = "belts: Rev 0.1"
instructions = "Place stack(s) of conveyor belts starting in first slot."

usage = "Usage: belts <length> <width>"

x = 0
y = 0
z = 0
face = 0

-- The following 'face' directions are relative to the starting position of the turtle in this program
north = 0
west = 1
south = 2
east = 3

goForward = 0
goBackward = 1
direction = goForward

currentSlot = 1

function setFace(f)
	if f == 0 then
	  if face == 0 then return end
	  if face == 1 then right() return end
	  if face == 2 then right() right() return end
	  if face == 3 then left() return end
	end

	if f == 1 then
	  if face == 0 then left() return end
	  if face == 1 then return end
	  if face == 2 then right() return end
	  if face == 3 then right() right() return end
	end

	if f == 2 then
	  if face == 0 then left() left() return end
	  if face == 1 then left() return end
	  if face == 2 then return end
	  if face == 3 then right() return end
	end

	if f == 3 then
	  if face == 0 then right() return end
	  if face == 1 then left() left() return end
	  if face == 2 then left() return end
	  if face == 3 then return end
	end
end

function left()
 if face == 0 then face = 1 turtle.turnLeft() return end
 if face == 1 then face = 2 turtle.turnLeft() return end
 if face == 2 then face = 3 turtle.turnLeft() return end
 if face == 3 then face = 0 turtle.turnLeft() return end
 print("function left\(\): Bad face value: ", face)
end

function right()
 if face == 0 then face = 3 turtle.turnRight() return end
 if face == 1 then face = 0 turtle.turnRight() return end
 if face == 2 then face = 1 turtle.turnRight() return end
 if face == 3 then face = 2 turtle.turnRight() return end
 print("function right\(\): Bad face value: ", face)
end

function up()
	while turtle.detectUp() do	-- This loop added in case of falling sand or whatever
	  turtle.digUp()
	end
  turtle.up()
  y = y+1
end

function rise(nBlocks)
  local i
  for i=1,nBlocks do
    up()
  end
end

function down()
  if turtle.detectDown() then
    turtle.digDown()
  end
  turtle.down()
  y = y-1
end

function moveForward(nBlocks)
	for i = 1, nBlocks do
		turtle.forward()
		if face == north then
			z = z + 1
		elseif face == south then
			z = z - 1
		elseif face == east then
			x = x + 1
		elseif face == west then
			x = x - 1
		end
	end

end

function moveBackward(nBlocks)
	for i = 1, nBlocks do
		turtle.back()
		if face == north then
			z = z - 1
		elseif face == south then
			z = z + 1
		elseif face == east then
			x = x - 1
		elseif face == west then
			x = x + 1
		end
	end
end

function home(targetY)
--  print("home:face ", face, ", x = ", x, ", z = ", z)
  if x < 0 then
	setFace(east)
	while x < 0 do
	  moveForward(1)
	end
  else
    if x > 0 then
  	  setFace(west)
	  while x > 0 do
	    moveForward(1)
	  end
    end
  end

  if z < 0 then
	setFace(north)
	while z < 0 do
	  moveForward(1)
	end
  else
    if z > 0 then
  	  setFace(south)
	  while z > 0 do
	    moveForward(1)
	  end
    end
  end

  if y > 0 then
  	while y > 0 do
		down()
	end
  end

  setFace(0)
end

function layBeltRow(direction, length)
	for j=1,length do
		if turtle.getItemCount(currentSlot) < 1 then
			currentSlot = currentSlot + 1
			if turtle.getItemCount(currentSlot) < 1 then
				abort("No more belts in inventory.")
			end
			turtle.select(currentSlot)
		end
		turtle.placeDown()
		if j < length then
			if direction == goForward then
				moveForward(1)
			else
				moveBackward(1)
			end
		end
	end
end

rowHeading = west

function goToNextRow()
	currentFace = face
	if face == north or face == south then
		setFace(rowHeading)
		moveForward(1)
		setFace(currentFace)
	else
		setFace(rowHeading)
		moveForward(1)
		setFace(currentFace)
	end
end

function reverseDirection()
	if direction == goForward then
		direction = goBackward
	else
		direction = goForward
	end
end

function layBeltSection(length, width)
	for i=1,width do
		layBeltRow(direction, length)
		if i < width then
			goToNextRow()
			reverseDirection()
		end
	end
end


if nArgs == 0 or (nArgs == 1 and args[1]== "help") then
	print(version)
	print(instructions)
	print(usage)
	return
end

if nArgs < 2 or nArgs > 3 then
  print(usage)
  return
end

length = tonumber(args[1])
if length == nil then
  print("\"", args[1], "\" is not a valid length")
  return
end
if length < 1 then
  print("length must be a positive number greater than zero")
end

width = tonumber(args[2])
if width == nil then
  print("\"", args[2], "\" is not a valid width")
  return
end
if width < 1 then
  print("width must be a positive number greater than zero")
end

layBeltSection(length, width)
home()