farm

-- Left chest: Seed
-- Back chest: Product
-- Right chest: Fuel

-- Constants
local seedSlot = 15
local chestSlot = 16
local NORTH = 1
local EAST = 2
local SOUTH = 3
local WEST = 4

-- States
local loop = true
local power = turtle.getFuelLevel()
local selected = 1 -- Top left
turtle.select(selected)
local facing = NORTH
local position = {}
position.x = 1
position.y = 1

-- Turn right, incrementing facing
local function TurnRight()
  facing = facing + 1
  if (facing > 4) then
    facing = 1
  end
  turtle.turnRight()
end

-- Turn left, decrementing facing
local function TurnLeft()
  facing = facing - 1
  if (facing < 1) then
    facing = 4
  end
  turtle.turnRight()
end

-- Move forward, increment/decrement facing coordinate position
local function MoveForward()
  if (facing == NORTH) then
    position.y = position.y + 1
  elseif (facing == EAST) then
    position.x = position.x + 1
  elseif (facing == SOUTH) then
    position.y = position.y - 1
  else
    position.x = position.x - 1
  end
  turtle.forward()
end

-- Find the direction towards the first farm plot
local function Initialize()
  local facingChest = true
  turtle.select(chestSlot)
  facingChest = turtle.compare()
  while (facingChest) do
    turtle.turnRight()
    turtle.select(chestSlot)
    facingChest = turtle.compare()
  end
  facing = 1
end

-- Plant a crop, harvesting any existing plant and plowing
local function PlantCrop()
  turtle.digDown()
end

local function Farm(x, y)
  --Initialize()
  MoveForward()

  while (loop) do
    print(string.format(
      "CURRENT POS (%s, %s)",
      position.x, position.y))

    if (position.y < y) then
      MoveForward()
    elseif (position.x < x) then
      TurnRight()
      TurnRight()
      while (position.x > 1) do
        MoveForward()
      end
      TurnLeft()
      MoveForward()
      TurnLeft()
    else
      loop = false
    end
  end
end

Farm(3, 3)