Computercraft Turtle Self-GPS

-- Turtle Self-tracking System created by Latias1290.
-- Original code stolen from:http://www.computercraft.info/wiki/Turtle_GPS_self-tracker_expansion_(tutorial) (04/29/2016)
-- Original code has been modified to be more useful. (supports loading and saving)

local xPos, yPos, zPos = nil
face = 1 -- 1 is west, 2 is south, 3 is east, 0 is north
cal = false
local fileLoc = "MatthewC/appdata/turtleLoc" -- The name of the file.
local debug = false -- Stores whether or not we are in debug mode (if true, print our location after every move)
local slowPrint = false -- Stores whether to use slowprint or fast print when printing location

function setDebug(val)
  debug = val
end

function getDebug(val)
  return debug
end

function setSlowPrint(val)
  slowPrint = val
end

function getSlowPrint()
  return slowPrint
end

-- Converts a string direction into a face EG N or NORTH (case insensitive) gets converted to 0
function convertStringToFace(f)
  if string.upper(f) == "N" or string.upper(f) == "NORTH" then
    return 0
  elseif string.upper(f) == "W" or string.upper(f) == "WEST" then
    return 1
  elseif string.upper(f) == "S" or string.upper(f) == "SOUTH" then
    return 2
  elseif string.upper(f) == "E" or string.upper(f) == "EAST" then
    return 3
  else
    return nil
  end
end

-- Converts an int into a direction EG 0 : North, 1: West, 2: South, 3: East
function convertFaceToString(f)
  if f == 0 then
    return "N"
  elseif f == 1 then
    return "W"
  elseif f == 2 then
    return "S"
  elseif f == 3 then
    return "E"
  else
    return nil
  end
end

function getLocationAsString()
  if not cal then
    return "Location: Not Calibrated!"
  end

  return "Location: x="..xPos..", y="..yPos..", z="..zPos..", Direction="..convertFaceToString(face)
end

function printLocation()
  if slowPrint then
    textutils.slowPrint(getLocationAsString())
  else
    print(getLocationAsString())
  end
  return printVal
end

function saveLocation() -- save the location of the turtle, for persistence.
  if not cal then
    return false
  end

  local h = fs.open(fileLoc, "w")
  h.writeLine(xPos)
  h.writeLine(yPos)
  h.writeLine(zPos)
  h.writeLine(face)
  h.close()
  return true
end

function loadLocation() -- Load the location of the turtle, for persistence.
  local h = fs.open(fileLoc, "r")
  if not h then
    return false
  end

  local h = fs.open(fileLoc, "r")
  xPos = tonumber(h.readLine())
  yPos = tonumber(h.readLine())
  zPos = tonumber(h.readLine())
  face = tonumber(h.readLine())
  cal = true
  h.close()
  return true
end

function setLocation(face) -- get gps using other computers
  xPos, yPos, zPos = gps.locate()
  face = convertStringToFace(direction)
  cal = true
  saveLocation()
end

function manSetLocation(x, y, z, direction) -- manually set location
  xPos = x
  yPos = y
  zPos = z
  face = convertStringToFace(direction)
  cal = true
  saveLocation()
end

function getLocation() -- return the location
  if not xPos then
    return nil
  else
    return xPos, yPos, zPos, convertFaceToString(face)
  end
end

function isCalibrated() -- Return whether or not the api is calibrated
  return cal
end

function turnLeft() -- turn left
  if not turtle.turnLeft() then
    return false
  end

  if face == 0 then
    face = 1
  elseif face == 1 then
    face = 2
  elseif face == 2 then
    face = 3
  elseif face == 3 then
    face = 0
  end

  saveLocation()
  return true
end

function turnRight() -- turn right
  if not turtle.turnRight() then
    return false
  end

  if face == 0 then
    face = 3
  elseif face == 1 then
    face = 0
  elseif face == 2 then
    face = 1
  elseif face == 3 then
    face = 2
 end

  saveLocation()
  return true
end


function turnToOrientation(direction) -- Turn to a specified N, E, S or W direction. Returns true if successful, or false it not successul.
  inFace = convertStringToFace(direction)

  if not inFace then
    return false
  end

  -- Special case where we are already facing the correct direction
  if inFace == face then
    return true
  end

  -- Special cases where we just turn once.
  -- Cases for turning left
  if (inFace == 0 and face == 3) or (inFace == 3 and face == 2) or (inFace == 2 and face == 1) or (inFace == 1 and face == 0) then
    return turnLeft()
  -- Cases for turning right
  elseif (inFace == 0 and face == 1) or (inFace == 1 and face == 2) or (inFace == 2 and face == 3) or (inFace == 3 and face == 0) then
    return turnRight()
  end

  -- If we get to this point, we are guaranteed to need to turn exactly twice, so lets do so.
  turnSuccess = turnLeft()

  if not turnSuccess then
    return false
  end

  return turnLeft()
end

function forward() -- go forward
  if not turtle.forward() then
    return false
  end

  if cal == true then
    if face == 0 then
      zPos = zPos - 1
    elseif face == 1 then
      xPos = xPos - 1
    elseif face == 2 then
      zPos = zPos + 1
    elseif face == 3 then
      xPos = xPos + 1
    end
    else
    print("Not Calibrated.")
  end

  saveLocation()
  printLocation()
  return true
end

function back() -- go back
  if not turtle.back() then
    return false
  end

  if cal == true then
    if face == 0 then
      zPos = zPos + 1
    elseif face == 1 then
      xPos = xPos + 1
    elseif face == 2 then
      zPos = zPos - 1
    elseif face == 3 then
      xPos = xPos - 1
    end
  else
    print("Not Calibrated.")
  end

  saveLocation()
  printLocation()
  return true
end

function up() -- go up
  if not turtle.up() then
    return false
  end

  if cal == true then
    yPos = yPos + 1
  else
    print("Not Calibrated.")
  end

  saveLocation()
  printLocation()
  return true
end

function down() -- go down
  if not turtle.down() then
    return false
  end

  if cal == true then
    yPos = yPos - 1
  else
    print("Not Calibrated.")
  end

  saveLocation()
  printLocation()
  return true
end

function jump() -- perform a jump. useless? yup!
  turtle.up()
  turtle.down()
end

loadLocation() -- Try to load the location of the turtle, if it's already cached.