Gpsi

function update(dir)
        if dir == "forward" then
            if face == "north" then
                lengthPos = lengthPos - 1
            elseif face == "south" then
                lengthPos = lengthPos + 1
            elseif face == "west" then
                widthPos = widthPos - 1
            elseif face == "east" then
                widthPos = widthPos + 1
            end
        elseif dir == "backward" then
                if face == "north" then
                        lengthPos = lengthPos + 1
                elseif face == "south" then
                        lengthPos = lengthPos - 1
                elseif face == "west" then
                        widthPos = widthPos + 1
                elseif face == "east" then
                        widthPos = widthPos - 1
                end
        elseif dir == "up" then
                heightPos = heightPos + 1
        elseif dir == "down" then
                heightPos = heightPos - 1
        elseif dir == "right" then
                if face == "north" then
                        face = "east"
                elseif face == "east" then
                        face = "south"
                elseif face == "south" then
                        face = "west"
                elseif face == "west" then
                        face = "north"
                end
        elseif dir == "left" then
                if face == "north" then
                        face = "west"
                elseif face == "west" then
                        face = "south"
                elseif face == "south" then
                        face = "east"
                elseif face == "east" then
                        face = "north"
                end
        end
        recordPos(heightPos,widthPos,lengthPos,face)
end

function goto(heightGoal,widthGoal,lengthGoal)
    shell.run("position")
    if turtle.getFuelLevel() < 200 then
        refill()
    end
    if heightGoal > heightPos then
        while heightGoal > heightPos do
            up()
        end
    elseif heightGoal < heightPos then
        while heightGoal < heightPos do
            down()
        end
    end
    if widthGoal > widthPos then
        turn("east")
        while widthGoal > widthPos do
            forward()
        end
    elseif widthGoal < widthPos then
        turn("west")
        while widthGoal < widthPos do
            forward()
        end
    end
    if lengthGoal > lengthPos then
        turn("south")
        while lengthGoal > lengthPos do
            forward()
        end
    elseif lengthGoal < lengthPos then
        turn("north")
        while lengthGoal < lengthPos do
            forward()
        end
    end
end

function recordPos(heightPos,widthPos,lengthPos,face)
    local h = fs.open("position","w")
    h.writeLine("heightPos = "..tostring(heightPos))
    h.writeLine("widthPos = "..tostring(widthPos))
    h.writeLine("lengthPos = "..tostring(lengthPos))
    h.writeLine("face = ".."\""..tostring(face).."\"")
    h.close()
end

function gpsi.forward()
  update("forward")
  while not turtle.forward() do
    turtle.dig()
  end
end

function gpsi.up()
  update("up")
  while not turtle.up() do
    turtle.digUp()
  end
end

function gpsi.down()
  update("down")
  while not turtle.down() do
    turtle.digDown()
  end
end

function gpsi.right()
  update("right")
  turtle.turnRight()
end

function gpsi.left()
  update("left")
  turtle.turnLeft()
end

function turn(dir)
    if face == "north" then
        if dir == "east" then
            while face ~= dir do
                right()
            end
        else
            while face ~= dir do
                left()
            end
        end
   elseif face == "east" then
        if dir == "south" then
            while face ~= dir do
                right()
            end
        else
            while face ~= dir do
                left()
            end
        end
    elseif face == "south" then
        if dir == "west" then
            while face ~= dir do
                right()
            end
        else
            while face ~= dir do
                left()
            end
        end
    elseif face == "west" then
        if dir == "north" then
            while face ~= dir do
                right()
            end
        else
            while face ~= dir do
                left()
            end
        end
    end
end

function gpsi.init()
    if fs.exists("position") then
        shell.run("position")
    else
        recordPos(0,0,0,"south")
    end
end